Spring Framework

org.springframework.web.filter
Class DelegatingFilterProxy

java.lang.Object
  extended by org.springframework.web.filter.GenericFilterBean
      extended by org.springframework.web.filter.DelegatingFilterProxy
All Implemented Interfaces:
javax.servlet.Filter, Aware, BeanNameAware, DisposableBean, InitializingBean, EnvironmentAware, ServletContextAware

public class DelegatingFilterProxy
extends GenericFilterBean

Proxy for a standard Servlet 2.3 Filter, delegating to a Spring-managed bean that implements the Filter interface. Supports a "targetBeanName" filter init-param in web.xml, specifying the name of the target bean in the Spring application context.

web.xml will usually contain a DelegatingFilterProxy definition, with the specified filter-name corresponding to a bean name in Spring's root application context. All calls to the filter proxy will then be delegated to that bean in the Spring context, which is required to implement the standard Servlet 2.3 Filter interface.

This approach is particularly useful for Filter implementation with complex setup needs, allowing to apply the full Spring bean definition machinery to Filter instances. Alternatively, consider standard Filter setup in combination with looking up service beans from the Spring root application context.

NOTE: The lifecycle methods defined by the Servlet Filter interface will by default not be delegated to the target bean, relying on the Spring application context to manage the lifecycle of that bean. Specifying the "targetFilterLifecycle" filter init-param as "true" will enforce invocation of the Filter.init and Filter.destroy lifecycle methods on the target bean, letting the servlet container manage the filter lifecycle.

As of Spring 3.1, DelegatingFilterProxy has been updated to optionally accept constructor parameters when using Servlet 3.0's instance-based filter registration methods, usually in conjunction with Spring 3.1's WebApplicationInitializer SPI. These constructors allow for providing the delegate Filter bean directly, or providing the application context and bean name to fetch, avoiding the need to look up the application context from the ServletContext.

This class was originally inspired by Spring Security's FilterToBeanProxy class, written by Ben Alex.

Since:
1.2
Author:
Juergen Hoeller, Sam Brannen, Chris Beams
See Also:
setTargetBeanName(java.lang.String), setTargetFilterLifecycle(boolean), Filter.doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain), Filter.init(javax.servlet.FilterConfig), Filter.destroy(), DelegatingFilterProxy(Filter), DelegatingFilterProxy(String), DelegatingFilterProxy(String, WebApplicationContext), ServletContext.addFilter(String, Filter), WebApplicationInitializer

Field Summary
 
Fields inherited from class org.springframework.web.filter.GenericFilterBean
logger
 
Constructor Summary
DelegatingFilterProxy()
          Create a new DelegatingFilterProxy.
DelegatingFilterProxy(javax.servlet.Filter delegate)
          Create a new DelegatingFilterProxy with the given Filter delegate.
DelegatingFilterProxy(java.lang.String targetBeanName)
          Create a new DelegatingFilterProxy that will retrieve the named target bean from the Spring WebApplicationContext found in the ServletContext (either the 'root' application context or the context named by setContextAttribute(java.lang.String)).
DelegatingFilterProxy(java.lang.String targetBeanName, WebApplicationContext wac)
          Create a new DelegatingFilterProxy that will retrieve the named target bean from the given Spring WebApplicationContext.
 
Method Summary
 void destroy()
          Subclasses may override this to perform custom filter shutdown.
protected  void destroyDelegate(javax.servlet.Filter delegate)
          Destroy the Filter delegate.
 void doFilter(javax.servlet.ServletRequest request, javax.servlet.ServletResponse response, javax.servlet.FilterChain filterChain)
           
