/**
* 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.Key;
import com.google.inject.Singleton;
import com.google.inject.TypeLiteral;
import com.google.inject.internal.Lists;
import com.google.inject.internal.Maps;
import com.google.inject.internal.Preconditions;
import com.google.inject.internal.Sets;
import java.io.IOException;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
/**
* A wrapping dispatcher for servlets, in much the same way as {@link ManagedFilterPipeline} is for
* filters.
*
* @author dhanji@gmail.com (Dhanji R. Prasanna)
*/
@Singleton
class ManagedServletPipeline {
private final List<ServletDefinition> servletDefinitions;
private static final TypeLiteral<List<ServletDefinition>> SERVLET_DEFS =
new TypeLiteral<List<ServletDefinition>>() {};
@Inject
public ManagedServletPipeline(Injector injector) {
this.servletDefinitions = Collections.unmodifiableList(collectServletDefinitions(injector));
}
boolean hasServletsMapped() {
return !servletDefinitions.isEmpty();
}
/**
* Introspects the injector and collects all instances of bound {@code List<ServletDefinition>}
* 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 List<ServletDefinition> collectServletDefinitions(Injector injector) {
List<ServletDefinition> servletDefinitions = Lists.newArrayList();
for (Binding<?> entry : injector.findBindingsByType(SERVLET_DEFS)) {
@SuppressWarnings("unchecked") //guarded by findBindingsByType()
Key<List<ServletDefinition>> defsKey = (Key<List<ServletDefinition>>) entry.getKey();
servletDefinitions.addAll(injector.getInstance(defsKey));
}
return servletDefinitions;
}
public void init(ServletContext servletContext, Injector injector) throws ServletException {
Set<HttpServlet> initializedSoFar
= Sets.newSetFromMap(Maps.<HttpServlet, Boolean>newIdentityHashMap());
for (ServletDefinition servletDefinition : servletDefinitions) {
servletDefinition.init(servletContext, injector, initializedSoFar);
}
}
public boolean service(ServletRequest request, ServletResponse response)
throws IOException, ServletException {
//stop at the first matching servlet and service
for (ServletDefinition servletDefinition : servletDefinitions) {
if (servletDefinition.service(request, response)) {
return true;
}
}
//there was no match...
return false;
}
public void destroy() {
Set<HttpServlet> destroyedSoFar
= Sets.newSetFromMap(Maps.<HttpServlet, Boolean>newIdentityHashMap());
for (ServletDefinition servletDefinition : servletDefinitions) {
servletDefinition.destroy(destroyedSoFar);
}
}
/**
* @return Returns a request dispatcher wrapped with a servlet mapped to
* the given path or null if no mapping was found.
*/
RequestDispatcher getRequestDispatcher(String path) {
final String newRequestUri = path;
for (final ServletDefinition servletDefinition : servletDefinitions) {
if (servletDefinition.shouldServe(path)) {
return new RequestDispatcher() {
public void forward(ServletRequest servletRequest, ServletResponse servletResponse)
throws ServletException, IOException {
Preconditions.checkState(!servletResponse.isCommitted(),
"Response has been committed--you can only call forward before"
+ " committing the response (hint: don't flush buffers)");
// clear buffer before forwarding
servletResponse.resetBuffer();
ServletRequest requestToProcess;
if (servletRequest instanceof HttpServletRequest) {
requestToProcess =
new HttpServletRequestWrapper((HttpServletRequest) servletRequest) {
public String getRequestURI() {
return newRequestUri;
}
};
} else {
// This should never happen, but instead of throwing an exception
// we will allow a happy case pass thru for maximum tolerance to
// legacy (and internal) code.
requestToProcess = servletRequest;
}
// now dispatch to the servlet
servletDefinition.doService(requestToProcess, servletResponse);
}
public void include(ServletRequest servletRequest, ServletResponse servletResponse)
throws ServletException, IOException {
// route to the target servlet
servletDefinition.doService(servletRequest, servletResponse);
}
};
}
}
//otherwise, can't process
return null;
}
}