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Nutz:重新发明*:自己动手,用字节码工具做一个Aop拦截器 博客分类： Nutz AOPJavaF#SVNGoogle 

程序员文章站 2024-02-04 16:55:10
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Aop听得太多了, 用过Aop的JEer也不少,什么Spring Aop,AspectJ等等.

换个角度,为啥不自己写一个Aop拦截器呢? 重新发明*又如何?

现在就用最基本的字节码工具来DIY一个Aop. 用反射就太没风度了,那东西,谁不会?!

效果预览:
原有的类 
public class Aop1{

    public void doSomething() throws Throwable{
        //打我啊,拍我啊!
    }

}


改造后 

public class Aop1$$Aop extend Aop1{

    @Override
    public void doSomething() throws Throwable{
	try {
		if (_Nut_before(188)) {
			super.doSomething();
		}
		_Nut_after(188, null);
	} catch (Exception e) {
		if(_Nut_Exception(188, e))
			throw e;
	} catch (Throwable e) {
		if(_Nut_Error(188, e))
			throw e;
	}
    }

    private static Method[] _$$Nut_methodArray;

    private static List<MethodInterceptor>[] _$$Nut_methodInterceptorList;

    private boolean _Nut_before(int flag_int, Object... args) {
	Method method = _$$Nut_methodArray[flag_int];
	List<MethodInterceptor> miList = _$$Nut_methodInterceptorList[flag_int];
	boolean flag = true;
	for (MethodInterceptor methodInterceptor : miList)
		flag &= methodInterceptor.beforeInvoke(this, method, args);
	return flag;
    }

    private Object _Nut_after(int flag_int, Object src_return, Object... args) {
	Method method = _$$Nut_methodArray[flag_int];
	List<MethodInterceptor> miList = _$$Nut_methodInterceptorList[flag_int];
	for (MethodInterceptor methodInterceptor : miList)
		src_return = methodInterceptor.afterInvoke(this, src_return, method, args);
	return src_return;
    }

    private boolean _Nut_Exception(int flag_int, Exception e, Object... args) {
	Method method = _$$Nut_methodArray[flag_int];
	List<MethodInterceptor> miList = _$$Nut_methodInterceptorList[flag_int];
	boolean flag = true;
	for (MethodInterceptor methodInterceptor : miList)
		flag &= methodInterceptor.whenException(e, this, method, args);
	return flag;
    }

    private boolean _Nut_Error(int flag_int, Throwable e, Object... args) {
	Method method = _$$Nut_methodArray[flag_int];
	List<MethodInterceptor> miList = _$$Nut_methodInterceptorList[flag_int];
	boolean flag = true;
	for (MethodInterceptor methodInterceptor : miList)
		flag &= methodInterceptor.whenError(e, this, method, args);
	return flag;
    }

}


其中MethodInterceptor是方法拦截器接口: 
public interface MethodInterceptor {

	/**
	 * 在被拦截方法调用之前，将调用该方法。 你可用通过这个方法的返回值，来控制是否真正的调用"被拦截方法"。
	 * 
	 * @param obj
	 *            被调用实例
	 * @param method
	 *            实例被调用方法
	 * @param args
	 *            被调用方法所需参数
	 * @return true，继续调用被拦截方法。false 将不会调用被拦截方法
	 */
	boolean beforeInvoke(Object obj, Method method, Object... args);

	/**
	 * 你可以通过这个函数，修改被拦截方法的返回值。默认的，你直接将 returnObj 返回即可
	 * 
	 * @param obj
	 *            被调用实例
	 * @param returnObj
	 *            实例被调用方法的返回
	 * @param method
	 *            实例被调用方法
	 * @param args
	 *            被调用方法所需参数
	 * @return 调用者真正将拿到的对象。 如果，你返回的对象类型是错误的，比如调用者希望得到一个 long， 但是，你拦截了这个方法，并返回一个
	 *         String，那么将发生一个类型转换的错误
	 */
	Object afterInvoke(Object obj, Object returnObj, Method method, Object... args);

	/**
	 * 当被拦截方法发生异常(Exception)，这个方法会被调用。
	 * 
	 * @param e
	 *            异常
	 * @param obj
	 *            被调用实例
	 * @param method
	 *            被调用方法
	 * @param args
	 *            被调用方法所需参数
	 * 
	 * @return 是否继续抛出异常
	 */
	boolean whenException(Exception e, Object obj, Method method, Object... args);

	/**
	 * 当被拦截方法发生错误(Error)，这个方法会被调用。
	 * 
	 * @param e
	 *            错误
	 * @param obj
	 *            被调用实例
	 * @param method
	 *            被调用方法
	 * @param args
	 *            被调用方法所需参数
	 * 
	 * @return 是否继续抛出错误
	 */
	boolean whenError(Throwable e, Object obj, Method method, Object... args);

}


好,开工!

