• 动态代理记录

    Cglib代理

    定义目标类

    public class Person {
    public void sayHello() {
        System.out.println("Hello!");
    }
}

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    Cglib代理后的类的Class

      

    System.setProperty(
DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E://xiaobaidemo");

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    这行代码用来生成cglib生成的代理类，输出到指定目录

    System.setProperty(
DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E://xiaobaidemo")

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    代理逻辑
    public class Test20221111 {
    public static void main(String[] args) {
    System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E://xiaobaidemo");
        Enhancer.create(Person.class, new MethodInterceptor() {
            @Override
            public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
                System.out.println("Intercept!");
                methodProxy.invokeSuper(o, objects);
                return null;
            }
        });
    }
}

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    反编译后的Class

    https://juejin.cn/post/6844904077877313549

    public class Person$$EnhancerByCGLIB$$34b905e4
extends Person {
    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$emptyArgs;
    private static final Method CGLIB$equals$1$Method;
    private static final MethodProxy CGLIB$equals$1$Proxy;
    private static final Method CGLIB$toString$2$Method;
    private static final MethodProxy CGLIB$toString$2$Proxy;
    private static final Method CGLIB$hashCode$3$Method;
    private static final MethodProxy CGLIB$hashCode$3$Proxy;
    private static final Method CGLIB$clone$4$Method;
    private static final MethodProxy CGLIB$clone$4$Proxy;

    static void CGLIB$STATICHOOK2() {
        CGLIB$THREAD_CALLBACKS = new ThreadLocal();
        CGLIB$emptyArgs = new Object[0];
        Class class_ = Class.forName("Person$$EnhancerByCGLIB$$34b905e4");
        Class class_2 = Class.forName("java.lang.Object");
        Method[] arrmethod = ReflectUtils.findMethods((String[])new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (Method[])class_2.getDeclaredMethods());
        CGLIB$equals$1$Method = arrmethod[0];
        CGLIB$equals$1$Proxy = MethodProxy.create(class_2, class_, (String)"(Ljava/lang/Object;)Z", (String)"equals", (String)"CGLIB$equals$1");
        CGLIB$toString$2$Method = arrmethod[1];
        CGLIB$toString$2$Proxy = MethodProxy.create(class_2, class_, (String)"()Ljava/lang/String;", (String)"toString", (String)"CGLIB$toString$2");
        CGLIB$hashCode$3$Method = arrmethod[2];
        CGLIB$hashCode$3$Proxy = MethodProxy.create(class_2, class_, (String)"()I", (String)"hashCode", (String)"CGLIB$hashCode$3");
        CGLIB$clone$4$Method = arrmethod[3];
        CGLIB$clone$4$Proxy = MethodProxy.create(class_2, class_, (String)"()Ljava/lang/Object;", (String)"clone", (String)"CGLIB$clone$4");
        class_2 = Class.forName("Person");
        CGLIB$sayHello$0$Method = ReflectUtils.findMethods((String[])new String[]{"sayHello", "()V"}, (Method[])class_2.getDeclaredMethods())[0];
        CGLIB$sayHello$0$Proxy = MethodProxy.create(class_2, class_, (String)"()V", (String)"sayHello", (String)"CGLIB$sayHello$0");
    }

    final void CGLIB$sayHello$0() {
        super.sayHello();
    }

    public final void sayHello() {
        MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
        if (methodInterceptor == null) {
            Person$$EnhancerByCGLIB$$34b905e4.CGLIB$BIND_CALLBACKS((Object)this);
            methodInterceptor = this.CGLIB$CALLBACK_0;
        }
        if (methodInterceptor != null) {
            Object object = methodInterceptor.intercept((Object)this, CGLIB$sayHello$0$Method, CGLIB$emptyArgs, CGLIB$sayHello$0$Proxy);
            return;
        }
        super.sayHello();
    }

    final boolean CGLIB$equals$1(Object object) {
        return super.equals(object);
    }

