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/**
* Copyright (C) 2008 Google Inc.
*
* 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
*
* http://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 com.google.inject.servlet;
import com.google.inject.Binding;
import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.Provider;
import com.google.inject.Singleton;
import com.google.inject.TypeLiteral;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import java.io.IOException;
import java.util.List;
import java.util.Set;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
/**
* Central routing/dispatch class handles lifecycle of managed filters, and delegates to the servlet
* pipeline.
*
* @author dhanji@gmail.com (Dhanji R. Prasanna)
*/
@Singleton
class ManagedFilterPipeline implements FilterPipeline{
private final FilterDefinition[] filterDefinitions;
private final ManagedServletPipeline servletPipeline;
private final Provider<ServletContext> servletContext;
//Unfortunately, we need the injector itself in order to create filters + servlets
private final Injector injector;
//Guards a DCL, so needs to be volatile
private volatile boolean initialized = false;
private static final TypeLiteral<FilterDefinition> FILTER_DEFS =
TypeLiteral.get(FilterDefinition.class);
@Inject
public ManagedFilterPipeline(Injector injector, ManagedServletPipeline servletPipeline,
Provider<ServletContext> servletContext) {
this.injector = injector;
this.servletPipeline = servletPipeline;
this.servletContext = servletContext;
this.filterDefinitions = collectFilterDefinitions(injector);
}
/**
* Introspects the injector and collects all instances of bound {@code List<FilterDefinition>}
* into a master list.
*
* We have a guarantee that {@link com.google.inject.Injector#getBindings()} returns a map
* that preserves insertion order in entry-set iterators.
*/
private FilterDefinition[] collectFilterDefinitions(Injector injector) {
List<FilterDefinition> filterDefinitions = Lists.newArrayList();
for (Binding<FilterDefinition> entry : injector.findBindingsByType(FILTER_DEFS)) {
filterDefinitions.add(entry.getProvider().get());
}
// Convert to a fixed size array for speed.
return filterDefinitions.toArray(new FilterDefinition[filterDefinitions.size()]);
}
public synchronized void initPipeline(ServletContext servletContext)
throws ServletException {
//double-checked lock, prevents duplicate initialization
if (initialized)
return;
// Used to prevent duplicate initialization.
Set<Filter> initializedSoFar = Sets.newSetFromMap(Maps.<Filter, Boolean>newIdentityHashMap());
for (FilterDefinition filterDefinition : filterDefinitions) {
filterDefinition.init(servletContext, injector, initializedSoFar);
}
//next, initialize servlets...
servletPipeline.init(servletContext, injector);
//everything was ok...
initialized = true;
}
public void dispatch(ServletRequest request, ServletResponse response,
FilterChain proceedingFilterChain) throws IOException, ServletException {
//lazy init of filter pipeline (OK by the servlet specification). This is needed
//in order for us not to force users to create a GuiceServletContextListener subclass.
if (!initialized) {
initPipeline(servletContext.get());
}
//obtain the servlet pipeline to dispatch against
new FilterChainInvocation(filterDefinitions, servletPipeline, proceedingFilterChain)
.doFilter(withDispatcher(request, servletPipeline), response);
}
/**
* Used to create an proxy that dispatches either to the guice-servlet pipeline or the regular
* pipeline based on uri-path match. This proxy also provides minimal forwarding support.
*
* We cannot forward from a web.xml Servlet/JSP to a guice-servlet (because the filter pipeline
* is not called again). However, we can wrap requests with our own dispatcher to forward the
* *other* way. web.xml Servlets/JSPs can forward to themselves as per normal.
*
* This is not a problem cuz we intend for people to migrate from web.xml to guice-servlet,
* incrementally, but not the other way around (which, we should actively discourage).
*/
@SuppressWarnings({ "JavaDoc", "deprecation" })
private ServletRequest withDispatcher(ServletRequest servletRequest,
final ManagedServletPipeline servletPipeline) {
HttpServletRequest request = (HttpServletRequest) servletRequest;
// don't wrap the request if there are no servlets mapped. This prevents us from inserting our
// wrapper unless it's actually going to be used. This is necessary for compatibility for apps
// that downcast their HttpServletRequests to a concrete implementation.
if (!servletPipeline.hasServletsMapped()) {
return servletRequest;
}
//noinspection OverlyComplexAnonymousInnerClass
return new HttpServletRequestWrapper(request) {
@Override
public RequestDispatcher getRequestDispatcher(String path) {
final RequestDispatcher dispatcher = servletPipeline.getRequestDispatcher(path);
return (null != dispatcher) ? dispatcher : super.getRequestDispatcher(path);
}
};
}
public void destroyPipeline() {
//destroy servlets first
servletPipeline.destroy();
//go down chain and destroy all our filters
Set<Filter> destroyedSoFar = Sets.newSetFromMap(Maps.<Filter, Boolean>newIdentityHashMap());
for (FilterDefinition filterDefinition : filterDefinitions) {
filterDefinition.destroy(destroyedSoFar);
}
}
}
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