Fetching Value of Form Field Using Java Servlet

Satyapriya Nayak
Sep 04, 2011
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Fetching value of form field using servlet.rar

A servlet can fetch the value of a form field using the getParameter() method of the servlet request. The HTML form can submit a value of the form fields by using url pattern of the servlet into the action attribute of the form tag. If the method attribute contains Get as its value and destination servlet is a sub-class of the Http servlet then doGet() method gets invoked. If the method attribute contains post as its value and destination servlet is a sub-class of http servlet then doPost() method of the servlet gets invoked. If the destination servlet is a sub-class of Generic servlet then the service() method gets invoked without depending upon value of method attribute. The getParameter() method of request accepts name of the form field as its arguments and returns value of the form fields as a string. If the specified form field does not exist in the request then the getParameter() method returns Null. If the form exists in a servlet and it requires submission of the form into the current servlet then the action attribute does not need to be used in the form tag.

Example

A servlet to receive two numbers and display the addition.

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class number extends HttpServlet
{
   public void doGet(HttpServletRequest req,HttpServletResponse res)throws IOException,ServletException
   {
       String s1=req.getParameter("t1");
       String s2=req.getParameter("t2");
       PrintWriter out=res.getWriter();
       out.println("<html><body>");
       if(s1 ==null)
       {
           out.println("<form>");
           out.println("<h1>Enter No1<input type='text' name='t1'></h1>");
           out.println("<input type='submit' value='submit'>");
           out.println("</form>");
       }
       else if(s2 ==null)
       {
           out.println("<form>");
           out.println("<h1>Enter No2<input type='text' name='t2'></h1>");
           out.println("<input type='hidden' name='t1' value='"+s1+"'>");
           out.println("<input type='submit' value='submit'>");
           out.println("<form>");
       }
       else
       {
           int x=Integer.parseInt(s1);
           int y=Integer.parseInt(s2);
           out.println("<h1>Result is "+(x+y)+"</h1>");
       }
       out.println("</body></html>");
   }
}

Storing and Compiling

Store the file inside class folder of the context (E:\Servlet\WEB-INF\classes).

Compile the file as below:

javac -cp servlet-api.jar number.java (for tomcat 6.0)

Servlet in java

Setting in web.xml file

Note: - Note the Highlighted or bold portion in the below web.xml file, to be added.

<?xml version="1.0" encoding="ISO-8859-1" ?>
- 
--<web-appxmlns=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">
  <servlet>
<servlet-name>number</servlet-name>
<servlet-class>number</servlet-class>
</servlet>
  <servlet-mapping>
<servlet-name>number</servlet-name>
<url-pattern>/number</url-pattern>
</servlet-mapping>
</web-app>

Running it in web browser

First start the Apache tomcat 6.0, which is a web server. Then type the below URL.

http://localhost:8082/x/number

Here x is the context path location, which we have to give in the server.xml file, which is present inside Tomcat installation directory (E:\Program Files\Apache Software Foundation\Tomcat 6.0\conf)

Server.xml settings

Note: - In the below server.xml file we have to specify the context path as below.

<Context path="/x" docBase="E:\Servlet" reloadable="true" debug="0" />

server.xml file

<?xml version='1.0' encoding='utf-8'?>


<Server port="8005" shutdown="SHUTDOWN">


<Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" />

<Listener className="org.apache.catalina.core.JasperListener" />

<Listener className="org.apache.catalina.mbeans.ServerLifecycleListener" />
<Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" />


<GlobalNamingResources>

<Resource name="UserDatabase" auth="Container"
type="org.apache.catalina.UserDatabase"
description="User database that can be updated and saved"
factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
pathname="conf/tomcat-users.xml" />
</GlobalNamingResources>


<Service name="Catalina">





<Connector port="8082" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" />






<Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />




<Engine name="Catalina" defaultHost="localhost">








<Realm className="org.apache.catalina.realm.UserDatabaseRealm"
resourceName="UserDatabase"/>


<Host name="localhost" appBase="webapps"
unpackWARs="true" autoDeploy="true"
xmlValidation="false" xmlNamespaceAware="false">






<Context path="/x" docBase="E:\Servlet" reloadable="true" debug="0" />
</Host>
</Engine>
</Service>
</Server>

Output

Thanks for reading and please be kind enough to give the feedback.