Jdk动态代理和CGLIB动态代理大比拼

前言：

这2种动态代理算是老生常谈的吧，面试还是会经常问到的，下面做下分析：

jdk动态代理：

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class JdkHanler implements InvocationHandler {
    
    private Object target;
    
    public Object invoke(Object proxy, Method method, Object[] arg) throws Throwable {
        System.out.println("before");
        Object o=method.invoke(target, arg);
        System.out.println("after");
        return o;
    }
    public JdkHanler(Object target) {
        super();
        this.target = target;
    }
    public Object getInstance(){
        return Proxy.newProxyInstance(target.getClass().getClassLoader(), 
                target.getClass().getInterfaces(), this);
    }
}

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cglib动态代理：

import java.lang.reflect.Method;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

public class HelloWorldInterceptor implements MethodInterceptor {

    private Object target;
    
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        System.out.println("before");
        Object r=proxy.invokeSuper(obj, args);
        System.out.println("after");
        return r;
    }
    public HelloWorldInterceptor(Object target) {
        super();
        this.target = target;
    }
    public Object getInstance(){
        Enhancer enhancer=new Enhancer();
        enhancer.setSuperclass(target.getClass());
        enhancer.setCallback(this);
        return enhancer.create();
    }
}

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测试类：

public class AllTest {
    
    public static final String output="D:/SpringWorkSpace/";
    //cglib生成代理类字节码文件
    static{
        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, output);
    }
    
    @Test
    public void proxyTest(){
        HelloWorldInterceptor interceptor=new HelloWorldInterceptor(new HelloWorldImpl());
        HelloWorld h=(HelloWorld) interceptor.getInstance();
        h.sayHello();
    }
    //@Test
    public void jdkproxyTest() throws IOException{
        JdkHanler hanler=new JdkHanler(new HelloWorldImpl());
        HelloWorld h=(HelloWorld) hanler.getInstance();
        h.sayHello();
        jdkToFile(h);
    }
//jdk代理类字节码文件
    public static void jdkToFile(HelloWorld obj) throws IOException {
        Class clazz = obj.getClass();
        String className = clazz.getName();
        byte[] classFile = ProxyGenerator.generateProxyClass(className, HelloWorldImpl.class.getInterfaces());
        FileOutputStream fos = new FileOutputStream(output+"proxy.class");
        fos.write(classFile);
    }
}

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利用jd-gui工具反编译字节码文件：

生成的jdk代理类：

public final class $Proxy4 extends Proxy
  implements HelloWorld
{
  private static Method m3;
  private static Method m1;
  private static Method m0;
  private static Method m2;

  public $Proxy4(InvocationHandler paramInvocationHandler)
    throws 
  {
    super(paramInvocationHandler);
  }
  //调用sayHello方法
  public final String sayHello()
    throws 
  {
    try
    {
     //调用JdkHanler的invoke方法
      return (String)this.h.invoke(this, m3, null);
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  static
  {
    try
    {
      m3 = Class.forName("com.selrain.DynamicProxy.HelloWorld").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]);
      return;
    }
    catch (NoSuchMethodException localNoSuchMethodException)
    {
      throw new NoSuchMethodError(localNoSuchMethodException.getMessage());
    }
    catch (ClassNotFoundException localClassNotFoundException)
    {
      throw new NoClassDefFoundError(localClassNotFoundException.getMessage());
    }
  }

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生成的cglib代理类：

public class HelloWorld$$EnhancerByCGLIB$$d87b5f2a extends HelloWorld
  implements Factory
{
  private boolean CGLIB$BOUND;
  public static Object CGLIB$FACTORY_DATA;
  private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
  private static final Callback[] CGLIB$STATIC_CALLBACKS;
  private MethodInterceptor CGLIB$CALLBACK_0;
  private static Object CGLIB$CALLBACK_FILTER;
  private static final Method CGLIB$sayHello$0$Method;
  private static final MethodProxy CGLIB$sayHello$0$Proxy;
  private static final Object[] CGLIB$emptyArgs;
  private static final Method CGLIB$hashCode$1$Method;
  private static final MethodProxy CGLIB$hashCode$1$Proxy;
  private static final Method CGLIB$clone$2$Method;
  private static final MethodProxy CGLIB$clone$2$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;

