org.objectweb.asm.ClassWriter#COMPUTE_MAXS源码实例Demo

private static void loadAdaptedClass(File file,
        Map<String, String> typeMappnigs, Map<Class<?>, byte[]> result)
        throws IOException, ClassNotFoundException {

    ClassWriter writer = new ClassWriter(
            ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);
    TestClassAdapter adapter = new TestClassAdapter(writer, typeMappnigs);

    InputStream in = new FileInputStream(file);
    try {
        new ClassReader(in).accept(adapter, ClassReader.EXPAND_FRAMES);
    } finally {
        try {
            in.close();
        } catch (IOException e) {
            // Ignore.
        }
    }
    byte[] bytes = writer.toByteArray();
    String className = adapter.getClassName().replace('/', '.');
    result.put(Class.forName(className), bytes); // FIXME: ClassLoader...
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiIngameForge (%s)", Names.guiIngameForge.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiEditSign (%s)", Names.guiEditSign.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("Minecraft (%s)", Names.minecraft.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiTextfield (%s)", Names.guiTextfield.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("Minecraft (%s)", Names.minecraft.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiIngameForge (%s)", Names.guiIngameForge.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiEditSign (%s)", Names.guiEditSign.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiDisconnected (%s)", Names.guiDisconnected.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiGameOver (%s)", Names.guiGameOver.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiTextfield (%s)", Names.guiTextfield.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

private LazyDefinedClass generate() {
    LazyDefinedClass methodMetaClass = null;
    if (methodMetaInternalName != null) {
        methodMetaClass = generateMethodMetaClass(config);
    }
    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS + ClassWriter.COMPUTE_FRAMES);
    String[] interfaces = null;
    if (!config.enabledProperty().isEmpty() || !config.traceEntryEnabledProperty().isEmpty()) {
        interfaces = new String[] {"org/glowroot/agent/plugin/api/config/ConfigListener"};
    }
    cw.visit(V1_5, ACC_PUBLIC + ACC_SUPER, adviceInternalName, null, "java/lang/Object",
            interfaces);
    addClassAnnotation(cw);
    addStaticFields(cw);
    addStaticInitializer(cw);
    boolean checkNotInTransaction = config.isTransaction()
            && config.alreadyInTransactionBehavior() == AlreadyInTransactionBehavior.DO_NOTHING;
    boolean checkPropertyNotEnabled = pluginId != null && !config.enabledProperty().isEmpty();
    addIsEnabledMethodIfNeeded(cw, checkNotInTransaction, checkPropertyNotEnabled);
    if (config.isTraceEntryOrGreater()) {
        // methodMetaInternalName is non-null when entry or greater
        checkNotNull(methodMetaInternalName);
        addOnBeforeMethod(cw);
        addOnThrowMethod(cw);
        addOnReturnMethod(cw);
    } else if (config.captureKind() == CaptureKind.TIMER) {
        addOnBeforeMethodTimerOnly(cw);
        addOnAfterMethodTimerOnly(cw);
    } else {
        addOnBeforeMethodOther(cw);
    }
    cw.visitEnd();
    ImmutableLazyDefinedClass.Builder builder = ImmutableLazyDefinedClass.builder()
            .type(Type.getObjectType(adviceInternalName))
            .bytes(cw.toByteArray());
    if (methodMetaClass != null) {
        builder.addDependencies(methodMetaClass);
    }
    return builder.build();
}
 

default byte[] transform(byte[] input, String classname, BuildContext context) {
    ClassReader reader = new ClassReader(input);
    ClassNode cn = new ClassNode();
    reader.accept(cn, 0);
    transform(cn, classname, context);
    SafeClassWriter writer = new SafeClassWriter(context.task.reader, ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);
    cn.accept(writer);
    return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiOptions (%s)", Names.guiOptions.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiOptions (%s)", Names.guiOptions.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiIngameForge (%s)", Names.guiIngameForge.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiEditSign (%s)", Names.guiEditSign.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Override
public byte[] transform(String s, String s1, byte[] bytes) {
	LogUtil.startClass("GuiEditSign (%s)", Names.guiEditSign.getName());

	ClassReader reader = new ClassReader(bytes);
	ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
	ClassPatcher visitor = new ClassPatcher(writer);
	reader.accept(visitor, 0);
	LogUtil.endClass();
	return writer.toByteArray();
}
 

@Test
public void test() throws Throwable {

    ClassReader cr = new ClassReader(Config.class.getName());
    ClassWriter cw = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS);
    ClassVisitor cv = new MethodChangeClassAdapter(cw);
    cr.accept(cv, Opcodes.ASM5);

    //Add a new method
    MethodVisitor mw = cw.visitMethod(ACC_PUBLIC + ACC_STATIC,
                                      "add",
                                      "([Ljava/lang/String;)V",
                                      null,
                                      null);

    // pushes the 'out' field (of type PrintStream) of the System class
    mw.visitFieldInsn(GETSTATIC,
                      "java/lang/System",
                      "out",
                      "Ljava/io/PrintStream;");
    // pushes the "Hello World!" String constant
    mw.visitLdcInsn("this is add method print!");
    // invokes the 'println' method (defined in the PrintStream class)
    mw.visitMethodInsn(INVOKEVIRTUAL,
                       "java/io/PrintStream",
                       "println",
                       "(Ljava/lang/String;)V");
    mw.visitInsn(RETURN);
    // this code uses a maximum of two stack elements and two local
    // variables
    mw.visitMaxs(0, 0);
    mw.visitEnd();


    //Type.getDescriptor(AdviceFlowOuterHolder.class)
    FieldVisitor fv = cw.visitField(ACC_PUBLIC + ACC_STATIC + ACC_FINAL,
                                     "age",
                                    Type.INT_TYPE.toString(),
                                     null,
                                     1);
    fv.visitEnd();

    FieldVisitor fv2 = cw.visitField(ACC_PUBLIC + ACC_STATIC + ACC_FINAL,
                                    "name2",
                                    Type.getDescriptor(String.class),
                                    null,
                                    "name2");
    fv2.visitEnd();


    ModifyClassVisiter cv2 = new ModifyClassVisiter(Opcodes.ASM5);
    cv2.addRemoveField("name");
    cr.accept(cv2, Opcodes.ASM5);

    FieldVisitor fv3 = cw.visitField(ACC_PUBLIC + ACC_STATIC + ACC_FINAL,
                                     "name",
                                     Type.getDescriptor(String.class),
                                     null,
                                     "name");
    fv3.visitEnd();




    byte[] code = cw.toByteArray();
    File file = new File("Config.class");
    System.out.println(file.getAbsolutePath());
    FileOutputStream fos = new FileOutputStream(file);
    fos.write(code);
    fos.close();

}
 

@Override
public int mergeWriter(int flags)
{
    return flags | ClassWriter.COMPUTE_MAXS;
}