JDK动态代理和cglib代理
Posted wangsong
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了JDK动态代理和cglib代理相关的知识，希望对你有一定的参考价值。
写一个简单的测试用例，Pig实现了Shout接口
public class MyInvocation implements InvocationHandler {
Object k;
public MyInvocation(Object k) {
this.k = k;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
//System.out.println(proxy);
System.out.println("----- before -----");
Object result = method.invoke(k, args);
System.out.println("----- after -----");
return result;
}
public Object getProxy() {
return Proxy.newProxyInstance(Thread.currentThread()
.getContextClassLoader(), k.getClass().getInterfaces(),
this);
}
public static void main(String[] args) {
Shout p = (Shout) new MyInvocation(new Pig()).getProxy(); //接口
p.f();
}
}
//进入Proxy
public static Object newProxyInstance(ClassLoader loader,
Class<?>[] interfaces,
InvocationHandler h)
throws IllegalArgumentException
{
if (h == null) {
throw new NullPointerException();
}
final Class<?>[] intfs = interfaces.clone();
...
Class<?> cl = getProxyClass0(loader, intfs);//获得代理类
final Constructor<?> cons = cl.getConstructor(constructorParams);
final InvocationHandler ih = h;
return newInstance(cons, ih); //反射生成实例
}
private static Class<?> getProxyClass0(ClassLoader loader,
Class<?>... interfaces) {
...
return proxyClassCache.get(loader, interfaces); //如果有实现了这些接口的代理类存在就直接返回了，否则创建一个新的
}
//proxyClassCache是一个弱引用
private static final WeakCache<ClassLoader, Class<?>[], Class<?>>
proxyClassCache = new WeakCache<>(new KeyFactory(), new ProxyClassFactory()); //泛型分别代表K键,P参数,V值
public WeakCache(BiFunction<K, P, ?> subKeyFactory,
BiFunction<K, P, V> valueFactory) {
this.subKeyFactory = Objects.requireNonNull(subKeyFactory); //为空抛异常
this.valueFactory = Objects.requireNonNull(valueFactory);
}
public V get(K key, P parameter) {
...
while (true) {
if (supplier != null) {
V value = supplier.get(); //获得生成的Class对象
if (value != null) {
return value;
}
}
...
}
}
中间是WeakCache的代码，好长，省略掉
//进入Proxy的静态内部类ProxyClassFactory
public Class<?> apply(ClassLoader loader, Class<?>[] interfaces) {
Map<Class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
for (Class<?> intf : interfaces) { //对代理接口做检验
Class<?> interfaceClass = null;
interfaceClass = Class.forName(intf.getName(), false, loader);
if (!interfaceClass.isInterface()) {
throw new IllegalArgumentException(
interfaceClass.getName() + " is not an interface");
}
...
}
String proxyPkg = null; // package to define proxy class in
....
if (proxyPkg == null) {
proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
}
long num = nextUniqueNumber.getAndIncrement();
String proxyName = proxyPkg + proxyClassNamePrefix + num; //形如com.sun.proxy.$Proxy0
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces); //生成字节码
return defineClass0(loader, proxyName,
proxyClassFile, 0, proxyClassFile.length); //生成Class对象
}
}
我们看一下生成的字节码
byte[] c = ProxyGenerator.generateProxyClass("com.sun.proxy.$Proxy0", Pig.class.getInterfaces());
FileUtil.appendBytes(new File("/Users/ws/Desktop/ttt.class"), c);
idea反编译打开看看
package com.sun.proxy;
...
public final class $Proxy0 extends Proxy implements Shout {
private static Method m1;
private static Method m3;
private static Method m0;
private static Method m2;
public $Proxy0(InvocationHandler var1) throws {
super(var1);
}
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 void f() throws {
super.h.invoke(this, m3, (Object[])null);
}
...
