jdk动态代理源码剖析

摘要

相比于静态代理，动态代理避免了开发人员编写各个繁锁的静态代理类，只需简单地指定一组接口及目标类对象就能动态的获得代理对象。

代理模式



使用代理模式必须要让代理类和目标类实现相同的接口，客户端通过代理类来调用目标方法，代理类会将所有的方法调用分派到目标对象上反射执行，还可以在分派过程中添加”前置通知”和后置处理（如在调用目标方法前校验权限，在调用完目标方法后打印日志等）等功能。

使用动态代理的五大步骤

1.通过实现InvocationHandler接口来自定义自己的InvocationHandler;

2.通过Proxy.getProxyClass获得动态代理类

3.通过反射机制获得代理类的构造方法，方法签名为getConstructor(InvocationHandler.class)

4.通过构造函数获得代理对象并将自定义的InvocationHandler实例对象传为参数传入

5.通过代理对象调用目标方法

动态代理的使用

例1(方式一)

public class MyProxy {
public interface IHello{
void sayHello();
}
static class Hello implements IHello{
public void sayHello() {
System.out.println("Hello world!!");
}
}
//自定义InvocationHandler
static  class HWInvocationHandler implements InvocationHandler{
//目标对象
private Object target;
public HWInvocationHandler(Object target){
this.target = target;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("------插入前置通知代码-------------");
//执行相应的目标方法
Object rs = method.invoke(target,args);
System.out.println("------插入后置处理代码-------------");
return rs;
}
}
public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetExc    eption, InstantiationException {
//生成$Proxy0的class文件
System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
//获取动态代理类
Class proxyClazz = Proxy.getProxyClass(IHello.class.getClassLoader(),IHello.class);
//获得代理类的构造函数，并传入参数类型InvocationHandler.class
Constructor constructor = proxyClazz.getConstructor(InvocationHandler.class);
//通过构造函数来创建动态代理对象，将自定义的InvocationHandler实例传入
IHello iHello = (IHello) constructor.newInstance(new HWInvocationHandler(new Hello()));
//通过代理对象调用目标方法
iHello.sayHello();
}
}

输出：

------插入前置通知代码-------------
Hello world!!
------插入后置处理代码-------------

Proxy类中还有个将2~4步骤封装好的简便方法来创建动态代理对象，其方法签名为：newProxyInstance(ClassLoader loader,Class

public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
//生成$Proxy0的class文件
System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
IHello  ihello = (IHello) Proxy.newProxyInstance(IHello.class.getClassLoader(),  //加载接口的类加载器
new Class[]{IHello.class},      //一组接口
new HWInvocationHandler(new Hello())); //自定义的InvocationHandler
ihello.sayHello();
}

输出结果一样.

下面以newProxyInstance方法为切入点来剖析代理类的生成及代理方法的调用

（为了篇幅整洁去掉了次要的代码）

public static Object newProxyInstance(ClassLoader loader,
Class<?>[] interfaces,
InvocationHandler h)
throws IllegalArgumentException
{
if (h == null) {   //如果h为空直接抛出异常，所以InvocationHandler实例对象是必须的
throw new NullPointerException();
}
//对象的拷贝,暂不知道这里拷贝下的意义是啥？
final Class<?>[] intfs = interfaces.clone();
//一些安全的权限检查
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
}
//产生代理类
Class<?> cl = getProxyClass0(loader, intfs);

//获取代理类的构造函数对象
//参数constructorParames为常量值：private static final Class<?>[] constructorParams = { InvocationHandler.class };
final Constructor<?> cons = cl.getConstructor(constructorParames);
final InvocationHandler ih = h;
//根据代理类的构造函数对象来创建代理类对象
return newInstance(cons, ih);

}

这段代码就是对代理类对象的创建，就是对例1中34~38行封装，其中getProxyClass0就是生成代理类的方法

getProxyClass0方法剖析

private static Class<?> getProxyClass0(ClassLoader loader,
Class<?>... interfaces) {
//接口数不得超过65535个
if (interfaces.length > 65535) {
throw new IllegalArgumentException("interface limit exceeded");
}
//代理类缓存，如果缓存中有代理类了直接返回，否则将由ProxyClassFactory创建代理类
return proxyClassCache.get(loader, interfaces);
}

