Configuring And Running Servlet Program into tomcat 6

Structure of a Servlet

          Java Servlets are server side Java programs that require either a Web Server or an Application Server for execution. Examples for Web Servers include Apache’s Tomcat Server and Macromedia’s JRun. Web Servers include IBM’s Weblogic and BEA’s Websphere server. Examples for other Server programs include Java Server Pages (JSPs) and Enterprise Java Beans (EJBs).

          Here's the outline of a basic servlet that handles GET requests. GET requests are requests made by browsers when the user types in a URL on the address line, follows a link from a Web page, or makes an HTML form that does not specify a METHOD. Servlets can also very easily handle POST requests, which are generated when someone creates an HTML form that specifies METHOD="POST".

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class <<ServletName>> extends HttpServlet { public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException, IOException  {     // Use "request" to read incoming HTTP headers (e.g. cookies)     // and HTML form data (e.g. data the user entered and submitted)     // Use "response" to specify the HTTP response line and headers     // (e.g. specifying the content type, setting cookies).    PrintWriter out = response.getWriter();     // Use "out" to send content to browser } }

            To be a servlet, a class should extend HttpServlet and override doGet or doPost (or both), depending on whether the data is being sent by GET or by POST. These methods take two arguments: an HttpServletRequest and an HttpServletResponse. The doGet and doPost throw two exceptions, so you are required to include them in the declaration. You have to import classes in java.io (for PrintWriter, etc.), javax.servlet (for HttpServlet, etc.), and javax.servlet.http (for HttpServletRequest and HttpServletResponse). The doGet and doPost are called by the service method, and sometimes you may want to override service directly, e.g. for a servlet that handles both GET and POST request.

Configuring Apache Tomcat to run Servlets

1.    Download the Apache Tomcat Software

Go to http://tomcat.apache.org/download-60.cgi and download and unpack the zip file for the current release build of Tomcat 6

2.    Set the JAVA_HOME Variable

8  Next, you must set the JAVA_HOME environment variable to tell Tomcat where to find Java. Failing to properly set this variable prevents Tomcat from compiling JSP pages. This variable should list the base JDK installation directory, not the bin subdirectory.

8  On Windows XP, you could also go to the Start menu, select Control Panel, choose System, click on the Advanced tab, press the Environment Variables button at the bottom, and enter the JAVA_HOME variable and value directly.

3.    Turn on Servlet Reloading

To turn on servlet reloading, edit Edit install_dir/conf/context.xml and change

  <Context>   to

  <Context reloadable="true" privileged="true">

4.    Enable the Invoker Servlet

• The invoker servlet lets you run servlets without first making changes to your Web application's deployment descriptor (i.e., the WEB-INF/web.xml file). Instead, you just drop your servlet into WEB-INF/classes and use the URL http://host/servlet/ServletName
• To enable the invoker servlet, uncomment the following servlet and servlet-mapping elements in install_dir/conf/web.xml. Do not confuse this Apache Tomcat-specific web.xml file with the standard one that goes in the WEB-INF directory of each Web application.

    <servlet>
        <servlet-name>invoker</servlet-name>
        <servlet-class>
          org.apache.catalina.servlets.InvokerServlet
        </servlet-class>
        ...</servlet>
    ...<servlet-mapping>
        <servlet-name>invoker</servlet-name>
        <url-pattern>/servlet/*</url-pattern>
    </servlet-mapping>
   

                            

5.    Turn on Directory Listings (Optional)

To make this change, edit install_dir/conf/web.xml and change the init-param value of listings for the default servlet, as below.

    <servlet>
        <servlet-name>default</servlet-name>
        <servlet-class>org.apache.catalina.servlets.DefaultServlet</servlet-class>
        <init-param>
            <param-name>debug</param-name>
            <param-value>0</param-value>
        </init-param>
        <init-param>
            <param-name>listings</param-name>
            <param-value>true</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
   

6. Set the CATALINA_HOME Variable (Optional)

Set the CATALINA_HOME environment variable to refer to the top-level directory of the Apache Tomcat installation (e.g., C:\apache-tomcat-6.0.28). This variable identifies the Tomcat installation directory to the server.

7. Running the Tomcat Server

           For Running Tomcat, click on install_dir/bin/startup.bat.

