org.springframework.web.servlet
Class FrameworkServlet

java.lang.Object
  extended by javax.servlet.GenericServlet
      extended by javax.servlet.http.HttpServlet
          extended by org.springframework.web.servlet.HttpServletBean
              extended by org.springframework.web.servlet.FrameworkServlet
All Implemented Interfaces:
Serializable, Servlet, ServletConfig, Aware, EnvironmentAware
Direct Known Subclasses:
DispatcherServlet

public abstract class FrameworkServlet
extends HttpServletBean

Base servlet for Spring's web framework. Provides integration with a Spring application context, in a JavaBean-based overall solution.

This class offers the following functionality:

Subclasses must implement doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) to handle requests. Because this extends HttpServletBean rather than HttpServlet directly, bean properties are automatically mapped onto it. Subclasses can override initFrameworkServlet() for custom initialization.

Detects a "contextClass" parameter at the servlet init-param level, falling back to the default context class, XmlWebApplicationContext, if not found. Note that, with the default FrameworkServlet, a custom context class needs to implement the ConfigurableWebApplicationContext SPI.

Passes a "contextConfigLocation" servlet init-param to the context instance, parsing it into potentially multiple file paths which can be separated by any number of commas and spaces, like "test-servlet.xml, myServlet.xml". If not explicitly specified, the context implementation is supposed to build a default location from the namespace of the servlet.

Note: In case of multiple config locations, later bean definitions will override ones defined in earlier loaded files, at least when using Spring's default ApplicationContext implementation. This can be leveraged to deliberately override certain bean definitions via an extra XML file.

The default namespace is "'servlet-name'-servlet", e.g. "test-servlet" for a servlet-name "test" (leading to a "/WEB-INF/test-servlet.xml" default location with XmlWebApplicationContext). The namespace can also be set explicitly via the "namespace" servlet init-param.

Author:
Rod Johnson, Juergen Hoeller, Sam Brannen
See Also:
doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), setContextClass(java.lang.Class), setContextConfigLocation(java.lang.String), setNamespace(java.lang.String), Serialized Form

Field Summary
static Class DEFAULT_CONTEXT_CLASS
          Default context class for FrameworkServlet.
static String DEFAULT_NAMESPACE_SUFFIX
          Suffix for WebApplicationContext namespaces.
static String SERVLET_CONTEXT_PREFIX
          Prefix for the ServletContext attribute for the WebApplicationContext.
 
Fields inherited from class org.springframework.web.servlet.HttpServletBean
logger
 
Constructor Summary
FrameworkServlet()
           
