CGLIB 动态代理原理

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案例代码

被代理类Calculator

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public class Calculator {
    public int add(int i, int j) {
        return i + j;
    }

    public int sub(int i, int j) {
        return i - j;
    }

    public int mult(int i, int j) {
        return i * j;
    }

    public int div(int i, int j) {
        return i / j;
    }
}

MethodInterceptor

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public class MyCglib implements MethodInterceptor {
    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("调用cglib动态代理");
        return methodProxy.invokeSuper(o, objects);
    }
}

程序入口

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public class CglibTest {
    public static void main(String[] args) {
        // 设置cglib生成的class文件保存路径
        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\mashibing\\spring");
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(Calculator.class);
        enhancer.setCallback(new MyCglib());
        Calculator myCalculator = (Calculator) enhancer.create();
        myCalculator.add(1, 1);
        System.out.println(myCalculator.getClass());
    }
}

从add(1, 1)开始说起

代理对象的class文件

当程序运行完成之后，会在指定位置生成代理对象的class文件。为了后续讲解，这里先将生成的class文件展示。

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package com.eitan.proxy.cglib;

import java.lang.reflect.Method;
import org.springframework.cglib.core.ReflectUtils;
import org.springframework.cglib.core.Signature;
import org.springframework.cglib.proxy.Callback;
import org.springframework.cglib.proxy.Factory;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;

public class Calculator$$EnhancerByCGLIB$$345a285a extends Calculator 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$add$0$Method;
    private static final MethodProxy CGLIB$add$0$Proxy;
    private static final Object[] CGLIB$emptyArgs;
    private static final Method CGLIB$sub$1$Method;
    private static final MethodProxy CGLIB$sub$1$Proxy;
    private static final Method CGLIB$mult$2$Method;
    private static final MethodProxy CGLIB$mult$2$Proxy;
    private static final Method CGLIB$div$3$Method;
    private static final MethodProxy CGLIB$div$3$Proxy;
    private static final Method CGLIB$equals$4$Method;
    private static final MethodProxy CGLIB$equals$4$Proxy;
    private static final Method CGLIB$toString$5$Method;
    private static final MethodProxy CGLIB$toString$5$Proxy;
    private static final Method CGLIB$hashCode$6$Method;
    private static final MethodProxy CGLIB$hashCode$6$Proxy;
    private static final Method CGLIB$clone$7$Method;
    private static final MethodProxy CGLIB$clone$7$Proxy;

    static void CGLIB$STATICHOOK1() {
        CGLIB$THREAD_CALLBACKS = new ThreadLocal();
        CGLIB$emptyArgs = new Object[0];
        Class var0 = Class.forName("com.eitan.proxy.cglib.Calculator$$EnhancerByCGLIB$$345a285a");
        Class var1;
        Method[] var10000 = ReflectUtils.findMethods(new String[]{"add", "(II)I", "sub", "(II)I", "mult", "(II)I", "div", "(II)I"}, (var1 = Class.forName("com.eitan.proxy.cglib.Calculator")).getDeclaredMethods());
        CGLIB$add$0$Method = var10000[0];
        CGLIB$add$0$Proxy = MethodProxy.create(var1, var0, "(II)I", "add", "CGLIB$add$0");
        CGLIB$sub$1$Method = var10000[1];
        CGLIB$sub$1$Proxy = MethodProxy.create(var1, var0, "(II)I", "sub", "CGLIB$sub$1");
        CGLIB$mult$2$Method = var10000[2];
        CGLIB$mult$2$Proxy = MethodProxy.create(var1, var0, "(II)I", "mult", "CGLIB$mult$2");
        CGLIB$div$3$Method = var10000[3];
        CGLIB$div$3$Proxy = MethodProxy.create(var1, var0, "(II)I", "div", "CGLIB$div$3");
        var10000 = ReflectUtils.findMethods(new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
        CGLIB$equals$4$Method = var10000[0];
        CGLIB$equals$4$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$4");
        CGLIB$toString$5$Method = var10000[1];
        CGLIB$toString$5$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$5");
        CGLIB$hashCode$6$Method = var10000[2];
        CGLIB$hashCode$6$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$6");
        CGLIB$clone$7$Method = var10000[3];
        CGLIB$clone$7$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$7");
    }

