FilterChainInvocation.java revision 9afcdd8a24ee225e21c461144b524b3fc55c4033 
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;
21import com.google.common.collect.Sets;
22
23import java.io.IOException;
24import java.util.List;
25import java.util.Set;
26
27import javax.servlet.FilterChain;
28import javax.servlet.ServletException;
29import javax.servlet.ServletRequest;
30import javax.servlet.ServletResponse;
31import javax.servlet.http.HttpServletRequest;
32import javax.servlet.http.HttpServletResponse;
33
34/**
35 * A Filter chain impl which basically passes itself to the "current" filter and iterates the chain
36 * on {@code doFilter()}. Modeled on something similar in Apache Tomcat.
37 *
38 * Following this, it attempts to dispatch to guice-servlet's registered servlets using the
39 * ManagedServletPipeline.
40 *
41 * And the end, it proceeds to the web.xml (default) servlet filter chain, if needed.
42 *
43 * @author Dhanji R. Prasanna
44 * @since 1.0
45 */
46class FilterChainInvocation implements FilterChain {
47
48  private static final Set<String> SERVLET_INTERNAL_METHODS = ImmutableSet.of(
49      FilterDefinition.class.getName() + ".doFilter",
50      FilterChainInvocation.class.getName() + ".doFilter");
51
52  private final FilterDefinition[] filterDefinitions;
53  private final FilterChain proceedingChain;
54  private final ManagedServletPipeline servletPipeline;
55
56  //state variable tracks current link in filterchain
57  private int index = -1;
58  // whether or not we've caught an exception & cleaned up stack traces
59  private boolean cleanedStacks = false;
60
61  public FilterChainInvocation(FilterDefinition[] filterDefinitions,
62      ManagedServletPipeline servletPipeline, FilterChain proceedingChain) {
63
64    this.filterDefinitions = filterDefinitions;
65    this.servletPipeline = servletPipeline;
66    this.proceedingChain = proceedingChain;
67  }
68
69  public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse)
70      throws IOException, ServletException {
71    index++;
72
73    GuiceFilter.Context previous = GuiceFilter.localContext.get();
74    HttpServletRequest request = (HttpServletRequest) servletRequest;
75    HttpServletResponse response = (HttpServletResponse) servletResponse;
76    HttpServletRequest originalRequest
77        = (previous != null) ? previous.getOriginalRequest() : request;
78    GuiceFilter.localContext.set(new GuiceFilter.Context(originalRequest, request, response));
79    try {
80      //dispatch down the chain while there are more filters
81      if (index < filterDefinitions.length) {
82        filterDefinitions[index].doFilter(servletRequest, servletResponse, this);
83      } else {
84        //we've reached the end of the filterchain, let's try to dispatch to a servlet
85        final boolean serviced = servletPipeline.service(servletRequest, servletResponse);
86
87        //dispatch to the normal filter chain only if one of our servlets did not match
88        if (!serviced) {
89          proceedingChain.doFilter(servletRequest, servletResponse);
90        }
91      }
92    } catch (Throwable t) {
93      // Only clean on the first pass through -- one exception deep in a filter
94      // will propogate upward & hit this catch clause multiple times.  We don't
95      // want to iterate through the stack elements for every filter.
96      if (!cleanedStacks) {
97        cleanedStacks = true;
98        pruneStacktrace(t);
99      }
100      Throwables.propagateIfInstanceOf(t, ServletException.class);
101      Throwables.propagateIfInstanceOf(t, IOException.class);
102      throw Throwables.propagate(t);
103    } finally {
104      GuiceFilter.localContext.set(previous);
105    }
106  }
107
108  /**
109   * Removes stacktrace elements related to AOP internal mechanics from the
110   * throwable's stack trace and any causes it may have.
111   */
112  private void pruneStacktrace(Throwable throwable) {
113    for (Throwable t = throwable; t != null; t = t.getCause()) {
114      StackTraceElement[] stackTrace = t.getStackTrace();
115      List<StackTraceElement> pruned = Lists.newArrayList();
116      for (StackTraceElement element : stackTrace) {
117        String name = element.getClassName() + "." + element.getMethodName();
118        if (!SERVLET_INTERNAL_METHODS.contains(name)) {
119          pruned.add(element);
120        }
121      }
122      t.setStackTrace(pruned.toArray(new StackTraceElement[pruned.size()]));
123    }
124  }
125}
126