protected  WebApplicationContext findWebApplicationContext()
          Return the WebApplicationContext passed in at construction time, if available.
 java.lang.String getContextAttribute()
          Return the name of the ServletContext attribute which should be used to retrieve the WebApplicationContext from which to load the delegate Filter bean.
protected  java.lang.String getTargetBeanName()
          Return the name of the target bean in the Spring application context.
protected  javax.servlet.Filter initDelegate(WebApplicationContext wac)
          Initialize the Filter delegate, defined as bean the given Spring application context.
protected  void initFilterBean()
          Subclasses may override this to perform custom initialization.
protected  void invokeDelegate(javax.servlet.Filter delegate, javax.servlet.ServletRequest request, javax.servlet.ServletResponse response, javax.servlet.FilterChain filterChain)
          Actually invoke the delegate Filter with the given request and response.
protected  boolean isTargetFilterLifecycle()
          Return whether to invoke the Filter.init and Filter.destroy lifecycle methods on the target bean.
 void setContextAttribute(java.lang.String contextAttribute)
          Set the name of the ServletContext attribute which should be used to retrieve the WebApplicationContext from which to load the delegate Filter bean.
 void setTargetBeanName(java.lang.String targetBeanName)
          Set the name of the target bean in the Spring application context.
 void setTargetFilterLifecycle(boolean targetFilterLifecycle)
          Set whether to invoke the Filter.init and Filter.destroy lifecycle methods on the target bean.
 
Methods inherited from class org.springframework.web.filter.GenericFilterBean
addRequiredProperty, afterPropertiesSet, getFilterConfig, getFilterName, getServletContext, init, initBeanWrapper, setBeanName, setEnvironment, setServletContext
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

DelegatingFilterProxy

public DelegatingFilterProxy()
Create a new DelegatingFilterProxy. For traditional (pre-Servlet 3.0) use in web.xml.

See Also:
setTargetBeanName(String)

DelegatingFilterProxy

public DelegatingFilterProxy(javax.servlet.Filter delegate)
Create a new DelegatingFilterProxy with the given Filter delegate. Bypasses entirely the need for interacting with a Spring application context, specifying the target bean name, etc.

For use in Servlet 3.0+ environments where instance-based registration of filters is supported.

Parameters:
delegate - the Filter instance that this proxy will delegate to and manage the lifecycle for (must not be null).
See Also:
doFilter(ServletRequest, ServletResponse, FilterChain), invokeDelegate(Filter, ServletRequest, ServletResponse, FilterChain), destroy(), GenericFilterBean.setEnvironment(org.springframework.core.env.Environment)

DelegatingFilterProxy

public DelegatingFilterProxy(java.lang.String targetBeanName)
Create a new DelegatingFilterProxy that will retrieve the named target bean from the Spring WebApplicationContext found in the ServletContext (either the 'root' application context or the context named by setContextAttribute(java.lang.String)).

For use in Servlet 3.0+ environments where instance-based registration of filters is supported.

The target bean must implement the standard Servlet Filter.

Parameters:
targetBeanName - name of the target filter bean to look up in the Spring application context (must not be null).
See Also:
findWebApplicationContext(), GenericFilterBean.setEnvironment(org.springframework.core.env.Environment)

DelegatingFilterProxy

public DelegatingFilterProxy(java.lang.String targetBeanName,
                             WebApplicationContext wac)
Create a new DelegatingFilterProxy that will retrieve the named target bean from the given Spring WebApplicationContext.

For use in Servlet 3.0+ environments where instance-based registration of filters is supported.

The target bean must implement the standard Servlet Filter interface.

The given WebApplicationContext may or may not be refreshed when passed in. If it has not, and if the context implements ConfigurableApplicationContext, a refresh() will be attempted before retrieving the named target bean.

This proxy's Environment will be inherited from the given WebApplicationContext.

Parameters:
targetBeanName - name of the target filter bean in the Spring application context (must not be null).
wac - the application context from which the target filter will be retrieved; if null, an application context will be looked up from ServletContext as a fallback.
See Also:
findWebApplicationContext(), GenericFilterBean.setEnvironment(org.springframework.core.env.Environment)
Method Detail

setContextAttribute

public void setContextAttribute(java.lang.String contextAttribute)
Set the name of the ServletContext attribute which should be used to retrieve the WebApplicationContext from which to load the delegate Filter bean.


getContextAttribute

public java.lang.String getContextAttribute()
Return the name of the ServletContext attribute which should be used to retrieve the WebApplicationContext from which to load the delegate Filter bean.


setTargetBeanName

public void setTargetBeanName(java.lang.String targetBeanName)
Set the name of the target bean in the Spring application context. The target bean must implement the standard Servlet 2.3 Filter interface.

