本文详细剖析了Java动态代理的实现原理，从源码角度解释了如何通过Proxy类和InvocationHandler接口创建代理对象，以及代理类的生成过程。
在研究代码之前，我们先看看一个实例，然后我们根据实例来进行源码研究。
实例代码如下：
package com.jd.dynamicproxy.dynamicproxy;
import java.io.Serializable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
* Created by IntelliJ IDEA.
* User: MessengerOfSpring
* Date: 2017/12/3
* Time: 21:39
*/
public class App {
private interface Account {
public Account deposit (double value);
public double getBalance ();
}
private class ExampleInvocationHandler implements InvocationHandler {
private double balance;
@Override
public Object invoke (Object proxy, Method method, Object[] args) throws Throwable {
// simplified method checks, would need to check the parameter count and types too
if ("deposit".equals(method.getName())) {
Double value = (Double) args[0];
System.out.println("deposit: " + value);
balance += value;
return proxy; // here we use the proxy to return 'this'
}
if ("getBalance".equals(method.getName())) {
return balance;
}
return null;
}
}
public static void main(String[] args) {
new App();
}
public App() {
//设置保存属性，用来将代理类字节码文件保存下来
System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
Account account = (Account) Proxy.newProxyInstance( getClass().getClassLoader(),
new Class[] {Account.class,Serializable.class},
new ExampleInvocationHandler());
// method chaining for the win!
account.deposit(5000).deposit(4000).deposit(-2500);
System.out.println("Balance: " + account.getBalance());
}
}我们从Proxy中的public static Object newProxyInstance(ClassLoader loader,Class<?>[] interfaces,InvocationHandler h)函数开始讲起，这个函数的代码如下：
@CallerSensitive
public static Object newProxyInstance(ClassLoader loader,
Class<?>[] interfaces,
InvocationHandler h)
throws IllegalArgumentException
{
//判断h是否为null，如果为null的话就跑出NullPointerException异常
Objects.requireNonNull(h);
//将interfaces接口数组拷贝到intfs中
final Class<?>[] intfs = interfaces.clone();
//进行权限检查，关于这个可以查相关资料，这里不展开讲
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
}
/*
* 该方法先从缓存获取代理类, 如果没有再去生成一个代理类
*/
Class<?> cl = getProxyClass0(loader, intfs);
/*
* Invoke its constructor with the designated invocation handler.
*/
try {
if (sm != null) {
checkNewProxyPermission(Reflection.getCallerClass(), cl);
}
//
final Constructor<?> cons = cl.getConstructor(constructorParams);
final InvocationHandler ih = h;
if (!Modifier.isPublic(cl.getModifiers())) {
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
cons.setAccessible(true);
return null;
}
});
}
return cons.newInstance(new Object[]{h});
} catch (IllegalAccessException|InstantiationException e) {
throw new InternalError(e.toString(), e);
} catch (InvocationTargetException e) {
Throwable t = e.getCause();
if (t instanceof RuntimeException) {
throw (RuntimeException) t;
} else {
throw new InternalError(t.toString(), t);
}
} catch (NoSuchMethodException e) {
throw new InternalError(e.toString(), e);
}
}我们开始解析getProxyClass0函数，这个函数用来创建一个代理类对象，代码如下：
/**
* Generate a proxy class. Must call the checkProxyAccess method
* to perform permission checks before calling this.
*/
private static Class<?> getProxyClass0(ClassLoader loader,
Class<?>... interfaces) {
if (interfaces.length > 65535) {
throw new IllegalArgumentException("interface limit exceeded");
}
// If the proxy class defined by the given loader implementing
// the given interfaces exists, this will simply return the cached copy;
// otherwise, it will create the proxy class via the ProxyClassFactory
//如果缓存中存在代理类对象，那么就直接返回，否则就会调用ProxyClassFactory这个工厂去生成一个代理类。
return proxyClassCache.get(loader, interfaces);
}我们现在进入proxyClassCache.get函数中(proxyClassCache类对象的创建代码如下：
private static final WeakCache<ClassLoader, Class<?>[], Class<?>> proxyClassCache = new WeakCache<>(new KeyFactory(), new ProxyClassFactory());)KeyFactory实现BiFunction<ClassLoader, Class<?>[], Object>,ProxyClassFactory实现BiFunction<ClassLoader, Class<?>[], Class<?>>。
其中KeyFactory的代码如下：
/**
* A function that maps an array of interfaces to an optimal key where
* Class objects representing interfaces are weakly referenced.
