SenthilKumar's Blog: 2009

1)Core JAVA

Oops Concept

Polymorphisms:

Overriding:

Should not change the method ars types.

Return type can not change. But can be the subtype of super,

Can throw runTime excpetion. Can throe subtype of super class exception.

Access level can not be more restrictive.

In case of exception, overrided method can not throw boarder unchecked exceptions or any new unchecked exception.

It can always throw a checked exception (runtime)

Run time

Overloading:

Arguments number or type should change.

Overloaded method can throw any type of exception,

Method args list should be different.

Return type can be changed.

Compile time

->Can I overload an extended method. Then how

->How to access overridded method in base class and extended class, by using base class object and extended class object.

Here polymorphisms is nothing but the concept that using base class object you can call the method of extended class.

ObjectA will call different methods, depending on the object type which it points.

Casting can be done downwards. But ClassCastexception occur in run time.

Casting done in the following cases with out any run time excp.

A a = new C();

C c = (C) a;

In this case of with out casting into C, compiler will not allow you to compile.

->In case for 3 rd level inheritance, how to access using the 3 types of objects.

Base class object ref can be assigned to extended class Object. Reverse is not allowed.

->Access specifier while doing overriding, overloading, implementing interfaces.

public – should be public

protected – can increase the visibility can not reduce(only public)

default - can increase the visibility can not reduce(public///protected)

private method – can not override

->Method with same name and type in two interfaces and abstract methods.

Its possible. Only thump rule is the child class has to implement the method

->Method with different return type

Never can have two methods with diff return type and 0 arguments and same name.

Never can different return type and same argumentno and type and same name.

Can have methods with diff return type and different argument type(arg no or type) with same name.

that is polymorphisms achived through overloading.

->Overriding static methods through abstract and interfaces

no static method in interface.

static method can not be overriden. But you can create two methods with same sign in both super and sub classes. But you can't achienve run time polymorphism there.

Overiding means run time polymorphism.

but we can't call super.paranetmethod() from a overrided static method.

->How jvm binds the methods, early binding or late binding?

All class methods are early binded, that is static and final methods and private methods.

instruction used is invokestatic.

Methods which can be accessile by instants are late binding by the virtual machine

instruction used is invokevirtual

->Overriding Constructor

Cant override constructor.

but u can overload.

super() will call parent constructor.

->final keyword. for a class, for method, for variables,

making final to class makes only methods final, that class cant extend

making final to class doesn't make the members final

If we want a member variable final we need to explicitly declare as final

Abstraction:

Hiding the inner details by projecting only the required details.

Method hiding.

→ Difference protected and default

dafult > instant access in the same package. Subclass access with in the same package. No subclass access in the other package. No instant access in the other package.

Protected > instant access in the same package, subclass anywhere.

->Advantages of using abstract class, different usage,using with inheritance.

If one method is abstract class must be abstract.

Class A implements interface I and extends class B. If a method in I is already implemented in B, compiler wont force to override that in A.

A method in abstract class can not be abstract static,by default its public ,

Variables in abstract are final.

->protected, default specifier for abstract method.

->Difference between method implementation with semi col and with out semi col

->Constructor in abstract class. What happens while extending this.

->Overloading and overriding of constructor.

->Can I make a Constructor as private, what will happen while making the object of this class.

Encapsulation:

Wrapping up of data and the functionality which works on this data is single unit: class

data hiding

-> Access Specification for class

In a java file we can only have 1 public class and more than one default classes. Other combinations not permitted.

Once a java file with 2 default and 1 public classes compiled, 3 .class filed will be created.

Default classes can be created more than one public class. Separate class files in the form of pubclassname$defaultclassname, wille be created from 1^st repetition of default classes.

First case will create newdefaultclass, so that we cann't create new class after that.

private classes can be inside of other top level classes.

->Different type of inner classes, inside public class,

->Inner class inside default class,

->Inner class inside interfaces.

->Can an interface object can call static variables in interface.

->Can I have other classes under a abstract class. If yes what type of class.

Inheritance:

->How class casting works

->Method access specification after overriding

->Exception handling of extended method

Aggregation:

Car and driver

Class A having a private member object Class B

Composition:

Car and Engine

Class A having a inner class B

Coupling:

No tight coupling. Should be loose

Lose coupling.

Cohesion:

tight cohesion. Logical relationship between the items in object.

Delegation:

Refers to delegation of responsibility. One object delegate the method call to another object through messages.

->Tight enacapsulation, loose coupling nad higher cohesson. what is this stands for?

->Difference between Abstraction and Encapsulation:

Abstraction: Method implementation hiding. how?

Encapsulation:Data hiding, how?

JVM:

->Use of finalize method. Can I override? other way to start GC

When ever an object is eligible for garbage collection, it will call the object finalize method.

-> Mark & sweep algorithm

Disadvatag is entire memory will scanned by suspending the operations.

-> Tri color Marking: different state of the object will be marked with different colors

->System.gc() and other methods OR Runtime.getRuntime.gc()

Force the jvm to do best effort for making the free memory by garbage collections

→ System.runFinalization or Runtime.getRuntime.runFinalization()

This cause the JVM to call finalize method for object which found to be gc collected.

->Weak reference and hard reference

->Different type of class loaders?

JVM has internal classloader called bootstrap loader which loads class from CLASSPATH.

Dynamic Loading: Inside the code

->Diff Class.forName() and ClassLoader.loadClass()?

Reflection:

java.lang:

->What is serialization, transient keyword, private get serialized?

->How are we use final keyword.

->Difference between mutable and immutable.

->Difference

String,

Immutable

Stringbuffer.

Sychronized . So Thread safe

Mutable

Stringbuilder,

Not Sychronized

Faster than StringBuffer

->Shallow comparison & Deep comparison

equals :

Deep comparison

Compare the values

== :

Shallow comparison

Compare the object references.

String a =”hi”

String b = “hi”

a==b is true. But

String a = new String(”hi”)

String b = new String(“hi”)

a==b is false.

Because, when ever new string in declared, jvm looks string pool to find this constant is alrdeady assigned to any reference or not. If yes maked the

new reference to point that object. But while creating with new, new memmory area has been created.

->Operator overload is not there in java, Then how string+another works

->What is mean by the hash code of an Object?

return the integer number created from the physical address

->Methods in Object, purpose.Can I override equals method then how?

Override equal for redifining the equality.

Person class with name, age equal means person objects equals.

there is contract to override hascode when u redifine equels, because equal there is a contract in java spec, which force equality of object means same hashcode.

producing distinct integer results for unequal objects may improve the performance of hashtables.

table bucket arrangement

->How gc works ?

System.runFinalization();

System.gc

Overriding finalize method.

->Transient declaration and Serialization

transient to switch of that particular element while serialization. Can use only with variables. When an object get serialized, only that object state get saved. No static member will be serialized.No final member will get serialized. No need of explicit transient declaration for final, static members.

If u are giving transient to a method, that should be static method. But no need of giving

transient to static method. Anyway all static are transient only. Will not consider while serialization.

->Difference between Comparator Comparable interfaces. Scenarios where we implement this.

comparable interfaces >> CompareTo

all the wrapper class implements comparable interfaces

The Collection.sort() does the sorting by calling compareTo method of comparable interface if the list passed is set of wrapper objects.

If the list having our own objects we can implement either comparable in the object and override compareTo(Obj1)

comparator interface >> Compare(Obj1, obj2)

Another way of sorting is pass list and along with another object which implements comparator which is overrided compare(obj1,obj2) method.

->Try to access String's private class method compare ??...

->How do you use System.setProperty, what will happen if you set a property,

Using this in a web application.