    final int CGLIB$add$0(int var1, int var2) {
        return super.add(var1, var2);
    }

    public final int add(int var1, int var2) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var3 = var10000.intercept(this, CGLIB$add$0$Method, new Object[]{new Integer(var1), new Integer(var2)}, CGLIB$add$0$Proxy);
            return var3 == null ? 0 : ((Number)var3).intValue();
        } else {
            return super.add(var1, var2);
        }
    }

    final int CGLIB$sub$1(int var1, int var2) {
        return super.sub(var1, var2);
    }

    public final int sub(int var1, int var2) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var3 = var10000.intercept(this, CGLIB$sub$1$Method, new Object[]{new Integer(var1), new Integer(var2)}, CGLIB$sub$1$Proxy);
            return var3 == null ? 0 : ((Number)var3).intValue();
        } else {
            return super.sub(var1, var2);
        }
    }

    final int CGLIB$mult$2(int var1, int var2) {
        return super.mult(var1, var2);
    }

    public final int mult(int var1, int var2) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var3 = var10000.intercept(this, CGLIB$mult$2$Method, new Object[]{new Integer(var1), new Integer(var2)}, CGLIB$mult$2$Proxy);
            return var3 == null ? 0 : ((Number)var3).intValue();
        } else {
            return super.mult(var1, var2);
        }
    }

    final int CGLIB$div$3(int var1, int var2) {
        return super.div(var1, var2);
    }

    public final int div(int var1, int var2) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var3 = var10000.intercept(this, CGLIB$div$3$Method, new Object[]{new Integer(var1), new Integer(var2)}, CGLIB$div$3$Proxy);
            return var3 == null ? 0 : ((Number)var3).intValue();
        } else {
            return super.div(var1, var2);
        }
    }

    final boolean CGLIB$equals$4(Object var1) {
        return super.equals(var1);
    }

    public final boolean equals(Object var1) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var2 = var10000.intercept(this, CGLIB$equals$4$Method, new Object[]{var1}, CGLIB$equals$4$Proxy);
            return var2 == null ? false : (Boolean)var2;
        } else {
            return super.equals(var1);
        }
    }

    final String CGLIB$toString$5() {
        return super.toString();
    }

    public final String toString() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$5$Method, CGLIB$emptyArgs, CGLIB$toString$5$Proxy) : super.toString();
    }

    final int CGLIB$hashCode$6() {
        return super.hashCode();
    }

    public final int hashCode() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var1 = var10000.intercept(this, CGLIB$hashCode$6$Method, CGLIB$emptyArgs, CGLIB$hashCode$6$Proxy);
            return var1 == null ? 0 : ((Number)var1).intValue();
        } else {
            return super.hashCode();
        }
    }

    final Object CGLIB$clone$7() throws CloneNotSupportedException {
        return super.clone();
    }

    protected final Object clone() throws CloneNotSupportedException {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        return var10000 != null ? var10000.intercept(this, CGLIB$clone$7$Method, CGLIB$emptyArgs, CGLIB$clone$7$Proxy) : super.clone();
    }

