What is the difference between HttpSession mySession=request.getSession(true) and HttpSession mySession=request.getSession()

What is the difference between HttpSession mySession=request.getSession(true) and HttpSession mySession=request.getSession().?

Answer:

request.getSession() will return the current session and if one does not exist, a new session will be cretaed.

request.getSession(true) will return the current session if one exists, if one doesn't exits a new one will be created.

So there is actually no difference between the two methods HOWEVER, if you use request.getSession(false), it will return the current session if one exists and if one DOES NOT exist a new one will NOT be cretaed.

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Java™ Servlet Specification.pdf download

Java™ Servlet Specification
Version 2.4
Please send technical comments to: servletapi-feedback@eng.sun.com
Please send business comments to: danny.coward@sun.com
Public Draft June 24th 2002
Danny Coward (danny.coward@sun.com)
Yutaka Yoshida (yutaka.yoshida@sun.com)

Java™ Servlet Specification Version 2.4 . . . . . . . . . . . . . . . .i
Changes since version 2.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
Changes in this document since version 2.3 . . . . . . . . . . . . . . . . . xiii
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
Additional Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
Who Should Read This Specification . . . . . . . . . . . . . . . . . . . . . . xvi
API Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi
Other Java™ Platform Specifications . . . . . . . . . . . . . . . . . . . . . . xvi
Other Important References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
Providing Feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii
SRV.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
SRV.1.1 What is a Servlet? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
SRV.1.2 What is a Servlet Container? . . . . . . . . . . . . . . . . . . . . . . 19
SRV.1.3 An Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
SRV.1.4 Comparing Servlets with Other Technologies . . . . . . . . 20
SRV.1.5 Relationship to Java 2, Platform Enterprise Edition . . . . 21
SRV.2 The Servlet Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SRV.2.1 Request Handling Methods . . . . . . . . . . . . . . . . . . . . . . . 23
SRV.2.1.1 HTTP Specific Request Handling Methods . . . . 23
SRV.2.1.2 Additional Methods . . . . . . . . . . . . . . . . . . . . . . 24
SRV.2.1.3 Conditional GET Support . . . . . . . . . . . . . . . . . . 24
CONTENTS vi
SRV.2.2 Number of Instances . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
SRV.2.2.1 Note About The Single Thread Model . . . . . . . . 25
SRV.2.3 Servlet Life Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
SRV.2.3.1 Loading and Instantiation . . . . . . . . . . . . . . . . . . 25
SRV.2.3.2 Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
SRV.2.3.3 Request Handling . . . . . . . . . . . . . . . . . . . . . . . . 26
SRV.2.3.4 End of Service . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
SRV.3 Servlet Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
SRV.3.1 Introduction to the ServletContext Interface . . . . . . . . . . 29
SRV.3.2 Scope of a ServletContext Interface . . . . . . . . . . . . . . . . 29
SRV.3.3 Initialization Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 30
SRV.3.4 Context Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
SRV.3.4.1 Context Attributes in a Distributed Container . . 30
SRV.3.5 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
SRV.3.6 Multiple Hosts and Servlet Contexts . . . . . . . . . . . . . . . 31
SRV.3.7 Reloading Considerations . . . . . . . . . . . . . . . . . . . . . . . . 31
SRV.3.7.1 Temporary Working Directories . . . . . . . . . . . . . 32
SRV.4 The Request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
SRV.4.1 HTTP Protocol Parameters . . . . . . . . . . . . . . . . . . . . . . . 33
SRV.4.1.1 When Parameters Are Available . . . . . . . . . . . . . 34