其中代理缓存是使用WeakCache实现的，如下

/**
* a cache of proxy classes
*/
private static final WeakCache<ClassLoader, Class<?>[], Class<?>>
proxyClassCache = new WeakCache<>(new KeyFactory(), new ProxyClassFactory());

具体的缓存逻辑这里暂不关心，只需要关心ProxyClassFactory是如何生成代理类的，ProxyClassFactory是Proxy的一个静态内部类，实现了WeakCache的内部接口BiFunction的apply方法：

(下面介绍一下怎么定位到生成代理的类是ProxyClassFactory)

跟踪： proxyClassCache.get(loader, interfaces);方法：

/**
* Look-up the value through the cache. This always evaluates the
* {@code subKeyFactory} function and optionally evaluates
* {@code valueFactory} function if there is no entry in the cache for given
* pair of (key, subKey) or the entry has already been cleared.
*
* @param key       possibly null key
* @param parameter parameter used together with key to create sub-key and
*                  value (should not be null)
* @return the cached value (never null)
* @throws NullPointerException if {@code parameter} passed in or
*                              {@code sub-key} calculated by
*                              {@code subKeyFactory} or {@code value}
*                              calculated by {@code valueFactory} is null.
*/
public V get(K key, P parameter) {
Objects.requireNonNull(parameter);

expungeStaleEntries();

Object cacheKey = CacheKey.valueOf(key, refQueue);

// lazily install the 2nd level valuesMap for the particular cacheKey
ConcurrentMap<Object, Supplier<V>> valuesMap = map.get(cacheKey);
if (valuesMap == null) {
ConcurrentMap<Object, Supplier<V>> oldValuesMap
= map.putIfAbsent(cacheKey,
valuesMap = new ConcurrentHashMap<>());
if (oldValuesMap != null) {
valuesMap = oldValuesMap;
}
}

// create subKey and retrieve the possible Supplier<V> stored by that
// subKey from valuesMap
Object subKey = Objects.requireNonNull(subKeyFactory.apply(key, parameter));
Supplier<V> supplier = valuesMap.get(subKey);
Factory factory = null;
//这段代码初始化了supplier 对象为Factory对象的一个
//所以当运行supplier.get();方法的时候，实际是调用的Factory对象的get()方法
while (true) {
//首次运行supplier 为null，if不成立
if (supplier != null) {
// supplier might be a Factory or a CacheValue<V> instance
//这里调用的是Factory对象的get()方法
V value = supplier.get();
if (value != null) {
return value;
}
}
// else no supplier in cache
// or a supplier that returned null (could be a cleared CacheValue
// or a Factory that wasn't successful in installing the CacheValue)

// lazily construct a Factory
if (factory == null) {
//首次运行后初始化factory 对象
factory = new Factory(key, parameter, subKey, valuesMap);
}

if (supplier == null) {
//首次运行，初始化supplier对象
supplier = valuesMap.putIfAbsent(subKey, factory);//首次获取，这里supplier对象为null
if (supplier == null) {
// successfully installed Factory
supplier = factory;
}
// else retry with winning supplier
} else {
if (valuesMap.replace(subKey, supplier, factory)) {
// successfully replaced
// cleared CacheEntry / unsuccessful Factory
// with our Factory
supplier = factory;
} else {
// retry with current supplier
supplier = valuesMap.get(subKey);
}
}
}
}

有以上代码分析可得：调用了Factory实例的get()方法：

@Override
public synchronized V get() { // serialize access
// re-check
Supplier<V> supplier = valuesMap.get(subKey);
if (supplier != this) {
// something changed while we were waiting:
// might be that we were replaced by a CacheValue
// or were removed because of failure ->
// return null to signal WeakCache.get() to retry
// the loop
return null;
}
// else still us (supplier == this)

// create new value
V value = null;
try {
value = Objects.requireNonNull(valueFactory.apply(key, parameter));
} finally {
if (value == null) { // remove us on failure
valuesMap.remove(subKey, this);
}
}
// the only path to reach here is with non-null value
assert value != null;