    public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
        String var10000 = var0.toString();
        switch(var10000.hashCode()) {
        case -2131682232:
            if (var10000.equals("sub(II)I")) {
                return CGLIB$sub$1$Proxy;
            }
            break;
        case -1287932281:
            if (var10000.equals("add(II)I")) {
                return CGLIB$add$0$Proxy;
            }
            break;
        case -1267343528:
            if (var10000.equals("mult(II)I")) {
                return CGLIB$mult$2$Proxy;
            }
            break;
        case -508378822:
            if (var10000.equals("clone()Ljava/lang/Object;")) {
                return CGLIB$clone$7$Proxy;
            }
            break;
        case 303407255:
            if (var10000.equals("div(II)I")) {
                return CGLIB$div$3$Proxy;
            }
            break;
        case 1826985398:
            if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
                return CGLIB$equals$4$Proxy;
            }
            break;
        case 1913648695:
            if (var10000.equals("toString()Ljava/lang/String;")) {
                return CGLIB$toString$5$Proxy;
            }
            break;
        case 1984935277:
            if (var10000.equals("hashCode()I")) {
                return CGLIB$hashCode$6$Proxy;
            }
        }

        return null;
    }

    public Calculator$$EnhancerByCGLIB$$345a285a() {
        CGLIB$BIND_CALLBACKS(this);
    }

    public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
        CGLIB$THREAD_CALLBACKS.set(var0);
    }

    public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) {
        CGLIB$STATIC_CALLBACKS = var0;
    }

    private static final void CGLIB$BIND_CALLBACKS(Object var0) {
        Calculator$$EnhancerByCGLIB$$345a285a var1 = (Calculator$$EnhancerByCGLIB$$345a285a)var0;
        if (!var1.CGLIB$BOUND) {
            var1.CGLIB$BOUND = true;
            Object var10000 = CGLIB$THREAD_CALLBACKS.get();
            if (var10000 == null) {
                var10000 = CGLIB$STATIC_CALLBACKS;
                if (var10000 == null) {
                    return;
                }
            }

            var1.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
        }

    }

    public Object newInstance(Callback[] var1) {
        CGLIB$SET_THREAD_CALLBACKS(var1);
        Calculator$$EnhancerByCGLIB$$345a285a var10000 = new Calculator$$EnhancerByCGLIB$$345a285a();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Callback var1) {
        CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
        Calculator$$EnhancerByCGLIB$$345a285a var10000 = new Calculator$$EnhancerByCGLIB$$345a285a();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
        CGLIB$SET_THREAD_CALLBACKS(var3);
        Calculator$$EnhancerByCGLIB$$345a285a var10000 = new Calculator$$EnhancerByCGLIB$$345a285a;
        switch(var1.length) {
        case 0:
            var10000.<init>();
            CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
            return var10000;
        default:
            throw new IllegalArgumentException("Constructor not found");
        }
    }

    public Callback getCallback(int var1) {
        CGLIB$BIND_CALLBACKS(this);
        MethodInterceptor var10000;
        switch(var1) {
        case 0:
            var10000 = this.CGLIB$CALLBACK_0;
            break;
        default:
            var10000 = null;
        }

        return var10000;
    }

    public void setCallback(int var1, Callback var2) {
        switch(var1) {
        case 0:
            this.CGLIB$CALLBACK_0 = (MethodInterceptor)var2;
        default:
        }
    }

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

    public void setCallbacks(Callback[] var1) {
        this.CGLIB$CALLBACK_0 = (MethodInterceptor)var1[0];
    }

    static {
        CGLIB$STATICHOOK1();
    }
}

add(int var1, int var2)

当主程序调用 add 方法后，实际调用的是被代理对象的 add 方法。

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public final int add(int var1, int var2) {
    MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
    if (var10000 == null) {
        CGLIB$BIND_CALLBACKS(this);
        var10000 = this.CGLIB$CALLBACK_0;
    }

    if (var10000 != null) {
        Object var3 = var10000.intercept(this, CGLIB$add$0$Method, new Object[]{new Integer(var1), new Integer(var2)}, CGLIB$add$0$Proxy);
        return var3 == null ? 0 : ((Number)var3).intValue();
    } else {
        return super.add(var1, var2);
    }
}

当首次进入时 this.CGLIB$CALLBACK_0 并未赋值，因此 var1000 为 null，将会执行 CGLIB$BIND_CALLBACKS(this) 。