SRV.4.2 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
SRV.4.3 Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
SRV.4.4 Request Path Elements . . . . . . . . . . . . . . . . . . . . . . . . . . 35
SRV.4.5 Path Translation Methods . . . . . . . . . . . . . . . . . . . . . . . . 37
SRV.4.6 Cookies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
SRV.4.7 SSL Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
SRV.4.8 Internationalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
SRV.4.9 Request data encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 39
SRV.4.10 Lifetime of the Request Object . . . . . . . . . . . . . . . . . . . . 39
SRV.5 The Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
SRV.5.1 Buffering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
SRV.5.2 Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
SRV.5.3 Convenience Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
CONTENTS vii
SRV.5.4 Internationalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
SRV.5.5 Closure of Response Object . . . . . . . . . . . . . . . . . . . . . . 44
SRV.5.6 Lifetime of the Response Object . . . . . . . . . . . . . . . . . . . 45
SRV.6 Filtering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
SRV.6.1 What is a filter? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
SRV.6.1.1 Examples of Filtering Components . . . . . . . . . . 48
SRV.6.2 Main Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
SRV.6.2.1 Filter Lifecycle . . . . . . . . . . . . . . . . . . . . . . . . . . 48
SRV.6.2.2 Wrapping Requests and Responses . . . . . . . . . . 50
SRV.6.2.3 Filter Environment . . . . . . . . . . . . . . . . . . . . . . . 50
SRV.6.2.4 Configuration of Filters in a Web Application . . 51
SRV.6.2.5 Filters and the RequestDispatcher . . . . . . . . . . . 52
SRV.7 Sessions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
SRV.7.1 Session Tracking Mechanisms . . . . . . . . . . . . . . . . . . . . 55
SRV.7.1.1 Cookies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
SRV.7.1.2 SSL Sessions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
SRV.7.1.3 URL Rewriting . . . . . . . . . . . . . . . . . . . . . . . . . . 56
SRV.7.1.4 Session Integrity . . . . . . . . . . . . . . . . . . . . . . . . . 56
SRV.7.2 Creating a Session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
SRV.7.3 Session Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
SRV.7.4 Binding Attributes into a Session . . . . . . . . . . . . . . . . . . 57
SRV.7.5 Session Timeouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
SRV.7.6 Last Accessed Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
SRV.7.7 Important Session Semantics . . . . . . . . . . . . . . . . . . . . . 58
J2EE.7.7.1 Threading Issues . . . . . . . . . . . . . . . . . . . . . . . . . 58
SRV.7.7.2 Distributed Environments . . . . . . . . . . . . . . . . . . 58
SRV.7.7.3 Client Semantics . . . . . . . . . . . . . . . . . . . . . . . . . 59
SRV.8 Dispatching Requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
SRV.8.1 Obtaining a RequestDispatcher . . . . . . . . . . . . . . . . . . . . 61
SRV.8.1.1 Query Strings in Request Dispatcher Paths . . . . 62
SRV.8.2 Using a Request Dispatcher . . . . . . . . . . . . . . . . . . . . . . 62
SRV.8.3 The Include Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
SRV.8.3.1 Included Request Parameters . . . . . . . . . . . . . . . 63
SRV.8.4 The Forward Method . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
CONTENTS viii
SRV.8.4.1 Query String . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
SRV.8.5 Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
SRV.9 Web Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
SRV.9.1 Web Applications Within Web Servers . . . . . . . . . . . . . 65
SRV.9.2 Relationship to ServletContext . . . . . . . . . . . . . . . . . . . 65
SRV.9.3 Elements of a Web Application . . . . . . . . . . . . . . . . . . . 66
SRV.9.4 Deployment Hierarchies . . . . . . . . . . . . . . . . . . . . . . . . 66
SRV.9.5 Directory Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
