Friday, 2 May 2014

Servlets : ServletContext [context-param]


Click here to watch in Youtube : https://www.youtube.com/watch?v=u0YYCV9IxK4

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ServletContextInitParam Project Dir Structure

SevletContextDemoServlet.java
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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 SevletContextDemoServlet extends HttpServlet
{

    private static final long serialVersionUID = 1L;

    public void init() throws ServletException
    {
        System.out
                .println("------------------------------------------------------");
        System.out.println(" Init method is called in "
                + this.getClass().getName());
        System.out
                .println("------------------------------------------------------");
    }

    // Method to handle GET method request.
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        ServletContext context = getServletContext();

        out.print("<b>Read specfic initParam using context.getInitParameter"
                + "(String paramName )</b> <br><br>");

        String driverName = context.getInitParameter("drivername");
        out.print(driverName + "<br><br>");

        out.print("<b>Read All InitParameters using "
                + "getInitParameterNames() method</b> <br>");

        Enumeration<String> initParamNamesEnum = context
                .getInitParameterNames();
        String paramName = "";
        while (initParamNamesEnum.hasMoreElements())
        {
            paramName = initParamNamesEnum.nextElement();
            String paramValue = context.getInitParameter(paramName);
            out.print("<br> " + paramName + " : " + paramValue);
        }
    }

    // Method to handle POST method request.
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
        doGet(request, response);
    }

    public void destroy()
    {
        System.out
                .println("------------------------------------------------------");
        System.out.println(" destroy method is called in "
                + this.getClass().getName());
        System.out
                .println("------------------------------------------------------");
    }
}

web.xml
<?xml version="1.0" encoding="ISO-8859-1"?>
<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_3_0.xsd"
    metadata-complete="true" version="3.0">
    <display-name>ServletContextInitParam</display-name>
    <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>

    <context-param>
        <param-name>drivername</param-name>
        <param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>
    </context-param>

    <context-param>
        <param-name>username</param-name>
        <param-value>system</param-value>
    </context-param>

    <context-param>
        <param-name>password</param-name>
        <param-value>oracle</param-value>
    </context-param>
    
    <servlet>
        <servlet-name>context</servlet-name>
        <servlet-class>SevletContextDemoServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>context</servlet-name>
        <url-pattern>/context</url-pattern>
    </servlet-mapping>
</web-app>

index.html
<!DOCTYPE HTML>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Context Test</title>
</head>
<body>
    <li><a href="context">Context Test</a></li>
</body>
</html>


Environment Used

JDK version :1.6.0_30
Tomcat version : 7.0.50 

To Download ServletContextInitParamApp Project Click the below link

https://sites.google.com/site/javaee4321/servlets/ServletContextInitParamApp.zip?attredirects=0&d=1

 See also:

  • Servlets Tutorial
  • All Design Patterns Links
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