【分享】纯手工打造Emit，实现AOP，附源码下载

NqIceCoffee 2011-07-14 02:44:58

加精

比较喜欢Emit，所以就胡乱写点东西。这个是新鲜出炉的，分享给大家

AOP具体的原理我就不多讲了，大家可以查查资料，我这里用的【继承+重写+动态植入IL代码】

好了，废话少说，下载地址如下

http://download.csdn.net/source/3441835

在附上一个代码片段，嘿嘿。欢迎大虾拍砖

private static void OverrideMethods(TypeBuilder tb, MethodInfo method)

        {

            if (!method.IsPublic|| !method.IsVirtual || IsObjectMethod(method)) return;



            Type[] paramTypes = GetParameterTypes(method);

            MethodAttributes attr = MethodAttributes.Public | MethodAttributes.Family | MethodAttributes.HideBySig | MethodAttributes.Virtual;

            MethodBuilder mb = tb.DefineMethod(method.Name, attr, method.ReturnType, paramTypes);



            LocalBuilder result = null;

            ILGenerator il = mb.GetILGenerator();

            bool is_void = method.ReturnType != typeof(void);



            if (is_void == false)

                result = il.DeclareLocal(method.ReturnType);



            object[] attrs = method.GetCustomAttributes(typeof(AspectAttribute), false);

            if (attrs != null)

            {

                //初始化所有当前方法用到的参数object[]

                CreateLocalParameterArr(il, paramTypes);



                //初始化AspectContext

                Type ctxType = typeof(AspectContext);

                ConstructorInfo info = ctxType.GetConstructor(Type.EmptyTypes);



                var ctx = il.DeclareLocal(ctxType);

                il.Emit(OpCodes.Newobj, info);

                il.Emit(OpCodes.Stloc, ctx);



                //给AspectContext的参数值属性ParameterArgs赋值

                var propMethod = ctxType.GetMethod("set_ParameterArgs");

                il.Emit(OpCodes.Ldloc, ctx);

                il.Emit(OpCodes.Ldloc_0);

                il.Emit(OpCodes.Call, propMethod);



                int m = attrs.Length;

                LocalBuilder[] lbs = new LocalBuilder[m];

                MethodInfo[] endInvokeMethods = new MethodInfo[m];



                //初始化标记的横切对象，并调用横切对象的BeforeInvoke方法

                for (int i = 0; i < m; i++)

                {

                    var tmpType = attrs[i].GetType();

                    var aspect = il.DeclareLocal(tmpType);

                    ConstructorInfo tmpInfo = tmpType.GetConstructor(Type.EmptyTypes);



                    il.Emit(OpCodes.Newobj, tmpInfo);

                    il.Emit(OpCodes.Stloc, aspect);



                    var before_invoke_method = tmpType.GetMethod("BeforeInvoke");

                    endInvokeMethods[i] = tmpType.GetMethod("AfterInvoke");



                    il.Emit(OpCodes.Ldloc, aspect);

                    il.Emit(OpCodes.Ldloc, ctx);

                    il.Emit(OpCodes.Callvirt, before_invoke_method);

                    il.Emit(OpCodes.Nop);



                    lbs[i] = aspect;

                }



                //类对象，参数值依次入栈

                for (int i = 0; i <= paramTypes.Length; i++)

                    il.Emit(OpCodes.Ldarg, i);



                //调用基类的方法

                il.Emit(OpCodes.Call, method);



                //如果有返回值，保存返回值到局部变量

                if (is_void == false)

                    il.Emit(OpCodes.Stloc, result);



                //调用横切对象的AfterInvoke方法

                for (int i = 0; i < m; i++)

                {

                    il.Emit(OpCodes.Ldloc, lbs[i]);

                    il.Emit(OpCodes.Ldloc, ctx);

                    il.Emit(OpCodes.Callvirt, endInvokeMethods[i]);

                    il.Emit(OpCodes.Nop);

                }



                //如果有返回值，则把返回值压栈

                if (is_void == false)

                    il.Emit(OpCodes.Ldloc, result);



                //返回

                il.Emit(OpCodes.Ret);

            }

        }