SRV.9.5.1 Example of Application Directory Structure . . . 67
SRV.9.6 Web Application Archive File . . . . . . . . . . . . . . . . . . . . 68
SRV.9.7 Web Application Deployment Descriptor . . . . . . . . . . . 68
SRV.9.7.1 Dependencies On Extensions . . . . . . . . . . . . . . . 68
SRV.9.7.2 Web Application Classloader . . . . . . . . . . . . . . 69
SRV.9.8 Replacing a Web Application . . . . . . . . . . . . . . . . . . . . 69
SRV.9.9 Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
SRV.9.9.1 Request Attributes . . . . . . . . . . . . . . . . . . . . . . . 70
SRV.9.9.2 Error Pages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
SRV.9.10 Welcome Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
SRV.9.11 Web Application Environment . . . . . . . . . . . . . . . . . . . 73
SRV.10 Application Lifecycle Events . . . . . . . . . . . . . . . . . . . . . . . 75
SRV.10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
SRV.10.2 Event Listeners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
SRV.10.2.1 Event Types and Listener Interfaces . . . . . . . . . 75
SRV.10.2.2 An Example of Listener Use . . . . . . . . . . . . . . . 77
SRV.10.3 Listener Class Configuration . . . . . . . . . . . . . . . . . . . . . 77
SRV.10.3.1 Provision of Listener Classes . . . . . . . . . . . . . . . 77
SRV.10.3.2 Deployment Declarations . . . . . . . . . . . . . . . . . . 77
SRV.10.3.3 Listener Registration . . . . . . . . . . . . . . . . . . . . . 77
SRV.10.3.4 Notifications At Shutdown . . . . . . . . . . . . . . . . 78
SRV.10.4 Deployment Descriptor Example . . . . . . . . . . . . . . . . . . 78
SRV.10.5 Listener Instances and Threading . . . . . . . . . . . . . . . . . 78
SRV.10.6 Listener Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
SRV.10.7 Distributed Containers . . . . . . . . . . . . . . . . . . . . . . . . . . 79
CONTENTS ix
SRV.10.8 Session Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
SRV.11 Mapping Requests to Servlets . . . . . . . . . . . . . . . . . . . . . . 81
SRV.11.1 Use of URL Paths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
SRV.11.2 Specification of Mappings . . . . . . . . . . . . . . . . . . . . . . . 82
SRV.11.2.1 Implicit Mappings . . . . . . . . . . . . . . . . . . . . . . . 82
SRV.11.2.2 Example Mapping Set . . . . . . . . . . . . . . . . . . . . 83
SRV.12 Security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
SRV.12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
SRV.12.2 Declarative Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
SRV.12.3 Programmatic Security . . . . . . . . . . . . . . . . . . . . . . . . . . 86
SRV.12.4 Roles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
SRV.12.5 Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
SRV.12.5.1 HTTP Basic Authentication . . . . . . . . . . . . . . . . 88
SRV.12.5.2 HTTP Digest Authentication . . . . . . . . . . . . . . . 89
SRV.12.5.3 Form Based Authentication . . . . . . . . . . . . . . . . 89
SRV.12.5.4 HTTPS Client Authentication . . . . . . . . . . . . . . 91
SRV.12.6 Server Tracking of Authentication Information . . . . . . . 91
SRV.12.7 Propagation of Security Identity in EJBTM Calls . . . . . 91
SRV.12.8 Specifying Security Constraints . . . . . . . . . . . . . . . . . . . 92
SRV.12.9 Default Policies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
SRV.12.10Login and Logout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
SRV.12.10.1 Login . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
SRV.12.10.2 Logout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
SRV.13 Deployment Descriptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
SRV.13.1 Extensibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
SRV.13.1.1 Example of Extensibility: ACME servlets . . . . . 96
SRV.13.2 Deployment Descriptor Elements . . . . . . . . . . . . . . . . . 98
SRV.13.3 Rules for Processing the Deployment Descriptor . . . . . 99
SRV.13.4 Deployment Descriptor . . . . . . . . . . . . . . . . . . . . . . . . . 99
SRV.13.5 Picture of the structure of a Deployment Descriptor . . 132