*/
private static final class KeyFactory
implements BiFunction<ClassLoader, Class<?>[], Object>
{
@Override
public Object apply(ClassLoader classLoader, Class<?>[] interfaces) {
switch (interfaces.length) {
case 1: return new Key1(interfaces[0]); // the most frequent
case 2: return new Key2(interfaces[0], interfaces[1]);
case 0: return key0;
default: return new KeyX(interfaces);
}
}
}ProxyClassFactory类代码如下：
/**
* A factory function that generates, defines and returns the proxy class given
* the ClassLoader and array of interfaces.
*/
private static final class ProxyClassFactory
implements BiFunction<ClassLoader, Class<?>[], Class<?>>
{
// prefix for all proxy class names
private static final String proxyClassNamePrefix = "$Proxy";
// next number to use for generation of unique proxy class names
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) {
/*
* Verify that the class loader resolves the name of this
* interface to the same Class object.
*/
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");
}
/*
* Verify that the Class object actually represents an
* interface.
*/
if (!interfaceClass.isInterface()) {
throw new IllegalArgumentException(
interfaceClass.getName() + " is not an interface");
}
/*
* Verify that this interface is not a duplicate.
*/
if (interfaceSet.put(interfaceClass, Boolean.TRUE) != null) {
throw new IllegalArgumentException(
"repeated interface: " + interfaceClass.getName());
}
}
String proxyPkg = null; // package to define proxy class in
int accessFlags = Modifier.PUBLIC | Modifier.FINAL;
/*
* Record the package of a non-public proxy interface so that the
* proxy class will be defined in the same package. Verify that
* all non-public proxy interfaces are in the same package.
*/
for (Class<?> intf : interfaces) {
int flags = intf.getModifiers();
if (!Modifier.isPublic(flags)) {
accessFlags = Modifier.FINAL;
String name = intf.getName();
int n = name.lastIndexOf('.');
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) {
// if no non-public proxy interfaces, use com.sun.proxy package
proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
}
/*
* Choose a name for the proxy class to generate.
*/
long num = nextUniqueNumber.getAndIncrement();
String proxyName = proxyPkg + proxyClassNamePrefix + num;
/*
* Generate the specified proxy class.
*/
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces, accessFlags);
try {
return defineClass0(loader, proxyName,
proxyClassFile, 0, proxyClassFile.length);
} catch (ClassFormatError e) {
/*
* A ClassFormatError here means that (barring bugs in the
* proxy class generation code) there was some other
* invalid aspect of the arguments supplied to the proxy
* class creation (such as virtual machine limitations
* exceeded).
*/
throw new IllegalArgumentException(e.toString());
}
}
}上面两个类我们后面再讲，在进入到proxyClassCache.get(loader, interfaces)的get函数前，我们先看看它的构造函数和成员变量，它们所在的类为WeakCache，代码如下：
//Reference引用队列
private final ReferenceQueue<K> refQueue = new ReferenceQueue<>();
// the key type is Object for supporting null key
//缓存的底层实现, key为一级缓存, value为二级缓存。 为了支持null, map的key类型设置为Object
private final ConcurrentMap<Object, ConcurrentMap<Object, Supplier<V>>> map = new ConcurrentHashMap<>();
//reverseMap记录了所有代理类生成器是否可用, 这是为了实现缓存的过期机制
private final ConcurrentMap<Supplier<V>, Boolean> reverseMap = new ConcurrentHashMap<>();
//生成二级缓存key的工厂, 这里传入的是KeyFactory
private final BiFunction<K, P, ?> subKeyFactory;
//生成二级缓存value的工厂, 这里传入的是ProxyClassFactory
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.
