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.Filter;
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      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    GuiceFilter.Context previous = GuiceFilter.localContext.get();
71    HttpServletRequest request = (HttpServletRequest) servletRequest;
72    HttpServletResponse response = (HttpServletResponse) servletResponse;
73    HttpServletRequest originalRequest
74        = (previous != null) ? previous.getOriginalRequest() : request;
75    GuiceFilter.localContext.set(new GuiceFilter.Context(originalRequest, request, response));
76    try {
77      Filter filter = findNextFilter(request);
78      if (filter != null) {
79        // call to the filter, which can either consume the request or
80        // recurse back into this method. (in which case we will go to find the next filter,
81        // or dispatch to the servlet if no more filters are left)
82        filter.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   * Iterates over the remaining filter definitions.
110   * Returns the first applicable filter, or null if none apply.
111   */
112  private Filter findNextFilter(HttpServletRequest request) {
113    while (++index < filterDefinitions.length) {
114      Filter filter = filterDefinitions[index].getFilterIfMatching(request);
115      if (filter != null) {
116        return filter;
117      }
118    }
119    return null;
120  }
121
122  /**
123   * Removes stacktrace elements related to AOP internal mechanics from the
124   * throwable's stack trace and any causes it may have.
125   */
126  private void pruneStacktrace(Throwable throwable) {
127    for (Throwable t = throwable; t != null; t = t.getCause()) {
128      StackTraceElement[] stackTrace = t.getStackTrace();
129      List<StackTraceElement> pruned = Lists.newArrayList();
130      for (StackTraceElement element : stackTrace) {
131        String name = element.getClassName() + "." + element.getMethodName();
132        if (!SERVLET_INTERNAL_METHODS.contains(name)) {
133          pruned.add(element);
134        }
135      }
136      t.setStackTrace(pruned.toArray(new StackTraceElement[pruned.size()]));
137    }
138  }
139}
140