 
Method Summary
protected  LocaleContext buildLocaleContext(HttpServletRequest request)
          Build a LocaleContext for the given request, exposing the request's primary locale as current locale.
protected  WebApplicationContext createWebApplicationContext(ApplicationContext parent)
          Instantiate the WebApplicationContext for this servlet, either a default XmlWebApplicationContext or a custom context class, if set.
protected  WebApplicationContext createWebApplicationContext(WebApplicationContext parent)
          Instantiate the WebApplicationContext for this servlet, either a default XmlWebApplicationContext or a custom context class, if set.
 void destroy()
          Close the WebApplicationContext of this servlet.
protected  void doDelete(HttpServletRequest request, HttpServletResponse response)
          Delegate DELETE requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse).
protected  void doGet(HttpServletRequest request, HttpServletResponse response)
          Delegate GET requests to processRequest/doService.
protected  void doOptions(HttpServletRequest request, HttpServletResponse response)
          Delegate OPTIONS requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), if desired.
protected  void doPost(HttpServletRequest request, HttpServletResponse response)
          Delegate POST requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse).
protected  void doPut(HttpServletRequest request, HttpServletResponse response)
          Delegate PUT requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse).
protected abstract  void doService(HttpServletRequest request, HttpServletResponse response)
          Subclasses must implement this method to do the work of request handling, receiving a centralized callback for GET, POST, PUT and DELETE.
protected  void doTrace(HttpServletRequest request, HttpServletResponse response)
          Delegate TRACE requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), if desired.
protected  WebApplicationContext findWebApplicationContext()
          Retrieve a WebApplicationContext from the ServletContext attribute with the configured name.
 String getContextAttribute()
          Return the name of the ServletContext attribute which should be used to retrieve the WebApplicationContext that this servlet is supposed to use.
 Class getContextClass()
          Return the custom context class.
 String getContextConfigLocation()
          Return the explicit context config location, if any.
 String getNamespace()
          Return the namespace for this servlet, falling back to default scheme if no custom namespace was set: e.g.
 String getServletContextAttributeName()
          Return the ServletContext attribute name for this servlet's WebApplicationContext.
protected  String getUsernameForRequest(HttpServletRequest request)
          Determine the username for the given request.
 WebApplicationContext getWebApplicationContext()
          Return this servlet's WebApplicationContext.
protected  void initFrameworkServlet()
          This method will be invoked after any bean properties have been set and the WebApplicationContext has been loaded.
protected  void initServletBean()
          Overridden method of HttpServletBean, invoked after any bean properties have been set.
protected  WebApplicationContext initWebApplicationContext()
          Initialize and publish the WebApplicationContext for this servlet.
 void onApplicationEvent(ContextRefreshedEvent event)
          Callback that receives refresh events from this servlet's WebApplicationContext.
protected  void onRefresh(ApplicationContext context)
          Template method which can be overridden to add servlet-specific refresh work.
protected  void postProcessWebApplicationContext(ConfigurableWebApplicationContext wac)
          Post-process the given WebApplicationContext before it is refreshed and activated as context for this servlet.
protected  void processRequest(HttpServletRequest request, HttpServletResponse response)
          Process this request, publishing an event regardless of the outcome.
 void refresh()
          Refresh this servlet's application context, as well as the dependent state of the servlet.
 void setContextAttribute(String contextAttribute)
          Set the name of the ServletContext attribute which should be used to retrieve the WebApplicationContext that this servlet is supposed to use.
 void setContextClass(Class contextClass)
          Set a custom context class.
 void setContextConfigLocation(String contextConfigLocation)
          Set the context config location explicitly, instead of relying on the default location built from the namespace.
 void setDispatchOptionsRequest(boolean dispatchOptionsRequest)
          Set whether this servlet should dispatch an HTTP OPTIONS request to the doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) method.
 void setDispatchTraceRequest(boolean dispatchTraceRequest)
          Set whether this servlet should dispatch an HTTP TRACE request to the doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) method.
 void setNamespace(String namespace)
          Set a custom namespace for this servlet, to be used for building a default context config location.
 void setPublishContext(boolean publishContext)
          Set whether to publish this servlet's context as a ServletContext attribute, available to all objects in the web container.
 void setPublishEvents(boolean publishEvents)
          Set whether this servlet should publish a ServletRequestHandledEvent at the end of each request.
 void setThreadContextInheritable(boolean threadContextInheritable)
          Set whether to expose the LocaleContext and RequestAttributes as inheritable for child threads (using an InheritableThreadLocal).
 
Methods inherited from class org.springframework.web.servlet.HttpServletBean
addRequiredProperty, getServletContext, getServletName, init, initBeanWrapper, setEnvironment
 
Methods inherited from class javax.servlet.http.HttpServlet
doHead, getLastModified, service, service
 
Methods inherited from class javax.servlet.GenericServlet
getInitParameter, getInitParameterNames, getServletConfig, getServletInfo, init, log, log
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

DEFAULT_NAMESPACE_SUFFIX

public static final String DEFAULT_NAMESPACE_SUFFIX
Suffix for WebApplicationContext namespaces. If a servlet of this class is given the name "test" in a context, the namespace used by the servlet will resolve to "test-servlet".

See Also:
Constant Field Values

DEFAULT_CONTEXT_CLASS

public static final Class DEFAULT_CONTEXT_CLASS
Default context class for FrameworkServlet.

