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

   1 // Copyright 2009 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.tools.development.agent.impl;
   4
   5 import org.objectweb.asm.ClassVisitor;
   6 import org.objectweb.asm.MethodVisitor;
   7 import org.objectweb.asm.Opcodes;
   8 import org.objectweb.asm.Type;
   9
  10 import java.util.Arrays;
  11 import java.util.HashSet;
  12 import java.util.Set;
  13
  14 /**
  15  * Visits ClassLoader constructions so that we can record them in the agent
  16  * and fixup their parents.
  17  *
  18  */
  19 public class ClassLoaderVisitor extends ClassVisitor {
  20
  21   private static final String RECORD_CLASSLOADER = "recordClassLoader";
  22
  23   private static final String RECORD_CLASSLOADER_DESCRIPTOR = "(Ljava/lang/ClassLoader;)V";
  24
  25   private static final String CHECK_PARENT_CLASSLOADER = "checkParentClassLoader";
  26
  27   private static final String CHECK_PARENT_CLASSLOADER_DESCRIPTOR =
  28       "(Ljava/lang/ClassLoader;)Ljava/lang/ClassLoader;";
  29
  30   private static final String URL_CLASSLOADER_CLASS = "java/net/URLClassLoader";
  31   private static final String SECURE_CLASSLOADER_CLASS = "java/security/SecureClassLoader";
  32   private static final String CLASSLOADER_CLASS = "java/lang/ClassLoader";
  33
  34   private static final String CONSTRUCTOR_METHOD = "<init>";
  35
  36   private static final String NEW_INSTANCE_METHOD = "newInstance";
  37
  38   private Set<String> classLoaderTypes = new HashSet<String>(Arrays.asList(URL_CLASSLOADER_CLASS,
  39       SECURE_CLASSLOADER_CLASS, CLASSLOADER_CLASS));
  40
  41   public ClassLoaderVisitor(final ClassVisitor classVisitor) {
  42     super(Opcodes.ASM4, classVisitor);
  43   }
  44
  45   private static final Type CLASSLOADER_TYPE = Type.getType(ClassLoader.class);
  46
  47   @Override
  48   public MethodVisitor visitMethod(int access, String name, String desc, String signature,
  49       String[] exceptions) {
  50     MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions);
  51     return (mv == null) ? null : new MethodTranslator(mv, access, name, desc);
  52   }
  53
  54   enum InitType {
  55     None,
  56     Init,
  57     NewInstance,
  58   }
  59
  60   private class MethodTranslator extends NonRecordingGeneratorAdapter {
  61     MethodTranslator(MethodVisitor methodVisitor, int access, String name, String desc) {
  62       super(methodVisitor, access, name, desc);
  63     }
  64
  65     @Override
  66     public void visitMethodInsn(int opcode, String owner, String name, String desc) {
  67       InitType initType = initsNewClassLoader(owner, name);
  68       if (initType == InitType.None) {
  69         super.visitMethodInsn(opcode, owner, name, desc);
  70         return;
  71       }
  72
  73       Type[] argTypes = Type.getArgumentTypes(desc);
  74
  75       boolean acceptsParentClassLoader = argTypes.length > 0 &&
  76           argTypes[argTypes.length - 1].equals(CLASSLOADER_TYPE);
  77
  78       if (!acceptsParentClassLoader) {
  79         super.visitInsn(Opcodes.ACONST_NULL);
  80       }
  81
  82       super.visitMethodInsn(Opcodes.INVOKESTATIC, AgentImpl.AGENT_RUNTIME,
  83         CHECK_PARENT_CLASSLOADER, CHECK_PARENT_CLASSLOADER_DESCRIPTOR);
  84
  85       if (!acceptsParentClassLoader) {
  86         Type[] newArgTypes = new Type[argTypes.length + 1];
  87         System.arraycopy(argTypes, 0, newArgTypes, 0, argTypes.length);
  88         newArgTypes[argTypes.length] = CLASSLOADER_TYPE;
  89         argTypes = newArgTypes;
  90       }
  91
  92       if (initType == InitType.Init) {
  93         int[] locals = new int[argTypes.length];
  94
  95         for (int i = argTypes.length - 1; i >= 0; --i) {
  96           locals[i] = super.newLocal(argTypes[i]);
  97           super.storeLocal(locals[i]);
  98         }
  99
 100         super.dup();
 101
 102         for (int i = 0; i < locals.length; ++i) {
 103           super.loadLocal(locals[i]);
 104         }
 105       }
 106
 107       super.visitMethodInsn(opcode, owner, name,
 108           Type.getMethodDescriptor(Type.getReturnType(desc), argTypes));
 109
 110       if (initType == InitType.NewInstance) {
 111         super.dup();
 112       }
 113
 114       super.visitMethodInsn(Opcodes.INVOKESTATIC, AgentImpl.AGENT_RUNTIME, RECORD_CLASSLOADER,
 115           RECORD_CLASSLOADER_DESCRIPTOR);
 116     }
 117
 118     private InitType initsNewClassLoader(String owner, String name) {
 119       if (classLoaderTypes.contains(owner) && name.equals(CONSTRUCTOR_METHOD)) {
 120         return InitType.Init;
 121       }
 122
 123       if (owner.equals(URL_CLASSLOADER_CLASS) && name.equals(NEW_INSTANCE_METHOD)) {
 124         return InitType.NewInstance;
 125       }
 126
 127       return InitType.None;
 128     }
 129   }
 130 }