How do I split a string?

public class StringSplit
{
public static void main(String[] args)
{
String data = "1,srirama, java programmer,50000";
String[] items = data.split(",");
for (String item : items)
{
System.out.println("item = " + item);
}
}
}

PersistentManager for sessions in Tomcat

in Context.xml,
under tag
add the below code..

note :

Tomcat provides a way to store web sessions data that is resilient to server reboots using the org.apache.catalina.session.PersistentManager as described in http://tomcat.apache.org/tomcat-6.0-doc/config/manager.html

and

http://community.jboss.org/thread/39492

Create JAR file in Java

Let us see how to create a JAR file using Java’s jar command as well as using Eclipse IDE. The JAR file format is based on the popular ZIP file format. Usually these file are used for archiving and distribution the files and implementing various libraries, components and plug-ins in java applications. Compiler and JVMs (Java Virtual Machine) can understand and implement these formats for java application.

JAR file using Java commands

Create a JAR file
view source
print?
1 jar cf JAR_FILE_NAME FILE_NAMES_OR_DIRECTORY_NAME
2 e.g.
3 jar cf MyApp1.jar C:\JavaProject\MyApp

View contents of a JAR file
view source
print?
1 jar tf JAR_FILE_NAME
2 e.g.
3 jar tf MyApp1.jar
View contents with detail of a JAR file
view source
print?
1 jar tvf JAR_FILE_NAME
2 e.g.
3 jar tvf MyApp1.jar

Note that we have used v (verbose) option to see the detail of JAR.

Extract content of JAR file
view source
print?
1 jar xf JAR_FILE_NAME
2 e.g.
3 jar xf MyApp1.jar

Extract specific file from JAR file
view source
print?
1 jar xf JAR_FILE_NAME FILE_NAME(S)_FROM_JAR_FILE
2 e.g.
3 jar xf MyApp1.jar Test1.class

Update a JAR file
view source
print?
1 jar uf JAR_FILE_NAME FILE_NAMES_FROM_JAR_FILE
2 e.g.
3 jar uf MyApp1.jar Test1.class

Executing a JAR file
view source
print?
1 java -jar JAR_FILE_NAME
2 e.g.
3 java -jar MyApp.jar

Create an executable JAR file

In order to create an executable JAR, one of the classes that we include in our JAR must be a main class.
Create a text file called MANIFEST.MF using any text editor and copy following content in it.
view source
print?
1 Manifest-Version: 1.0
2 Main-Class: MyMainClass

Where MyMainClass is the name of the class that contents main method. Also note that you have to specify fully qualified class name here.
Use following command to create an executable JAR file.
view source
print?
1 jar cvfm MyApp.jar MANIFEST.MF FILE_NAMES_OR_DIRECTORY_NAME

JAR file using Eclipse IDE

Creating JAR file using Eclipse IDE is pretty much easy. Follow the simple steps.
Right click on your project, which you want to create a JAR file of. And select Export from the context menu.

Navigating from an ordinary java class(POJO) to a JSP/Servlet.

1.TestURLConn.java
------------------
package com;

import java.io.IOException;

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

public class TestURLConn {

HttpServletRequest req;
HttpServletResponse resp;

public TestURLConn(HttpServletRequest req,HttpServletResponse resp){

this.req=req;
this.resp=resp;
}
public void getControl(){

try {
this.req.setAttribute("name","sriRama");
req.getRequestDispatcher("TestURLConn.jsp").forward(req, resp);
} catch (ServletException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

}
---------------------------------------------------------------------------

2. index.jsp
-------------
<% request.setAttribute("val","srirama navami sadsad"); TestURLConn tuc=new TestURLConn(request,response); tuc.getControl(); %>
---------------------------------------------------------------------------
3.TestURLConn.jsp
-----------------


this is TestURLConn.jsp


<%if(request.getAttribute("val").toString()!=null){ System.out.println(request.getAttribute("val").toString()); out.println(request.getAttribute("val").toString()); }%>