SRV.13.6 DTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
SRV.13.7 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
SRV.13.7.1 A Basic Example . . . . . . . . . . . . . . . . . . . . . . . 135
SRV.13.7.2 An Example of Security . . . . . . . . . . . . . . . . . . 136
CONTENTS x
SRV.14 javax.servlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
SRV.14.1 Generic Servlet Interfaces and Classes . . . . . . . . . . . . . 139
SRV.14.2 The javax.servlet package . . . . . . . . . . . . . . . . . . . . . . . 139
SRV.14.2.1 Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
SRV.14.2.2 FilterChain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
SRV.14.2.3 FilterConfig . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
SRV.14.2.4 GenericServlet . . . . . . . . . . . . . . . . . . . . . . . . . . 145
SRV.14.2.5 RequestDispatcher . . . . . . . . . . . . . . . . . . . . . . 149
SRV.14.2.6 Servlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
SRV.14.2.7 ServletConfig . . . . . . . . . . . . . . . . . . . . . . . . . . 153
SRV.14.2.8 ServletContext . . . . . . . . . . . . . . . . . . . . . . . . . . 154
SRV.14.2.9 ServletContextAttributeEvent . . . . . . . . . . . . . . 163
SRV.14.2.10 ServletContextAttributeListener . . . . . . . . . . . 164
SRV.14.2.11 ServletContextEvent . . . . . . . . . . . . . . . . . . . . 164
SRV.14.2.12 ServletContextListener . . . . . . . . . . . . . . . . . . . 165
SRV.14.2.13 ServletException . . . . . . . . . . . . . . . . . . . . . . . 166
SRV.14.2.14 ServletInputStream . . . . . . . . . . . . . . . . . . . . . . 167
SRV.14.2.15 ServletOutputStream . . . . . . . . . . . . . . . . . . . . 168
SRV.14.2.16 ServletRequest . . . . . . . . . . . . . . . . . . . . . . . . . 172
SRV.14.2.17 ServletRequestAttributeEvent . . . . . . . . . . . . . 179
SRV.14.2.18 ServletRequestAttributeListener . . . . . . . . . . . 180
SRV.14.2.19 ServletRequestEvent . . . . . . . . . . . . . . . . . . . . 181
SRV.14.2.20 ServletRequestListener . . . . . . . . . . . . . . . . . . 182
SRV.14.2.21 ServletRequestWrapper . . . . . . . . . . . . . . . . . . 182
SRV.14.2.22 ServletResponse . . . . . . . . . . . . . . . . . . . . . . . . 187
SRV.14.2.23 ServletResponseWrapper . . . . . . . . . . . . . . . . . 192
SRV.14.2.24 SingleThreadModel . . . . . . . . . . . . . . . . . . . . . 196
SRV.14.2.25 UnavailableException . . . . . . . . . . . . . . . . . . . 196
SRV.15 javax.servlet.http . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
SRV.15.1 Servlets Using HTTP Protocol . . . . . . . . . . . . . . . . . . . 199
SRV.15.1.1 Cookie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
SRV.15.1.2 HttpServlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
SRV.15.1.3 HttpServletRequest . . . . . . . . . . . . . . . . . . . . . . 214
SRV.15.1.4 HttpServletRequestWrapper . . . . . . . . . . . . . . . 221
SRV.15.1.5 HttpServletResponse . . . . . . . . . . . . . . . . . . . . . 226
SRV.15.1.6 HttpServletResponseWrapper . . . . . . . . . . . . . . 237
SRV.15.1.7 HttpSession . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
CONTENTS xi
SRV.15.1.8 HttpSessionActivationListener . . . . . . . . . . . . . 246
SRV.15.1.9 HttpSessionAttributeListener . . . . . . . . . . . . . . 247
SRV.15.1.10 HttpSessionBindingEvent . . . . . . . . . . . . . . . . 248
SRV.15.1.11 HttpSessionBindingListener . . . . . . . . . . . . . . 249
SRV.15.1.12 HttpSessionContext . . . . . . . . . . . . . . . . . . . . . 250
SRV.15.1.13 HttpSessionEvent . . . . . . . . . . . . . . . . . . . . . . . 250
SRV.15.1.14 HttpSessionListener . . . . . . . . . . . . . . . . . . . . . 251
SRV.15.1.15 HttpUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
SRV.A Deployment Descriptor Version 2.2 . . . . . . . . . . . . . . . . 255
SRV.A.1 Deployment Descriptor DOCTYPE . . . . . . . . . . . . . . . 255
SRV.A.2 DTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
SRV.A.1 Deployment Descriptor DOCTYPE . . . . . . . . . . . . . . . 269
SRV.A.2 DTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
SRV.B Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