CGLIB$BIND_CALLBACKS(Object var0)

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private static final void CGLIB$BIND_CALLBACKS(Object var0) {
    Calculator$$EnhancerByCGLIB$$345a285a var1 = (Calculator$$EnhancerByCGLIB$$345a285a)var0;
    if (!var1.CGLIB$BOUND) {
        var1.CGLIB$BOUND = true;
        Object var10000 = CGLIB$THREAD_CALLBACKS.get();
        if (var10000 == null) {
            var10000 = CGLIB$STATIC_CALLBACKS;
            if (var10000 == null) {
                return;
            }
        }

        var1.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
    }

}

CGLIB$CALLBACK_0 为 CGLIB$THREAD_CALLBACKS 调用 get() 方法后返回的 Callback[] 数组的第0个元素，而 CGLIB$THREAD_CALLBACKS 为一个静态的 ThreadLocal 对象且通过一个静态方法进行赋值。

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public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
    CGLIB$THREAD_CALLBACKS.set(var0);
}

因此，我们只需要明白 CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) 是何时被调用的，且传入的参数 Callback[] var0 为何值就能清楚代理对象在调用被代理方法的具体流程，而这个静态方法被调用的时机在 Calculator myCalculator = (Calculator) enhancer.create() 方法中。

浅析代理对象的创建方法 enhancer.create()

我们跳过各种对数据的包装和缓存的代码，可以看到真正对代理对象的创建代码在 Enhancer 的父类 AbstractClassGenerator 的 create(Object key) 方法中。

create()

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public Object create() {
	classOnly = false;
	argumentTypes = null;
	return createHelper();
}

createHelper()

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private Object createHelper() {
	preValidate();
	Object key = KEY_FACTORY.newInstance((superclass != null) ? superclass.getName() : null,
			ReflectUtils.getNames(interfaces),
			filter == ALL_ZERO ? null : new WeakCacheKey<CallbackFilter>(filter),
			callbackTypes,
			useFactory,
			interceptDuringConstruction,
			serialVersionUID);
	this.currentKey = key;
	Object result = super.create(key);
	return result;
}

super.create(key)

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protected Object create(Object key) {
	try {
		ClassLoader loader = getClassLoader();
		Map<ClassLoader, ClassLoaderData> cache = CACHE;
		ClassLoaderData data = cache.get(loader);
		if (data == null) {
			synchronized (AbstractClassGenerator.class) {
				cache = CACHE;
				data = cache.get(loader);
				if (data == null) {
					Map<ClassLoader, ClassLoaderData> newCache = new WeakHashMap<ClassLoader, ClassLoaderData>(cache);
					data = new ClassLoaderData(loader);
					newCache.put(loader, data);
					CACHE = newCache;
				}
			}
		}
		this.key = key;
           // 这一步是生成代理对象的class文件的包装对象EnhancerFactoryData
		Object obj = data.get(this, getUseCache());
		if (obj instanceof Class) {
			return firstInstance((Class) obj);
		}
           // 这一步通过代理对象的class文件将代理对象创建出来
		return nextInstance(obj);
	}
	catch (RuntimeException | Error ex) {
		throw ex;
	}
	catch (Exception ex) {
		throw new CodeGenerationException(ex);
	}
}

其中 Object obj = data.get(this, getUseCache()) 是生成代理对象的class文件的方法，而 nextInstance(obj) 方法则是通过代理对象的class文件将代理对象创建出来。代理对象的静态方法 CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) 肯定是在其class文件生成之后被调用的，因此我们继续跟踪 nextInstance(obj) 方法。

Enhancer的nextInstance(Object instance)

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protected Object nextInstance(Object instance) {
	EnhancerFactoryData data = (EnhancerFactoryData) instance;

	if (classOnly) {
		return data.generatedClass;
	}

	Class[] argumentTypes = this.argumentTypes;
	Object[] arguments = this.arguments;
	if (argumentTypes == null) {
		argumentTypes = Constants.EMPTY_CLASS_ARRAY;
		arguments = null;
	}
	return data.newInstance(argumentTypes, arguments, callbacks);
}

