public class

DelegatingFilterProxy

extends GenericFilterBean
java.lang.Object
   ↳ org.springframework.web.filter.GenericFilterBean
     ↳ org.springframework.web.filter.DelegatingFilterProxy

Class Overview

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.

This class is inspired by Acegi Security's FilterToBeanProxy class, written by Ben Alex.

See Also

Summary

[Expand]
Inherited Fields
From class org.springframework.web.filter.GenericFilterBean
Public Constructors
DelegatingFilterProxy()
Public Methods
void destroy()
Subclasses may override this to perform custom filter shutdown.
void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
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.
void setContextAttribute(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(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.
Protected Methods
void destroyDelegate(Filter delegate)
Destroy the Filter delegate.
WebApplicationContext findWebApplicationContext()
Retrieve a WebApplicationContext from the ServletContext attribute with the configured name.
String getTargetBeanName()
Return the name of the target bean in the Spring application context.
Filter initDelegate(WebApplicationContext wac)
Initialize the Filter delegate, defined as bean the given Spring application context.
void initFilterBean()
Subclasses may override this to perform custom initialization.
void invokeDelegate(Filter delegate, ServletRequest request, ServletResponse response, FilterChain filterChain)
Actually invoke the delegate Filter with the given request and response.
boolean isTargetFilterLifecycle()
Return whether to invoke the Filter.init and Filter.destroy lifecycle methods on the target bean.
[Expand]
Inherited Methods
From class org.springframework.web.filter.GenericFilterBean
From class java.lang.Object
From interface javax.servlet.Filter
From interface org.springframework.beans.factory.BeanNameAware
From interface org.springframework.beans.factory.DisposableBean
From interface org.springframework.beans.factory.InitializingBean
From interface org.springframework.context.EnvironmentAware
From interface org.springframework.web.context.ServletContextAware

Public Constructors

public DelegatingFilterProxy ()

Public Methods

public void destroy ()

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.

public void doFilter (ServletRequest request, ServletResponse response, FilterChain filterChain)

Throws
IOException
ServletException

public 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.

public void setContextAttribute (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.

public void setTargetBeanName (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.

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.

Protected Methods

protected void destroyDelegate (Filter delegate)

Destroy the Filter delegate. Default implementation simply calls Filter.destroy on it.

Parameters
delegate the Filter delegate (never null)
See Also

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 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

protected String getTargetBeanName ()

Return the name of the target bean in the Spring application context.

protected Filter initDelegate (WebApplicationContext wac)

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
ServletException if thrown by the Filter
See Also

protected void initFilterBean ()

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.

Throws
ServletException

protected void invokeDelegate (Filter delegate, ServletRequest request, ServletResponse response, FilterChain filterChain)

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
ServletException if thrown by the Filter
IOException if thrown by the Filter

protected boolean isTargetFilterLifecycle ()

Return whether to invoke the Filter.init and Filter.destroy lifecycle methods on the target bean.