See Also:
XmlWebApplicationContext

SERVLET_CONTEXT_PREFIX

public static final String SERVLET_CONTEXT_PREFIX
Prefix for the ServletContext attribute for the WebApplicationContext. The completion is the servlet name.

Constructor Detail

FrameworkServlet

public FrameworkServlet()
Method Detail

setContextAttribute

public void setContextAttribute(String contextAttribute)
Set the name of the ServletContext attribute which should be used to retrieve the WebApplicationContext that this servlet is supposed to use.


getContextAttribute

public String getContextAttribute()
Return the name of the ServletContext attribute which should be used to retrieve the WebApplicationContext that this servlet is supposed to use.


setContextClass

public void setContextClass(Class contextClass)
Set a custom context class. This class must be of type WebApplicationContext.

When using the default FrameworkServlet implementation, the context class must also implement the ConfigurableWebApplicationContext interface.

See Also:
createWebApplicationContext(org.springframework.context.ApplicationContext)

getContextClass

public Class getContextClass()
Return the custom context class.


setNamespace

public void setNamespace(String namespace)
Set a custom namespace for this servlet, to be used for building a default context config location.


getNamespace

public String getNamespace()
Return the namespace for this servlet, falling back to default scheme if no custom namespace was set: e.g. "test-servlet" for a servlet named "test".


setContextConfigLocation

public void setContextConfigLocation(String contextConfigLocation)
Set the context config location explicitly, instead of relying on the default location built from the namespace. This location string can consist of multiple locations separated by any number of commas and spaces.


getContextConfigLocation

public String getContextConfigLocation()
Return the explicit context config location, if any.


setPublishContext

public void setPublishContext(boolean publishContext)
Set whether to publish this servlet's context as a ServletContext attribute, available to all objects in the web container. Default is "true".

This is especially handy during testing, although it is debatable whether it's good practice to let other application objects access the context this way.


setPublishEvents

public void setPublishEvents(boolean publishEvents)
Set whether this servlet should publish a ServletRequestHandledEvent at the end of each request. Default is "true"; can be turned off for a slight performance improvement, provided that no ApplicationListeners rely on such events.

See Also:
ServletRequestHandledEvent

setThreadContextInheritable

public void setThreadContextInheritable(boolean threadContextInheritable)
Set whether to expose the LocaleContext and RequestAttributes as inheritable for child threads (using an InheritableThreadLocal).

Default is "false", to avoid side effects on spawned background threads. Switch this to "true" to enable inheritance for custom child threads which are spawned during request processing and only used for this request (that is, ending after their initial task, without reuse of the thread).

WARNING: Do not use inheritance for child threads if you are accessing a thread pool which is configured to potentially add new threads on demand (e.g. a JDK ThreadPoolExecutor), since this will expose the inherited context to such a pooled thread.


setDispatchOptionsRequest

public void setDispatchOptionsRequest(boolean dispatchOptionsRequest)
Set whether this servlet should dispatch an HTTP OPTIONS request to the doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) method.

Default is "false", applying HttpServlet's default behavior (i.e. enumerating all standard HTTP request methods as a response to the OPTIONS request).

Turn this flag on if you prefer OPTIONS requests to go through the regular dispatching chain, just like other HTTP requests. This usually means that your controllers will receive those requests; make sure that those endpoints are actually able to handle an OPTIONS request.

Note that HttpServlet's default OPTIONS processing will be applied in any case. Your controllers are simply available to override the default headers and optionally generate a response body.


setDispatchTraceRequest

public void setDispatchTraceRequest(boolean dispatchTraceRequest)
Set whether this servlet should dispatch an HTTP TRACE request to the doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) method.

Default is "false", applying HttpServlet's default behavior (i.e. reflecting the message received back to the client).

Turn this flag on if you prefer TRACE requests to go through the regular dispatching chain, just like other HTTP requests. This usually means that your controllers will receive those requests; make sure that those endpoints are actually able to handle a TRACE request.

