How to use web.xml in Servlet 3.0

In this tutorial you will learn how to use web.xml in Servlet 3.0.

Here I am giving the simple example of a Servlet in which I make a simple servlet class using @WebServlet annotaion into which the initial parameter is given using @WebInitParameter annotation. To find the context value I have mapped the <context-param> element in web.xml. Because there is no any annotation is defined for the ServletContext.

Example :

ContextParamServlet.java

package roseindia.webContext;

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

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.annotation.WebServlet;
import javax.servlet.annotation.WebInitParam;

@WebServlet(name = "ContextParamServlet",
urlPatterns = {"/ContextParamServlet"},
initParams={
@WebInitParam(name="URL", value="jdbc:mysql://192.168.10.13"),
@WebInitParam(name="USER", value="root"),
@WebInitParam(name="PASSWORD", value="root")
} 
)
public class ContextParamServlet extends HttpServlet 
{
public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException 
{

res.setContentType("text/plain");
PrintWriter out = res.getWriter();

String url = getInitParameter("URL");

ServletConfig config = getServletConfig();
ServletContext context = getServletContext();

String uid = config.getInitParameter("USER");
String psw = config.getInitParameter("PASSWORD");
String id= context.getInitParameter("userId");

out.println("Context and InitParameters values :");
out.println("URL: " + url);
out.println("User: " + uid);
out.println("PSW: " + psw);
out.println("User Id : " + id);
}
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
<context-param>
<param-name>userId</param-name>
<param-value>bipul</param-value>
</context-param>
</web-app>

Output :

When you will execute the above example you will get the output as :

Download Source Code

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