    public final boolean equals(Object object) {
        MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
        if (methodInterceptor == null) {
            Person$$EnhancerByCGLIB$$34b905e4.CGLIB$BIND_CALLBACKS((Object)this);
            methodInterceptor = this.CGLIB$CALLBACK_0;
        }
        if (methodInterceptor == null) return super.equals(object);
        Object object2 = methodInterceptor.intercept((Object)this, CGLIB$equals$1$Method, new Object[]{object}, CGLIB$equals$1$Proxy);
        if (object2 == null) {
            return false;
        }
        boolean bl = (Boolean)object2;
        return bl;
    }

    final String CGLIB$toString$2() {
        return super.toString();
    }

    public final String toString() {
        MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
        if (methodInterceptor == null) {
            Person$$EnhancerByCGLIB$$34b905e4.CGLIB$BIND_CALLBACKS((Object)this);
            methodInterceptor = this.CGLIB$CALLBACK_0;
        }
        if (methodInterceptor == null) return super.toString();
        return (String)methodInterceptor.intercept((Object)this, CGLIB$toString$2$Method, CGLIB$emptyArgs, CGLIB$toString$2$Proxy);
    }

    final int CGLIB$hashCode$3() {
        return super.hashCode();
    }

    public final int hashCode() {
        MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
        if (methodInterceptor == null) {
            Person$$EnhancerByCGLIB$$34b905e4.CGLIB$BIND_CALLBACKS((Object)this);
            methodInterceptor = this.CGLIB$CALLBACK_0;
        }
        if (methodInterceptor == null) return super.hashCode();
        Object object = methodInterceptor.intercept((Object)this, CGLIB$hashCode$3$Method, CGLIB$emptyArgs, CGLIB$hashCode$3$Proxy);
        if (object == null) {
            return 0;
        }
        int n = ((Number)object).intValue();
        return n;
    }

    final Object CGLIB$clone$4() throws CloneNotSupportedException {
        return super.clone();
    }

    protected final Object clone() throws CloneNotSupportedException {
        MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
        if (methodInterceptor == null) {
            Person$$EnhancerByCGLIB$$34b905e4.CGLIB$BIND_CALLBACKS((Object)this);
            methodInterceptor = this.CGLIB$CALLBACK_0;
        }
        if (methodInterceptor == null) return super.clone();
        return methodInterceptor.intercept((Object)this, CGLIB$clone$4$Method, CGLIB$emptyArgs, CGLIB$clone$4$Proxy);
    }

    public static MethodProxy CGLIB$findMethodProxy(Signature signature) {
        String string = signature.toString();
        switch (string.hashCode()) {
            case -508378822: {
                if (!string.equals("clone()Ljava/lang/Object;")) return null;
                return CGLIB$clone$4$Proxy;
            }
            case 1535311470: {
                if (!string.equals("sayHello()V")) return null;
                return CGLIB$sayHello$0$Proxy;
            }
            case 1826985398: {
                if (!string.equals("equals(Ljava/lang/Object;)Z")) return null;
                return CGLIB$equals$1$Proxy;
            }
            case 1913648695: {
                if (!string.equals("toString()Ljava/lang/String;")) return null;
                return CGLIB$toString$2$Proxy;
            }
            case 1984935277: {
                if (!string.equals("hashCode()I")) return null;
                return CGLIB$hashCode$3$Proxy;
            }
        }
        return null;
    }

    public Person$$EnhancerByCGLIB$$34b905e4() {
        Person$$EnhancerByCGLIB$$34b905e4 person$$EnhancerByCGLIB$$34b905e4 = this;
        Person$$EnhancerByCGLIB$$34b905e4.CGLIB$BIND_CALLBACKS((Object)person$$EnhancerByCGLIB$$34b905e4);
    }

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

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

    private static final void CGLIB$BIND_CALLBACKS(Object object) {
        Person$$EnhancerByCGLIB$$34b905e4 person$$EnhancerByCGLIB$$34b905e4 = (Person$$EnhancerByCGLIB$$34b905e4)object;
        if (person$$EnhancerByCGLIB$$34b905e4.CGLIB$BOUND) return;
        person$$EnhancerByCGLIB$$34b905e4.CGLIB$BOUND = true;
        Object t = CGLIB$THREAD_CALLBACKS.get();
        if (t == null && (v783 = CGLIB$STATIC_CALLBACKS) == null) {
            return;
        }
        person$$EnhancerByCGLIB$$34b905e4.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])t)[0];
    }