<%if(request.getAttribute("name").toString()!=null){ System.out.println(request.getAttribute("name").toString()); out.println(request.getAttribute("name").toString()); } %>

----------------------------------------------------
out put
-------
srirama navami
sriRama

MySQL -JDBC connection Syntax

Connecting to the MySQL Server

import java.sql.*;

public class Connect
{
public static void main (String[] args)
{
Connection conn = null;

try
{
String userName = "testuser";
String password = "testpass";
String url = "jdbc:mysql://localhost/test";
Class.forName ("com.mysql.jdbc.Driver").newInstance ();
conn = DriverManager.getConnection (url, userName, password);
System.out.println ("Database connection established");
}
catch (Exception e)
{
System.err.println ("Cannot connect to database server");
}
finally
{
if (conn != null)
{
try
{
conn.close ();
System.out.println ("Database connection terminated");
}
catch (Exception e) { /* ignore close errors */ }
}
}
}
}

Database Connection Pooling in Tomcat using dbcp with Eclipse

Database Connection Pooling is a great technique used by lot of application servers to optimize the performance. Database Connection creation is a costly task thus it impacts the performance of application. Hence lot of application server creates a database connection pool which are pre initiated db connections that can be leverage to increase performance.

Apache Tomcat also provide a way of creating DB Connection Pool. Let us see an example to implement DB Connection Pooling in Apache Tomcat server. We will create a sample web application with a servlet that will get the db connection from tomcat db connection pool and fetch the data using a query. We will use Eclipse as our development environment. This is not a prerequisite i.e. you may want to use any IDE to create this example.
Step 1: Create Dynamic Web Project in Eclipse

Create a Dynamic Web Project in Eclipse by selecting:
File - New -Project - Dynamic Web Project.

Step 2: Create context.xml

Apache Tomcat allow the applications to define the resource used by the web application in a file called context.xml (from Tomcat 5.x version onwards). We will create a file context.xml under META-INF directory.

Copy following content in the context.xml file.







In above code snippet, we have specify a database connection pool. The name of the resource is jdbc/testdb. We will use this name in our application to get the data connection. Also we specify db username and password and connection URL of database. Note that I am using Oracle as the database for this example. You may want to change this Driver class with any of other DB Providers (like MySQL Driver Class).

Step 3: Create Test Servlet and WEB xml entry

Create a file called TestServlet.java. I have created this file under package: net.viralpatel.servlet. Copy following code into it.
package net.viralpatel.servlet;
02
03 import java.io.IOException;
04 import java.sql.Connection;
05 import java.sql.ResultSet;
06 import java.sql.SQLException;
07 import java.sql.Statement;
08
09 import javax.naming.Context;
10 import javax.naming.InitialContext;
11 import javax.naming.NamingException;
12 import javax.servlet.ServletException;
13 import javax.servlet.http.HttpServlet;
14 import javax.servlet.http.HttpServletRequest;
15 import javax.servlet.http.HttpServletResponse;
16 import javax.sql.DataSource;
17
18 public class TestServlet extends HttpServlet {
19
20 private DataSource dataSource;
21 private Connection connection;
22 private Statement statement;
23
24 public void init() throws ServletException {
25 try {
26 // Get DataSource
27 Context initContext = new InitialContext();
28 Context envContext = (Context)initContext.lookup("java:/comp/env");
29 dataSource = (DataSource)envContext.lookup("jdbc/testdb");
30
31 } catch (NamingException e) {
32 e.printStackTrace();
33 }
34 }
35
36 public void doGet(HttpServletRequest req, HttpServletResponse resp)
37 throws ServletException, IOException {
38
39 ResultSet resultSet = null;
40 try {
41 // Get Connection and Statement
42 connection = dataSource.getConnection();
43 statement = connection.createStatement();
44 String query = "SELECT * FROM STUDENT";
45 resultSet = statement.executeQuery(query);
46 while (resultSet.next()) {
47 System.out.println(resultSet.getString(1) + resultSet.getString(2) + resultSet.getString(3));
48 }
49 } catch (SQLException e) {
50 e.printStackTrace();
51 }finally {
52 try { if(null!=resultSet)resultSet.close();} catch (SQLException e)
53 {e.printStackTrace();}
54 try { if(null!=statement)statement.close();} catch (SQLException e)
55 {e.printStackTrace();}
56 try { if(null!=connection)connection.close();} catch (SQLException e)
57 {e.printStackTrace();}
58 }
59 }
60 }