// wrap value with CacheValue (WeakReference)
CacheValue<V> cacheValue = new CacheValue<>(value);

// try replacing us with CacheValue (this should always succeed)
if (valuesMap.replace(subKey, this, cacheValue)) {
// put also in reverseMap
reverseMap.put(cacheValue, Boolean.TRUE);
} else {
throw new AssertionError("Should not reach here");
}

// successfully replaced us with new CacheValue -> return the value
// wrapped by it
return value;
}

可以看到核心代码为：valueFactory.apply(key, parameter)；

那么valueFactory是谁呢？

//可以看到valueFactory是WeakCache 类的一个私有的成员变量，通过下面的构造方法来初始化
private final BiFunction<K, P, V> valueFactory;

/**
* Construct an instance of {@code WeakCache}
*
* @param subKeyFactory a function mapping a pair of
*                      {@code (key, parameter) -> sub-key}
* @param valueFactory  a function mapping a pair of
*                      {@code (key, parameter) -> value}
* @throws NullPointerException if {@code subKeyFactory} or
*                              {@code valueFactory} is null.
*/
public WeakCache(BiFunction<K, P, ?> subKeyFactory,
BiFunction<K, P, V> valueFactory) {
this.subKeyFactory = Objects.requireNonNull(subKeyFactory);
this.valueFactory = Objects.requireNonNull(valueFactory);
}

通过Proxy类我们又知道：WeakCache 的初始化为：

/**
* a cache of proxy classes
*/
private static final WeakCache<ClassLoader, Class<?>[], Class<?>>
proxyClassCache = new WeakCache<>(new KeyFactory(), new ProxyClassFactory());

所以最终的valueFactory.apply(key, parameter)方法，其实是调用的ProxyClassFactory类的apply方法：

看看ProxyClassFactory是怎样生成代理类的?

private static final class ProxyClassFactory
implements BiFunction<classloader, class<?="">[], Class<!--?-->>
{
//统一代理类的前缀名都以$Proxy开关
private static final String proxyClassNamePrefix = "$Proxy";
//使用唯一的编号给作为代理类名的一部分，如$Proxy0,$Proxy1等
private static final AtomicLong nextUniqueNumber = new AtomicLong();
@Override
public Class<!--?--> apply(ClassLoader loader, Class<!--?-->[] interfaces) {
Map<class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
for (Class<!--?--> intf : interfaces) {
//验证指定的类加载器(loader)加载接口所得到的Class对象(interfaceClass)是否与intf对象相同
Class<!--?--> interfaceClass = null;
try {
interfaceClass = Class.forName(intf.getName(), false, loader);
} catch (ClassNotFoundException e) {
}
if (interfaceClass != intf) {
throw new IllegalArgumentException(
intf + " is not visible from class loader");
}
//验证该Class对象是不是接口
if (!interfaceClass.isInterface()) {
throw new IllegalArgumentException(
interfaceClass.getName() + " is not an interface");
}
// 验证该接口是否重复了
if (interfaceSet.put(interfaceClass, Boolean.TRUE) != null) {
throw new IllegalArgumentException(
"repeated interface: " + interfaceClass.getName());
}
}
//声明代理类所在包
String proxyPkg = null;
/*验证你传入的接口中是否有非public接口，只要有一个接口是非public的，那么这些接口都必须在同一包中
这里的接口修饰符直接影响到System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true")所生成
的代理类的路径，往下看！！*/
for (Class<!--?--> intf : interfaces) {
int flags = intf.getModifiers();
if (!Modifier.isPublic(flags)) {
String name = intf.getName();
int n = name.lastIndexOf('.');
//截取完整包名
String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
if (proxyPkg == null) {
proxyPkg = pkg;
} else if (!pkg.equals(proxyPkg)) {
throw new IllegalArgumentException(
"non-public interfaces from different packages");
}
}
}

if (proxyPkg == null) {
/*如果都是public接口，那么生成的代理类就在com.sun.proxy包下如果报java.io.FileNotFoundException: com\sun\proxy\$Proxy0.c                  lass (系统找不到指定的路径。)的错误，就先在你项目中创建com.sun.proxy路径*/
proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
}