->java.lang.Runtime

static getRuntime()

getRunTime().exit()

0 indicated the JVM that the programm exit normally

None zero value indicates the abnormal situation

There are 2 steps for JVM shutdown. First strep it

exec()

gc()

difference between

Object.finilize() & System.runFinalization() or Runtime.getRuntime().runFinalization()

->ProcessBuilder

its a final class.

start()

directory()

environment()

ProcessEnvironment.environment()

new ProcessBuilder(cmdarray).environment(envp).directory(dir).start();

->ProcessEnvironment

its final class extended hashmap

static environment()

->java.lang.Process

Its an abstracy class

destroy

getOutputStream

->java.lang.System

static arraycopy()

static PrintStream out

static PrintStream err

static InputStream in

static gc()

static getenv() returns a map

System.exit(0) internally calls RunTime.getRuntime().exit(0)

->How to run a shell script in java

->java.lang.Object

clone()

creates another reference no new object.

Other class can implement cloneable() to mark that is conable

->java.lang.Class

All Class extends Object. Its a final Class.

Class.formname(name) returns the Class object associated with this name.

Class x = Class.formname(“x”);

URL x = x.getResources(“resName”)

// this statement in turn calls ClssLoader.getSystemResource(“resourceName”) and

get the url of the resource.

->java.lang.ClassLoader

Its an abstract class, its extended in security related application to load class in the program itself.

->java.lang.Enum

Its an abstract class,

->java.io.Serializable

->How to hang a machine using java program

->Two arrays, we have find the element occur in both arrays

->How to check circular link in Linked list.

->How memory is allocated

->Create an object on which garbage collection never execute.

->what is weakhashmap

java.lang.Thread

->Two ways to implement thread.

extend Thread class,

how to start a thread?

implements Runnable

how to start a thread?

->Main static methods in Thread class and their purpose.

static sleep(long milsec) >> Current thread goes to sleep. all lock on object will not be released. For other threads to get cpu cycle.

static yeild() >> While threads with priority, Thread.yield() couse current thread to go runnable, so that threads with same priority will get slot. NO gauranty

static interupted() >> If the current thread status interrupted, this method call will clear that state and return false.

isinterupted()

interupt() current thread goes blocked state.

join() Current thread goes wait for, until the called thread die.

join(long sec) Current thread goes wait for milliseconds, while called thread is alive

start()

stop() depreicated

suspend() deprecated because this may cause to arise deadlock situation.

Resume() also deprecated

-> Class level lock & Object level Lock

Lets say we have

Class A{

}

Thread1 and trhead2 trying to access Class A instance methods using class Aobject.

Object level lock >>

If threa1 accessing synchronized instance method, thread2 cant access other synchronized instance method using the same Class A object.
Other none syschronized methods can be accessed by thread2

Class level lock >>>

If thred1 accessing sycronized statis method, thread2 can't access other static sychrnoized methods,
but other sychronized instance method (if it get the lock means no other thread have the object level lock), none sychrozed static and instant method can be accessed,

->Main methods in Object using with thread programming. Uses for thread interaction.

Following will call with in the synchronized block

wait() >> thread temp orly releasing the lock on the object. and goes to block states. It will resume only if it get the lock again.

notify() >> One of the thread which waits the lock will get notified. No gurantie.depends JVM

notifyall() >> Notify all objects waiting...that particular object lock...

notify notify all doesn't release the lock, but just cause the notified thread to go to runnable state from blocked state.

Using read/write sample

->Thread states

New >> Runnable >> Running >> Dead

waiting/timedwaiting/block/sleep

->Differece Synchronized block and synchronized methods.which is best.

->Different types locks.Can a lock happen on memeber varable.

->How it works when a static method become synchronized.

->Why some methods are deprecated in Thread class.

->What is demone thread.

setDemon(true) final method , indicates jvm. JVM will exist if all nonedemon threads are killed. means they are in dead state.

In linux cron is demonthread. Its background thread.

->How volatile works?

This is a indication to the JVM that, the variable declared as volatile may be modified from different threads. Why we are giving this because, different threads will be using its own local memory forstoring the varialbes value. and there will be a master copy of the varaible in the main memory . By giving volaile jvm will synch up these two values.

->Why synchronization on constructor is not allowed?

->What is common exception occurs in thread programming and when

InteruptException

IllegalMonitorStateException >> When the current thread is not owner of the lock and still we calls objectName.wait()

IllegalThreadStatementException

->Declare a volatile variable. Create two threads to access this.

java.util.cuncurrent

->All classes under this package, how to use

->Creating a thread pool

->Cuncurrent hashmap how to use and advantages?

java.util

->All collection implements Iterator. Why and how it uses internally.

Iteration in two ways can be done

For(InteraTor<string> it = s.Iterator(); it.hasNext())

String s = it.Next()

foreach(String s: col)

syso(s)

->Main Util classes in collection Framework?

Arrays,

binarasearch

copyof

fill

sort

asList

Collections

binarysearch

newSetFromMap

raplaceAll(List,oldValue,newValue)

synchronizedMap

synchronizedList

synchronizedSet

reverse

sort

Main interfaces and implementation in collection

Iterable

Collection

List

Ordered collection

(ArrayList)

-> permits null

-> Not synchronized

->Array implementation, insertion is costly

->Slower than arrays

->Crates a new array internaly when u add

->ensureCapacity(min capacity) needs to set, so array will be created only once.

(Linked List)

→ insertion deletion faster than arrayList

->Linked implementation.

->Implements Queue interface

poll(),remove(), peak(), element()

->Permits null

(Vector)

->synchronizedList

(Stack) extends Vector

->LIFO

->push(),pop(),peek(),search()

Queue

(ArrayDeque)

-> push pop peek remove

-> Its a resizable array, no capacity restrictions.

-> Allows null

Set

No duplicates

(Hash Set)

->hashmap implimentation of set.

->permits null

->Not synchronized

(LinkedHashSet)

->Hash table and linkedList implementation.

->permits null

->Doubly linked list

->Not Synchronized

SortedSet

(TreeSet)

->tree map implementation

->Ascending order

->ts.add(null) is possible.

->Second time add will check the compareTo then it will

give nullpointer exception

->Not Synchronized

NavigableSet(1.6)

Map

Key value pair implementation

ConcurrentMap

(HashMap)

->Null values and null keys are accepted

->Not Synchronized

->Key object should override equals & hashcode methods.

put

putAll

remove

get

(LinkedHashMap)

->permits nulls

->retaining the insertion order.

Sample print ABCB 1234. LinkedHashMap prints ABC,B HashMap prints ACBB.

(HashTable)

->No nulls keys, No null values. if add it will throw NullPointerException

->Synchronized

->Key object should override equals & hashcode methods.

SortedMap

(TreeMap) → Not sychronized

Collections.sychronizedSortedMap(new TreeMap(....) will return the TreeMap which is sychronized

NavigatableMap

ConcurrentNavigatableMap

(ConcurrentSkipListMap)

Collection:

ArrayList:

-> Initial capacity will be 10

-> Does Arrays.copyOf(existingarray,newCapacity) for adding

-> does System.ArrayCopy() and then add that element in the coresponding position.

System.ArrayCopy(arrar, index, newarray, index+1,no_elemt_Needs_Cop_frm_FirstAr)

newArray(index) = element

-> Increases the array size by 50% when room full while adding new

->Fast iteration required and no need of thread safe

Linked List:

-> Contains a private static class for holding the structure of node.

-> Constructor having the element, previous,next

How to find the loop in a single linked list

How to find the loop in doubly linked list

Scenario where we have frequent insertion deletion

Vector:

added

set

remove

-> All methods are synchronized

-> Initial capacity will be 10

-> We can set the increment capacity also in the constructor

-> By default increases the array size by doubling the existing capacity

-> Scenario where we know the the increment rate, and required thread safe.

Map

Collections:

Arrays:

Generics:

Inner Classes

->where is Iterator interface is implemented?

->When ConcurrentModificationException occure ?