  static void CGLIB$STATICHOOK1()
  {
    CGLIB$THREAD_CALLBACKS = new ThreadLocal();
    CGLIB$emptyArgs = new Object[0];
    Class localClass1 = Class.forName("com.selrain.DynamicProxy.HelloWorld$$EnhancerByCGLIB$$d87b5f2a");
    Class localClass2;
    Method[] tmp50_47 = ReflectUtils.findMethods(new String[] { "sayHello", "()Ljava/lang/String;" }, (localClass2 = Class.forName("com.selrain.DynamicProxy.HelloWorld")).getDeclaredMethods());
    CGLIB$sayHello$0$Method = tmp50_47[0];
    CGLIB$sayHello$0$Proxy = MethodProxy.create(localClass2, localClass1, "()Ljava/lang/String;", "sayHello", "CGLIB$sayHello$0");
    tmp50_47;
    Method[] tmp131_128 = ReflectUtils.findMethods(new String[] { "hashCode", "()I", "clone", "()Ljava/lang/Object;", "equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;" }, (localClass2 = Class.forName("java.lang.Object")).getDeclaredMethods());
    CGLIB$hashCode$1$Method = tmp131_128[0];
    CGLIB$hashCode$1$Proxy = MethodProxy.create(localClass2, localClass1, "()I", "hashCode", "CGLIB$hashCode$1");
    Method[] tmp151_131 = tmp131_128;
    CGLIB$clone$2$Method = tmp151_131[1];
    CGLIB$clone$2$Proxy = MethodProxy.create(localClass2, localClass1, "()Ljava/lang/Object;", "clone", "CGLIB$clone$2");
    Method[] tmp171_151 = tmp151_131;
    CGLIB$equals$3$Method = tmp171_151[2];
    CGLIB$equals$3$Proxy = MethodProxy.create(localClass2, localClass1, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$3");
    Method[] tmp191_171 = tmp171_151;
    CGLIB$toString$4$Method = tmp191_171[3];
    CGLIB$toString$4$Proxy = MethodProxy.create(localClass2, localClass1, "()Ljava/lang/String;", "toString", "CGLIB$toString$4");
    tmp191_171;
  }

  final String CGLIB$sayHello$0()
  {
    return super.sayHello();
  }
 //调用sayHello方法
  public final String sayHello()
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null)
//HelloWorldInterceptor 的intercept 方法
      return (String)tmp17_14.intercept(this, CGLIB$sayHello$0$Method, CGLIB$emptyArgs, CGLIB$sayHello$0$Proxy);
    return super.sayHello();
  }

  final int CGLIB$hashCode$1()
  {
    return super.hashCode();
  }

  public final int hashCode()
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null)
    {
      Object tmp36_31 = tmp17_14.intercept(this, CGLIB$hashCode$1$Method, CGLIB$emptyArgs, CGLIB$hashCode$1$Proxy);
      tmp36_31;
      return tmp36_31 == null ? 0 : ((Number)tmp36_31).intValue();
    }
    return super.hashCode();
  }

  final Object CGLIB$clone$2()
    throws CloneNotSupportedException
  {
    return super.clone();
  }

  protected final Object clone()
    throws CloneNotSupportedException
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null)
      return tmp17_14.intercept(this, CGLIB$clone$2$Method, CGLIB$emptyArgs, CGLIB$clone$2$Proxy);
    return super.clone();
  }

  final boolean CGLIB$equals$3(Object paramObject)
  {
    return super.equals(paramObject);
  }

  public final boolean equals(Object paramObject)
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null)
    {
      Object tmp41_36 = tmp17_14.intercept(this, CGLIB$equals$3$Method, new Object[] { paramObject }, CGLIB$equals$3$Proxy);
      tmp41_36;
      return tmp41_36 == null ? false : ((Boolean)tmp41_36).booleanValue();
    }
    return super.equals(paramObject);
  }

  final String CGLIB$toString$4()
  {
    return super.toString();
  }

  public final String toString()
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null)
      return (String)tmp17_14.intercept(this, CGLIB$toString$4$Method, CGLIB$emptyArgs, CGLIB$toString$4$Proxy);
    return super.toString();
  }

  public static MethodProxy CGLIB$findMethodProxy(Signature paramSignature)
  {
    String tmp4_1 = paramSignature.toString();
    switch (tmp4_1.hashCode())
    {
    case -508378822:
      if (tmp4_1.equals("clone()Ljava/lang/Object;"))
        return CGLIB$clone$2$Proxy;
      break;
    case 1459740658:
    case 1826985398:
    case 1913648695:
    case 1984935277:
    }
  }

  public HelloWorld$$EnhancerByCGLIB$$d87b5f2a()
  {
    CGLIB$BIND_CALLBACKS(this);
  }

  public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] paramArrayOfCallback)
  {
    CGLIB$THREAD_CALLBACKS.set(paramArrayOfCallback);
  }

  public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] paramArrayOfCallback)
  {
    CGLIB$STATIC_CALLBACKS = paramArrayOfCallback;
  }