//将当前nextUniqueNumber的值以原子的方式的加1，所以第一次生成代理类的名字为$Proxy0.class
long num = nextUniqueNumber.getAndIncrement();
//代理类的完全限定名，如com.sun.proxy.$Proxy0.calss,
String proxyName = proxyPkg + proxyClassNamePrefix + num;
//生成代理类字节码文件
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces);
try {
return defineClass0(loader, proxyName,
proxyClassFile, 0, proxyClassFile.length);
} catch (ClassFormatError e) {
throw new IllegalArgumentException(e.toString());
}
}
}

而生成代理类字节码文件又主要通过ProxyGenerate的generateProxyClass(proxyName，interfaces)

public static byte[] generateProxyClass(final String var0, Class[] var1) {
ProxyGenerator var2 = new ProxyGenerator(var0, var1);
//生成代理类字节码文件的真正方法
final byte[] var3 = var2.generateClassFile();
//保存文件
// 这里根据参数配置，决定是否把生成的字节码（.class文件）保存到本地磁盘，我们可以通过把相应的class文件保存到本地，再反编译来看看具体的实现，这样更直观
if(saveGeneratedFiles) {
AccessController.doPrivileged(new PrivilegedAction() {
public Void run() {
try {
FileOutputStream var1 = new FileOutputStream(ProxyGenerator.dotToSlash(var0) + ".class");
var1.write(var3);
var1.close();
return null;
} catch (IOException var2) {
throw new InternalError("I/O exception saving generated file: " + var2);
}
}
});
}
return var3;
}

saveGeneratedFiles这个属性的值从哪里来呢：

private static final boolean saveGeneratedFiles = ((Boolean)AccessController.doPrivileged(new GetBooleanAction("sun.misc.ProxyGenerator.saveGeneratedFiles"))).booleanValue();

GetBooleanAction实际上是调用Boolean.getBoolean(propName)来获得的，而Boolean.getBoolean(propName)调用了System.getProperty(name)，所以我们可以设置sun.misc.ProxyGenerator.saveGeneratedFiles这个系统属性为true来把生成的class保存到本地文件来查看。

这里要注意，当把这个属性设置为true时，生成的class文件及其所在的路径都需要提前创建，否则会抛出FileNotFoundException异常。如:在jdk1.7及以上则不会出现这种情况（1.7以前的自己验证），如果出现以下异常：

Exception in thread "main" java.lang.InternalError: I/O exception saving generated file: java.io.FileNotFoundException: com/sun/proxy/$Proxy0.class (No such file or directory)
at sun.misc.ProxyGenerator$1.run(ProxyGenerator.java:336)
at sun.misc.ProxyGenerator$1.run(ProxyGenerator.java:327)
at java.security.AccessController.doPrivileged(Native Method)
at sun.misc.ProxyGenerator.generateProxyClass(ProxyGenerator.java:326)
at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:672)
at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:592)
at java.lang.reflect.WeakCache$Factory.get(WeakCache.java:244)
at java.lang.reflect.WeakCache.get(WeakCache.java:141)
at java.lang.reflect.Proxy.getProxyClass0(Proxy.java:455)
at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:738)
at com.mikan.proxy.ProxyTest.main(ProxyTest.java:15)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)

则：即我们要在运行当前main方法的路径下创建com/sun/proxy目录，并创建一个$Proxy0.class文件，才能够正常运行并保存class文件内容。

层层调用后，最终generateClassFile才是真正生成代理类字节码文件的方法，注意开头的三个addProxyMethod方法是只将Object的hashcode,equals,toString方法添加到代理方法容器中，代理类除此之外并没有重写其他Object的方法，所以除这三个方法外，代理类调用其他方法的行为与Object调用这些方法的行为一样不通过Invoke