Note that HttpServlet's default TRACE processing will be applied in any case. Your controllers are simply available to override the default headers and the default body, calling response.reset() if necessary.


initServletBean

protected final void initServletBean()
                              throws ServletException
Overridden method of HttpServletBean, invoked after any bean properties have been set. Creates this servlet's WebApplicationContext.

Overrides:
initServletBean in class HttpServletBean
Throws:
ServletException - if subclass initialization fails

initWebApplicationContext

protected WebApplicationContext initWebApplicationContext()
Initialize and publish the WebApplicationContext for this servlet.

Delegates to createWebApplicationContext(org.springframework.context.ApplicationContext) for actual creation of the context. Can be overridden in subclasses.

Returns:
the WebApplicationContext instance
See Also:
setContextClass(java.lang.Class), setContextConfigLocation(java.lang.String)

findWebApplicationContext

protected WebApplicationContext findWebApplicationContext()
Retrieve a WebApplicationContext from the ServletContext attribute with the configured name. The WebApplicationContext must have already been loaded and stored in the ServletContext before this servlet gets initialized (or invoked).

Subclasses may override this method to provide a different WebApplicationContext retrieval strategy.

Returns:
the WebApplicationContext for this servlet, or null if not found
See Also:
getContextAttribute()

createWebApplicationContext

protected WebApplicationContext createWebApplicationContext(ApplicationContext parent)
Instantiate the WebApplicationContext for this servlet, either a default XmlWebApplicationContext or a custom context class, if set.

This implementation expects custom contexts to implement the ConfigurableWebApplicationContext interface. Can be overridden in subclasses.

Do not forget to register this servlet instance as application listener on the created context (for triggering its callback, and to call ConfigurableApplicationContext.refresh() before returning the context instance.

Parameters:
parent - the parent ApplicationContext to use, or null if none
Returns:
the WebApplicationContext for this servlet
See Also:
XmlWebApplicationContext

createWebApplicationContext

protected WebApplicationContext createWebApplicationContext(WebApplicationContext parent)
Instantiate the WebApplicationContext for this servlet, either a default XmlWebApplicationContext or a custom context class, if set. Delegates to #createWebApplicationContext(ApplicationContext).

Parameters:
parent - the parent WebApplicationContext to use, or null if none
Returns:
the WebApplicationContext for this servlet
See Also:
XmlWebApplicationContext, createWebApplicationContext(ApplicationContext)

postProcessWebApplicationContext

protected void postProcessWebApplicationContext(ConfigurableWebApplicationContext wac)
Post-process the given WebApplicationContext before it is refreshed and activated as context for this servlet.

The default implementation is empty. refresh() will be called automatically after this method returns.

Parameters:
wac - the configured WebApplicationContext (not refreshed yet)
See Also:
createWebApplicationContext(org.springframework.context.ApplicationContext), ConfigurableApplicationContext.refresh()

getServletContextAttributeName

public String getServletContextAttributeName()
Return the ServletContext attribute name for this servlet's WebApplicationContext.

The default implementation returns SERVLET_CONTEXT_PREFIX + servlet name.

See Also:
SERVLET_CONTEXT_PREFIX, HttpServletBean.getServletName()

getWebApplicationContext

public final WebApplicationContext getWebApplicationContext()
Return this servlet's WebApplicationContext.


initFrameworkServlet

protected void initFrameworkServlet()
                             throws ServletException
This method will be invoked after any bean properties have been set and the WebApplicationContext has been loaded. The default implementation is empty; subclasses may override this method to perform any initialization they require.

Throws:
ServletException - in case of an initialization exception

refresh

public void refresh()
Refresh this servlet's application context, as well as the dependent state of the servlet.

See Also:
getWebApplicationContext(), ConfigurableApplicationContext.refresh()

onApplicationEvent

public void onApplicationEvent(ContextRefreshedEvent event)
Callback that receives refresh events from this servlet's WebApplicationContext.