->How collections.synchronizedcollection(), Collections.synchronizedSet

usefull

How Collection.sort works?How can we decide the sorting base?

How Collection.srot can be use for sorting the elements of a Hashmap

WeakHashMap and weakreference:

8)What are all the sorted maps and sets in what basis it sort elements, how can we make the sorting criteria.

How maps implementation in memory(check docjar of map impls)

Difference Hashmap and Linked hashmap

Use of >>>>>>>> java.util.random

Use of >>>>>>>> java.util.Date

Use of >>>>>>>>

java.lang.Throwable

java.lang.Error

AssertionError

VirtualMachineError

OutOfMemoryError

StackOverflowError

UnknownError

InternalError

ThreadDeath

java.lang.Exceptions >>>>> checked forced

java.text.ParseException

ClassNotFoundException

InvocationTargetException

IOException

FileNotFoundException

javax.servlet.excpetion

java.lang.RunTimeException >>>> unchecked/runtime/not forced

ClassCastException

ArithmeticException

NullPointerException

IllegalMonitorStateException

InterruptedException

ConcurrentModificationException

BufferOverflowException

IndexOutofBound

ArrayIndexOutOfBoundsException

StringIndexOutOfBoundsException

IllegalArgumentException

NumberFormatException

IllegalThreadStateException

InvalidParameterException

IllegalSelectorException

UnsupportedOperationException

ReadOnlyBufferException

ArrayStoreException

SecurityException

AccessControlException

RMISecurityException

IllegalStateException

AlreadyConnectedException

.....

org.omg.corbra.SystemException

org.omg.CORBA.TRANSACTION_ROLLEDBACK

......

javax.net.*

java.io.*

IO streams are made for 3 purpose

read bytes to characters
Read bytes to text

File >> File or Diractory path name

InputStream >> Reading character

ByteArrayInputStream

FileInputStream

FilterInputStream

BufferedInputStream

OutputStream >> writing character

ByteArrayOutputStream

FileOutputStream

FilterOutputStream

BufferedOutputStream

DataOutPutStream

PrintStream >> No IO exception will be thrown

Automatic flushing happens after each println

Convert each character data to byte

Reader >> Reading text

Writer >> Writing text

BufferedWriter

CharacterArrayWriter

OutputStreamWriter

FileWriter >> Use while writing character data.

Need flush and close after writing

Throughs IO exception

PrintWriter >> Automatic flushing after each line

No io Exception

Error flag can be obtained checkError() method

StringWriter

in, out,error etc are public static final variables in System class.

RandomAccessFile

Can do both read and write to a file

readByte()

readLine()

readChar()

writeByte()

writeChars()

seek()

length()

java.nio.file

java.nio.*

java.lang.ref:

javax.swing:

javax.awt:

Annotations:

Earlier versions also have ad hoc annotation like @deprecated, transient etc

In java 5 we can create our own annotation types.

Java5 & java6 difference:

Scripting language support

Reorganized some interfaces and added some concreate classes in collections frmwk.

ArrrayDeque

Metod in Collectios util newSetFromMap

Added more classed in Swings package

Serialization:

need to impliment serializable interface. Its a markable interface. All collection concrete class impented this. Why it is implimented is to nottify jvm to store the object state.

Convert object into byte while passing to stream. Example writing an object to a file, passing throgh a network.

While getting that object from the stream, jvm automatically deserialize.

transient declaration to avoid instant varialbles state to be stored.

java Tricky Qts:

Can I give private access modifier to a class. Where?.how?.

2)JAVA Utilities

->Random Text image creation

->Base-64 encoding of images.

->xml parsing and other operation

DOM

Load the xml in memory, Use with small docuemts, while random access or needs to modify the document.

DocumentBuilderFactory

DocumentBuilder

Document = builder.pars(“xml file or url to xml”)

Element

NodeList

Node

getNodeValue

getNodeElement

SAX

Works based on event and listener,

SaxParserFactory

SaxParser >> SaxParser.pars(uri, handlerObject)

Handler extends DefdaultHandler

Inside the overrided method, we have to give the logic to implement on each event

Jaxp

Use sax, dom, xslt

->xsl transformation

->Calling perl or shell scripts

->Using POI

->Using Apache FOP pdf generation

->Zip and unzipping

->Xtream API

->org.apache.commons.collections.DoubleOrderedMap

3)JDBC and SQL

->Two steps to make connectionusing DriverManager

Load the driver

Class.forname(“driver name”)

this will intialize the driver class. Basically instantiate the driver and register driver.

We can give the drivername in the ~/.java/properties file and load the file.

get the connection

Connection con =DriverManager .getConnection(url) has its own logic to find out the loaded driver class object using that driver it will return the connection object corresponding to the parameter specified in the url.

Statement stmt = con.createStatement();
Resultset rt=stmt.executeUpdate("CREATE DATABASE JunkDB");

A JBC driver is the code that implements the JDBC API interfaces.

Type -1:

not multi threaded

Build on top of other native drivers

Use native client library to implement jdbc api interface. Probably written in c++

ex JDBC ODBC bridge driver

Type-2:

jdbc interfaces were implemented partially in java and partially native code c++

thick drivers

not portable

has native client library specific to DataSource

Type-3:

Uses a pure java clinet for Communication

Clinet Communicate with the middleware server using database indpenedent protocaol. http.

Middileware server communicate with datasource

Type:-4

Pure java implimentation. So platform independent

so they thin drivers

No clinet program required

Communicate directly with data source using java socket

→ Using DataSource

using JNDI

using pooled Connection

Main interfaces & classes in java.sql package

DriverManager

Connection

statement

ResultSet

Main interfaces and classes in javax.sql package

new ConnectionEvent(ConnectionPool obj)

DataSource

ConnectionPoolDataSource

PooledConnection

RawSet

->Difference types of statements

callable stmt

prepared stmt

->Different ways to connect db

->Connection pooling

using apache dbcp

4)Servlets

ServletConfig(Containts that particular servlet configuration info given in the web.xml file) contains ServletContext(Gives the info of that webapplication).

ServletRequest

HttpServletRequest

getRequestDispather(String) gives the path of the resource and get the RequestDispatcher

getSession():

getSession(boolean): Return current session. if passed true&no current session,create new

getRemteAddr >> ip

getRemoteHost >> hostname

getAttribute >> get the object assigned to the request

getParameter(name) >> get the params value attached in the querystring or form

getParameterNames >> return enumerated list.

getParameterValue >> String[] of all values

getCookies() >> return all cockie info in an array Cookie[]

getMethod() >> retunr POST or GET ...which used by client for submitting

getQueryString() >> url after the path

SetAttribute()

removeAttribute()

getServerName()

getSession() >> session infor in HttpSession:

HttpSession:

ivalidate()

getAtributes() return all sessionsin enumaration

setAttributes.

isNew()

Container maintain the session in 2 ways.

Using coockies client based.
URL rewriting server based.
Hidden Form fields

ServletResponse

HttpServletResponse

addCookie

addHeader

getWriter() return a PrintWriter object

reset() >> clear data in buffer, status code and header

isCommitted()

sc_accpted = 202

sc_continue = 100

sc_ok = 200

encodeURL() >> addthe session id along with the url

sendError(code, message);

sendRedirect(location) >> give relative url. Container will convert that to absolute url.

Update the broswer hstory

New request, nd response object getting created.So no way to

setAttribute in reuest

setStatus(StatuCode) >> sc_OK, SC_ABORT etc

GenericSrvlet implemetes Servlets, ServletConfig

HttpServlet extends GenericServlet

getInitParameter(pramName in web.xml)

getInitPrameters() return the Enumeration obj of init params

getServletConfig() returns conf inof as

ServletConfig

getServletContext()

getInitParameterNames >> Enumerated output

getInitParameter(name) >> return the value

getservletName()

getServletContext return webapp info as

ServletContext

getContext(path)>> return the contex inof corre to the path

getNameDispatcher(nam) >> return RequestDispatcher

getRequestDispatcher(path) >> return RequestDispatcher

log() >> log message in he servlet log file.