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Java™Servlet Specification Version 2.3 (pdf) Download

Contents

Status ................................................................................................. 12
Changes in this document since v2.2........................................... 12
Preface ............................................................................................... 14
Who should read this document .................................................. 14
API Reference ............................................................................. 14
Other Java™ Platform Specifications.......................................... 14
Other Important References ........................................................ 15
Providing Feedback..................................................................... 16
Acknowledgements ..................................................................... 16
Chapter 1:Overview.......................................................................... 18
What is a Servlet?........................................................................ 18
What is a Servlet Container? ....................................................... 18
An Example................................................................................. 19
Comparing Servlets with Other Technologies ............................. 19
Relationship to Java 2 Platform Enterprise Edition ..................... 20
Chapter 2: The Servlet Interface ...................................................... 22
Request Handling Methods ......................................................... 22
HTTP Specific Request Handling Methods........................ 22
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Conditional GET Support ...................................................23
Number of Instances ....................................................................23
Note about SingleThreadModel ..........................................24
Servlet Life Cycle ........................................................................24
Loading and Instantiation ...................................................24
Initialization........................................................................24
Request Handling ...............................................................25
End of Service ....................................................................27
Chapter 3: Servlet Context ................................................................28
Scope of a ServletContext............................................................28
Initialization Parameters ..............................................................28
Context Attributes........................................................................29
Context Attributes in a Distributed Container.....................29
Resources.....................................................................................29
Multiple Hosts and Servlet Contexts............................................30
Reloading Considerations ............................................................30
Temporary Working Directories ..................................................31
Chapter 4: The Request .....................................................................32
Parameters ...................................................................................32
Attributes .....................................................................................33
Headers ........................................................................................33
Request Path Elements.................................................................34
Path Translation Methods ............................................................35
Cookies ........................................................................................36
SSL Attributes .............................................................................36
Internationalization ......................................................................37
Request data encoding .................................................................37
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Chapter 5: The Response .................................................................. 38
Buffering ..................................................................................... 38
Headers........................................................................................ 39
Convenience Methods ................................................................. 40
Internationalization...................................................................... 40
Closure of Response Object ........................................................ 41
Chapter 6: Servlet Filtering .............................................................. 42
What is a filter ? .......................................................................... 42
Examples of Filtering Components .................................... 43
Main Concepts............................................................................. 43
Filter Lifecycle................................................................... 43
Filter environment .............................................................. 45
Configuration of Filters in a Web Application ................... 45
Chapter 7: Sessions ............................................................................ 48
Session Tracking Mechanisms .................................................... 48
URL Rewriting................................................................... 48
Cookies .............................................................................. 49
SSL Sessions...................................................................... 49
Session Integrity................................................................. 49
Creating a Session ....................................................................... 49
Session Scope.............................................................................. 50
Binding Attributes into a Session ................................................ 50
Session Timeouts......................................................................... 50
Last Accessed Times ................................................................... 51
Important Session Semantics....................................................... 51
Threading Issues ................................................................ 51
Distributed Environments................................................... 51
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Client Semantics .................................................................52
Chapter 8: Dispatching Requests ......................................................54
Obtaining a RequestDispatcher....................................................54
Query Strings in Request Dispatcher Paths.........................55
Using a Request Dispatcher .........................................................55
Include .........................................................................................56
Included Request Parameters ..............................................56
Forward........................................................................................56
Query String .......................................................................57
Error Handling .............................................................................57
