org.springframework.web.servlet
Class DispatcherServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          org.springframework.web.servlet.HttpServletBean
              org.springframework.web.servlet.FrameworkServlet
                  org.springframework.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 web MVC framework. Dispatches to registered handlers for processing a web request.

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. Default is SimpleControllerHandlerAdapter; additional HandlerAdapter objects can be added through the application context. Like HandlerMappings, HandlerAdapters can be given any bean name (tested by type).
• Its view resolution strategy can be specified via a ViewResolver implementation. Standard implementations support mapping URLs to bean names, and explicit mappings. The ViewResolver bean name is "viewResolver"; default is InternalResourceViewResolver.
• Its strategy for resolving multipart requests is determined by a MultipartResolver implementation. Implementations for Jakarta Commons FileUpload and Jason Hunter's COS are included. The MultipartResolver bean name is "multipartResolver"; default is none.
• Its locale resolution strategy is determined by a LocaleResolver implementation. Out-of-the-box implementations work via HTTP accept header, cookie, or session. The LocaleResolver bean name is "localeResolver"; default is AcceptHeaderLocaleResolver.
• Its theme resolution strategy is determined by a ThemeResolver implementation. Implementations for a fixed theme and for cookie and session storage are included. The ThemeResolver bean name is "themeResolver"; default is FixedThemeResolver.

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

Version:

$Id: DispatcherServlet.java,v 1.29 2004/03/18 02:46:07 trisberg Exp $

Author:

Rod Johnson, Juergen Hoeller

See Also:

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

Field Summary

static java.lang.String	EXCEPTION_RESOLVER_BEAN_NAME Well-known name for the ExceptionResolver object in the bean factory for this namespace.
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	MULTIPART_RESOLVER_ATTRIBUTE Request attribute to hold current multipart resolver, retrievable by views/binders.
static java.lang.String	MULTIPART_RESOLVER_BEAN_NAME Well-known name for the MultipartResolver object in the bean factory for this namespace.
protected org.apache.commons.logging.Log	pageNotFoundLogger Additional logger for use when no mapping handlers are found for a request.
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 org.springframework.web.servlet.FrameworkServlet

DEFAULT_CONTEXT_CLASS, DEFAULT_NAMESPACE_SUFFIX, SERVLET_CONTEXT_PREFIX

Fields inherited from class org.springframework.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 long	getLastModified(javax.servlet.http.HttpServletRequest request) Override HttpServlet's getLastModified to evaluate the Last-Modified value of the mapped handler.
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 org.springframework.web.servlet.FrameworkServlet

createWebApplicationContext, destroy, doGet, doPost, getContextClass, getContextConfigLocation, getNamespace, getServletContextAttributeName, getWebApplicationContext, initServletBean, initWebApplicationContext, isPublishContext, setContextClass, setContextConfigLocation, setNamespace, setPublishContext

Methods inherited from class org.springframework.web.servlet.HttpServletBean

init, setRequiredProperty

Methods inherited from class javax.servlet.http.HttpServlet

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

Methods inherited from class javax.servlet.GenericServlet

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

MULTIPART_RESOLVER_BEAN_NAME

public static final java.lang.String MULTIPART_RESOLVER_BEAN_NAME

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

See Also:

Constant Field Values

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.

See Also:

Constant Field Values

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.

See Also:

Constant Field Values

EXCEPTION_RESOLVER_BEAN_NAME

public static final java.lang.String EXCEPTION_RESOLVER_BEAN_NAME

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

See Also:

Constant Field Values

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.

See Also:

Constant Field Values

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

MULTIPART_RESOLVER_ATTRIBUTE

public static final java.lang.String MULTIPART_RESOLVER_ATTRIBUTE

Request attribute to hold current multipart resolver, retrievable by views/binders.

See Also:

RequestContextUtils

THEME_RESOLVER_ATTRIBUTE

public static final java.lang.String THEME_RESOLVER_ATTRIBUTE

Request attribute to hold current theme, retrievable by views.

See Also:

RequestContext

pageNotFoundLogger

protected final org.apache.commons.logging.Log pageNotFoundLogger

Additional logger for use when no mapping handlers are found for a request.

Constructor Detail

DispatcherServlet

public DispatcherServlet()

Method Detail

initFrameworkServlet

protected void initFrameworkServlet()
                             throws javax.servlet.ServletException,
                                    BeansException

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

Throws:

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

BeansException - if thrown by ApplicationContext methods

doService

protected void doService(javax.servlet.http.HttpServletRequest request,
                         javax.servlet.http.HttpServletResponse response)
                  throws java.lang.Exception

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.

Specified by:

doService in class FrameworkServlet

Throws:

java.lang.Exception - in case of any kind of processing failure

See Also:

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

getLastModified

protected long getLastModified(javax.servlet.http.HttpServletRequest request)

Override HttpServlet's getLastModified to evaluate the Last-Modified value of the mapped handler.