    static {
        Person$$EnhancerByCGLIB$$34b905e4.CGLIB$STATICHOOK2();
    }
}

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      在创建一个代理类的对象的时候，会先加载这个Cglib创建的代理类的静态方法CGLIB$STATICHOOK2()。这个函数中对类的其他静态字段进行了初始化。例如：对那个每个需要代理的方法都生成两个字段，一个用于反射的Method对象，另一个用于加快方法调用，避免反射带来的开销的MethodProxy对象。然后在构造函数里面调用了GCLIB$BIND_CALLBACKS(this),在CGLIB$BIND_CALLBACKS方法中会把private MethodInterceptor CGLIB$CALLBACK_0字段和设置的静态变量ThreadLocal CGLIB$THREAD_CALLBACKS进行绑定，也就是说，设置的Callback并不是硬编码在生成代理类里面的，而是可以动态的设置。
      由于代理类继承了被代理类，所以调用sayHello()方法时会直接调用代理类的sayHello()方法，而在代理类的方法中，调用了Callback的逻辑。
      MethodInterceptor的interceptor方法参数：

     if (methodInterceptor != null) {
            Object object = methodInterceptor.intercept((Object)this, CGLIB$sayHello$0$Method, CGLIB$emptyArgs, CGLIB$sayHello$0$Proxy);
            return;
        }

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      ①代理对象
      ②目标类的方法 CGLIB$sayHello$0$Method。通过目标类反射获取的方法
      ③方法参数
      ④目标类的代理方法CGLIB$sayHello$0$Proxy

    MethodProxy.create

      MethodProxy是cglib包中提供的一个类。

    package org.springframework.cglib.proxy;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import org.springframework.cglib.core.AbstractClassGenerator;
import org.springframework.cglib.core.CodeGenerationException;
import org.springframework.cglib.core.GeneratorStrategy;
import org.springframework.cglib.core.NamingPolicy;
import org.springframework.cglib.core.Signature;
import org.springframework.cglib.reflect.FastClass;

/**
 * Classes generated by {@link Enhancer} pass this object to the
 * registered {@link MethodInterceptor} objects when an intercepted method is invoked. It can
 * be used to either invoke the original method, or call the same method on a different
 * object of the same type.
 * @version $Id: MethodProxy.java,v 1.16 2009/01/11 20:09:48 herbyderby Exp $
 */
@SuppressWarnings({"rawtypes", "unchecked"})
public class MethodProxy {

	private Signature sig1;

	private Signature sig2;

	private CreateInfo createInfo;

	private final Object initLock = new Object();

	private volatile FastClassInfo fastClassInfo;

	/**
	 * For internal use by {@link Enhancer} only; see the {@link org.springframework.cglib.reflect.FastMethod} class
	 * for similar functionality.
	 *  看这里。看这里。看这里。create方法构建一个MethodProxy对象。
	 *  ① Class c1 是目标对象的Class
	 *  ② Class c2 是代理对象的Class
	 *  ③ desc 是否方法描述
	 *  ④ name1 是目标对象的方法名
	 *  ⑤ name2 是代理对象的方法名
	 */
	public static MethodProxy create(Class c1, Class c2, String desc, String name1, String name2) {
		MethodProxy proxy = new MethodProxy();
		proxy.sig1 = new Signature(name1, desc);
		proxy.sig2 = new Signature(name2, desc);
		proxy.createInfo = new CreateInfo(c1, c2);
		return proxy;
	}

	private void init() {
		/*
		 * Using a volatile invariant allows us to initialize the FastClass and
		 * method index pairs atomically.
		 *
		 * Double-checked locking is safe with volatile in Java 5.  Before 1.5 this
		 * code could allow fastClassInfo to be instantiated more than once, which
		 * appears to be benign.
		 */
		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;
				}
			}
		}
	}


	private static class FastClassInfo {

		FastClass f1;

		FastClass f2;

		int i1;

		int i2;
	}


	private static class CreateInfo {

		Class c1;

		Class c2;

		NamingPolicy namingPolicy;