By default, the filter-name as specified for the DelegatingFilterProxy in web.xml will be used.


getTargetBeanName

protected java.lang.String getTargetBeanName()
Return the name of the target bean in the Spring application context.


setTargetFilterLifecycle

public void setTargetFilterLifecycle(boolean targetFilterLifecycle)
Set whether to invoke the Filter.init and Filter.destroy lifecycle methods on the target bean.

Default is "false"; target beans usually rely on the Spring application context for managing their lifecycle. Setting this flag to "true" means that the servlet container will control the lifecycle of the target Filter, with this proxy delegating the corresponding calls.


isTargetFilterLifecycle

protected boolean isTargetFilterLifecycle()
Return whether to invoke the Filter.init and Filter.destroy lifecycle methods on the target bean.


initFilterBean

protected void initFilterBean()
                       throws javax.servlet.ServletException
Description copied from class: GenericFilterBean
Subclasses may override this to perform custom initialization. All bean properties of this filter will have been set before this method is invoked.

Note: This method will be called from standard filter initialization as well as filter bean initialization in a Spring application context. Filter name and ServletContext will be available in both cases.

This default implementation is empty.

Overrides:
initFilterBean in class GenericFilterBean
Throws:
javax.servlet.ServletException - if subclass initialization fails
See Also:
GenericFilterBean.getFilterName(), GenericFilterBean.getServletContext()

doFilter

public void doFilter(javax.servlet.ServletRequest request,
                     javax.servlet.ServletResponse response,
                     javax.servlet.FilterChain filterChain)
              throws javax.servlet.ServletException,
                     java.io.IOException
Throws:
javax.servlet.ServletException
java.io.IOException

destroy

public void destroy()
Description copied from class: GenericFilterBean
Subclasses may override this to perform custom filter shutdown.

Note: This method will be called from standard filter destruction as well as filter bean destruction in a Spring application context.

This default implementation is empty.

Specified by:
destroy in interface javax.servlet.Filter
Specified by:
destroy in interface DisposableBean
Overrides:
destroy in class GenericFilterBean

findWebApplicationContext

protected WebApplicationContext findWebApplicationContext()
Return the WebApplicationContext passed in at construction time, if available. Otherwise, attempt to retrieve a WebApplicationContext from the ServletContext attribute with the configured name if set. Otherwise look up a WebApplicationContext under the well-known "root" application context attribute. The WebApplicationContext must have already been loaded and stored in the ServletContext before this filter gets initialized (or invoked).

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

Returns:
the WebApplicationContext for this proxy, or null if not found
See Also:
DelegatingFilterProxy(String, WebApplicationContext), getContextAttribute(), WebApplicationContextUtils.getWebApplicationContext(javax.servlet.ServletContext), WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE

initDelegate

protected javax.servlet.Filter initDelegate(WebApplicationContext wac)
                                     throws javax.servlet.ServletException
Initialize the Filter delegate, defined as bean the given Spring application context.

The default implementation fetches the bean from the application context and calls the standard Filter.init method on it, passing in the FilterConfig of this Filter proxy.

Parameters:
wac - the root application context
Returns:
the initialized delegate Filter
Throws:
javax.servlet.ServletException - if thrown by the Filter
See Also:
getTargetBeanName(), isTargetFilterLifecycle(), GenericFilterBean.getFilterConfig(), Filter.init(javax.servlet.FilterConfig)

invokeDelegate

protected void invokeDelegate(javax.servlet.Filter delegate,
                              javax.servlet.ServletRequest request,
                              javax.servlet.ServletResponse response,
                              javax.servlet.FilterChain filterChain)
                       throws javax.servlet.ServletException,
                              java.io.IOException
Actually invoke the delegate Filter with the given request and response.

Parameters:
delegate - the delegate Filter
request - the current HTTP request
response - the current HTTP response
filterChain - the current FilterChain
Throws:
javax.servlet.ServletException - if thrown by the Filter
java.io.IOException - if thrown by the Filter

destroyDelegate

protected void destroyDelegate(javax.servlet.Filter delegate)
Destroy the Filter delegate. Default implementation simply calls Filter.destroy on it.

Parameters:
delegate - the Filter delegate (never null)
See Also:
isTargetFilterLifecycle(), Filter.destroy()

Spring Framework