private byte[] generateClassFile() {
/addProxyMethod系列方法就是将接口的方法和Object的hashCode,equals,toString方法添加到代理方法容器(proxyMethods),
其中方法签名作为key,proxyMethod作为value*/
/*hashCodeMethod方法位于静态代码块中通过Object对象获得，hashCodeMethod=Object.class.getMethod("hashCode",new Class[0]),
相当于从Object中继承过来了这三个方法equalsMethod,toStringMethod*/
this.addProxyMethod(hashCodeMethod, Object.class);   -->
this.addProxyMethod(equalsMethod, Object.class);
this.addProxyMethod(toStringMethod, Object.class);
int var1;
int var3;
//获得所有接口中的所有方法，并将方法添加到代理方法中
for(var1 = 0; var1 < this.interfaces.length; ++var1) {
Method[] var2 = this.interfaces[var1].getMethods();
for(var3 = 0; var3 < var2.length; ++var3) {
this.addProxyMethod(var2[var3], this.interfaces[var1]);
}
}

Iterator var7 = this.proxyMethods.values().iterator();
List var8;
while(var7.hasNext()) {
var8 = (List)var7.next();
checkReturnTypes(var8);    //验证具有相同方法签名的的方法的返回值类型是否一致，因为不可能有两个方法名相同,参数相同，而返回值却不同的方法
};
//接下来就是写代理类文件的步骤了
Iterator var11
try {
//生成代理类的构造函数
this.methods.add(this.generateConstructor());
var7 = this.proxyMethods.values().iterator();
while(var7.hasNext()) {
var8 = (List)var7.next();
var11 = var8.iterator();
while(var11.hasNext()) {
ProxyGenerator.ProxyMethod var4 = (ProxyGenerator.ProxyMethod)var11.next();
/将代理字段声明为Method，10为ACC_PRIVATE和ACC_STATAIC的与运算，表示该字段的修饰符为private static
所以代理类的字段都是private static Method XXX*/
this.fields.add(new ProxyGenerator.FieldInfo(var4.methodFieldName, "Ljava/lang/reflect/Method;", 10));
//生成代理类的代理方法
this.methods.add(var4.generateMethod());
}
}
//为代理类生成静态代码块，对一些字段进行初始化
this.methods.add(this.generateStaticInitializer());
} catch (IOException var6) {
throw new InternalError("unexpected I/O Exception");
}

if(this.methods.size() > '\uffff') {  //代理方法超过65535将抛出异常
throw new IllegalArgumentException("method limit exceeded");
} else if(this.fields.size() > '\uffff') {   //代理类的字段超过65535将抛出异常
throw new IllegalArgumentException("field limit exceeded");
} else {
//这里开始就是一些代理类文件的过程，此过程略过
this.cp.getClass(dotToSlash(this.className));
this.cp.getClass("java/lang/reflect/Proxy");
for(var1 = 0; var1 < this.interfaces.length; ++var1) {
this.cp.getClass(dotToSlash(this.interfaces[var1].getName()));
}
this.cp.setReadOnly();
ByteArrayOutputStream var9 = new ByteArrayOutputStream();
DataOutputStream var10 = new DataOutputStream(var9);
try {
var10.writeInt(-889275714);
var10.writeShort(0);
var10.writeShort(49);
this.cp.write(var10);
var10.writeShort(49);
var10.writeShort(this.cp.getClass(dotToSlash(this.className)));
var10.writeShort(this.cp.getClass("java/lang/reflect/Proxy"));
var10.writeShort(this.interfaces.length);
for(var3 = 0; var3 < this.interfaces.length; ++var3) {
var10.writeShort(this.cp.getClass(dotToSlash(this.interfaces[var3].getName())));
}
var10.writeShort(this.fields.size());
var11 = this.fields.iterator();
while(var11.hasNext()) {
ProxyGenerator.FieldInfo var12 = (ProxyGenerator.FieldInfo)var11.next();
var12.write(var10);
}
var10.writeShort(this.methods.size());
var11 = this.methods.iterator();
while(var11.hasNext()) {
ProxyGenerator.MethodInfo var13 = (ProxyGenerator.MethodInfo)var11.next();
var13.write(var10);
}
var10.writeShort(0);
return var9.toByteArray();
} catch (IOException var5) {
throw new InternalError("unexpected I/O Exception");
}
}
}