实现步骤,用个接口来表达吧: 
public interface ClassEnhander{

    void addFields();
    void addConstructors();
    void addAopMethods();
    void enhandMethod();
}


第一步,新建一个类Aop1$$Aop, 等一下, 是用你的字节码工具新建一个类哦,可不要打开eclipse的new class对话框了
asm示例代码: 
ClassWriter cw= new ClassWriter(ClassWriter.COMPUTE_MAXS);
cw.visit(V1_6, ACC_PUBLIC, myName, "", enhancedSuperName, new String[]{});


其中,myName就是"Aop1$$Aop", enhancedSuperName就是父类的名字

第二步, 插入字段(回想一下改造后的类,可是有两个静态私有字段的哦)
asm示例代码: 
FieldVisitor fv = cv.visitField(ACC_PRIVATE + ACC_STATIC, "_$$Nut_methodArray", "[Ljava/lang/reflect/Method;", null, null);
fv.visitEnd();


FieldVisitor fv = cv.visitField(ACC_PRIVATE + ACC_STATIC, "_$$Nut_methodInterceptorList", "[Ljava/util/List;", 
"[Ljava/util/List<Lorg/nutz/aop/MethodInterceptor;>;", null);
fv.visitEnd();


第三步,继承父类的构造方法(除了private的构造方法),记得添加父类构造方法抛出的异常哦:
asm示例代码: 
MethodVisitor mv = cw.visitMethod(access, "<init>", desc,null, expClasses);
mv.visitCode();
mv.visitVarInsn(ALOAD, 0);
loadArgs();
mv.visitMethodInsn(INVOKESPECIAL, superClassName, "<init>", desc);
mv.visitInsn(RETURN);
mv.visitMaxs(2, 2);
mv.visitEnd();


第四步,插入Aop模板方法(就是那几个private的_Nut_开头的方法)
asm示例代码:
例如插入_Nut_whenError 
MethodVisitor mv = cw.visitMethod(ACC_PRIVATE + ACC_VARARGS, "_Nut_Error", "(ILjava/lang/Throwable;[Ljava/lang/Object;)Z", null, null);
mv.visitCode();
mv.visitFieldInsn(GETSTATIC, _Nut_myName, "_$$Nut_methodArray", "[Ljava/lang/reflect/Method;");
mv.visitVarInsn(ILOAD, 1);
mv.visitInsn(AALOAD);
mv.visitVarInsn(ASTORE, 4);
mv.visitFieldInsn(GETSTATIC, _Nut_myName, "_$$Nut_methodInterceptorList", "[Ljava/util/List;");
mv.visitVarInsn(ILOAD, 1);
mv.visitInsn(AALOAD);
mv.visitVarInsn(ASTORE, 5);
mv.visitInsn(ICONST_1);
mv.visitVarInsn(ISTORE, 6);
mv.visitVarInsn(ALOAD, 5);
mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "iterator", "()Ljava/util/Iterator;");
mv.visitVarInsn(ASTORE, 8);
Label l0 = new Label();
mv.visitJumpInsn(GOTO, l0);
Label l1 = new Label();
mv.visitLabel(l1);
mv.visitFrame(Opcodes.F_FULL, 9, new Object[] {_Nut_myName, Opcodes.INTEGER, "java/lang/Throwable", "[Ljava/lang/Object;", 

"java/lang/reflect/Method", "java/util/List", Opcodes.INTEGER, Opcodes.TOP, "java/util/Iterator"}, 0, new Object[] {});
mv.visitVarInsn(ALOAD, 8);
mv.visitMethodInsn(INVOKEINTERFACE, "java/util/Iterator", "next", "()Ljava/lang/Object;");
mv.visitTypeInsn(CHECKCAST, "org/nutz/aop/MethodInterceptor");
mv.visitVarInsn(ASTORE, 7);
mv.visitVarInsn(ILOAD, 6);
mv.visitVarInsn(ALOAD, 7);
mv.visitVarInsn(ALOAD, 2);
mv.visitVarInsn(ALOAD, 0);
mv.visitVarInsn(ALOAD, 4);
mv.visitVarInsn(ALOAD, 3);
mv.visitMethodInsn(INVOKEINTERFACE, "org/nutz/aop/MethodInterceptor", "whenError", 