*/
//构造器, 传入生成二级缓存key的工厂和生成二级缓存value的工厂
public WeakCache(BiFunction<K, P, ?> subKeyFactory,
BiFunction<K, P, V> valueFactory) {
this.subKeyFactory = Objects.requireNonNull(subKeyFactory);
this.valueFactory = Objects.requireNonNull(valueFactory);
}proxyClassCache.get(loader, interfaces)中get代码如下：
/**
* 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);
//清除过期的缓存
expungeStaleEntries();
//将ClassLoader包装成CacheKey, 作为一级缓存的key,其中cacheKey中的referent成员变量值为key,queue成员变量为refQueue
Object cacheKey = CacheKey.valueOf(key, refQueue);
// lazily install the 2nd level valuesMap for the particular cacheKey
//获取得到二级缓存
ConcurrentMap<Object, Supplier<V>> valuesMap = map.get(cacheKey);
//如果根据ClassLoader没有获取到对应的值
if (valuesMap == null) {
//以CAS方式放入, 如果不存在则放入，否则返回原先的值
ConcurrentMap<Object, Supplier<V>> oldValuesMap = map.putIfAbsent(cacheKey, valuesMap = new ConcurrentHashMap<>());
//如果oldValuesMap有值, 说明放入失败,即cacheKey存在(至于为什么可以去看看putIfAbsent这个方法),否则cacheKey不存在
if (oldValuesMap != null) {
valuesMap = oldValuesMap;
}
}
// create subKey and retrieve the possible Supplier<V> stored by that
// subKey from valuesMap
//根据代理类实现的接口数组来生成二级缓存key, 分为key0, key1, key2, keyx,这里apply调用的是KeyFactory类中的,返回Key2类型对 //象,其中parameter中两个接口，其中第一个存储到Key2中的referent成员变量,第二个在此基础上创建一个新的WeakReference类对 //象中，这个类对象中的referent成员变量为第二个接口。
Object subKey = Objects.requireNonNull(subKeyFactory.apply(key, parameter));
//这里通过subKey获取到二级缓存的值
Supplier<V> supplier = valuesMap.get(subKey);
Factory factory = null;
while (true) {
//如果通过subKey取出来的值不为空
if (supplier != null) {
// supplier might be a Factory or a CacheValue<V> instance
//在这里supplier可能是一个Factory也可能会是一个CacheValue，在这里不作判断, 而是在Supplier实现类的get方法里面进行验证
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) {
//新建一个Factory实例作为subKey对应的值
factory = new Factory(key, parameter, subKey, valuesMap);
}
if (supplier == null) {
//到这里表明subKey没有对应的值, 就将factory作为subKey的值放入
supplier = valuesMap.putIfAbsent(subKey, factory);
if (supplier == null) {
// successfully installed Factory
supplier = factory;
}
// else retry with winning supplier
} else {
//期间可能其他线程修改了值, 那么就将原先的值替换
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);
}
}
}
}进入Factory类，代码如下：
/**
* A factory {@link Supplier} that implements the lazy synchronized
* construction of the value and installment of it into the cache.
*/
private final class Factory implements Supplier<V> {
//一级缓存key, 根据ClassLoader生成
private final K key;
//代理类实现的接口数组
private final P parameter;
//二级缓存key, 根据接口数组生成
private final Object subKey;
//二级缓存
private final ConcurrentMap<Object, Supplier<V>> valuesMap;
Factory(K key, P parameter, Object subKey,
ConcurrentMap<Object, Supplier<V>> valuesMap) {
this.key = key;
this.parameter = parameter;
this.subKey = subKey;
this.valuesMap = valuesMap;
}
@Override
public synchronized V get() { // serialize access
//这里再一次去二级缓存里面获取Supplier, 用来验证是否是Factory本身
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
//在这里验证supplier是否是Factory实例本身, 如果不则返回null让调用者继续轮询重试
//期间supplier可能替换成了CacheValue, 或者由于生成代理类失败被从二级缓存中移除了
return null;
}
// else still us (supplier == this)
// create new value
V value = null;
try {
//委托valueFactory去生成代理类, 这里会通过传入的ProxyClassFactory去生成代理类
value = Objects.requireNonNull(valueFactory.apply(key, parameter));
} finally {
if (value == null) { // remove us on failure
//如果生成代理类失败, 就将这个二级缓存删除
valuesMap.remove(subKey, this);
}
}
// the only path to reach here is with non-null value
//只有value的值不为空才能到达这里
assert value != null;
// wrap value with CacheValue (WeakReference)
//使用弱引用包装生成的代理类
CacheValue<V> cacheValue = new CacheValue<>(value);
// put into reverseMap
//对cacheValue进行标记
reverseMap.put(cacheValue, Boolean.TRUE);
// try replacing us with CacheValue (this should always succeed)
//将包装后的cacheValue放入二级缓存中, 这个操作必须成功, 否则就报错
if (!valuesMap.replace(subKey, this, cacheValue)) {
throw new AssertionError("Should not reach here");
}
// successfully replaced us with new CacheValue -> return the value
// wrapped by it
return value;
}
}流程如下：
接下来我们进入ProxyClassFactory类中的apply函数中，相关代码如下：
/**
* A factory function that generates, defines and returns the proxy class given
* the ClassLoader and array of interfaces.