The default implementation calls onRefresh(org.springframework.context.ApplicationContext), triggering a refresh of this servlet's context-dependent state.

Parameters:
event - the incoming ApplicationContext event

onRefresh

protected void onRefresh(ApplicationContext context)
Template method which can be overridden to add servlet-specific refresh work. Called after successful context refresh.

This implementation is empty.

Parameters:
context - the current WebApplicationContext
See Also:
refresh()

doGet

protected final void doGet(HttpServletRequest request,
                           HttpServletResponse response)
                    throws ServletException,
                           IOException
Delegate GET requests to processRequest/doService.

Will also be invoked by HttpServlet's default implementation of doHead, with a NoBodyResponse that just captures the content length.

Overrides:
doGet in class HttpServlet
Throws:
ServletException
IOException
See Also:
doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), HttpServlet.doHead(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)

doPost

protected final void doPost(HttpServletRequest request,
                            HttpServletResponse response)
                     throws ServletException,
                            IOException
Delegate POST requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse).

Overrides:
doPost in class HttpServlet
Throws:
ServletException
IOException
See Also:
doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)

doPut

protected final void doPut(HttpServletRequest request,
                           HttpServletResponse response)
                    throws ServletException,
                           IOException
Delegate PUT requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse).

Overrides:
doPut in class HttpServlet
Throws:
ServletException
IOException
See Also:
doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)

doDelete

protected final void doDelete(HttpServletRequest request,
                              HttpServletResponse response)
                       throws ServletException,
                              IOException
Delegate DELETE requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse).

Overrides:
doDelete in class HttpServlet
Throws:
ServletException
IOException
See Also:
doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)

doOptions

protected void doOptions(HttpServletRequest request,
                         HttpServletResponse response)
                  throws ServletException,
                         IOException
Delegate OPTIONS requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), if desired.

Applies HttpServlet's standard OPTIONS processing first.

Overrides:
doOptions in class HttpServlet
Throws:
ServletException
IOException
See Also:
doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)

doTrace

protected void doTrace(HttpServletRequest request,
                       HttpServletResponse response)
                throws ServletException,
                       IOException
Delegate TRACE requests to processRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), if desired.

Applies HttpServlet's standard TRACE processing first.

Overrides:
doTrace in class HttpServlet
Throws:
ServletException
IOException
See Also:
doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)

processRequest

protected final void processRequest(HttpServletRequest request,
                                    HttpServletResponse response)
                             throws ServletException,
                                    IOException
Process this request, publishing an event regardless of the outcome.

The actual event handling is performed by the abstract doService(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) template method.

Throws:
ServletException
IOException

buildLocaleContext

protected LocaleContext buildLocaleContext(HttpServletRequest request)
Build a LocaleContext for the given request, exposing the request's primary locale as current locale.

Parameters:
request - current HTTP request
Returns:
the corresponding LocaleContext

getUsernameForRequest

protected String getUsernameForRequest(HttpServletRequest request)
Determine the username for the given request.

The default implementation takes the name of the UserPrincipal, if any. Can be overridden in subclasses.

Parameters:
request - current HTTP request
Returns:
the username, or null if none found
See Also:
HttpServletRequest.getUserPrincipal()

doService

protected abstract void doService(HttpServletRequest request,
                                  HttpServletResponse response)
                           throws Exception
Subclasses must implement this method to do the work of request handling, receiving a centralized callback for GET, POST, PUT and DELETE.

The contract is essentially the same as that for the commonly overridden doGet or doPost methods of HttpServlet.

This class intercepts calls to ensure that exception handling and event publication takes place.

Parameters:
request - current HTTP request
response - current HTTP response
Throws:
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)

destroy

public void destroy()
Close the WebApplicationContext of this servlet.

Specified by:
destroy in interface Servlet
Overrides:
destroy in class GenericServlet
See Also:
ConfigurableApplicationContext.close()