This will be a singleton object for a web application. This instance can be shared amonng different servlet in that web application. This sores as member varibale in ServletConfig object, which will be pass to init method by the container.

RequestDispatcher

forward(request,reponse) >> Attributes can be set to the req

include(request,response)

->Life cycle

Init

Container calls this by passing ServletConfig object which containts container specific

information.

Service

doGet

If client uses getmothod only 1024 characters can be send to server

doPost

Unlimited length of data can be send to the server.

DoPut

Use to place a file to server like FTP.

Dodelete

delete a document or webpage from server

doHead

reurns only header info. No response body

doOption

doTrace

destroy

->javax.servlet.Filter

doFilter(ServletReq, ServletResp, FilterChain)

init(FilterConfig)

distroy

FilterConfig

getFilterItem()

getInitParameterName()

getParameter()

getServletContext()

FilterChain

doFilter(HttpRequest req, HttpResponse resp)

Can be used to change the request/response.pre or post process of servlet

A servlet can n filters. 1 filter can use by n servlets

doFilter will be invoked by container passing req,resp and FilterChain object which can be use to call next filter or the configures resource (servlet, htmlfile).

Without doing filterchainObj.doFilter(req,resp) the servlet to which filter configured will not execute.

To get container info in filter, we have to override the filters init(FilterConfig) method in our filter and using that

filterconfig.getServleContext();

->Can I override the methods. how?

->difference generics and http servlet

->Redirecting form one servlet to another. different types

reqobject.sendRedirect(servlet_name);

getServletConfig().getRequestDispatcher(“servlet_name_to_redirect”).forqard(req.resp)

->Inite params to Servlet

->How filters work.

->Passing arguments from one servlet to another.

->Get other servlet info from a servlet

->How to get the container info from servlet

getServletConfig().getServletContext() will give the info of web application

->Deployment descriptor configs. Sample tomcat web.xml configurations

web-app is the root element of deployment descriptor

filter >> filter-name

filter-class

init-param

init-name

init-value

filter-mapping

filter-name

url-pattern

dispatcher

dispatcher value can be either REQUEST, FORWARD, INCLUDE, ERROR

listener >> listener

listener-class

Listerner object will be called by the container whenever some event object. and Passes the eventObject to corresponding implemented Listeners. These can any of the following type

ServletContextListener

Class which implement this interface has to configure in web.xml. 2 methods

contextIntiated(ServletContextEvent_Obj). When container intialize the app

contextDestroyed(ServletContextEvent_Obj) .When context deleted by user

ServletContext cntx = ServletContextEvent_Obj.getServletContext();

ServletContextAttributeListener

HttpSessionListener

Class which implement this interface has to configure in web.xml. Methods are

sessionCreatd(HttpSessonEvent_obj)). When session created

sessionDestroyed(HttpSessonEvent_obj)). When session about to invalidated

HttpSessionActivationListener

HttpSessionAtributeListener

HttpsSessinBindingListener

Implemented by the object for which we have to track the session state.

valueBound(HttpSessionBindingEvent)

valueUnbound(HttpSessionBindingEvent)

HttpSessionBindingEvent

getName

getValue

getSession

ServletRequestListener

ServletRequestAttributeListener

servlet

servlet-name

servlet-class

description

init-param

param-name

param-value

load-on-startup . The servlet will be initialized when the container starts.

run-at

servlet-mapping

servlet-name

url-mapping

session-config

session-timeout

jsp-config

tag-lib

taglib-uri

taglib-location

context-param : Mention the params needed for entire web application.

description

param-name

param-value

distributable

Self closing tag to specify this is an distributable application, so that container can replicate the session from one jvm to another.

resource-ref

resource-env-ref

locale-encoding-mapping-list

env-entry

login-config

Servelets difference 2.3 2.4 2.5

: introduced Filters and FilterChains

Context and session listerners.

: introduced new methods in ServletRequest, for eg

getRemotePort()

getLocalName()

getLocalAddress

getLocalPort

Introduced Requestlisterners

: Intriduced annotations. Works only with jdk -1.5

In web.xml mutiple “url-pattern” can be given for filters. Or “servlet-name” can be *

for filter-mapping.

Tomcat difference 4, 5, 6

5)JSP

JSP Life cycle:

First is translation phase:

Syntax checking

Code generation

Compilation phase:

Compile the servlet code and create the class file.

these two phases happens just before the first request

Load Servlet classification:

create instance:

best practice is creating single instance, depends on the container

Multiple threads of this single instance serves the multiple requests

call the jspinit method:

call the _jspService method

call the jspDistroy method

All generated servlet will be extending the container Servlet. And generated servlet will override the methods _jspService

tomcat: org.apashe.jasper.runtime.HttpJspBase

This should

extend HttpServlet >> GenericServlet

implement HttpJspPage >>

_JspService

JspPage >>

jspDestroy

jspInit

Servlet

init, service,destoy

Page Elements:

Directive Elements:

page

import

session

isThreadSafe

include

taglig

Action Elements:

forward

usebean

Implecit Objects:

request

response

application

Scripts:

expression:

peace of code to give output directly to the page: <%= new Date() %>

scriptlet:

The code written here will go to _jspService() method. And this will not show in the

front end. <% SYSO(“something”) %>

declarations :

If we want to override the init method or or the code which we dont need to go inside _jspServce() method will written here.

<%! public void jspInit() {super.init()} %>

comments:

Comments which appear in jsp page source. No where else

<%-- some comment --%>

PageContext is the abstract class which will be extended by the container specific class which provides the JspWritter object to response, session to response etc.

out is an insstance in JspWritter object and will be part of response. This mechanism cotrolled by PagContext extended class in the container.

Eg: <%= new Date()%> will be converted into out.print(new Date())

The template element will be changed as out.writ(<table>...</table>)

JSP Directives :

page:

import

<%@ page import=”java.util.ArrrayList %>”

session

contentType

isEliIgnore

language

extends

isThreadSafe

errorPage

isErrorPage

include

<%@ include file=”a/x.xml”%>

<%@ include file=”/a/x.xml”%>

appName

WEB-INF

web.xmls

classes

lib

jsp

image

html

src

taglib:

<%@ taglib prefix=”mytag” uri=”http://..url” %>

Implict Objects:

request:

HttpServletRequest

response:

HttpServletResponse

out:

JspWriter object.

Session

HttpSession

config:

ServletConfig

application:

ServletContext

page:

corresponding to current servlet. Page.getMymethod() to get the private method defined in the servlet

pageContext:

container implementation of Jsp.PageContext extends jsp.JspContext

used to get context patams

exception:

uses in error page. Page should defind ad isErrorPage=”true”.

The error page will not be called directly. In every page we will add like

<%@ page errorPage=”/raleative path”>

JSP Actions:

<jsp:useBean id=”a” class=”com.test.NameofClass” scope=”session”/>

<jsp:getPropery name=”a” property=”weight” value=”10”/>

<jsp:setProperty name=”a” property=”weight”/ > request params should be same

<jsp:setProperty name=”a” property=”*”/ >

<jsp:include page=”somepage.jsp” flush=”true/false”>

it should be the url inside the webapp.

/ means relative path from the context directory

no / means the relative path from the directory contains the source page

<jsp:frward page=”pagename.jsp”>

<jsp:param name=”messagekey” value=”message”>

</jsp:farward>

Difference jsp @ include directive & jsp:include action

directive is evaluated at translation time ; action at runtime

static ; dynamic

1 servlet ; 2 servlet will be created

Use if resource not changing frequently : Use for resource which changes dynamically

Difference between jsp:include & jsp:forward action:

In include page should be inside the same server.