		GeneratorStrategy strategy;

		boolean attemptLoad;

		public CreateInfo(Class c1, Class c2) {
			this.c1 = c1;
			this.c2 = c2;
			AbstractClassGenerator fromEnhancer = AbstractClassGenerator.getCurrent();
			if (fromEnhancer != null) {
				namingPolicy = fromEnhancer.getNamingPolicy();
				strategy = fromEnhancer.getStrategy();
				attemptLoad = fromEnhancer.getAttemptLoad();
			}
		}
	}


	private static FastClass helper(CreateInfo ci, Class type) {
		FastClass.Generator g = new FastClass.Generator();
		g.setType(type);
		// SPRING PATCH BEGIN
		g.setContextClass(type);
		// SPRING PATCH END
		g.setClassLoader(ci.c2.getClassLoader());
		g.setNamingPolicy(ci.namingPolicy);
		g.setStrategy(ci.strategy);
		g.setAttemptLoad(ci.attemptLoad);
		return g.create();
	}

	private MethodProxy() {
	}

	/**
	 * Return the signature of the proxied method.
	 */
	public Signature getSignature() {
		return sig1;
	}

	/**
	 * Return the name of the synthetic method created by CGLIB which is
	 * used by {@link #invokeSuper} to invoke the superclass
	 * (non-intercepted) method implementation. The parameter types are
	 * the same as the proxied method.
	 */
	public String getSuperName() {
		return sig2.getName();
	}

	/**
	 * Return the {@link org.springframework.cglib.reflect.FastClass} method index
	 * for the method used by {@link #invokeSuper}. This index uniquely
	 * identifies the method within the generated proxy, and therefore
	 * can be useful to reference external metadata.
	 * @see #getSuperName
	 */
	public int getSuperIndex() {
		init();
		return fastClassInfo.i2;
	}

	// For testing
	FastClass getFastClass() {
		init();
		return fastClassInfo.f1;
	}

	// For testing
	FastClass getSuperFastClass() {
		init();
		return fastClassInfo.f2;
	}

	/**
	 * Return the MethodProxy used when intercepting the method
	 * matching the given signature.
	 * @param type the class generated by Enhancer
	 * @param sig the signature to match
	 * @return the MethodProxy instance, or null if no applicable matching method is found
	 * @throws IllegalArgumentException if the Class was not created by Enhancer or does not use a MethodInterceptor
	 */
	public static MethodProxy find(Class type, Signature sig) {
		try {
			Method m = type.getDeclaredMethod(MethodInterceptorGenerator.FIND_PROXY_NAME,
					MethodInterceptorGenerator.FIND_PROXY_TYPES);
			return (MethodProxy) m.invoke(null, new Object[]{sig});
		}
		catch (NoSuchMethodException ex) {
			throw new IllegalArgumentException("Class " + type + " does not use a MethodInterceptor");
		}
		catch (IllegalAccessException | InvocationTargetException ex) {
			throw new CodeGenerationException(ex);
		}
	}

	/**
	 * Invoke the original method, on a different object of the same type.
	 * @param obj the compatible object; recursion will result if you use the object passed as the first
	 * argument to the MethodInterceptor (usually not what you want)
	 * @param args the arguments passed to the intercepted method; you may substitute a different
	 * argument array as long as the types are compatible
	 * @throws Throwable the bare exceptions thrown by the called method are passed through
	 * without wrapping in an InvocationTargetException
	 * @see MethodInterceptor#intercept
	 */
	public Object invoke(Object obj, Object[] args) throws Throwable {
		try {
			init();
			FastClassInfo fci = fastClassInfo;
			return fci.f1.invoke(fci.i1, obj, args);
		}
		catch (InvocationTargetException ex) {
			throw ex.getTargetException();
		}
		catch (IllegalArgumentException ex) {
			if (fastClassInfo.i1 < 0)
				throw new IllegalArgumentException("Protected method: " + sig1);
			throw ex;
		}
	}