*/
private static final class ProxyClassFactory
implements BiFunction<ClassLoader, Class<?>[], Class<?>>
{
// prefix for all proxy class names
//代理类名称前缀
private static final String proxyClassNamePrefix = "$Proxy";
// next number to use for generation of unique proxy class names
//采用一个原子类对象，用来生成一个计数，这个计数用来拼成代理类对象名称
private static final AtomicLong nextUniqueNumber = new AtomicLong();
@Override
//loader为加载器类对象，interfaces为接口数组
public Class<?> apply(ClassLoader loader, Class<?>[] interfaces) {
Map<Class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
//遍历接口数组
for (Class<?> intf : interfaces) {
/*
* Verify that the class loader resolves the name of this
* interface to the same Class object.
*/
Class<?> interfaceClass = null;
try {
//通过loader加载器获取到接口对应的Class类对象
interfaceClass = Class.forName(intf.getName(), false, loader);
} catch (ClassNotFoundException e) {
}
if (interfaceClass != intf) {
throw new IllegalArgumentException(
intf + " is not visible from class loader");
}
/*
* Verify that the Class object actually represents an
* interface.
*/
if (!interfaceClass.isInterface()) {
throw new IllegalArgumentException(
interfaceClass.getName() + " is not an interface");
}
/*
* Verify that this interface is not a duplicate.
*/
//将该接口的Class类对象保存到map容器interfaceSet中
if (interfaceSet.put(interfaceClass, Boolean.TRUE) != null) {
throw new IllegalArgumentException(
"repeated interface: " + interfaceClass.getName());
}
}
//整个循环下来，将所有的接口的Class类对象都保存在了interfaceSet中
String proxyPkg = null; // package to define proxy class in
int accessFlags = Modifier.PUBLIC | Modifier.FINAL;
/*
* Record the package of a non-public proxy interface so that the
* proxy class will be defined in the same package. Verify that
* all non-public proxy interfaces are in the same package.
*/
//继续对接口进行循环
for (Class<?> intf : interfaces) {
int flags = intf.getModifiers();
//如果该接口不为public
if (!Modifier.isPublic(flags)) {
accessFlags = Modifier.FINAL;
//返回接口名称(例如String.class.getName()获得java.lang.String)
String name = intf.getName();
int n = name.lastIndexOf('.');
//获取该接口对应的包名称
String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
if (proxyPkg == null) {
proxyPkg = pkg;
} else if (!pkg.equals(proxyPkg)) {
//走到这里说明有些接口不在同一个包中，也就是这些接口要么都是public，要么都不为public且要在同一个包中。
throw new IllegalArgumentException(
"non-public interfaces from different packages");
}
}
}
//如果proxyPkg为null,那么就采用默认的包名称
if (proxyPkg == null) {
// if no non-public proxy interfaces, use com.sun.proxy package
//此时proxyPkg为com.sun.proxy.
proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
}
/*
* Choose a name for the proxy class to generate.
*/
//获取一个唯一计数值
long num = nextUniqueNumber.getAndIncrement();
//拼成代理类名称,如果num为0且在默认包的情况下那么proxyName为com.sun.proxy.$Proxy0
String proxyName = proxyPkg + proxyClassNamePrefix + num;
/*
* Generate the specified proxy class.
*/
//开始针对该代理类名称获取相应的class字节码内容
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces, accessFlags);
try {
//根据该字节码内容生成一个对应的Class类对象。
return defineClass0(loader, proxyName,
proxyClassFile, 0, proxyClassFile.length);
} catch (ClassFormatError e) {
/*
* A ClassFormatError here means that (barring bugs in the
* proxy class generation code) there was some other
* invalid aspect of the arguments supplied to the proxy
* class creation (such as virtual machine limitations
* exceeded).