note : copy the jar file in the %catalina%/lib folder

Apache Tomcat 6.0 - JNDI Datasource HOW-TO

Apache Tomcat 6.0 JNDI Datasource HOW-TO

JSP Response Object

In this JSP tutorial, you will learn about JSP Response object, Methods of response Object, setContentType(), addCookie(Cookie cookie), containsHeader(String name), setHeader(String name, String value), sendRedirect(String) and sendError(int status_code).

The response object denotes the HTTP Response data. The result or the information of a request is denoted with this object. The response object handles the output of the client. This contrasts with the request object. The class or the interface name of the response object is http.HttpServletResponse.

The response object is written: Javax.servlet.http.httpservletresponse.

The response object is generally used by cookies.

The response object is also used with HTTP Headers.

Methods of response Object:

There are numerous methods available for response object. Some of them are:

* setContentType()
* addCookie(Cookie cookie)
* addHeader(String name, String value)
* containsHeader(String name)
* setHeader(String name, String value)
* sendRedirect(String)
* sendError(int status_code)

List below details the usage with syntax, example and explanation of each of these methods.

setContentType():

setContentType() method of response object is used to set the MIME type and character encoding for the page.

General syntax of setContentType() of response object is as follows:


response.setContentType();

For example:


response.setContentType("text/html");

The above statement is used to set the content type as text/html dynamically.

addCookie(Cookie cookie):

addCookie() method of response object is used to add the specified cookie to the response. The addcookie() method is used to write a cookie to the response. If the user wants to add more than one cookie, then using this method by calling it as many times as the user wants will add cookies.

General syntax of addCookie() of response object is as follows:


response.addCookie(Cookie cookie)

For example:


response.addCookie(Cookie exforsys);

The above statement adds the specified cookie exforsys to the response.

addHeader(String name, String value):

addHeader() method of response object is used to write the header as a pair of name and value to the response. If the header is already present, then value is added to the existing header values.

General syntax of addHeader() of response object is as follows:


response.addHeader(String name, String value)

Here the value of string is given as second parameter and this gets assigned to the header given in first parameter as string name.

For example:


response.addHeader("Author", "Exforsys");

The output of above statement is as below:


Author: Exforsys

containsHeader(String name):

containsHeader() method of response object is used to check whether the response already includes the header given as parameter. If the named response header is set then it returns a true value. If the named response header is not set, the value is returned as false. Thus, the containsHeader method is used to test the presence of a header before setting its value. The return value from this method is a Boolean value of true or false.

General syntax of containsHeader() of response object is as follows:


response.containsHeader(String name)

Return value of the above containsHeader() method is a Boolean value true or false.

setHeader(String name, String value):

setHeader method of response object is used to create an HTTP Header with the name and value given as string. If the header is already present, then the original value is replaced by the current value given as parameter in this method.

General syntax of setHeader of response object is as follows:


response.setHeader(String name, String value)

For example:


response.setHeader("Content_Type","text/html");

The above statement would give output as


Content_Type: text/html

sendRedirect(String):

sendRedirect method of response object is used to send a redirect response to the client temporarily by making use of redirect location URL given in parameter. Thus the sendRedirect method of the response object enables one to forward a request to a new target. But one must note that if the JSP executing has already sent page content to the client, then the sendRedirect() method of response object will not work and will fail.

General syntax of sendRedirect of response object is as follows:


response.sendRedirect(String)

In the above the URL is given as string.

For example:


response.sendRedirect("http://xxx.test.com/error.html");