	/**
	 * Invoke the original (super) method on the specified object.
	 * @param obj the enhanced object, must be the object passed as the first
	 * argument to the MethodInterceptor
	 * @param args the arguments passed to the intercepted method; you may substitute a different
	 * argument array as long as the types are compatible
	 * @throws Throwable the bare exceptions thrown by the called method are passed through
	 * without wrapping in an InvocationTargetException
	 * @see MethodInterceptor#intercept
	 *  看这里，看这里，看这里
	 *  当调用methodProxy的invokeSuper方法的时候。传入的是代理对象obj，方法参数args。
	 *  ①首先调用init方法。
	 *  ②构建FastClassInfo对象，FastClassInfo对象的成员变量赋值。f1是目标对象的FastClass对象，f2是代理对象的FastClass对象。注意：FastClassInfo和FastClass对象是不一样的。
	 *  ③ FastClassInfo对象设置属性i1 = 目标对象方法的索引。i2 = 代理对象方法的索引
	 *  ④ 设置methodProxy的变量fastClassInfo = 创建的fastClassInfo对象
	 *  ⑤ 调用f2对象的fastClass对象的invoke方法。传入方法的坐标，代理对象，方法参数。
	 *  (1) fci.f2 = 代理对象的fastClass对象。调用代理对象的fastClass的invoke方法。
	 *  (2) invoke方法参数中fci.i2表示的是代理对象方法的索引。比如上文中sayHello(目标对象的方法)，CGLIB$sayHello$0(代理对象的方法)。这里执行的是代理对象的方法。obj是代理对象，args是方法参数。
	 *  (3)根据索引找到匹配的方法，直接执行obj对象的方法。
	 */
	public Object invokeSuper(Object obj, Object[] args) throws Throwable {
		try {
			init();
			FastClassInfo fci = fastClassInfo;
			return fci.f2.invoke(fci.i2, obj, args);
		}
		catch (InvocationTargetException e) {
			throw e.getTargetException();
		}
	}

}

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      java反射调用方法是比较“重”的操作，要经过一系列的权限验证、通过native方法请求jvm去方法区查找方法定义、以及最后的invoke仍然可能要通过JNI调用native方法。而相比之下，FastClass方式则跟一般的一个普通的对象方法调用没啥区别、只是多了一步根据index判断调用委托类的哪个方法这一步骤、性能损耗基本没有。
      cglib的大概逻辑如下：
      (1)ASM构建代理类。继承目标类。代理类实例化过程：
      ①调用静态代码块，调用静态方法，对类中静态属性赋值。关键点是。对目标类中的所有方法，生成两个变量，一个Method，表示目标类方法。一个MethodProxy，表示通过MethodProxy构建的methodProxy。
      ②MethodProxy里面的fastClassInfo属性，保存了代理类fastClass，目标类fastClass，代理类方法索引，目标类方法索引。
      ③方法拦截中执行MethodProxy的invokeSupper方法，里面通过fastClassInfo获取代理类的fastClass类，然后调用fastClass的invoke方法。
      ④fastclass的invoke方法根据传入的方法索引，直接对象的方法。
    fastClass机制
    在这里插入图片描述
      综上可以看出，FastClass调用invoke，其实就是将Object转换为目标类或者代理类。根据索引，直接调用对象的相关方法。

    拦截器中调用MethodProxy.invoke()方法会死循环，为什么？原因如下：

      (1)MethodProxy.invoke。调用的是目标对象的方法，多态特性，调用的还是代理类中的sayHello方法，接着还会去调用拦截方法，拦截方法中调用MethodProxy.invoke，接着调用代理类的sayHello方法…陷入死循环。

      public final void sayHello() {
        MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
        if (methodInterceptor == null) {
            Person$$EnhancerByCGLIB$$34b905e4.CGLIB$BIND_CALLBACKS((Object)this);
            methodInterceptor = this.CGLIB$CALLBACK_0;
        }
        if (methodInterceptor != null) {
           // 被代理方法(methodProxy.invoke会调用)
            Object object = methodInterceptor.intercept((Object)this, CGLIB$sayHello$0$Method, CGLIB$emptyArgs, CGLIB$sayHello$0$Proxy);
            return;
        }
        super.sayHello();
    }

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      (2)MethodProxy.invokeSuper。调用的是代理对象中的代理方法(CGLIB$sayHello$0)，调用的是目标类中的sayHello方法。

     final void CGLIB$sayHello$0() {
        super.sayHello();
    }

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    Method.invoke 和 MethodProxy.invokeSuper