*/
throw new IllegalArgumentException(e.toString());
}
}
}接下来我们进入到ProxyGenerator.generateProxyClass(proxyName, interfaces, accessFlags)函数中，代码如下：
public static byte[] generateProxyClass(String s, Class aclass[], int i)
{
ProxyGenerator proxygenerator = new ProxyGenerator(s, aclass, i);
//生成Class字节码内容
byte abyte0[] = proxygenerator.generateClassFile();
//判断是否要将该字节码内容保存到文件中，
//我们在实例代码中添加System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");就可以将字节码保 //存到相应的文件中
if(saveGeneratedFiles)
AccessController.doPrivileged(new PrivilegedAction(s, abyte0) {
public Void run()
{
try
{
int j = name.lastIndexOf('.');
Path path;
if(j > 0)
{
Path path1 = Paths.get(name.substring(0, j).replace('.', File.separatorChar), new String[0]);
Files.createDirectories(path1, new FileAttribute[0]);
path = path1.resolve((new StringBuilder()).append(name.substring(j + 1, name.length())).append(".class").toString());
} else
{
path = Paths.get((new StringBuilder()).append(name).append(".class").toString(), new String[0]);
}
Files.write(path, classFile, new OpenOption[0]);
return null;
}
catch(IOException ioexception)
{
throw new InternalError((new StringBuilder()).append("I/O exception saving generated file: ").append(ioexception).toString());
}
}
public volatile Object run()
{
return run();
}
final String val$name;
final byte val$classFile[];
{
name = s;
classFile = abyte0;
super();
}
}
);
//如果不用保存，那么就直接返回字节码内容
return abyte0;
}接下来我们开始分析defineClass0(loader, proxyName,proxyClassFile, 0, proxyClassFile.length);函数，这是一个native方法,负责字节码加载的实现，并返回对应的Class对象。根据上面的例子，我们得到的代理类字节码文件结构如下：
经过反编译后，代码如下：
package com.jd.dynamicproxy.dynamicproxy;
import java.io.Serializable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
final class $Proxy0 extends Proxy
implements App.Account, Serializable
{
private static Method m1;
private static Method m4;
private static Method m2;
private static Method m3;
private static Method m0;
public $Proxy0(InvocationHandler paramInvocationHandler)
throws
{
super(paramInvocationHandler);
}
public final boolean equals(Object paramObject)
throws
{
try
{
return ((Boolean)this.h.invoke(this, m1, new Object[] { paramObject })).booleanValue();
}
catch (RuntimeException localRuntimeException)
{
throw localRuntimeException;
}
catch (Throwable localThrowable)
{
}
throw new UndeclaredThrowableException(localThrowable);
}
public final double getBalance()
throws
{
try
{
return ((Double)this.h.invoke(this, m4, null)).doubleValue();
}
catch (RuntimeException localRuntimeException)
{
throw localRuntimeException;
}
catch (Throwable localThrowable)
{
}
throw new UndeclaredThrowableException(localThrowable);
}
public final String toString()
throws
{
try
{
return (String)this.h.invoke(this, m2, null);
}
catch (RuntimeException localRuntimeException)
{
throw localRuntimeException;
}
catch (Throwable localThrowable)
{
}
throw new UndeclaredThrowableException(localThrowable);
}
public final App.Account deposit(double paramDouble)
throws
{
try
{
return (Serializable)this.h.invoke(this, m3, new Object[] { Double.valueOf(paramDouble) });
}
catch (RuntimeException localRuntimeException)
{
throw localRuntimeException;
}
catch (Throwable localThrowable)
{
}
throw new UndeclaredThrowableException(localThrowable);
}
public final int hashCode()
throws
{
try
{
return ((Integer)this.h.invoke(this, m0, null)).intValue();
}
catch (RuntimeException localRuntimeException)
{
throw localRuntimeException;
}
catch (Throwable localThrowable)
{
}
throw new UndeclaredThrowableException(localThrowable);
}
static
{
try
{
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });
m4 = Class.forName("com.jd.dynamicproxy.dynamicproxy.App$Account").getMethod("getBalance", new Class[0]);
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
m3 = Class.forName("com.jd.dynamicproxy.dynamicproxy.App$Account").getMethod("deposit", new Class[] { Double.TYPE });
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
return;
}
catch (NoSuchMethodException localNoSuchMethodException)
{
throw new NoSuchMethodError(localNoSuchMethodException.getMessage());
}
catch (ClassNotFoundException localClassNotFoundException)
{
}
throw new NoClassDefFoundError(localClassNotFoundException.getMessage());
}
}从中可以看到，该代理类继承了Proxy类且实现了相关的接口，你调用接口方法都会去调用InvocationHandler实现类中的invoke函数，Proxy中有m0、m1、m2、m3、m4五个Method类对象，其中包括了实现接口的。在调用invoke函数的时候会将相应的Method类对象作为参数传入，从而实现代理的功能。
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