addProxyMethod方法剖析

private void addProxyMethod(Method var1, Class var2) {
String var3 = var1.getName();  //方法名
Class[] var4 = var1.getParameterTypes();   //方法参数类型数组
Class var5 = var1.getReturnType();    //返回值类型
Class[] var6 = var1.getExceptionTypes();   //异常类型
String var7 = var3 + getParameterDescriptors(var4);   //方法签名
Object var8 = (List)this.proxyMethods.get(var7);   //根据方法签名却获得proxyMethods的Value
if(var8 != null) {    //处理多个代理接口中重复的方法的情况
Iterator var9 = ((List)var8).iterator();
while(var9.hasNext()) {
ProxyGenerator.ProxyMethod var10 = (ProxyGenerator.ProxyMethod)var9.next();
if(var5 == var10.returnType) {
/*归约异常类型以至于让重写的方法抛出合适的异常类型，我认为这里可能是多个接口中有相同的方法，而这些相同的方法抛出的异常类                      型又不同，所以对这些相同方法抛出的异常进行了归约*/
ArrayList var11 = new ArrayList();
collectCompatibleTypes(var6, var10.exceptionTypes, var11);
collectCompatibleTypes(var10.exceptionTypes, var6, var11);
var10.exceptionTypes = new Class[var11.size()];
//将ArrayList转换为Class对象数组
var10.exceptionTypes = (Class[])var11.toArray(var10.exceptionTypes);
return;
}
}
} else {
var8 = new ArrayList(3);
this.proxyMethods.put(var7, var8);
}
((List)var8).add(new ProxyGenerator.ProxyMethod(var3, var4, var5, var6, var2, null));
/*24~27行的意思就是如果var8为空，就创建一个数组，并以方法签名为key,proxymethod对象数组为value添加到proxyMethods*/
}

InvocationHandler的作用

在动态代理中InvocationHandler是核心，每个代理实例都具有一个关联的调用处理程序(InvocationHandler)。对代理实例调用方法时，将对方法调用进行编码并将其指派到它的调用处理程序(InvocationHandler)的 invoke 方法。所以对代理方法的调用都是通InvocationHadler的invoke来实现中，而invoke方法根据传入的代理对象，方法和参数来决定调用代理的哪个方法

invoke方法签名：invoke（Object Proxy，Method method，Object[] args）

$Proxy0.class

来看看例1(MyProxy)的代理类是怎样的？

public final class $Proxy0 extends Proxy implements IHello {   //继承了Proxy类和实现IHello接口
//变量，都是private static Method  XXX
private static Method m3;
private static Method m1;
private static Method m0;
private static Method m2;
//代理类的构造函数，其参数正是是InvocationHandler实例，Proxy.newInstance方法就是通过通过这个构造函数来创建代理实例的
public $Proxy0(InvocationHandler var1) throws  {
super(var1);
}
//接口代理方法
public final void sayHello() throws  {
try {
super.h.invoke(this, m3, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
//以下Object中的三个方法
public final boolean equals(Object var1) throws  {
try {
return ((Boolean)super.h.invoke(this, m1, new Object[]{var1})).booleanValue();
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
}
public final int hashCode() throws  {
try {
return ((Integer)super.h.invoke(this, m0, (Object[])null)).intValue();
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final String toString() throws  {
try {
return (String)super.h.invoke(this, m2, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
//对变量进行一些初始化工作
static {
try {
m3 = Class.forName("com.mobin.proxy.IHello").getMethod("sayHello", new Class[0]);
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[]{Class.forName("java.lang.Object")});
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
} catch (NoSuchMethodException var2) {
throw new NoSuchMethodError(var2.getMessage());
} catch (ClassNotFoundException var3) {
throw new NoClassDefFoundError(var3.getMessage());
}
}
}

以上就是对代理类如何生成，代理类方法如何被调用的分析！在很多框架都使用了动态代理如Spring,HDFS的RPC调用等等！！

博客引用：http://www.cnblogs.com/MOBIN/p/5597215.html

http://blog.csdn.net/mhmyqn/article/details/48474815