If the resource is out side of the server, we have to use forward

<jsp:plugins>

JSP xml syntax

Scripts >> <jsp:scriptlet>

Expression >> <jsp:expression>

Declaration >> <jsp:declaration>

<%@ page >> <jsp:directive.jsp>

<%@ include> >> <jsp:directive.include>

<% @ taglib> >> xmlns:abc=”..url...”

JSP EL

pageScope

requestScope

sessionScope

applicationScope

param >> request.getParamer() Map contains first values of request parameters

paramValues >> request.getParamerValues() Map contains all request params

initParam

coockie

JSPTagLibs:

<%@ taglib prefix=”mytag” uri=”http://tagliburi”>

<mytags.tagname> ${3.2}</mytag.tagname>

The taglib uri should be defined in web.xml

<jsp-config>

<taglib-uri> tagliburi </taglib-uri>

<taglib-location> /WEB-INF/tags/mytag.tld </taglib-location>

tld file contains the the tag name and the class file which contains this tag

<function-name> tagname </function-name>

<function-class>classname </function-class>

…...

</function>

the functions should be static.

JSTL:

Mainly 5 catogaries taglibraries are already available with sun

<@ taglib prefix=”c” uri=”http://....../jsp/jstl/core”>

Core:

<c:out value=${value} dafault/>

<c:set value=09 var=”sampleVar”/>

<c:remove var=”sessionVar scope=”session””>

choose

when

otherwise

import

url

redirect

param

xml:

sql:

fmt:

function:

JSP Custom tags:

For creating custom tags we have to creat tag handling class and configure the tag in tld file.

TagHandler must implement

Tag

doEndTag

doStartTag

release

BodyTag

doInitBody

setBodyContent

TagSupport

BodyTagSupport

The generated servlet will create an object of the tag handler and calls methods in taghandler class.

The lifecycle is ,first it will call

hndlerObj.setPageContext

setParaent

setAtribute1

doStartTag

doEndTag

release

Usring the PageContext API we will get the jsp imlicit objects in the taglib class. Using this we can access the page elements in the jsp page in taglib class.

Avoiding browser caching while same url hits:

Set the header values

response.setHeader(“pragma”, no-cache)

cache-controll, no-cache

Expires, 0

Set http eqaulent in meta tags:

Difference jsp 1.2 & 2.0

In 2.0

introduced JSTL

introduced JspFragment interface

6)Design Patterns

Singleton Pattern:

What is

One to many

Make sure that only one object will get created for class, and client the access to that object through a public method.

Make a class with private constructor

The static getObject method will create the private static member object and return u.

Sample

Logger classed we uses this

Configuration classes.

Accessing resource in shared mode.

I used in the simulator framework.

We have to read a configuration file for response mapping. We need to check the configuration xml multiple times for every request. So we created an object, using that the caller will get the configuration properties given in the file. This object will read the xml file and set the configuration properties. Each time we check the status flag and return this object.

static getObject() return connection

Static flag to hold the status of object.

Users can make this flag active once it done with the object

static getObject return the private static object only if the flag is flase.

Adv&Disadv

cant be resused

difficult to extend

→ Is singleton thread safe.

→ How to make it thread safe

Factory Pattern:

What is it:

Client refers an object though an interface and and an another class which is called a factory engine decides and instantiate the object based on the parameter passed by client.

Make sure the inner object constructor to be private, so we can restrict the direct object creation and make it only through the Factory.

Makes a factory class which creates the object and return that based on the parameters used for initialization.

Sample: Name {} factory class.

public factoryName(“param”) based on the params it will return Name1 or Name2 object.The thump rule is Name1 and Name2 should extend Name.

Where u used in your project:

Messaging object

Advantages:

Achieves polymorphism

Its easy to add one more type of implementation. With out any change in the client side

In java:

xml parser

Both abstract classes DocumentBuilderFactory and SaxParserFactory has

newInstance()

This looks at the lib/jaxp.properties file and return the instance of the class configured there, which will be having the parser factory implementation.

newInstance(String filename, Classloader loaderobj)

New feature in 1.6, we can specify the implementaion class file name and classloader object, instead of configuring jaxp.propeties

java.land.URLConnection

How to make singleton inside factory: Just to confuse ..just use as it is

DOA pattern:

Not usfull when OR mapping tools avaialbel.

Proxy:

Deligates the method invocation on a particular object to another one.

Visitor Pattern:

Prototype:

Observer Pattern:

7)UML

->Representation of different relations

A extends B

A implements B

Aggregation

Composition

->Activity diagram

Purpose

How to show parallel process

Action state and state.

->Sequence diagram

Purpose

representation of synchronous&asynchronous messages

->deployment diagram

Purposes

Artifact and Node

->Class diagram

purposes

Representation of different elements

8)MySQL

9)Sybase

source /....sybase_install_dir/SYBASE.sh

isql -S USDTSIT -U tuxuser -P tuxedo -c -w 2000

Get the nth larget salary

select salary from (select distinct(salary) from emp where salary NOT NULL order by salary desc) where rownum=n

Get the nth smallect salary

select salary from (select distinct(salary) from emp where salary NOT NULL order by salary asc) where rownum=n

Joins:

Inner: Only matching values from both table.

(select * from emp, dep where emp.did = dep.did)

equi: Same result of inner join can be give differnet way. supported by mysql no sybase

(select * from emp inner join dep using(did))

natural: Implicitly takes the columns with same name

(select * from emp natural join dep )

Cross: (Cartesion product)

select * from emp cross join dep.

All in Emp to dep1

All in EMP to dep2

Outer Joins:

Left: Take all values in the first and matching values from the Right

(select * from emp left join dep where emp.did = dep.did) mysql syntax

instead of saying left out *= in syabase

Right: Take matching values in left and all values in the right

(select * from emp left join dep where emp.did = dep.did) mysql syntax

instead of saying left out =* in syabase

Full: Both matched and unmatched records and fill nulls for corr unmatched fileds

(select * from emp full join dep where emp.did = dep.did) mysql syntax

Self Joins: Joins the same column in a particular table.

Indexing:

Adv:

Faster access to data

ensure uniquness

Disadv:

Insert/delete/update operation may get slow

Type:

Composit Index: more than one column in the key

(create index indx on emp (smpno, devision, depid))

Clustered index:

Non Clustered Index:

sp_help

sp_helpdb

sp_spaceused

sp_helpjoins table1 table2

9)DS&Algoriths

->Linked list finding cycle

1 way is marking all visited once. and if met marked once before end means repeated

2 nd approach is take 2 heads and transverse once behind another. If two starters are equal

it means repetition.

->Sorting

Bubble sorting is the common approach

for 1 to n take each one compare with the next one and if greater swap it

After 1 st iteration of outer loop smallest goes to last.

10)Struts

Action Servlet >> ServletEnv > > Controller

ActionClass >> Compoents >> Model

struts-config.xml >> appconfig

Action Form >>

JSP >> xsl transformation >> View

We don't have the implementation of ActionForms, Message Rsource, Validation Framework

11)Spring

Inversion of Control

Aspect Oriented Programming

Based on Simple POJO (Plain Old Java Object)

org.springframework.beans.factory.BeanFactory

org.springframework.beans.factory.xml.XmlBeanFactory

org.springframework.web.context.ContextLoaderServlet:

org.springframework.web.servlet.DispatcherServlet

How af used spring and struts

12)HTML & XHTML

13)CSS

14)Java Script

Types:

Number String boolean Function Object Null Undefined

paseInt(3f,16) >> parse hexadecimal to decimal

isNan return true if the argument is not a number

Boolean operators:

&& || !