Chapter 9:Web Applications.............................................................58
Relationship to ServletContext ....................................................58
Elements of a Web Application ...................................................58
Distinction Between Representations...........................................59
Directory Structure ......................................................................59
Sample Web Application Directory Structure.....................60
Web Application Archive File .....................................................60
Web Application Configuration Descriptor .................................61
Dependencies on extensions: Library Files.........................61
Web Application Classloader..............................................62
Replacing a Web Application ......................................................62
Error Handling .............................................................................62
Welcome Files .............................................................................63
Web Application Environment ....................................................64
Chapter 10:Application Lifecycle Events ........................................66
Introduction .................................................................................66
Event Listeners ............................................................................66
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Configuration of Listener Classes ............................................... 68
Listener Instances and Threading ................................................ 69
Distributed Containers................................................................. 69
Session Events- Invalidation vs Timeout..................................... 69
Chapter 11: Mapping Requests to Servlets ...................................... 70
Use of URL Paths........................................................................ 70
Specification of Mappings........................................................... 71
Implicit Mappings .............................................................. 71
Example Mapping Set ........................................................ 71
Chapter 12: Security.......................................................................... 74
Introduction ................................................................................. 74
Declarative Security .................................................................... 75
Programmatic Security ................................................................ 75
Roles ........................................................................................... 76
Authentication ............................................................................. 76
HTTP Basic Authentication ............................................... 76
HTTP Digest Authentication.............................................. 77
Form Based Authentication................................................ 77
HTTPS Client Authentication ............................................ 78
Server Tracking of Authentication Information .......................... 79
Propogation of Security Identity.................................................. 79
Specifying Security Constraints .................................................. 80
Default Policies .................................................................. 80
Chapter 13: Deployment Descriptor................................................. 82
Deployment Descriptor Elements................................................ 82
Deployment Descriptor DOCTYPE ................................... 82
DTD ............................................................................................ 83
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Examples .....................................................................................96
A Basic Example ................................................................97
An Example of Security......................................................98
Chapter 14: API Details .....................................................................100
Config.................................................................................... 104
Filter ...................................................................................... 106
FilterConfig ........................................................................... 108
GenericServlet....................................................................... 110
RequestDispatcher ................................................................ 115
Servlet ................................................................................... 117
ServletConfig ........................................................................ 120
ServletContext....................................................................... 121
ServletContextAttributeEvent ............................................... 129
ServletContextAttributesListener.......................................... 131
ServletContextEvent ............................................................. 133
ServletContextListener.......................................................... 135
ServletException ................................................................... 136
ServletInputStream................................................................ 139
ServletOutputStream............................................................. 141
ServletRequest ...................................................................... 146
ServletRequestWrapper ........................................................ 153
ServletResponse .................................................................... 159
ServletResponseWrapper ...................................................... 163
SingleThreadModel............................................................... 167
UnavailableException ........................................................... 168
Cookie ................................................................................... 173
HttpServlet ............................................................................ 179
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HttpServletRequest ............................................................... 185
HttpServletRequestWrapper ................................................. 193
HttpServletResponse............................................................. 200
HttpServletResponseWrapper............................................... 212
HttpSession ........................................................................... 217
HttpSessionAttributesListener .............................................. 222
HttpSessionBindingEvent ..................................................... 224
HttpSessionBindingListener ................................................. 227
HttpSessionContext............................................................... 228
HttpSessionEvent .................................................................. 229
HttpSessionListener .............................................................. 231
HttpUtils................................................................................ 232
Appendix A: Deployment Descriptor Version 2.2............................ 236
Appendix B: Glossary........................................................................ 250

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