com.interface21.web.servlet
Class DispatcherServlet

java.lang.Object
  |
  +--javax.servlet.GenericServlet
        |
        +--javax.servlet.http.HttpServlet
              |
              +--com.interface21.web.servlet.HttpServletBean
                    |
                    +--com.interface21.web.servlet.FrameworkServlet
                          |
                          +--com.interface21.web.servlet.DispatcherServlet

All Implemented Interfaces:

java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

public class DispatcherServlet

extends FrameworkServlet

Concrete front controller for use within the Interface21 MVC framework.
This class and the MVC approach it delivers is discussed in Chapter 12 of Expert One-On-One J2EE Design and Development by Rod Johnson (Wrox, 2002).

This servlet is very flexible: It can be used with just about any workflow, with the installation of the appropriate adapter classes.

It offers the following functionality that distinguishes it from other MVC frameworks:

• It is based around a JavaBeans configuration mechanism.
• It can use any HandlerMapping implementation - whether standard, or provided as part of an application - to control the routing of requests to handler objects. Additional HandlerMapping objects can be added through defining beans in the servlet's application context that implement the HandlerMapping interface in this package. HandlerMappings can be given any bean name (they are tested by type).
• It can use any HandlerAdapter (additional HandlerAdapter objects can be added through the application context).
• Its view resoltion strategy can be specified via a ViewResolver implementation. Standard implementations support mapping URLs to bean names, and explicit mappings.
• Its locale resolution strategy is determined by a LocaleResolver implementation. Standard implementations work via HTTP accept header, cookie, or session.

A web application can use any number of controller servlets. Each servlet will operate in its own namespace. Only the default name space, and any config objects set for the application as a whole, will be shared.

Version:

$Revision: 1.3 $

Author:

Rod Johnson, Juergen Hoeller

See Also:

HandlerMapping, HandlerAdapter, ViewResolver, LocaleResolver, WebApplicationContext, ContextLoaderListener, Serialized Form

Field Summary

static java.lang.String	LOCALE_RESOLVER_ATTRIBUTE Request attribute to hold current locale, retrievable by views.
static java.lang.String	LOCALE_RESOLVER_BEAN_NAME Well-known name for the LocaleResolver object in the bean factory for this namespace.
static java.lang.String	THEME_RESOLVER_ATTRIBUTE Request attribute to hold current theme, retrievable by views.
static java.lang.String	THEME_RESOLVER_BEAN_NAME Well-known name for the ThemeResolver object in the bean factory for this namespace.
static java.lang.String	VIEW_RESOLVER_BEAN_NAME Well-known name for the ViewResolver object in the bean factory for this namespace.
static java.lang.String	WEB_APPLICATION_CONTEXT_ATTRIBUTE Request attribute to hold current web application context.

Fields inherited from class com.interface21.web.servlet.FrameworkServlet

DEFAULT_NAMESPACE_SUFFIX, SERVLET_CONTEXT_PREFIX

Fields inherited from class com.interface21.web.servlet.HttpServletBean

logger

Constructor Summary

DispatcherServlet()

Method Summary

protected void	doService(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Obtain and use the handler for this method.
protected void	initFrameworkServlet() Overridden method, invoked after any bean properties have been set and the WebApplicationContext and BeanFactory for this namespace is available.

Methods inherited from class com.interface21.web.servlet.FrameworkServlet

doGet, doPost, getNamespace, getServletContextAttributeName, getWebApplicationContext, initServletBean, setContextClass, setNamespace, setPublishContext

Methods inherited from class com.interface21.web.servlet.HttpServletBean

addRequiredProperty, getIdentifier, init

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LOCALE_RESOLVER_BEAN_NAME

public static final java.lang.String LOCALE_RESOLVER_BEAN_NAME

Well-known name for the LocaleResolver object in the bean factory for this namespace.

VIEW_RESOLVER_BEAN_NAME

public static final java.lang.String VIEW_RESOLVER_BEAN_NAME

Well-known name for the ViewResolver object in the bean factory for this namespace.

THEME_RESOLVER_BEAN_NAME

public static final java.lang.String THEME_RESOLVER_BEAN_NAME

Well-known name for the ThemeResolver object in the bean factory for this namespace.

WEB_APPLICATION_CONTEXT_ATTRIBUTE

public static final java.lang.String WEB_APPLICATION_CONTEXT_ATTRIBUTE

Request attribute to hold current web application context. Otherwise only the global web app context is obtainable by tags etc.

LOCALE_RESOLVER_ATTRIBUTE

public static final java.lang.String LOCALE_RESOLVER_ATTRIBUTE

Request attribute to hold current locale, retrievable by views.

See Also:

RequestContext

THEME_RESOLVER_ATTRIBUTE

public static final java.lang.String THEME_RESOLVER_ATTRIBUTE

Request attribute to hold current theme, retrievable by views.

See Also:

RequestContext

Constructor Detail

DispatcherServlet

public DispatcherServlet()

Method Detail

initFrameworkServlet

protected void initFrameworkServlet()
                             throws javax.servlet.ServletException

Overridden method, invoked after any bean properties have been set and the WebApplicationContext and BeanFactory for this namespace is available.

Loads HandlerMapping and HandlerAdapter objects, and configures a ViewResolver and a LocaleResolver.

Overrides:

initFrameworkServlet in class FrameworkServlet

Following copied from class: com.interface21.web.servlet.FrameworkServlet

Throws:

javax.servlet.ServletException - in case of an initialization exception

doService

protected void doService(javax.servlet.http.HttpServletRequest request,
                         javax.servlet.http.HttpServletResponse response)
                  throws javax.servlet.ServletException,
                         java.io.IOException

Obtain and use the handler for this method. The handler will be obtained by applying the servlet's HandlerMappings in order. The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters to find the first that supports the handler class. Both doGet() and doPost() are handled by this method. It's up to HandlerAdapters to decide which methods are acceptable.

Overrides:

doService in class FrameworkServlet

Following copied from class: com.interface21.web.servlet.FrameworkServlet

See Also:

HttpServlet.doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)