                                     Or

8  Open a command prompt.

8  Move the directory tomcat install-dir/bin

8  Type startup

          Next, enter the URL http://localhost:8080/ in your browser and make sure you get the Tomcat welcome page

Compile and Execute your Servlet

Step 1 – Compile your servlet program

Neither the javax.servlet.* nor the javax.servlet.http.* is part of the standard JDK. It has to be exclusively added in the CLASSPATH.

>Set classpath= C:\apache-tomcat-6.0.20\lib\servlet-api.jar

>javac servletfilename.java

Step 2 – Copy the servlet class to the classes folder

          Copy the servlet class file to the C:\apache-tomcat-6.0.20\webapps\ROOT\WEB-INF\classes folder in order to run the servlet that we created. If the classes folder is not present then create anew one.

Step 3: Run Tomcat server and then execute your Servlet

Start the tomcat server

Open a browser and type the URL as

          http://localhost:8080/sevlet/serveltname.

Example:

Program:

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

public class HelloServlet extends HttpServlet

{

          public void doGet(HttpServletRequest request,

          HttpServletResponse response)throws ServletException, IOException

          {

                     response.setContentType("text/html");

                     PrintWriter out = response.getWriter();

                     out.println("<HTML>");

                    out.println("<HEAD><TITLE>Hello</TITLE></HEAD>");

                    out.println("<BODY BGCOLOR=\"#FDF5E6\">");

                   out.println("<H1>Welcome to MSPVL</H1>");

                   out.println("</BODY>");

                    out.println("</HTML>");

          }

}

Output:

Configuring And Running Servlet Program into tomcat 6

Posted in : Servlet Posted on : October 30, 2010 at 5:52 PM Comments : [ 0 ]

Configuring And Running Servlet Program into tomcat 6

Follow the steps to compile and run servlet application

1. At first you need to install java ( jdk1.5 or above version ) .
2. Set the JAVA_HOME as- go to the Start ->Control Panel ->Performance And Maintenance ->System ->Advance -> Environment Variable -> New -> Then write the variable name "JAVA_HOME" and in Variable Value value write the full path of java install directory.
3. Then  download the tomcat 6 and then un-zip the zip the tomcat into the C:\ directory.
4. Then go to the apache-tomcat-6.0.29\webapps\ROOT\WEB-INF directory make a new folder name it "classes". Remember that the name of classes directory must be written in small latter.
5. Then write the following code in note pad or other editor you prefer and save it as TestServlet.java and save it to the apache-tomcat-6.0.29\webapps\ROOT\WEB-INF\classes directory-

        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 TestServlet extends HttpServlet {
       
            public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws IOException, ServletException
            {
                response.setContentType("text/html");
                PrintWriter out = response.getWriter();
                out.println("");        
                out.println("");
                out.println("<h1>This is my Fisrt Servlet</h1>");
                out.println("");
                out.println("");
            }
        }

6. Then for compilation open your command prompt and by command prompt go to the apache-tomcat-6.0.29\webapps\ROOT\WEB-INF\classes and type javac TestServlet.java -classpath "C:\apache-tomcat-6.0.29\lib\servlet-api.jar" and then press enter.
7. Now configure your servlet. To configure follow the steps go to the C:\apache-tomcat-6.0.29\webapps\ROOT\WEB-INF and open web.xml file in edit mode
8. write the following block of code within

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

<display-name>Welcome to Tomcat</display-name>
<description>
Welcome to Tomcat
</description>  
Write your code here .......................
</web-app>

Then write the fillowing mapping code

<servlet> <servlet-name>Test</servlet-name> <servlet-class>TestServlet</servlet-class> </servlet> <!-- servlet mapping --> <servlet-mapping> <servlet-name>Test</servlet-name> <url-pattern>/test</url-pattern> </servlet-mapping> Here Test within <servlet-name>Test</servlet-name> is name of your servlet. TestServlet is your servlet class and /test is your url pattern or your servlet name by which you call this servlet on browser

9. Then Start the tomcat, go to the apache-tomcat-6.0.29\bin and double click on the startup. if a window appears like this the your tomcat have been started. To check whether you tomcat started or not open your web browser and type URL http://localhost:8080 and press enter then a windows appears like this
10. To run your servlet write the following URL in your browser  http://localhost:8080/test and press enter then the output appears like this