"(Ljava/lang/Throwable;Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Z");
mv.visitInsn(IAND);
mv.visitVarInsn(ISTORE, 6);
mv.visitLabel(l0);
mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
mv.visitVarInsn(ALOAD, 8);
mv.visitMethodInsn(INVOKEINTERFACE, "java/util/Iterator", "hasNext", "()Z");
mv.visitJumpInsn(IFNE, l1);
mv.visitVarInsn(ILOAD, 6);
mv.visitInsn(IRETURN);
mv.visitMaxs(6, 9);
mv.visitEnd();


第五步,重头戏,覆写需要Aop拦截的方法:
首先,需要处理第一个难题: 有无返回值
对于无返回值的方法,解决方案比较简单:
asm示例代码: 
MethodVisitor mv = cw.visitMethod(methodAccess, methodName,methodDesc,null, convertExp(method.getExceptionTypes()));
mv.visitCode();
Label l0 = new Label();
Label l1 = new Label();
Label l2 = new Label();
		mv.visitTryCatchBlock(l0, l1, l2, "java/lang/Exception");
		Label l3 = new Label();
		mv.visitTryCatchBlock(l0, l1, l3, "java/lang/Throwable");
		mv.visitLabel(l0);
		mv.visitVarInsn(ALOAD, 0);
		mv.visitIntInsn(SIPUSH, methodIndex);
		loadArgsAsArray();
		mv.visitMethodInsn(INVOKESPECIAL, myName, "_Nut_before", "(I[Ljava/lang/Object;)Z");
		Label l4 = new Label();
		mv.visitJumpInsn(IFEQ, l4);
		mv.visitVarInsn(ALOAD, 0);
		loadArgs();
		mv.visitMethodInsn(INVOKESPECIAL, enhancedSuperName, methodName, desc);
		mv.visitLabel(l4);
		mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
		mv.visitVarInsn(ALOAD, 0);
		mv.visitIntInsn(SIPUSH, methodIndex);
		mv.visitInsn(ACONST_NULL);
		loadArgsAsArray();
		mv.visitMethodInsn(INVOKESPECIAL, myName, "_Nut_after", "(ILjava/lang/Object;[Ljava/lang/Object;)Ljava/lang/Object;");
		mv.visitInsn(POP);
		mv.visitLabel(l1);
		Label l5 = new Label();
		mv.visitJumpInsn(GOTO, l5);
		mv.visitLabel(l2);
		mv.visitFrame(Opcodes.F_SAME1, 0, null, 1, new Object[] {"java/lang/Exception"});
		mv.visitVarInsn(ASTORE, lastIndex);
		mv.visitVarInsn(ALOAD, 0);
		mv.visitIntInsn(SIPUSH, methodIndex);
		mv.visitVarInsn(ALOAD, lastIndex);
		loadArgsAsArray();
		mv.visitMethodInsn(INVOKESPECIAL, myName, "_Nut_Exception", "(ILjava/lang/Exception;[Ljava/lang/Object;)Z");
		mv.visitJumpInsn(IFEQ, l5);
		mv.visitVarInsn(ALOAD, lastIndex);
		mv.visitInsn(ATHROW);
		mv.visitLabel(l3);
		mv.visitFrame(Opcodes.F_SAME1, 0, null, 1, new Object[] {"java/lang/Throwable"});
		mv.visitVarInsn(ASTORE, lastIndex);
		mv.visitVarInsn(ALOAD, 0);
		mv.visitIntInsn(SIPUSH, methodIndex);
		mv.visitVarInsn(ALOAD, lastIndex);
		loadArgsAsArray();
		mv.visitMethodInsn(INVOKESPECIAL, myName, "_Nut_Error", "(ILjava/lang/Throwable;[Ljava/lang/Object;)Z");
		mv.visitJumpInsn(IFEQ, l5);
		mv.visitVarInsn(ALOAD, lastIndex);
		mv.visitInsn(ATHROW);
		mv.visitLabel(l5);
		mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
		mv.visitInsn(RETURN);
		mv.visitMaxs(1, 1); // 自动计算
		mv.visitEnd();


对于有返回值的方法,分三种情况, 返回Object(单单指这类方法 public Object dz()),返回基本数据类型,返回其他对象(如返回数组,字符串,枚举,接口,除

Object外的对象)
返回值为Object时,把_Nut_after的返回值直接返回即可,当抛出异常等,则返回null
返回值为基本数据类型时,如int/long/double,把_Nut_after的返回值解包,当抛出异常等,则返回0/false
返回值为其他对象时, 把_Nut_after的返回值 check cast一下,进行强转即可.