Redirecting:

location.href=”newlocation”

window.location.href=”newlocation”

Node

insertBefore

cloneNode

hasChildNodes

removeNode

Document

getElementById

getElementByTagName

createTextNode

createElement

HtmlDocument (document)

body

coockie

document.coocke=”String;strin2”

docment.coockie.indexOf(“;”,2)

url

window

Frames

Element

HtmlElement

Navigator:

Navigator contains the information about the visitors browser

navigator.appName gives broser name

navigator.appVersion

History:

back

forward

Window

Screen

Location

JS Time:

var t =SetTimeout(script, 5000)

clearTimeout(t)

Js Objects:

String

toUpperCase

toLoweCase

substring(start,end)

substr(start, length)

slice(start,end)

indexOf(searchStr, startPostion)

big

bold

Array

push

pop

slice

concat

join

shift

sort

reverse

Date

15)XML

XSL means >>> Xpath, Xslt, XSL-FO

16)XPath

Navigating xml document

17)XSLT

Can use to transform xml and create html and xml.

1)-> <xsl:template match=”path to the node / stands for root node”

//you can add tag which should come in out put

</xsl:template>

2)--> <xsl:for-each select="catalog/cd">

//iterate for each value in catalog/cd

</xsl:for-each>

Also we can add conditions with the nodes.Example given below,which selects,

unser catalog/cd all child nodes with artist='BobDylan'

Other conditions which we can use are

<xsl:for-each select="catalog/cd[artist='Bob Dylan']">

!= (not equal)

< less than

> greater than

3)-> <xsl:value-of select=”title”/>

//this write the value of the title node

//We can use this under for writing all chiled node values under the foreach selection.

4)<xsl:sort select="artist"/>

//We can use this under for each to sort all the child node values under the selected value to sort according to the artist.

If should be in a loop or some where ,there the nodes upto price should be selected.

Now we can apply condition on price

<xsl:if test="price > 10">

//under this we can give the nodes to print.

//this part will execute only if the above condition matches.

</xsl:if>

6)<xsl:choose>

<xsl:when test="expression">

... some output ...

</xsl:when>

<xsl:otherwise>

... some output ....

</xsl:otherwise>

</xsl:choose>

//need to do the sample.

7)The <xsl:apply-templates>

//need to look into this

we can @ to access atributes of the node.

<xsl:for-each select="tool/field">

<tr>

</tr>

</xsl:for-each>

Here it prints the value of “id”,which is an atribute for the node filed node.

<xsl:with-param

10)We can assign varialbe name

to a node

<xsl:variable name="articles" select="/articles" />

to a value.

<xsl:variable name="planet" select="'earth'" />

18)Ajax

1)xmlHttp=new ActiveXObject("Msxml2.XMLHTTP"); //for firefox

}catch (e){

xmlHttp=new ActiveXObject("Microsoft.XMLHTTP"); //IE

2)Propetry of xmlHttp. object

a)onreadystatechange=funName

xmlhttp.onreadystatechange=functioname

//function(){should be define which process the response from the server }

b)Readystate property->Holds the status of the server

if (xmlHttp.readyState==4){

var fileCnt=xmlHttp.responseText;

//response is ready and we can process the response

}

0->not initialized to 4

1->has been set-up

2->has been send

3->Inprocess

4->complete

c)responseText->Retreving the data from the server

d)Methods using open/send

xmlhttp.open(GET/POST,servername/jsp/action name,true)

xmlhttp.send(null);

3)Using with JSON

4)Sample PHP page, created with any of PHP framework

19)SOA

Intro

Basic idea is if two application know the following 2 points

1)how to construct and reconstruct SOAP messages and

2)how to send and receive HTTP transmissions.

It should be able to communicate regardless of the technologies.

Can be different type as follows:

*Core Web Services:

These technologies include solutions for the processing of XML content, databinding and the development SOAP based web services.

JAX-WS->java api and xml based.Also uses jax-rpc in web services and in web applications.

JAXB implementation also available

*Enhanced Web Services:(JAX-WS)

Giving features such as reliable messaging and atomic transactions.

WSIT->Using tech like web Service Interoperability Technologies(Microsoft comm foundation),make sure the featurs in web services like atomic transaction etc.

*Secure Web Services:(JAXB)

Ensure the secure channel

Using WSIT

Using XWSS

Using saaj also we can secure the transactions

*Legacy Web Services:

Same like core.But service which support older versions of java

Can be create for System Management also.

AXIS Engine

)What AxisServlet do

AxisServlet acts as a mediator between the Web request and the Axis Engine. It reads all the parameters from the Web request, constructs a SOAP request (XML), and hands the XML to the Axis Engine. The Axis Engine processes the request and returns the SOAP response message (XML). AxisServlet in turn writes the response back to the Web client. It roots the service request to Axis engine. Intern it calls reportAvailableFunction(request,response) and lists all services.

2)How AxisServlet processing the request comes as serviceName?wsdl

AxisServlet diverts the corresponding service call to the Axis engine

3)How AxisEngine uses the server-config.wsdd

Axis engine uses the server section of that service defined in the server-config.wsdd file and identify the java class to be invoked.Once its invokes the java classs we will get the wsdl file for that service.

Steps

The entry step of creating jws is creating a interface which describes the service.

->java2wsdl

java org.apache.axis.wsdl.Java2WSDL -o svc_cal.wsdl -lhttp://dummy_url -nurn:com.wsdl2java.gen -psamples.myTest.server urn:com.wsdl2java.gen samples.myTest.server.Calculator

->wsdl2java

java org.apache.axis.wsdl.WSDL2Java -avs -S true -d "Session" svc_cal.wsdl

generated file

This generates the client stubs and server side skeltons.

Calculator Interface ->Interface same like we created first,but this

extends the java.rmi.Remote

CalSoapBindingStub-> extends org.apache.axis.client.Stub

Creates the Data structeres like

org.apache.axis.description.OperationDesc

org.apache.axis.description.ParameterDesc

->implements Calculator and setPortName corresponding to each functions.

CalSoapBindingImpl->Impliments Calculator Interface,Service logic is calling from here which can be implimented in some other file and can be called here.

CalSoapBindingSkeleton->implements Calculator, and inside that Calls the functions implimented in SoapBindingImpl. ->impliments org.apache.axis.wsdl.Skeleton

CalculatorService ->Interface in server side,

declare getCal returns the Calculator interface,

declare getAddress

->extends javax.xml.rpc.Service

CalculatorServiceLocator->extends org.apache.axis.client.Service

->impliments CalculatorService which creates object of CalSoapBindingStub and setPortName

deploy.wsdd-> <service name=”” provider=”” etc>

undeploy.wsdd->

->Write Implementation code logic

Implimentation logic can be given seperatly and call this in soapBindingImpl.

->Create server-config.wsdd

->Build (maven or ant)/out put should be as web application

->deploy

->write client and test the service.

Flow in Axis based web service system

When we send a RPC-style soap message to axis it will hit the org.apache.soap.server.http.RPCRouterServlet

jars needed in class path

activation-1.0.2.jar -> activatin framework has been used by javax.mail to manage mime type from

mail-1.3.1.jar-> for messaging services sun's

axis-1.4.jar -> axis core from apache

axis-support-1.0-SNAPSHOT.jar ->etrade API having BindingImplbase class.

commons-discovery-0.2.jar->apache API for finding particular resource,for locating classes that implement a given Java interface etc.
commons-logging-1.0.4.jar->API for integrate different logging impimentation

jaxrpc-1.4.jar

jsx-1.0.jar

log4j-1.2.13.jar

saaj-1.4.jar

wsdl4j-1.5.1.jar

xercesImpl-2.6.2.jar

xmlsec-1.0.4.jar

axis/jars/axis-ant-1.4.jar

ant/jars/ant-1.6.5.jar

java2wsdl

Flow

From client->

XSD

Xml schema Definition: Gives the structure of an xml document.

Defines the each element type.

A wsdl file will be generated from xsd's.

