代理对象是AOP动态截入的关键部分 下面来分析一下代理对象是如何定义的
CreateProxyType
internal static Type CreateProxyType(Type[] interfaces IMixin[] mixins){
//
AssemblyName assemblyName = new AssemblyName();
assemblyNameName = DynamicAssemblyProxyGen;
AssemblyBuilder assemblyBuilder = AppDomainCurrentDomainDefineDynamicAssembly(
assemblyName AssemblyBuilderAccessRun);
// 以指定名称和访问模式定义动态程序集 这里以运行模式建立程序集
ModuleBuilder moduleBuilder = assemblyBuilderDefineDynamicModule( assemblyNameName true );
// 在动态程序集中定义动态模块 第二个参数发出符号信息
TypeBuilder typeBuilder = moduleBuilderDefineType( ProxyType
TypeAttributesPublic|TypeAttributesClass null MergeTypes(interfaces mixins) );
// 定义一个类类型 此类为public 且实现所有的interfaces和mixins接口
// MergeTypes用于将interfaces和mixins合并为一个Type[]
FieldBuilder handlerField = GenerateField( typeBuilder handlerFieldName typeof(IInvocationHandler) );
// 产生一个IInvocationHandler字段 等同于 public IInvocationHandler handler;
FieldBuilder mixinHandlerField = GenerateField( typeBuilder mixinHandlerFieldName
typeof(IMixinInvocationHandler) );
// 产生一个IMixinInvocation字段 等同于 public IMixinInvocationHandler mixinHandler;
FieldBuilder mixinsField = GenerateField( typeBuilder mixins typeof(IMixin[]) );
// 产生一个IMixin[]字段 等同于 public IMixin[] mixins;
ConstructorBuilder constr = GenerateConstructor( typeBuilder handlerField mixinsField mixinHandlerField );
// 产生一个构造方法
GenerateInterfaceImplementation( typeBuilder interfaces handlerField );
// 产生接口的实现部分
GenerateMixinImplementation( typeBuilder mixins mixinHandlerField mixinsField);
// 产生混合器接口的实现部分
}
GenerateConstructor
private static ConstructorBuilder GenerateConstructor( TypeBuilder typeBuilder
FieldBuilder handlerField FieldBuilder mixinsField FieldBuilder mixinHandlerField ) {
ConstructorBuilder consBuilder = typeBuilderDefineConstructor(
MethodAttributesPublic
CallingConventionsStandard
new Type[] { typeof(IInvocationHandler) typeof(IMixinInvocationHandler) typeof(IMixin[]) } );
// 定义一个构造方法 指定方法修饰为Public 调用约定为Standard
// 等同于 public ProxyType( IInvocationHandler handler IMixinInvocationHandler mixinHandler IMixin[] mixins );
ILGenerator ilGenerator = consBuilderGetILGenerator();
// 取得IL产生器 用于生成IL代码
ilGeneratorEmit(OpCodesLdarg_);
ilGeneratorEmit(OpCodesCall typeof(Object)GetConstructor(new Type[]));
// 调用Object类型的默认构造函数 等同于 public ProxyType() : base()
// handler
ilGeneratorEmit(OpCodesLdarg_);
ilGeneratorEmit(OpCodesLdarg_);
ilGeneratorEmit(OpCodesStfld handlerField);
// 对handlerField字段进行赋值 等同于 thishandler = handler;
// mixinHandler
ilGeneratorEmit(OpCodesLdarg_);
ilGeneratorEmit(OpCodesLdarg_);
ilGeneratorEmit(OpCodesStfld mixinHandlerField);
// 对mixinHandlerField字段进行赋值 等同于 thismixinHandler = mixinHandler;
// mixins
ilGeneratorEmit(OpCodesLdarg_);
ilGeneratorEmit(OpCodesLdarg_);
ilGeneratorEmit(OpCodesStfld mixinsField);
// 对mixinsField字段进行赋值 等同于 thismixins = mixins
ilGeneratorEmit(OpCodesRet);
return consBuilder;
}
代理对象的构造方法类似如下:
public Class ProxyType : 对象接口 混合器接口 {
private IInvocationHandler handler;
private IMixinvocationHandler mixinHandler;
private IMixin[] mixins;
