Sunday, 26 October 2014

ServletContext in Servlet

Earthcare Foundation NGO 12:40 Java, Servlet No comments

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>ServletContext</title>
</head>
<body>
<form action="MyServlet1">
<input type="submit" value="Go to Servlet1">
</form>
</body>

</html>

MyServlet1.java

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyServlet1 extends HttpServlet {
private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("text/html");
PrintWriter pw=response.getWriter();
ServletContext context=getServletContext();
context.setAttribute("name", "Abhi");
pw.println("We are in Servlet1 <br>");
pw.println("<a href='MyServlet2'>Click Me</a>");
pw.close();
}

}

MyServlet2.java

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class MyServlet2 extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("text/html");

PrintWriter pw=response.getWriter();

ServletContext context=getServletContext();

String name=(String)context.getAttribute("name");

pw.println("We are in Servlet2<br>");

pw.println("Welcome "+name);

pw.close();

}

web.xml

<display-name>MyServlet1</display-name>

<servlet-name>MyServlet1</servlet-name>

<servlet-class>MyServlet1</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>MyServlet1</servlet-name>

<url-pattern>/MyServlet1</url-pattern>

</servlet-mapping>

<display-name>MyServlet2</display-name>

<servlet-name>MyServlet2</servlet-name>

<servlet-class>MyServlet2</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>MyServlet2</servlet-name>

<url-pattern>/MyServlet2</url-pattern>

</servlet-mapping>

sendRedirect() method in Servlet

Earthcare Foundation NGO 12:10 Java, Servlet No comments

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>sendRedirect() Method Example</title>
</head>
<body>
<form action="SearchServlet" method="get">
<input type="text" name="name">
<input type="submit" value="Google Search">
</form>
</body>
</html>

SearchServlet.java

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class SearchServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

String name=request.getParameter("name");
response.sendRedirect("https://www.google.co.in/#query="+name);
}

}

web.xml

<display-name>SearchServlet</display-name>

<servlet-name>SearchServlet</servlet-name>

<servlet-class>SearchServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>SearchServlet</servlet-name>

<url-pattern>/SearchServlet</url-pattern>

</servlet-mapping>

</web-app>

Servlets in Java

Earthcare Foundation NGO 11:08 Java No comments

Servlet Program

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("text/html");
PrintWriter pw=response.getWriter();
String name=request.getParameter("firstName");
pw.println("Welcome "+name);
pw.close();
}

}

Html Page

<!DOCTYPE html>

<html>

<head>

<title>Index Page</title>

</head>

<body>

First Name:<input type="text" name="firstName"><br>

</form>

</body>

</html>

Web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

<display-name>ServletE</display-name>

<welcome-file-list>

<welcome-file>index.html</welcome-file>

<welcome-file>index.htm</welcome-file>

<welcome-file>index.jsp</welcome-file>

<welcome-file>default.html</welcome-file>

<welcome-file>default.htm</welcome-file>

<welcome-file>default.jsp</welcome-file>

</welcome-file-list>

<display-name>MyServlet</display-name>

<servlet-name>MyServlet</servlet-name>

<servlet-class>MyServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>MyServlet</servlet-name>

<url-pattern>/MyServlet</url-pattern>

</servlet-mapping>

</web-app>

HashMap in Java

Earthcare Foundation NGO 10:08 Java No comments

import java.util.*;

public class HashMapImp {

public static void main(String[] args) {

//If we take key as object
//Then key can be any datatype

Map<Object,Object> hMap=new HashMap<Object,Object>();
hMap.put(1, 1);
hMap.put(2, 3.0);
hMap.put(3.0, "Hello");
hMap.put(1, 2);
hMap.put("Abhi", 1);
System.out.println(hMap);

//Map contains Integer as key
//And String as value
Map<Integer,String> map=new HashMap<Integer,String>();

map.put(1, "Hi");
map.put(2, "Abhi");
map.put(3, "Hello");
map.put(1, "I");
map.put(3,"Abhi");
System.out.println(map);

