Java cglib动态代理原理分析

public class Target{
    public void f(){
        System.out.println("Target f()");
    }
    public void g(){
        System.out.println("Target g()");
    }
}

public class Interceptor implements MethodInterceptor {
    @Override
    public Object intercept(Object obj, Method method, Object[] args,    MethodProxy proxy) throws Throwable {
        System.out.println("I am intercept begin");
//Note: 此处一定要使用proxy的invokeSuper方法来调用目标类的方法
        proxy.invokeSuper(obj, args);
        System.out.println("I am intercept end");
        return null;
    }
}

public class Test {
    public static void main(String[] args) {
    System.setProperty(DebugginGClassWriter.DEBUG_LOCATioN_PROPERTY, "F:\\code");
         //实例化一个增强器，也就是cglib中的一个class generator
        Enhancer eh = new Enhancer();
         //设置目标类
        eh.setSuperclass(Target.class);
        // 设置拦截对象
        eh.setCallback(new Interceptor());
        // 生成代理类并返回一个实例
        Target t = (Target) eh.create();
        t.f();
        t.g();
    }
}

public class Target$$EnhancerByCGLIB$$788444a0 extends Target implements 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 static final Method CGLIB$g$0$Method;
	private static final MethodProxy CGLIB$g$0$Proxy;
	private static final Object[] CGLIB$emptyArgs;
	private static final Method CGLIB$f$1$Method;
	private static final MethodProxy CGLIB$f$1$Proxy;
	static void CGLIB$STATICHOOK1()
	{
		CGLIB$THREAD_CALLBACKS = new ThreadLocal();
		CGLIB$emptyArgs = new Object[0];
		Class localClass1 = Class.forName("net.sf.cglib.test.Target$$EnhancerByCGLIB$$788444a0");
		Class localClass2;
		Method[] tmp60_57 = ReflectUtils.findMethods(new String[] { "g", "()V", "f", "()V" }, (localClass2 = Class.forName("net.sf.cglib.test.Target")).getDeclaredMethods());
		CGLIB$g$0$Method = tmp60_57[0];
		CGLIB$g$0$Proxy = MethodProxy.create(localClass2, localClass1, "()V", "g", "CGLIB$g$0");
		CGLIB$f$1$Method = tmp60_57[1];
		CGLIB$f$1$Proxy = MethodProxy.create(localClass2, localClass1, "()V", "f", "CGLIB$f$1");
	}
	final void CGLIB$g$0()
	{
		super.g();
	}
	public final void g()
	{
		MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
		if (tmp4_1 == null)
		{
			CGLIB$BIND_CALLBACKS(this);
			tmp4_1 = this.CGLIB$CALLBACK_0;
		}
		if (this.CGLIB$CALLBACK_0 != null) {
			tmp4_1.intercept(this, CGLIB$g$0$Method, CGLIB$emptyArgs, CGLIB$g$0$Proxy);
		} else{
			super.g();
		}
	}
}

private static final void CGLIB$BIND_CALLBACKS(java.lang.Object);
  Code:
   0:   aload_0
   1:   checkcast       #2; //class net/sf/cglib/test/Target$$EnhancerByCGLIB$$788444a0
   4:   astore_1
   5:   aload_1
   6:   getfield        #212; //Field CGLIB$BOUND:Z
   9:   ifne    52
   12:  aload_1
   13:  iconst_1
   14:  putfield        #212; //Field CGLIB$BOUND:Z
   17:  getstatic       #24; //Field CGLIB$THREAD_CALLBACKS:Ljava/lang/ThreadLocal;
   20:  invokevirtual   #215; //Method java/lang/ThreadLocal.get:()Ljava/lang/Object;
   23:  dup
   24:  ifnonnull       39
   27:  pop
   28:  getstatic       #210; //Field CGLIB$STATIC_CALLBACKS:[Lnet/sf/cglib/proxy/Callback;
   31:  dup
   32:  ifnonnull       39
   35:  pop
   36:  Goto    52
   39:  checkcast       #216; //class "[Lnet/sf/cglib/proxy/Callback;"
   42:  aload_1
   43:  swap
   44:  iconst_0
   45:  aaload
   46:  checkcast       #48; //class net/sf/cglib/proxy/MethodInterceptor
   49:  putfield        #36; //Field CGLIB$CALLBACK_0:Lnet/sf/cglib/proxy/MethodInterceptor;
   52:  return

private static final void CGLIB$BIND_CALLBACKS(Object o){
        Target$$EnhancerByCGLIB$$788444a0 temp_1 = (Target$$EnhancerByCGLIB$$788444a0)o;
        Object temp_2;
        Callback[] temp_3
        if(temp_1.CGLIB$BOUND == true){
            return;
        }
        temp_1.CGLIB$BOUND = true;
        temp_2 = CGLIB$THREAD_CALLBACKS.get();
        if(temp_2!=null){
            temp_3 = (Callback[])temp_2;
        }
        else if(CGLIB$STATIC_CALLBACKS!=null){
            temp_3 = CGLIB$STATIC_CALLBACKS;
        }
        else{
            return;
        }
        temp_1.CGLIB$CALLBACK_0 = (MethodInterceptor)temp_3[0];
        return；
    }

public static void CGLIB$SET_THREAD_CALLBACKS(net.sf.cglib.proxy.Callback[]);
  Code:
   0:   getstatic       #24; //Field CGLIB$THREAD_CALLBACKS:Ljava/lang/ThreadLocal;
   3:   aload_0
   4:   invokevirtual   #207; //Method java/lang/ThreadLocal.set:(Ljava/lang/Object;)V
   7:   return

public class test10 {
    public static void main(String[] args){
        Test tt = new Test();
        Test2 fc = new Test2();
        int index = fc.getIndex("f()V");
        fc.invoke(index, tt, null);
    }
}

class Test{
    public void f(){
        System.out.println("f method");
    }
    
    public void g(){
        System.out.println("g method");
    }
}
class Test2{
    public Object invoke(int index, Object o, Object[] ol){
        Test t = (Test) o;
        switch(index){
        case 1:
            t.f();
            return null;
        case 2:
            t.g();
            return null;
        }
        return null;
    }
    
    public int getIndex(String signature){
        switch(signature.hashCode()){
        case 3078479:
            return 1;
        case 3108270:
            return 2;
        }
        return -1;
    }
}

Class localClass1 = Class.forName("net.sf.cglib.test.Target$$EnhancerByCGLIB$$788444a0");
localClass2 = Class.forName("net.sf.cglib.test.Target");
CGLIB$g$0$Proxy = MethodProxy.create(localClass2, localClass1, "()V", "g", "CGLIB$g$0");

private static class FastClassInfo
    {
        FastClass f1; // net.sf.cglib.test.Target的fastclass
        FastClass f2; // Target$$EnhancerByCGLIB$$788444a0 的fastclass
        int i1; //方法g在f1中的索引
        int i2; //方法CGLIB$g$0在f2中的索引
    }

    FastClassInfo fci = fastClassInfo;
    return fci.f2.invoke(fci.i2, obj, args);