java/src/main/com/google/appengine/tools/development/agent/impl/AgentImpl.java

   1 // Copyright 2009 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.tools.development.agent.impl;
   4
   5 import java.lang.instrument.Instrumentation;
   6 import java.lang.ref.ReferenceQueue;
   7 import java.lang.ref.WeakReference;
   8 import java.util.HashSet;
   9 import java.util.Iterator;
  10 import java.util.Set;
  11
  12 /**
  13  * Performs the actual agent work.
  14  *
  15  */
  16 public class AgentImpl implements Agent {
  17
  18   static final String AGENT_RUNTIME =
  19       "com/google/appengine/tools/development/agent/runtime/Runtime";
  20
  21   private static final AgentImpl instance = new AgentImpl();
  22
  23   private final Set<ClassLoaderReference> appUrlClassLoaders = new HashSet<ClassLoaderReference>();
  24   private final ReferenceQueue<ClassLoader> classLoaderReferenceQueue =
  25       new ReferenceQueue<ClassLoader>();
  26
  27   public void run(Instrumentation instrumentation,
  28       boolean treatRestrictedClassListViolationsAsErrors) {
  29     instrumentation.addTransformer(new Transformer(treatRestrictedClassListViolationsAsErrors));
  30   }
  31
  32   @Override
  33   public Set<String> getBlackList() {
  34     return BlackList.getBlackList();
  35   }
  36
  37   @Override
  38   public synchronized void recordAppClassLoader(ClassLoader loader) {
  39     prune();
  40     appUrlClassLoaders.add(new ClassLoaderReference(loader));
  41   }
  42
  43   public static AgentImpl getInstance() {
  44     return instance;
  45   }
  46
  47   private AgentImpl() {
  48     if (instance != null) {
  49       throw new IllegalStateException("There can only be one AgentImpl");
  50     }
  51   }
  52
  53   public synchronized boolean isAppConstructedURLClassLoader(ClassLoader loader) {
  54     prune();
  55     return appUrlClassLoaders.contains(new ClassLoaderReference(loader));
  56   }
  57
  58   private void prune() {
  59     boolean any = false;
  60     while (classLoaderReferenceQueue.poll() != null) {
  61       any = true;
  62     }
  63     if (any) {
  64       for (Iterator<ClassLoaderReference> it = appUrlClassLoaders.iterator(); it.hasNext(); ) {
  65         ClassLoaderReference classLoaderReference = it.next();
  66         if (classLoaderReference.get() == null) {
  67           it.remove();
  68         }
  69       }
  70     }
  71   }
  72
  73   private class ClassLoaderReference {
  74     private final WeakReference<ClassLoader> classLoaderReference;
  75     private final int hashCode;
  76
  77     ClassLoaderReference(ClassLoader classLoader) {
  78       this.classLoaderReference =
  79           new WeakReference<ClassLoader>(classLoader, classLoaderReferenceQueue);
  80       this.hashCode = System.identityHashCode(classLoader);
  81     }
  82
  83     ClassLoader get() {
  84       return classLoaderReference.get();
  85     }
  86
  87     @Override
  88     public boolean equals(Object obj) {
  89       if (obj instanceof ClassLoaderReference) {
  90         ClassLoaderReference that = (ClassLoaderReference) obj;
  91         return get() == that.get();
  92       } else {
  93         return false;
  94       }
  95     }
  96
  97     @Override
  98     public int hashCode() {
  99       return hashCode;
 100     }
 101   }
 102 }