Document Information


Part I Introduction

1.  Overview

2.  Using the Tutorial Examples

Part II The Web Tier

3.  Getting Started with Web Applications

4.  Java Servlet Technology

What Is a Servlet?

The Example Servlets

Troubleshooting Duke's Bookstore Database Problems

Servlet Life Cycle

Handling Servlet Life-Cycle Events

Defining the Listener Class

Specifying Event Listener Classes

Handling Servlet Errors

Sharing Information

Using Scope Objects

Controlling Concurrent Access to Shared Resources

Accessing Databases

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

Invoking Other Web Resources

Including Other Resources in the Response

Transferring Control to Another Web Component

Maintaining Client State

Accessing a Session

Associating Objects with a Session

Notifying Objects That Are Associated with a Session

Session Management

Session Tracking

Finalizing a Servlet

Tracking Service Requests

Notifying Methods to Shut Down

Creating Polite Long-Running Methods

Further Information about Java Servlet Technology

5.  JavaServer Pages Technology

6.  JavaServer Pages Documents

7.  JavaServer Pages Standard Tag Library

8.  Custom Tags in JSP Pages

9.  Scripting in JSP Pages

10.  JavaServer Faces Technology

11.  Using JavaServer Faces Technology in JSP Pages

12.  Developing with JavaServer Faces Technology

13.  Creating Custom UI Components

14.  Configuring JavaServer Faces Applications

15.  Internationalizing and Localizing Web Applications

Part III Web Services

16.  Building Web Services with JAX-WS

17.  Binding between XML Schema and Java Classes

18.  Streaming API for XML

19.  SOAP with Attachments API for Java

Part IV Enterprise Beans

20.  Enterprise Beans

21.  Getting Started with Enterprise Beans

22.  Session Bean Examples

23.  A Message-Driven Bean Example

Part V Persistence

24.  Introduction to the Java Persistence API

25.  Persistence in the Web Tier

26.  Persistence in the EJB Tier

27.  The Java Persistence Query Language

Part VI Services

28.  Introduction to Security in the Java EE Platform

29.  Securing Java EE Applications

30.  Securing Web Applications

31.  The Java Message Service API

32.  Java EE Examples Using the JMS API

33.  Transactions

34.  Resource Connections

35.  Connector Architecture

Part VII Case Studies

36.  The Coffee Break Application

37.  The Duke's Bank Application

Part VIII Appendixes

A.  Java Encoding Schemes

B.  About the Authors



Accessing the Web Context

The context in which web components execute is an object that implements the ServletContext interface. You retrieve the web context using the getServletContext method. The web context provides methods for accessing:

  • Initialization parameters

  • Resources associated with the web context

  • Object-valued attributes

  • Logging capabilities

The web context is used by the Duke’s Bookstore filters HitCounterFilter and OrderFilter, which are discussed in Filtering Requests and Responses. Each filter stores a counter as a context attribute. Recall from Controlling Concurrent Access to Shared Resources that the counter’s access methods are synchronized to prevent incompatible operations by servlets that are running concurrently. A filter retrieves the counter object using the context’s getAttribute method. The incremented value of the counter is recorded in the log.

public final class HitCounterFilter implements Filter {
    private FilterConfig filterConfig = null;
    public void doFilter(ServletRequest request,
        ServletResponse response, FilterChain chain)
         throws IOException, ServletException {
        StringWriter sw = new StringWriter();
        PrintWriter writer = new PrintWriter(sw);
        ServletContext context = filterConfig.
        Counter counter = (Counter)context.
        writer.println("The number of hits is: " +