public public ProxyType( IInvocationHandler handler
IMixinInvocationHandler mixinHandler IMixin[] mixins ); {
thishandler = handler;
thismixinHandler = mixinHandler;
thismixins = mixins;
}
//
}
产生接口的实现部分
static void GenerateInterfaceImplementation( TypeBuilder typeBuilder
Type[] interfaces FieldBuilder handlerField ) {
foreach(Type inter in interfaces) {
GenerateInterfaceImplementation( typeBuilder inter handlerField null );
}
// 遍历所有接口
}
private static void GenerateMixinImplementation( TypeBuilder typeBuilder
IMixin[] mixins FieldBuilder mixinHandlerField FieldBuilder mixinsField) {
if (mixins == null) return;
for(int i = ; i < mixins.Length; i++) {
Type[] interfaces = mixins[i].GetType().GetInterfaces();
foreach(Type inter in interfaces){
GenerateInterfaceImplementation( typeBuilder, inter, mixinHandlerField, mixinsField, i );
}
}
// 遍历所有的混合器接口
}
static void GenerateInterfaceImplementation( TypeBuilder typeBuilder,
Type inter, FieldBuilder handlerField, FieldBuilder mixinsField, int mixinPosition) {
// ...
Type[] baseInterfaces = inter.FindInterfaces( new TypeFilter( NoFilterImpl ), inter );
GenerateInterfaceImplementation( typeBuilder, baseInterfaces, handlerField);
// 这是一个递归过程, 用于遍历所有的接口.
PropertyInfo[] properties = inter.GetProperties();
PropertyBuilder[] propertiesBuilder = new PropertyBuilder[properties.Length];
for(int i=0; i < properties.Length; i++){
GeneratePropertyImplementation( typeBuilder, properties[i], ref propertiesBuilder[i] );
}
// 产生属性的实现.
MethodInfo[] methods = inter.GetMethods();
foreach(MethodInfo method in methods) {
GenerateMethodImplementation( typeBuilder, method, propertiesBuilder, inter,
handlerField, mixinsField, mixinPosition );
}
// 产生方法的实现.
}
// 属性的实现.
private static void GeneratePropertyImplementation( TypeBuilder typeBuilder,
PropertyInfo property, ref PropertyBuilder propertyBuilder ) {
propertyBuilder = typeBuilder.DefineProperty(
property.Name, property.Attributes, property.PropertyType, null);
// 通过调用DefindProperty方法来产生属性的实现部分.
}
// 方法的实现.
private static void GenerateMethodImplementation(TypeBuilder typeBuilder,
MethodInfo method, PropertyBuilder[] properties, Type inter,
FieldBuilder handlerField, FieldBuilder mixinsField, int mixinPosition ){
ParameterInfo[] parameterInfo = method.GetParameters();
// 取得参数信息.
System.Type[] parameters = new System.Type[parameterInfo.Length];
for (int i=0; iparameters[i] = parameterInfo[i].ParameterType;
}
// 取得参数的类型.
MethodAttributes atts = MethodAttributes.Public|MethodAttributes.Virtual;
if ( method.Name.StartsWith("set_") || method.Name.StartsWith("get_") ) {
atts = MethodAttributes.Public|MethodAttributes.SpecialName|MethodAttributes.Virtual;
}
// 指定方法的修饰.
MethodBuilder methodBuilder =typeBuilder.DefineMethod( method.Name, atts,
CallingConventions.Standard, method.ReturnType, parameters );
// 定义方法.
if ( method.Name.StartsWith("set_") || method.Name.StartsWith("get_") ) {
foreach( PropertyBuilder property in properties ){
if (property == null){
break;
}
if (!property.Name.Equals( method.Name.Substring(4) )) {
continue;
}