WSDL(Web Services Description Language)

The main structure of a wsdl file is

1)Port type shows the operations performed by the servi ce. The operations can be

a)One way operation :only input in operation tag

<operation name= > can be many

b)Request-Response Operation

<operation name= > can be many

c)Solicite response:

This type of portType will send a request and wait for the response

d)Notification

This type will send a request and they will not wait for response.

2)Messages shows the messages used by the webservice

Every message having the part name which is the parameter name type means the parameter type.

3)Types ->The data types used by the service

<types>

If the service defined by the WSDL document uses only the built-in XML Schema simple types, you don't have to include a <types> element; instead, you can use the element to define your own types.

4)Binding ->The communication protocaol used.

wsdl Syntax Order

->types

->message

->portType

->serviceType

->binding

->service

import:brings declaration in other namespace

include:brings declarations in current namespace

UDDI->Universal Description Discovery Integration

1)Its like a directory of web service interfaces described by wsdl.

2)UDDI developed under .Net Platform.

Alternatives for UDDI is :

IBM's recent standardized Web Services Inspection Language,

older ebXml standard.

wsdl2Java

java org.apache.axis.wsdl.WSDL2Java -avs -S true -d "Session" wsdl/svc_aggtr.wsdl

This class uses to generate clinet side java compents to access the services also Skelton for SoapBindingImpl.Also deploy.wsdd

SOAP(Simple Object Access Protocol)

Http standard is not capable for communication between two application objects.

Other altrantive is RPC which is using by DCOM and CORBA objects.But the problems with RPC is , the firewalls and proxy servers will block this kind of traffic.

Soap is created on top of http.Soap is a intiative from microsoftt.

Other xml bases messaging protocol is xml-RPC.

Below the soap Structure

<soap:Envelope>

<soap:Header>

...

</soap:Header>

<soap:Body>

...

<soap:Fault>

...

</soap:Fault>

</soap:Body>

</soap:Envelope>

WSDD(Web Services Deployment Descriptor)

AxisServlet uses the information in the wsdd to generate the corresponding wsdl.

deploy.wsdd & undeploy.wsdd

For each we can have a deploye.wsdd and undeploye.wsdd file which helps to deployment easily.diploy file containts the service name and the class defines that service name.

server-config.wsdd

The axis engine having a deployment descriptor of all service deployed,which is configures in server-config.wsdd.The file is like the web.xml for servlet configuration.

How to configure with tomcat

JWS Hello World

Ant

<ant > tag

antfile={build.xml path }

dir=??

<project> tag

name=”name of the project”

default=”what target should execute if the script execute with out any parameter”

somevar=”.” or “..” (indicates base dir name)

inside “ ” we can give shell commands which will execute as like any other scripts as

in (.bat or .sh)

we have <property> tag

name=”some name”

vale=”${basedir}” or value can be ${somename},value of some name

4) <java classname=”---”>

5)system commands

we have <taskdef name=”somename”

classname=”org.fds.fd...”>

we can define a task and corresponding class and this task can be include in an of the target.as like

<target-quick>

<taskChk argname=”dsd”

arg2=”fd”

arg3=”arg3Vales” we can give arguments inside the task tag>

</taskChk>

</target-quick>

How to call a WS

Using Axis clients

httpclient

bea.jolt.* clients for tuxe services

JAXB

Comapre Maven1.1 & Maven 2

1->have build.properties file can put in home folder or each project folder having info about the repository information

2->has the file called settings.xml,which we need to create and put in ${HOME}/.m2/repository/,which has the repo information.

3->Caching happens in maven1.

4->difference in pointing groupid,artifact id

5->maven site generation pluginn added with maven-2/can be use as mvn site

creates documentation site.Project doc can be given as .awt format.

Common Tips

Remote debugging in eclipse & tomcat

1)start tomcat in debug mode by replacing the existing configuration in start.sh as follows:

export CATALINA_OPTS="$CATALINA_OPTS -DAF_BUILD_FROM_JARS=$AF_BUILD_FROM_JARS -Xdebug -Xrunjdwp:transport=dt_socket,address=8787,server=y,suspend=n"

2)apache httpd.conf configuration

3)Tomcat server.xml configuration

4)WebLogic configuration

20)Linux Important

1)find a particular file format and greps a pattern in each and returns the pattern existing files.

->find ..... | xargs grep “ffsf”

-> find -name "*.pdf" -type f -maxdepth 1 >> Search only in current directory

-> ls -alrt | tail -14 | grep -v ^d | awk '{print $9}' | xargs -i mv {} /tmp/

-> sort data.txt | uniq -d -c

VI important short cuts

a) (search and replace all in a file)

:%s/old/new/g

b)cut paste lines

make the cursor at the starting line

Esc mk

make the cursor at ending

Esc “ ay'k

Esc “ ad'k for cut

and paste as

Esc “ap

cvs upd -dPA brachname cvspath ->this will sync newly created/deleted dir corr to the remote repo.

finds file name by .svn and deletes each one.

find . -name ".svn" | xargs rm -rf

cvs upd -r odc_1_13719

find tottal number of lines in all the files in the directory

bash$ls | xargs wc -l

Shell scrpting starts with

a)#!/bin/bash

this is for executing the next lines using this particular program.

&& and || can be use instaed of condition checking

b)For conditions execution starts from left to right

In case of &&

[-r simefile] && { echo “file readable” ; other commands }

do the stuff

If left returns false,it wont execute the right

if left returns true then it will execute right and comes to normal flow

c)Debugging in shell scripting

sh -x strangescript -->

Execute line by line and shows the execution

sh -n your_script -->

Check syntax correctness of the script.

Top ->shows the cpu usage
aprops command_name -> Gives the command for a scenario.

java

Creating RPM general

There are 8 sections in an RPM spec file:

a header:Source dir,version and other information

a prep section:

a build instruction section:

an installation section:

file cleanup:

pre- and post-installation:

optional uninstallation script:

a list of files in the package:

and a changelog:

Creating RPM using maven

12)Setting-Ctags

a)Create a file

at home -> bash$vim ~/.exrc

with

content

set tag=/etrade/home/ssuresh1/work/services/tags

b)type the following command at $SVC_HOME/services

bash$: ctags -R -h ".c.cpp.h.hpp.cp" --C-types=+defstupg-cxmnv

Use Ctrl [ , Ctrl ], Ctrl T, Ctrl G

Another Option:

Generate the tag file for the Ingres source:ctags -R -f ~/.vim/tags/ingres.ctags /home/grant/src/svn/ingres/main/

~/.vim/tags/ingres.ctags is the target tag file. Windows: Use $HOME in place of ~
/home/grant/src/svn/ingres/main/ is the full path to the Ingres source tree. The path used needs to absolute and not relative since Vim will need to navigate from the current working directory to the file containing the function definition.

Copy the following code into your $HOME/.vimrc:
" Tag files
set tags+=$HOME/.vim/tags/ingres.ctags
" Ctrl+Right Arrow to goto source of function under the cursor
map <silent><C-Left> <C-T>
" Ctrl+Left Arrow to go back
map <silent><C-Right> <C-]>

13)Change time zone

export TZ = “Asia/Culcutta”

tzset

14)SVN Important

svn mkdir file:///proj/svn_repository/project1/trunk -m 'New directory'

find -name *.java -print0 | xargs -0 grep -o acctListFromService
egrep -w 'acctListFromService|param' ~/test.txt

17)awk

awk '{print $NR}'

awk '{print $NC}'

awk '{print $NF}'

sub (. , new str, targetstr) >> replace the string represented by reg extression with new str

substr (str,start,length)>>

Show hai test in Hai Test

echo "hai test" |awk '{ for ( i=1; i <= NF; i++)

{ sub(".", substr(toupper($i),1,1) , $i) }

print }'

18)sed

sed '//'

19)crontab

EDITOR=VI && crontab -e

This will open the users crontab. We can configure our job here. crontab is simpe text file which keeps the job list.