}

}

HashSet In Java

Earthcare Foundation NGO 09:57 Java No comments

import java.util.*;

public class HashSetImp {

public static void main(String[] args) {

//General HashSet
Set<Object> hSet=new HashSet<Object>();
hSet.add(1);
hSet.add(3.0);
hSet.add("Hello");
hSet.add(1);
hSet.add("My");
hSet.add(3.0);
System.out.println(hSet);

//Specific HashSet of String
Set<String> set=new HashSet<String>();
set.add("Hello");
set.add("My");
set.add("My");
System.out.println(set);

}

}

Different ways to delete elements from ArrayList

Unknown 23:21 Java, Java Interview Questions No comments

import java.util.ArrayList;
import java.util.Iterator;

public class ArrayDeletion {

public static void main(String[] args) {

ArrayList<String> list=new ArrayList<String>();
list.add("a");
list.add("b");
list.add("c");
list.add("d");

ArrayList<String> list1=new ArrayList<String>();
list1.add("a");
list1.add("b");
list1.add("c");
list1.add("d");

ArrayList<String> list2=new ArrayList<String>();

list2.add("a");
list2.add("b");
list2.add("c");
list2.add("d");

ArrayList<String> list3=new ArrayList<String>();
list3.add("a");
list3.add("b");
list3.add("c");
list3.add("d");

System.out.println("Elements of list:"+list);
System.out.println("Elements of list1:"+list1);
System.out.println("Elements of list2:"+list2);

//Method 1 which is used by many which gives the wrong result
for(int i=0;i<list.size();i++)
{
System.out.println("Size:"+list.size());
list.remove(i);

}
System.out.println("After deletion list elements are "+list);

//Method 2 which gives right output and simplified form of method 1
//don't use i<list1.size() in for loop otherwise there will be an
//ArrayIndexOutOfBoundException
//because size of ArrayList will be decreased after deletion
//So it is advised to use a variable which stores the size of list and pass this variable to
// for loop
int length=list1.size();
for(int i=0;i<length;i++)
{
list1.remove(0);
}
System.out.println("After deletion list1 elements are "+list1);

//Method 3 using Iterator Class
Iterator<String> itr=list2.iterator();
while(itr.hasNext())
{
String element=itr.next();
itr.remove();
}
System.out.println("After deletion list2 elements are "+list2);

//Method 4 using foreach loop
//by using foreach loop we will get Exception i.e. ConcurrentModificaionException
//this is because for deleting elemens from arraylist
//we have to first use next() and then use remove() as done in method 3
//but in foreach loop compiler will first remove the element
//and then call the next() function
//so there will be this exception
for(String s:list3)
{
list3.remove(s);
}

System.out.println("After deletion list3 elements are "+list3);
}

}

Raw type of ArrayList And its Operations

Unknown 23:17 Java No comments

import java.util.ArrayList;

public class RawArrayList {

public static void main(String[] args) {

ArrayList<Object> list=new ArrayList<Object>();
list.add(1);
list.add(2.0);
list.add("Hello");
list.add('a');
for(Object o:list)
{
System.out.println(o);
}
}

}

User Defined Exception in Java

Unknown 22:24 Java, Java Interview Questions No comments

public class ExceptionExOther {

public void methodA() throws UserDefinedException
{
try
{
System.out.println("Inside MethodA");
throw new UserDefinedException("Demo");
}
finally
{
System.out.println("MethodA's finally");
}
}

public static void main(String[] args) {

ExceptionExOther ex=new ExceptionExOther();
try {
ex.methodA();
} catch (UserDefinedException e) {
System.out.println("Caught "+e);
}
}

}

User Defined Exception

public class UserDefinedException extends Exception {

private String string;

public UserDefinedException(String str)

{

string=str;

}

public String toString()

{

return "UserDefinedException "+string;

}

Hub Of Geekz

Sunday, 26 October 2014

ServletContext in Servlet

sendRedirect() method in Servlet

Wednesday, 22 October 2014

Servlets in Java

HashMap in Java

HashSet In Java

Friday, 17 October 2014

Different ways to delete elements from ArrayList

Raw type of ArrayList And its Operations

User Defined Exception in Java

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