Document Information


Part I Introduction

1.  Overview

2.  Using the Tutorial Examples

Part II The Web Tier

3.  Getting Started with Web Applications

4.  JavaServer Faces Technology

5.  Introduction to Facelets

6.  Expression Language

7.  Using JavaServer Faces Technology in Web Pages

8.  Using Converters, Listeners, and Validators

9.  Developing with JavaServer Faces Technology

10.  JavaServer Faces Technology: Advanced Concepts

11.  Using Ajax with JavaServer Faces Technology

12.  Composite Components: Advanced Topics and Example

13.  Creating Custom UI Components and Other Custom Objects

14.  Configuring JavaServer Faces Applications

15.  Java Servlet Technology

What Is a Servlet?

Servlet Lifecycle

Handling Servlet Lifecycle Events

Defining the Listener Class

Handling Servlet Errors

Sharing Information

Using Scope Objects

Controlling Concurrent Access to Shared Resources

Creating and Initializing a Servlet

Writing Service Methods

Getting Information from Requests

Constructing Responses

Filtering Requests and Responses

Programming Filters

Programming Customized Requests and Responses

Specifying Filter Mappings

To Specify Filter Mappings Using NetBeans IDE

Invoking Other Web Resources

Including Other Resources in the Response

Transferring Control to Another Web Component

Accessing the Web Context

Maintaining Client State

Accessing a Session

Associating Objects with a Session

Session Management

To Set the Timeout Period Using NetBeans IDE

Session Tracking

The mood Example Application

Components of the mood Example Application

Running the mood Example

To Run the mood Example Using NetBeans IDE

To Run the mood Example Using Ant

Further Information about Java Servlet Technology

16.  Uploading Files with Java Servlet Technology

17.  Internationalizing and Localizing Web Applications

Part III Web Services

18.  Introduction to Web Services

19.  Building Web Services with JAX-WS

20.  Building RESTful Web Services with JAX-RS

21.  JAX-RS: Advanced Topics and Example

Part IV Enterprise Beans

22.  Enterprise Beans

23.  Getting Started with Enterprise Beans

24.  Running the Enterprise Bean Examples

25.  A Message-Driven Bean Example

26.  Using the Embedded Enterprise Bean Container

27.  Using Asynchronous Method Invocation in Session Beans

Part V Contexts and Dependency Injection for the Java EE Platform

28.  Introduction to Contexts and Dependency Injection for the Java EE Platform

29.  Running the Basic Contexts and Dependency Injection Examples

30.  Contexts and Dependency Injection for the Java EE Platform: Advanced Topics

31.  Running the Advanced Contexts and Dependency Injection Examples

Part VI Persistence

32.  Introduction to the Java Persistence API

33.  Running the Persistence Examples

34.  The Java Persistence Query Language

35.  Using the Criteria API to Create Queries

36.  Creating and Using String-Based Criteria Queries

37.  Controlling Concurrent Access to Entity Data with Locking

38.  Using a Second-Level Cache with Java Persistence API Applications

Part VII Security

39.  Introduction to Security in the Java EE Platform

40.  Getting Started Securing Web Applications

41.  Getting Started Securing Enterprise Applications

42.  Java EE Security: Advanced Topics

Part VIII Java EE Supporting Technologies

43.  Introduction to Java EE Supporting Technologies

44.  Transactions

45.  Resources and Resource Adapters

46.  The Resource Adapter Example

47.  Java Message Service Concepts

48.  Java Message Service Examples

49.  Bean Validation: Advanced Topics

50.  Using Java EE Interceptors

Part IX Case Studies

51.  Duke's Bookstore Case Study Example

52.  Duke's Tutoring Case Study Example

53.  Duke's Forest Case Study Example



Finalizing a Servlet

The web container may determine that a servlet should be removed from service (for example, when a container wants to reclaim memory resources or when it is being shut down). In such a case, the container calls the destroy method of the Servlet interface. In this method, you release any resources the servlet is using and save any persistent state. The destroy method releases the database object created in the init method .

A servlet’s service methods should all be complete when a servlet is removed. The server tries to ensure this by calling the destroy method only after all service requests have returned or after a server-specific grace period, whichever comes first. If your servlet has operations that may run longer than the server’s grace period, the operations could still be running when destroy is called. You must make sure that any threads still handling client requests complete.

The remainder of this section explains how to do the following:

  • Keep track of how many threads are currently running the service method.

  • Provide a clean shutdown by having the destroy method notify long-running threads of the shutdown and wait for them to complete.

  • Have the long-running methods poll periodically to check for shutdown and, if necessary, stop working, clean up, and return.

Tracking Service Requests

To track service requests, include in your servlet class a field that counts the number of service methods that are running. The field should have synchronized access methods to increment, decrement, and return its value:

public class ShutdownExample extends HttpServlet {
    private int serviceCounter = 0;
    // Access methods for serviceCounter
    protected synchronized void enteringServiceMethod() {
    protected synchronized void leavingServiceMethod() {
    protected synchronized int numServices() {
        return serviceCounter;

The service method should increment the service counter each time the method is entered and should decrement the counter each time the method returns. This is one of the few times that your HttpServlet subclass should override the service method. The new method should call super.service to preserve the functionality of the original service method:

protected void service(HttpServletRequest req,
                       HttpServletResponse resp)
                       throws ServletException,IOException {
    try {
        super.service(req, resp);
    } finally {

Notifying Methods to Shut Down

To ensure a clean shutdown, your destroy method should not release any shared resources until all the service requests have completed. One part of doing this is to check the service counter. Another part is to notify the long-running methods that it is time to shut down. For this notification, another field is required. The field should have the usual access methods:

public class ShutdownExample extends HttpServlet {
    private boolean shuttingDown;
    //Access methods for shuttingDown
    protected synchronized void setShuttingDown(boolean flag) {
        shuttingDown = flag;
    protected synchronized boolean isShuttingDown() {
        return shuttingDown;

Here is an example of the destroy method using these fields to provide a clean shutdown:

public void destroy() {
    /* Check to see whether there are still service methods /*
    /* running, and if there are, tell them to stop. */
    if (numServices() > 0) {

    /* Wait for the service methods to stop. */
    while(numServices() > 0) {
        try {
        } catch (InterruptedException e) {

Creating Polite Long-Running Methods

The final step in providing a clean shutdown is to make any long-running methods behave politely. Methods that might run for a long time should check the value of the field that notifies them of shutdowns and should interrupt their work, if necessary:

public void doPost(...) {
    for(i = 0; ((i < lotsOfStuffToDo) &&
         !isShuttingDown()); i++) {
        try {
        } catch (InterruptedException e) {