解包的代码: 
if(type.equals(Type.BOOLEAN_TYPE)){
			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Boolean", "booleanValue", "()Z");
		}else if(type.equals(Type.BYTE_TYPE)){
			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Byte", "byteValue", "()B");
		}else if(type.equals(Type.CHAR_TYPE)){
			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Character", "charValue", "()C");
		}else if(type.equals(Type.SHORT_TYPE)){
			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Short", "shortValue", "()S");
		}else if(type.equals(Type.INT_TYPE)){
			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Integer", "intValue", "()I");
		}else if(type.equals(Type.LONG_TYPE)){
			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Long", "longValue", "()J");
		}else if(type.equals(Type.FLOAT_TYPE)){
			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Float", "floatValue", "()F");
		}else if(type.equals(Type.DOUBLE_TYPE)){
			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Double", "doubleValue", "()D");
		}


对了对了, 还有一个难点, 处理方法的参数列表,由于_Nut_XXX接受的是Object...args,即一个Object[].
问题就来了, 如果其中某个参数是基本类型呢?恩, 那就得封包了

封包的代码: 
if(type.equals(Type.BOOLEAN_TYPE)){
			mv.visitMethodInsn(INVOKESTATIC, "java/lang/Boolean", "valueOf", "(Z)Ljava/lang/Boolean;");
		}else if(type.equals(Type.BYTE_TYPE)){
			mv.visitMethodInsn(INVOKESTATIC, "java/lang/Byte", "valueOf", "(B)Ljava/lang/Byte;");
		}else if(type.equals(Type.CHAR_TYPE)){
			mv.visitMethodInsn(INVOKESTATIC, "java/lang/Character", "valueOf", "(C)Ljava/lang/Character;");
		}else if(type.equals(Type.SHORT_TYPE)){
			mv.visitMethodInsn(INVOKESTATIC, "java/lang/Short", "valueOf", "(S)Ljava/lang/Short;");
		}else if(type.equals(Type.INT_TYPE)){
			mv.visitMethodInsn(INVOKESTATIC, "java/lang/Integer", "valueOf", "(I)Ljava/lang/Integer;");
		}else if(type.equals(Type.LONG_TYPE)){
			mv.visitMethodInsn(INVOKESTATIC, "java/lang/Long", "valueOf", "(J)Ljava/lang/Long;");
		}else if(type.equals(Type.FLOAT_TYPE)){
			mv.visitMethodInsn(INVOKESTATIC, "java/lang/Float", "valueOf", "(F)Ljava/lang/Float;");
		}else if(type.equals(Type.DOUBLE_TYPE)){
			mv.visitMethodInsn(INVOKESTATIC, "java/lang/Double", "valueOf", "(D)Ljava/lang/Double;");
		}


参数转为Object[]的代码: 
int index = getArgIndex(0);
		for (int i = 0; i < argumentTypes.length; i++) {
			mv.visitInsn(DUP);
			visitX(i);
			Type t = argumentTypes[i];
	        loadInsn(t, index);
	        index += t.getSize();
	        packagePrivateData(t);
			mv.visitInsn(AASTORE);
		}

其中visitX为 
	void visitX(int i){
		if(i < 6){
			mv.visitInsn(i + ICONST_0);
		}else{
			mv.visitIntInsn(BIPUSH, i);
		}
	}

最后,完成!!

附具体实现(基于asm): [url]http://code.google.com/p/nutzlab/source/browse/#svn/trunk/Nutz.Aop-ASM/Nutz.Aop-ASM[/curl
或者参考另外一篇博文: http://wendal.iteye.com/blog/543681

再次,感谢一下Nutz社区和Peter的支持,没有你们就没有这博文了. O(∩_∩)O哈哈~
Nutz: http://code.google.com/p/nutz/
相关标签： AOP Java F# SVN Google

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