How do I create a HelloWorld Servlet?
Category: javax.servlet, viewed: 1781 time(s).
Servlet is a Java solution for creating a dynamic web application, it can be compared with the old CGI technology. Using Servlet we can create a web application that can display information from database, receive information from a web form to be stored on the application database.
This example show the very basic of servlet, it returns a hello world html document for the browser. At the very minimum a servlet will have a doPost() and doGet() method which handles the HTTP POST and GET request.
package org.kodejava.example.servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class HelloWorld extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet { public HelloWorld() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter writer = response.getWriter(); writer.println("<html>"); writer.println("<head><title>Hello World Servlet</title></head>"); writer.println("<body>Hello World! How are you doing?</body>"); writer.println("</html>"); writer.close(); } } |
For a servlet to works on a servlet container such as Apache Tomcat we need to add or register the servlet in the application's web.xml file. This configuration tells the container about our servlet class and a url that maps a request to the servlet.
<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<display-name>kodejava-example</display-name>
<servlet>
<description></description>
<display-name>HelloWorld</display-name>
<servlet-name>HelloWorld</servlet-name>
<servlet-class>
org.kodejava.example.servlet.HelloWorld
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloWorld</servlet-name>
<url-pattern>/HelloWorld</url-pattern>
</servlet-mapping>
</web-app>
When the servlet is deployed to the container we can access it from a url in a form of http://localhost:8080/app-name/HelloWorld
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