  private static final void CGLIB$BIND_CALLBACKS(Object paramObject)
  {
    // Byte code:
    //   0: aload_0
    //   1: checkcast 2    com/selrain/DynamicProxy/HelloWorld$$EnhancerByCGLIB$$d87b5f2a
    //   4: astore_1
    //   5: aload_1
    //   6: getfield 186    com/selrain/DynamicProxy/HelloWorld$$EnhancerByCGLIB$$d87b5f2a:CGLIB$BOUND    Z
    //   9: ifne +43 -> 52
    //   12: aload_1
    //   13: iconst_1
    //   14: putfield 186    com/selrain/DynamicProxy/HelloWorld$$EnhancerByCGLIB$$d87b5f2a:CGLIB$BOUND    Z
    //   17: getstatic 27    com/selrain/DynamicProxy/HelloWorld$$EnhancerByCGLIB$$d87b5f2a:CGLIB$THREAD_CALLBACKS    Ljava/lang/ThreadLocal;
    //   20: invokevirtual 189    java/lang/ThreadLocal:get    ()Ljava/lang/Object;
    //   23: dup
    //   24: ifnonnull +15 -> 39
    //   27: pop
    //   28: getstatic 184    com/selrain/DynamicProxy/HelloWorld$$EnhancerByCGLIB$$d87b5f2a:CGLIB$STATIC_CALLBACKS    [Lnet/sf/cglib/proxy/Callback;
    //   31: dup
    //   32: ifnonnull +7 -> 39
    //   35: pop
    //   36: goto +16 -> 52
    //   39: checkcast 190    [Lnet/sf/cglib/proxy/Callback;
    //   42: aload_1
    //   43: swap
    //   44: iconst_0
    //   45: aaload
    //   46: checkcast 52    net/sf/cglib/proxy/MethodInterceptor
    //   49: putfield 40    com/selrain/DynamicProxy/HelloWorld$$EnhancerByCGLIB$$d87b5f2a:CGLIB$CALLBACK_0    Lnet/sf/cglib/proxy/MethodInterceptor;
    //   52: return
  }

  public Object newInstance(Callback[] paramArrayOfCallback)
  {
    CGLIB$SET_THREAD_CALLBACKS(paramArrayOfCallback);
    CGLIB$SET_THREAD_CALLBACKS(null);
    return new d87b5f2a();
  }

  public Object newInstance(Callback paramCallback)
  {
    CGLIB$SET_THREAD_CALLBACKS(new Callback[] { paramCallback });
    CGLIB$SET_THREAD_CALLBACKS(null);
    return new d87b5f2a();
  }

  public Object newInstance(Class[] paramArrayOfClass, Object[] paramArrayOfObject, Callback[] paramArrayOfCallback)
  {
    CGLIB$SET_THREAD_CALLBACKS(paramArrayOfCallback);
    Class[] tmp9_8 = paramArrayOfClass;
    switch (tmp9_8.length)
    {
    case 0:
      tmp9_8;
      break;
    default:
      new d87b5f2a();
      throw new IllegalArgumentException("Constructor not found");
    }
    CGLIB$SET_THREAD_CALLBACKS(null);
  }

  public Callback getCallback(int paramInt)
  {
    CGLIB$BIND_CALLBACKS(this);
    switch (paramInt)
    {
    case 0:
      break;
    }
    return null;
  }

  public void setCallback(int paramInt, Callback paramCallback)
  {
    switch (paramInt)
    {
    case 0:
      this.CGLIB$CALLBACK_0 = ((MethodInterceptor)paramCallback);
      break;
    }
  }

  public Callback[] getCallbacks()
  {
    CGLIB$BIND_CALLBACKS(this);
    return new Callback[] { this.CGLIB$CALLBACK_0 };
  }

  public void setCallbacks(Callback[] paramArrayOfCallback)
  {
    this.CGLIB$CALLBACK_0 = ((MethodInterceptor)paramArrayOfCallback[0]);
  }

  static
  {
    CGLIB$STATICHOOK1();
  }
}

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MethodProxy 的invokeSuper方法：

public Object invokeSuper(Object obj, Object[] args) throws Throwable {
        try {
            init();
            FastClassInfo fci = fastClassInfo;
//调用代理类的CGLIB$sayHello$0方法
            return fci.f2.invoke(fci.i2, obj, args);
        } catch (InvocationTargetException e) {
            throw e.getTargetException();
        }
    }
//生成fastClass类：其中f1代表target，(其type属性为target)，f2代表生成的代理类；i1和i2分别代表方法sayHello和CGLIB$sayHello$0方法对应的索引位置
private void init()
    {
        if (fastClassInfo == null)
        {
            synchronized (initLock)
            {
                if (fastClassInfo == null)
                {
                    CreateInfo ci = createInfo;

                    FastClassInfo fci = new FastClassInfo();
                    fci.f1 = helper(ci, ci.c1);
                    fci.f2 = helper(ci, ci.c2);
                    fci.i1 = fci.f1.getIndex(sig1);
                    fci.i2 = fci.f2.getIndex(sig2);
                    fastClassInfo = fci;
                    createInfo = null;
                }
            }
        }
    }

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代理类的CGLIB$sayHello$0方法：

final String CGLIB$sayHello$0()
  {
//最终调用target的sayHello方法
    return super.sayHello();
  }

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区别：

1、jdk动态代理生成的代理类和委托类实现了相同的接口

2、jdk动态代理利用了Java的反射机制，cglib动态代理利用了索引的方式直接调用委托类的方法，效率更高

参考：

1、占小狼的博客-说说cglib动态代理

2、饿了么物流技术-动态代理的实现与案例