The is demon thread in linux based system, which keep own poll the crontab file of that particular user and execute the jobs configured there.

20)chown, chmod etc related with permission

21)Sample shell scripts assignments

22)at command

Kill the process in 1 line

kill -9 `ps -aux | grep kcalc | awk '{print $2}'`

Other options to the process other than -9

How to give one signal to the process

24)List last 2 lines in the recent touched file

tail -n 2 `ls -lrt testdata/*.log | awk '{print $9}' | tail -n 1`

25)Last 2 lines of last modified file

tail -1 `ls -lrt | tail -2 | awk '{print $9}' | head -1`

25)du -ah –max-depth=1

size of all child folders

26)How to show back ground process

27)make back ground process foreground

when we start some command from terminal and if we wnat to stop Ctrl C

If we want to suspend that process nad send to backgrount Ctrl Z

If we want to run that command in background while starting itself add & at the end

List all the backgoround jobs in that terminal>> jobs

Make the back ground job come to forground and start running >> fg

Continue a suspended job in back ground itself>> bg

28)grep lines which has last work “abc” : grep -irl “abc$”

29)grep lines which has first work “abc” : grep -irl “^abc”

30)grep or/and/not grep -e or egrep “abc|xyz”

30)find files touched on jan 2^nd

31)How to use CUT command

Creating debian package.deb apt
Download all contents in a particular folder >> wget -r url_upto_flodername
Result of the last command: $? .

if $? is 0 last command or function executed correctly.

else its 1 – 250, some error happened in the execution.

21)SMS

kannel gateway

WAP protocol

22)HSQL DB

1)Unzip the down loaded hsql

2)set classpath

3)Start in server mode

4)in process mode ->In same JVM along with the application in webserver

23)Ibatis

Its basically a data mapper using map table data and the corresponding object.

The basic idea behind the iBATIS introduction was to significantly reduce the amount of Java code that a Java developer normally needs to access a relational database with the use of XML files containing SQL queries.

version is ibatic.2.3. from apache.

hibernate is similar kind of tool using for O/R mapping.

Advantage as 80/20 .80% of jdbc functionality/with 20% of code.

com.ibatis.common.resources.Resources.getResourceAsReader(“path/to/SqlMapConfig.xml”)

This returns the reder object having the sql mappings.Using this reader object we have to build client.

com.ibatis.sqlmap.client.SqlMapClientBuilder.buildSqlMapClient(map_file_reader_object)

This return the object of the com.ibatis.sqlmap.client.SqlMapClient sql map client.

This client object can be used to query as like.

mapper_clinet.queryForList(crieteria_which_configured_in_mapping_xml)

mapper_clinet.queryForObject(crieteria_which_configured_in_mapping_xml)

In case of queryForobject, return type should be casted to the DO object,that should be

defined according to the mapping.

Reader reader = Resources.getResourceAsReader("config/SqlMapConfig.xml");

sqlMapper = SqlMapClientBuilder.buildSqlMapClient(reader);

Beanclassconfigured obj=(Beanclassconfigured)sqlMapper.queryForObject("selectAccountById", id);

sqlMapper.queryForList("selectAll") returns list

Queries corresponding to “selectAccountById” & “selectAll”

needs to be given sqlmap file.

SqlMapConfig.xml Configuration

property tag with name of

driver name,

db name

username

password

<sqlMap resource="config/AccountBalance.xml" /> points all the sql map files.

...

Then we have set of optional tags

</sqlMapConfig>

SqlMapfile.xml Configuration

for each table there will be one map file and DO class

//the result map can be more than one according to the queries

</resultMap>

//select statements

//parameters can be use as #name_passed_in the code#

</select>

//queries can be given inside

...

</statement>

<procedure>..<procedure> for stored procedure

24)C-Questions

1)Diff b/n malloc & calloc

2)How to debugg c code->> using dd

25)Perl

1)chomp & chop

2)How to debug in perl

different type of variables

functions on scalar variables

Modules to do other operations

Get Arguments @ARGV

No of arguments @#ARGV

Result of command functions execution _@

26)Site Minder:

27)Ping Federate:

IDP

IDM

29)About my testing experience

Started career as a tester. Worked around 2 years in testing. Both manual and automation in selenium.

Moved into development because we have better idea of there business. We get task like

small enhancement in there customer and CSR site.

30)Testing Concepts:

Life cycle

End to end flow

Which method used

Sample testcases

31)QC

32)Selenium

33)Junit

Difference junit 3 & 4

34)Using mock objects

29)About my scripting experience

Started my carrer as a java developer. Right now I am enagaged with the client called Etrade Financil CoOp. Open source client. We are using redhat AS3, AS4 machines here.

The batch jobs basically done in both perl and shell script. We have a customized sceduler here, which inturn makes the crontab entry and make job shceduled.

The jobs are basically file processing. For example we have the Cashtransfer system called ACH, Automatic Clearing house which handle the cash transfer between Etrade accounts and other external bank accounts.

Spike source was the first customer i worked with. There I worked infrastrucure kind of project basically we did the open source product development. One of the project we did was the core stack. In that I was part wrting build scripts and post installation scripts for the Coponent Stack

30)About Banking Experience

Working for customer called Etrade. They are online share trading company is US. Basically a brokerage firm. Which gives a platform for trading. Like icicidirect in india. Our team handles the banking operation in the customer site & customer care site.

We basically interacts with lot of third party tools through webservices. Like

We uses fidilities profile as our core banking solutions.

Uses Alogent system for check processing. and we have check free, its ASP solution, check free for check image scanning.

Also we have a dedicated batch system doing the ACH posting and handling return transfers. ACH (Automatic Clearing Houses) system in US just like NEFT here for handling interbank money transfers.

The main project we completed recently is HomeDesposits. The business requirment comes because of a new FED rule in US. FED is like our RBI in india.

The new fed rule says a check image have the same validity of a papper check. So all banks forced to accept checks as image files, also endof the day submitting to FED, FED also will accept images

As a module lead, first of all i have to understand the business requirement and decided how many resource needed for my module.

We do the middleware component development and webdevleopment

We uses SOA framework, which we costomuzed on top of struts.

We does the web develpment and middileware compoent development. So we have map appropriate resources for the requirement. Basically our projects are fixed billed projects.

The project i am doing right now ACH Check Hold.

31) QA Experience

I am working for as part etrade testing team, we are working along with the offshore dev team here.

The project which we are doing write now is SIT phase.

Before code goes to SIT we are doing alpha testing. we are doing in the developer integrated box called P6 environment. Its a combination of virtual envirnment.

Also we have webservice testing. We have a tester program, which is perl script.

When ever a service ready and its cehcked in, the code will be available in P6 box

and we have to do alpha testing on the service. The data setup will be done using the simulator.

I was involved in the initial RD along with the development team, and in the fecebility sturdy. Dev team developed a framework for selenium.

Using RC

We uses this framework for testing. Once we found that a test case can be automate, we will do that.

Banglore team does the actual regression.

My here is responsible for developing new scritps, maintaning the existing one as per the front end changes.

Setting up RC machines.

So that banglore team will do the regression.

Sample selenium generated java class.

Package testscript.retailbank

import com.thoughtworks.selnium.*

public class TestMessagingACH extends SeleniumTestCase{

public void setup() throws Exception {

setup(baseurl);

}

public void testnew() throws Exception{

selenium.click(“link=home”);

….

}

Sybase -- Store Query output to a file:

********************************************

isql -Utuxuser -Ptuxedo -SPSITDB1M25 -DUsLegalEntityDB -i input.txt -o output.txt

SenthilKumar's Blog

Monday, December 28, 2009

Immutable and Singelton

tech_notes_Rakesh

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