org.springframework.web.filter.DelegatingFilterProxy Maven / Gradle / Ivy
/*
* Copyright 2002-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.web.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.util.Assert;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
/**
* Proxy for a standard Servlet Filter, delegating to a Spring-managed bean that
* implements the Filter interface. Supports a "targetBeanName" filter init-param
* in {@code web.xml}, specifying the name of the target bean in the Spring
* application context.
*
* {@code web.xml} will usually contain a {@code DelegatingFilterProxy} definition,
* with the specified {@code 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 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 {@code Filter.init} and {@code Filter.destroy} lifecycle methods
* on the target bean, letting the servlet container manage the filter lifecycle.
*
*
As of Spring 3.1, {@code 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
* {@link org.springframework.web.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 {@code FilterToBeanProxy}
* class, written by Ben Alex.
*
* @author Juergen Hoeller
* @author Sam Brannen
* @author Chris Beams
* @since 1.2
* @see #setTargetBeanName
* @see #setTargetFilterLifecycle
* @see javax.servlet.Filter#doFilter
* @see javax.servlet.Filter#init
* @see javax.servlet.Filter#destroy
* @see #DelegatingFilterProxy(Filter)
* @see #DelegatingFilterProxy(String)
* @see #DelegatingFilterProxy(String, WebApplicationContext)
* @see javax.servlet.ServletContext#addFilter(String, Filter)
* @see org.springframework.web.WebApplicationInitializer
*/
public class DelegatingFilterProxy extends GenericFilterBean {
private String contextAttribute;
private WebApplicationContext webApplicationContext;
private String targetBeanName;
private boolean targetFilterLifecycle = false;
private volatile Filter delegate;
private final Object delegateMonitor = new Object();
/**
* Create a new {@code DelegatingFilterProxy}. For traditional (pre-Servlet 3.0) use
* in {@code web.xml}.
* @see #setTargetBeanName(String)
*/
public DelegatingFilterProxy() {
}
/**
* Create a new {@code DelegatingFilterProxy} with the given {@link Filter} delegate.
* Bypasses entirely the need for interacting with a Spring application context,
* specifying the {@linkplain #setTargetBeanName target bean name}, etc.
*
For use in Servlet 3.0+ environments where instance-based registration of
* filters is supported.
* @param delegate the {@code Filter} instance that this proxy will delegate to and
* manage the lifecycle for (must not be {@code null}).
* @see #doFilter(ServletRequest, ServletResponse, FilterChain)
* @see #invokeDelegate(Filter, ServletRequest, ServletResponse, FilterChain)
* @see #destroy()
* @see #setEnvironment(org.springframework.core.env.Environment)
*/
public DelegatingFilterProxy(Filter delegate) {
Assert.notNull(delegate, "Delegate Filter must not be null");
this.delegate = delegate;
}
/**
* Create a new {@code DelegatingFilterProxy} that will retrieve the named target
* bean from the Spring {@code WebApplicationContext} found in the {@code ServletContext}
* (either the 'root' application context or the context named by
* {@link #setContextAttribute}).
*
For use in Servlet 3.0+ environments where instance-based registration of
* filters is supported.
*
The target bean must implement the standard Servlet Filter.
* @param targetBeanName name of the target filter bean to look up in the Spring
* application context (must not be {@code null}).
* @see #findWebApplicationContext()
* @see #setEnvironment(org.springframework.core.env.Environment)
*/
public DelegatingFilterProxy(String targetBeanName) {
this(targetBeanName, null);
}
/**
* Create a new {@code DelegatingFilterProxy} that will retrieve the named target
* bean from the given Spring {@code 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 {@code WebApplicationContext} may or may not be refreshed when passed
* in. If it has not, and if the context implements {@link ConfigurableApplicationContext},
* a {@link ConfigurableApplicationContext#refresh() refresh()} will be attempted before
* retrieving the named target bean.
*
This proxy's {@code Environment} will be inherited from the given
* {@code WebApplicationContext}.
* @param targetBeanName name of the target filter bean in the Spring application
* context (must not be {@code null}).
* @param wac the application context from which the target filter will be retrieved;
* if {@code null}, an application context will be looked up from {@code ServletContext}
* as a fallback.
* @see #findWebApplicationContext()
* @see #setEnvironment(org.springframework.core.env.Environment)
*/
public DelegatingFilterProxy(String targetBeanName, WebApplicationContext wac) {
Assert.hasText(targetBeanName, "Target Filter bean name must not be null or empty");
this.setTargetBeanName(targetBeanName);
this.webApplicationContext = wac;
if (wac != null) {
this.setEnvironment(wac.getEnvironment());
}
}
/**
* Set the name of the ServletContext attribute which should be used to retrieve the
* {@link WebApplicationContext} from which to load the delegate {@link Filter} bean.
*/
public void setContextAttribute(String contextAttribute) {
this.contextAttribute = contextAttribute;
}
/**
* Return the name of the ServletContext attribute which should be used to retrieve the
* {@link WebApplicationContext} from which to load the delegate {@link Filter} bean.
*/
public String getContextAttribute() {
return this.contextAttribute;
}
/**
* Set the name of the target bean in the Spring application context.
* The target bean must implement the standard Servlet Filter interface.
