FilterChainInvocation.java revision fee2d237bd4d6f89ed510861a25d4f3eafa8f1d1 
1/**
2 * Copyright (C) 2008 Google Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16package com.google.inject.servlet;
17
18import com.google.common.base.Throwables;
19import com.google.common.collect.ImmutableSet;
20import com.google.common.collect.Lists;
21
22import java.io.IOException;
23import java.util.List;
24import java.util.Set;
25
26import javax.servlet.FilterChain;
27import javax.servlet.ServletException;
28import javax.servlet.ServletRequest;
29import javax.servlet.ServletResponse;
30import javax.servlet.http.HttpServletRequest;
31import javax.servlet.http.HttpServletResponse;
32
33/**
34 * A Filter chain impl which basically passes itself to the "current" filter and iterates the chain
35 * on {@code doFilter()}. Modeled on something similar in Apache Tomcat.
36 *
37 * Following this, it attempts to dispatch to guice-servlet's registered servlets using the
38 * ManagedServletPipeline.
39 *
40 * And the end, it proceeds to the web.xml (default) servlet filter chain, if needed.
41 *
42 * @author Dhanji R. Prasanna
43 * @since 1.0
44 */
45class FilterChainInvocation implements FilterChain {
46
47  private static final Set<String> SERVLET_INTERNAL_METHODS = ImmutableSet.of(
48      FilterDefinition.class.getName() + ".doFilter",
49      FilterChainInvocation.class.getName() + ".doFilter");
50
51  private final FilterDefinition[] filterDefinitions;
52  private final FilterChain proceedingChain;
53  private final ManagedServletPipeline servletPipeline;
54
55  //state variable tracks current link in filterchain
56  private int index = -1;
57  // whether or not we've caught an exception & cleaned up stack traces
58  private boolean cleanedStacks = false;
59
60  public FilterChainInvocation(FilterDefinition[] filterDefinitions,
61      ManagedServletPipeline servletPipeline, FilterChain proceedingChain) {
62
63    this.filterDefinitions = filterDefinitions;
64    this.servletPipeline = servletPipeline;
65    this.proceedingChain = proceedingChain;
66  }
67
68  public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse)
69      throws IOException, ServletException {
70    index++;
71
72    GuiceFilter.Context previous = GuiceFilter.localContext.get();
73    HttpServletRequest request = (HttpServletRequest) servletRequest;
74    HttpServletResponse response = (HttpServletResponse) servletResponse;
75    HttpServletRequest originalRequest
76        = (previous != null) ? previous.getOriginalRequest() : request;
77    GuiceFilter.localContext.set(new GuiceFilter.Context(originalRequest, request, response));
78    try {
79      //dispatch down the chain while there are more filters
80      if (index < filterDefinitions.length) {
81        filterDefinitions[index].doFilter(servletRequest, servletResponse, this);
82      } else {
83        //we've reached the end of the filterchain, let's try to dispatch to a servlet
84        final boolean serviced = servletPipeline.service(servletRequest, servletResponse);
85
86        //dispatch to the normal filter chain only if one of our servlets did not match
87        if (!serviced) {
88          proceedingChain.doFilter(servletRequest, servletResponse);
89        }
90      }
91    } catch (Throwable t) {
92      // Only clean on the first pass through -- one exception deep in a filter
93      // will propogate upward & hit this catch clause multiple times.  We don't
94      // want to iterate through the stack elements for every filter.
95      if (!cleanedStacks) {
96        cleanedStacks = true;
97        pruneStacktrace(t);
98      }
99      Throwables.propagateIfInstanceOf(t, ServletException.class);
100      Throwables.propagateIfInstanceOf(t, IOException.class);
101      throw Throwables.propagate(t);
102    } finally {
103      GuiceFilter.localContext.set(previous);
104    }
105  }
106
107  /**
108   * Removes stacktrace elements related to AOP internal mechanics from the
109   * throwable's stack trace and any causes it may have.
110   */
111  private void pruneStacktrace(Throwable throwable) {
112    for (Throwable t = throwable; t != null; t = t.getCause()) {
113      StackTraceElement[] stackTrace = t.getStackTrace();
114      List<StackTraceElement> pruned = Lists.newArrayList();
115      for (StackTraceElement element : stackTrace) {
116        String name = element.getClassName() + "." + element.getMethodName();
117        if (!SERVLET_INTERNAL_METHODS.contains(name)) {
118          pruned.add(element);
119        }
120      }
121      t.setStackTrace(pruned.toArray(new StackTraceElement[pruned.size()]));
122    }
123  }
124}
125