Java EE 6 Pocket Guide

Chapter 3. Servlets

Servlets are defined as JSR 315, and the complete specification can be downloaded from http://jcp.org/aboutJava/communityprocess/final/jsr315/index.html.

A servlet is a web component hosted in a servlet container and generates dynamic content. The web clients interact with a servlet using a request/response pattern. The servlet container is responsible for the lifecycle of the servlet, receives requests and sends responses, and performs any other encoding/decoding required as part of that.

Servlets

A servlet is defined using the @WebServlet annotation on a POJO, and must extend the javax.servlet.http.HttpServlet class.

Here is a sample servlet definition:

@WebServlet("/account")
public class AccountServlet 
  extends javax.servlet.http.HttpServlet {
  //. . .
}

The fully qualified class name is the default servlet name, and may be overridden using the name attribute of the annotation. The servlet may be deployed at multiple URLs:

@WebServlet(urlPatterns={"/account", "/accountServlet"})
public class AccountServlet 
  extends javax.servlet.http.HttpServlet {
  //. . .
}

The @WebInitParam can be used to specify an initialization parameter:

@WebServlet(urlPatterns="/account",
            initParams={
               @WebInitParam(name="type", value="checking")
                       }
           )
public class AccountServlet 
  extends javax.servlet.http.HttpServlet {
  //. . .
}

The Servlet interface has one doXXX method to handle each of HTTP GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE requests. Typically the developer is concerned with overriding ...