      先了解一个概念：FastClass机制。Cglib动态代理方法效率之所以比Jdk的高。就是因为Cglib采用了FastClass机制。
      FastClass机制：为代理类和目标类各生成一个Class，这个Class会为代理类或目标类的方法分配一个index(int类型)。这个index当做一个入参，FastClass就可以直接定位要调用的方法直接进行调用，这样省去了反射调用，所以调用效率比jdk动态代理通过反射调用高。
      FastClass反编译：

     //根据方法签名获取index
 public int getIndex(Signature var1) {
      String var10000 = var1.toString();
      switch(var10000.hashCode()) {
      case -2077043409:
         if(var10000.equals("getPerson(Ljava/lang/String;)Lcom/demo/pojo/Person;")) {
            return 21;
         }
         break;
      case -2055565910:
         if(var10000.equals("CGLIB$SET_THREAD_CALLBACKS([Lnet/sf/cglib/proxy/Callback;)V")) {
            return 12;
         }
         break;
      case -1902447170:
         if(var10000.equals("setPerson()V")) {
            return 7;
         }
         break;
   //省略部分代码.....
　
 //根据index直接定位执行方法
 public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
      eaaaed75 var10000 = (eaaaed75)var2;
      int var10001 = var1;

      try {
         switch(var10001) {
         case 0:
            return new Boolean(var10000.equals(var3[0]));
         case 1:
            return var10000.toString();
         case 2:
            return new Integer(var10000.hashCode());
         case 3:
            return var10000.newInstance((Class[])var3[0], (Object[])var3[1], (Callback[])var3[2]);
         case 4:
            return var10000.newInstance((Callback)var3[0]);
         case 5:
            return var10000.newInstance((Callback[])var3[0]);
         case 6:
            var10000.setCallback(((Number)var3[0]).intValue(), (Callback)var3[1]);
            return null;
         case 7:
            var10000.setPerson();
            return null;
         case 8:
            var10000.setCallbacks((Callback[])var3[0]);
            return null;
         case 9:
            return var10000.getCallback(((Number)var3[0]).intValue());
         case 10:
            return var10000.getCallbacks();
         case 11:
            eaaaed75.CGLIB$SET_STATIC_CALLBACKS((Callback[])var3[0]);
            return null;
         case 12:
            eaaaed75.CGLIB$SET_THREAD_CALLBACKS((Callback[])var3[0]);
            return null;
         case 13:
            return eaaaed75.CGLIB$findMethodProxy((Signature)var3[0]);
         case 14:
            return var10000.CGLIB$toString$3();
         case 15:
            return new Boolean(var10000.CGLIB$equals$2(var3[0]));
         case 16:
            return var10000.CGLIB$clone$5();
         case 17:
            return new Integer(var10000.CGLIB$hashCode$4());
         case 18:
            var10000.CGLIB$finalize$1();
            return null;
         case 19:
            var10000.CGLIB$setPerson$0();
            return null;
        //省略部分代码....
      } catch (Throwable var4) {
         throw new InvocationTargetException(var4);
      }

      throw new IllegalArgumentException("Cannot find matching method/constructor");
   }

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      FastClass并不是跟代理类一块生成的，而是在第一次执行MethodProxy的invoke/invokeSuper时生成并放在缓存中。

    private void init() {
        if(this.fastClassInfo == null) {
            Object var1 = this.initLock;
            synchronized(this.initLock) {
                if(this.fastClassInfo == null) {
                    MethodProxy.CreateInfo ci = this.createInfo;
                    MethodProxy.FastClassInfo fci = new MethodProxy.FastClassInfo();
                    fci.f1 = helper(ci, ci.c1);//如果缓存中就取出，没有就生成新的FastClass
                    fci.f2 = helper(ci, ci.c2);
                    fci.i1 = fci.f1.getIndex(this.sig1);//获取方法的index
                    fci.i2 = fci.f2.getIndex(this.sig2);
                    this.fastClassInfo = fci;
                    this.createInfo = null;
                }
            }
        }