static {
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[]{Class.forName("java.lang.Object")});
m3 = Class.forName("dynamic.Shout").getMethod("f", new Class[0]);
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
}
}
//cglib输出代理类字节码只需要如下设置
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "/Users/ws/Desktop/xxx");
Waiter target = new NaiveWaiter();
BeforeAdvice advice = new GreetingBeforeAdvice();
//spring提供的代理工厂
ProxyFactory pf = new ProxyFactory();
//设置代理目标
pf.setTarget(target);
//为代理目标添加增强
pf.addAdvice(advice);
//生成代理实例
Waiter proxy = (Waiter) pf.getProxy();
proxy.greetTo("Brian");
于是会在指定目录下生成代理类，打开看看
package com.brianway.learning.spring.aop.advice;
public class NaiveWaiter$$EnhancerBySpringCGLIB$$ef901900 extends NaiveWaiter implements SpringProxy, Advised, Factory {
private boolean CGLIB$BOUND;
private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
private static final Callback[] CGLIB$STATIC_CALLBACKS;
private MethodInterceptor CGLIB$CALLBACK_0;
private MethodInterceptor CGLIB$CALLBACK_1;
private NoOp CGLIB$CALLBACK_2;
private Dispatcher CGLIB$CALLBACK_3;
private Dispatcher CGLIB$CALLBACK_4;
private MethodInterceptor CGLIB$CALLBACK_5;
private MethodInterceptor CGLIB$CALLBACK_6;
private static final Method CGLIB$greetTo$0$Method;
private static final MethodProxy CGLIB$greetTo$0$Proxy;
private static final Object[] CGLIB$emptyArgs;
private static final Method CGLIB$serveTo$1$Method;
private static final MethodProxy CGLIB$serveTo$1$Proxy;
private static final Method CGLIB$equals$3$Method;
private static final MethodProxy CGLIB$equals$3$Proxy;
private static final Method CGLIB$toString$4$Method;
private static final MethodProxy CGLIB$toString$4$Proxy;
private static final Method CGLIB$hashCode$5$Method;
private static final MethodProxy CGLIB$hashCode$5$Proxy;
private static final Method CGLIB$clone$6$Method;
private static final MethodProxy CGLIB$clone$6$Proxy;
static {
...
CGLIB$STATICHOOK1();
}
static void CGLIB$STATICHOOK1() {
CGLIB$THREAD_CALLBACKS = new ThreadLocal();
CGLIB$emptyArgs = new Object[0];
Class var0 = Class.forName("com.brianway.learning.spring.aop.advice.NaiveWaiter$$EnhancerBySpringCGLIB$$ef901900");
Class var1;
Method[] var10000 = ReflectUtils.findMethods(new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
CGLIB$equals$3$Method = var10000[0];
CGLIB$equals$3$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$3");
CGLIB$toString$4$Method = var10000[1];
CGLIB$toString$4$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$4");
CGLIB$hashCode$5$Method = var10000[2];
CGLIB$hashCode$5$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$5");
CGLIB$clone$6$Method = var10000[3];
CGLIB$clone$6$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$6");
var10000 = ReflectUtils.findMethods(new String[]{"greetTo", "(Ljava/lang/String;)V", "serveTo", "(Ljava/lang/String;)V"}, (var1 = Class.forName("com.brianway.learning.spring.aop.advice.NaiveWaiter")).getDeclaredMethods());
CGLIB$greetTo$0$Method = var10000[0];
CGLIB$greetTo$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)V", "greetTo", "CGLIB$greetTo$0");
CGLIB$serveTo$1$Method = var10000[1];
CGLIB$serveTo$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)V", "serveTo", "CGLIB$serveTo$1");
}
//被代理的方法
public final void greetTo(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if(this.CGLIB$CALLBACK_0 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if(var10000 != null) {
//进入拦截器
var10000.intercept(this, CGLIB$greetTo$0$Method, new Object[]{var1}, CGLIB$greetTo$0$Proxy);
} else {
super.greetTo(var1);
}
}以上是关于JDK动态代理和cglib代理的主要内容，如果未能解决你的问题，请参考以下文章
深入理解设计模式-代理模式（静态代理动态代理jdk和cglib）