*
By default, the {@code filter-name} as specified for the
* DelegatingFilterProxy in {@code web.xml} will be used.
*/
public void setTargetBeanName(String targetBeanName) {
this.targetBeanName = targetBeanName;
}
/**
* Return the name of the target bean in the Spring application context.
*/
protected String getTargetBeanName() {
return this.targetBeanName;
}
/**
* Set whether to invoke the {@code Filter.init} and
* {@code 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.
*/
public void setTargetFilterLifecycle(boolean targetFilterLifecycle) {
this.targetFilterLifecycle = targetFilterLifecycle;
}
/**
* Return whether to invoke the {@code Filter.init} and
* {@code Filter.destroy} lifecycle methods on the target bean.
*/
protected boolean isTargetFilterLifecycle() {
return this.targetFilterLifecycle;
}
@Override
protected void initFilterBean() throws ServletException {
synchronized (this.delegateMonitor) {
if (this.delegate == null) {
// If no target bean name specified, use filter name.
if (this.targetBeanName == null) {
this.targetBeanName = getFilterName();
}
// Fetch Spring root application context and initialize the delegate early,
// if possible. If the root application context will be started after this
// filter proxy, we'll have to resort to lazy initialization.
WebApplicationContext wac = findWebApplicationContext();
if (wac != null) {
this.delegate = initDelegate(wac);
}
}
}
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
// Lazily initialize the delegate if necessary.
Filter delegateToUse = this.delegate;
if (delegateToUse == null) {
synchronized (this.delegateMonitor) {
delegateToUse = this.delegate;
if (delegateToUse == null) {
WebApplicationContext wac = findWebApplicationContext();
if (wac == null) {
throw new IllegalStateException("No WebApplicationContext found: " +
"no ContextLoaderListener or DispatcherServlet registered?");
}
delegateToUse = initDelegate(wac);
}
this.delegate = delegateToUse;
}
}
// Let the delegate perform the actual doFilter operation.
invokeDelegate(delegateToUse, request, response, filterChain);
}
@Override
public void destroy() {
Filter delegateToUse = this.delegate;
if (delegateToUse != null) {
destroyDelegate(delegateToUse);
}
}
/**
* Return the {@code WebApplicationContext} passed in at construction time, if available.
* Otherwise, attempt to retrieve a {@code WebApplicationContext} from the
* {@code ServletContext} attribute with the {@linkplain #setContextAttribute
* configured name} if set. Otherwise look up a {@code WebApplicationContext} under
* the well-known "root" application context attribute. The
* {@code WebApplicationContext} must have already been loaded and stored in the
* {@code ServletContext} before this filter gets initialized (or invoked).
*
Subclasses may override this method to provide a different
* {@code WebApplicationContext} retrieval strategy.
* @return the {@code WebApplicationContext} for this proxy, or {@code null} if not found
* @see #DelegatingFilterProxy(String, WebApplicationContext)
* @see #getContextAttribute()
* @see WebApplicationContextUtils#getWebApplicationContext(javax.servlet.ServletContext)
* @see WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE
*/
protected WebApplicationContext findWebApplicationContext() {
if (this.webApplicationContext != null) {
// The user has injected a context at construction time -> use it...
if (this.webApplicationContext instanceof ConfigurableApplicationContext) {
ConfigurableApplicationContext cac = (ConfigurableApplicationContext) this.webApplicationContext;
if (!cac.isActive()) {
// The context has not yet been refreshed -> do so before returning it...
cac.refresh();
}
}
return this.webApplicationContext;
}
String attrName = getContextAttribute();
if (attrName != null) {
return WebApplicationContextUtils.getWebApplicationContext(getServletContext(), attrName);
}
else {
return WebApplicationContextUtils.findWebApplicationContext(getServletContext());
}
}
/**
* 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 {@code Filter.init} method on it, passing
* in the FilterConfig of this Filter proxy.
* @param wac the root application context
* @return the initialized delegate Filter
* @throws ServletException if thrown by the Filter
* @see #getTargetBeanName()
* @see #isTargetFilterLifecycle()
* @see #getFilterConfig()
* @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
*/
protected Filter initDelegate(WebApplicationContext wac) throws ServletException {
Filter delegate = wac.getBean(getTargetBeanName(), Filter.class);
if (isTargetFilterLifecycle()) {
delegate.init(getFilterConfig());
}
return delegate;
}
/**
* Actually invoke the delegate Filter with the given request and response.
* @param delegate the delegate Filter
* @param request the current HTTP request
* @param response the current HTTP response
* @param filterChain the current FilterChain
* @throws ServletException if thrown by the Filter
* @throws IOException if thrown by the Filter
*/
protected void invokeDelegate(
Filter delegate, ServletRequest request, ServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
delegate.doFilter(request, response, filterChain);
}
/**
* Destroy the Filter delegate.
* Default implementation simply calls {@code Filter.destroy} on it.
* @param delegate the Filter delegate (never {@code null})
* @see #isTargetFilterLifecycle()
* @see javax.servlet.Filter#destroy()
*/
protected void destroyDelegate(Filter delegate) {
if (isTargetFilterLifecycle()) {
delegate.destroy();
}
}
}