    }

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    JDK动态代理

    定义目标类

    public interface HelloService {
   void sayHello();
}

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    public class HelloServiceImpl implements HelloService {
   @Override
   public void sayHello(){
       System.out.println(”hello Word“);
  }
}

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    public class HelloServiceImplHandle implements InvocationHandler{
   private Object target;

  public HelloServiceImplHandle(Object target) {
     this.target = target;
  }
  
   @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("proxy before=======");
        Object result = method.invoke(target, args);
        System.out.println("proxy end=======");
        return result;
    }
}

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    生成代理

    HelloService  helloService = new HelloServiceImplHandle();
HelloServiceImplHandle  helloServiceImplHandle  = new HelloServiceImplHandle();
Proxy.newProxyInstance(helloService .getClass().getClassLoad(),helloService .getClass().getInterfaces(),helloServiceImplHandle  )

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    代理类反编译

    public final class $Proxy0 extends Proxy implements HelloService {
    private static Method m1; //equals()方法
    private static Method m3; //我们的sayHello方法()
    private static Method m2; //toString()方法
    private static Method m0; //hashCode()方法
    
    //这里就是我们之前提交的InvocationHandler这个构造方法！！
    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);
        }
    }

    //看一看我们的代理类的sayHello()方法长什么样子呀！！
    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);
        }
    }

    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);
        }
    }

    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);
        }
    }

    static {
        try {
            m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[]{Class.forName("java.lang.Object")});
            m3 = Class.forName("proxy.service.HelloService").getMethod("sayHello", new Class[0]);
            m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
            m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
        } catch (NoSuchMethodException var2) {
            throw new NoSuchMethodError(var2.getMessage());
        } catch (ClassNotFoundException var3) {
            throw new NoClassDefFoundError(var3.getMessage());
        }
    }
}

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      代理类继承Proxy类，Proxy类里面保存了我们定义的InvocationHandler的实现。

    public class Proxy implements java.io.Serializable {
    private static final long serialVersionUID = -2222568056686623797L;
    // 这个就是我们定义的InvocationHandler 的实现
    protected InvocationHandler h;

    private Proxy() {
    }
    
    protected Proxy(InvocationHandler h) {
        Objects.requireNonNull(h);
        this.h = h;
    }
    
    // 我们构建代理对象的方法。这里面将InvocationHandler 进行赋值。
    @CallerSensitive
    public static Object newProxyInstance(ClassLoader loader,
                                          Class[] interfaces,
                                          InvocationHandler h)
        throws IllegalArgumentException
    {
        Objects.requireNonNull(h);

        final Class[] intfs = interfaces.clone();
        final SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
        }

        /*
         * Look up or generate the designated proxy class.
         */
        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);
            // 在这里进行赋值增强的逻辑
            final InvocationHandler ih = h;
            if (!Modifier.isPublic(cl.getModifiers())) {
                AccessController.doPrivileged(new PrivilegedAction() {
                    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);
        }
    }
    
    @CallerSensitive
    public static InvocationHandler getInvocationHandler(Object proxy)
        throws IllegalArgumentException
    {
        /*
         * Verify that the object is actually a proxy instance.
         */
        if (!isProxyClass(proxy.getClass())) {
            throw new IllegalArgumentException("not a proxy instance");
        }

        final Proxy p = (Proxy) proxy;
        final InvocationHandler ih = p.h;
        if (System.getSecurityManager() != null) {
            Class ihClass = ih.getClass();
            Class caller = Reflection.getCallerClass();
            if (ReflectUtil.needsPackageAccessCheck(caller.getClassLoader(),
                                                    ihClass.getClassLoader()))
            {
                ReflectUtil.checkPackageAccess(ihClass);
            }
        }

        return ih;
    }
}


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      代理类实例化，首先调用静态代码块。通过反射，获取Object，目标类的Method。赋值给代理类的静态属性。
      代理对象方法的调用。如下。逻辑很清晰，调用：Proxy的h(InvocationHandler的实现类)的invoke方法。
      invoke参数：①代理类 ②代理类的静态属性(目标对象的方法Method，本例中是sayHello的Method) ③方法参数

     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);
        }
    }

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  • 原文地址：https://blog.csdn.net/xiaopang2020/article/details/127802957