EnhancerFactoryData的newInstance(Class[] argumentTypes, Object[] arguments, Callback[] callbacks)

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public Object newInstance(Class[] argumentTypes, Object[] arguments, Callback[] callbacks) {
    // 调用代理的对象静态方法 CGLIB$SET_THREAD_CALLBACKS(Callback[] var0)
    setThreadCallbacks(callbacks);
    try {
        // Explicit reference equality is added here just in case Arrays.equals does not have one
        if (primaryConstructorArgTypes == argumentTypes ||
            Arrays.equals(primaryConstructorArgTypes, argumentTypes)) {
            // If we have relevant Constructor instance at hand, just call it
            // This skips "get constructors" machinery
            return ReflectUtils.newInstance(primaryConstructor, arguments);
        }
        // Take a slow path if observing unexpected argument types
        return ReflectUtils.newInstance(generatedClass, argumentTypes, arguments);
    }
    finally {
        // clear thread callbacks to allow them to be gc'd
        setThreadCallbacks(null);
    }

}

EnhancerFactoryData 是 Enhancer 的内部类，而这里的 setThreadCallbacks(callbacks) 的入参 callbacks 往上追溯来自于 Enhancer 类的属性private Callback[] callbacks，那这个属性是何时赋值的呢？将目光移向我们写道程序入口，我们将自定义的 MethodInterceptor 对象 MyCglib 创建并赋值给了 Enhancer 的对象。

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public class CglibTest {
    public static void main(String[] args) {
        // 设置cglib生成的class文件保存路径
        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\mashibing\\spring");
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(Calculator.class);
        // 对Enhancer类的callbacks属性赋值
        enhancer.setCallback(new MyCglib());
        Calculator myCalculator = (Calculator) enhancer.create();
        myCalculator.add(1, 1);
        System.out.println(myCalculator.getClass());
    }
}

setThreadCallbacks(Callback[] callbacks)

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private void setThreadCallbacks(Callback[] callbacks) {
    try {
        setThreadCallbacks.invoke(generatedClass, (Object) callbacks);
    }
    catch (IllegalAccessException e) {
        throw new CodeGenerationException(e);
    }
    catch (InvocationTargetException e) {
        throw new CodeGenerationException(e.getTargetException());
    }
}

setThreadCallbacks 是代理类静态方法 CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) 的 Method 对象，generatedClass 为代理对象的 class 对象。这两个对象都是 EnhancerFactoryData 的内部属性字段，是通过 EnhancerFactoryData 的构造方法赋值的。

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public EnhancerFactoryData(Class generatedClass, Class[] primaryConstructorArgTypes, boolean classOnly) {
    // 代理对象的class对象
    this.generatedClass = generatedClass;
    try {
        // 通过class对象和方法名获取Method对象
        setThreadCallbacks = getCallbacksSetter(generatedClass, SET_THREAD_CALLBACKS_NAME);
        if (classOnly) {
            this.primaryConstructorArgTypes = null;
            this.primaryConstructor = null;
        }
        else {
            this.primaryConstructorArgTypes = primaryConstructorArgTypes;
            this.primaryConstructor = ReflectUtils.getConstructor(generatedClass, primaryConstructorArgTypes);
        }
    }
    catch (NoSuchMethodException e) {
        throw new CodeGenerationException(e);
    }
}

MethodInterceptor的intercept方法是怎么实现代理的

通过以上讲解，我们得知代理对象 Calculator myCalculator = (Calculator) enhancer.create() 调用 myCalculator.add(1, 1) 方法，实际上会去调用我们在 Enhancer 对象中设置的回调对象 enhancer.setCallback(new MyCglib()) 的 intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) 方法。

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public final int add(int var1, int var2) {
    MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
    if (var10000 == null) {
        CGLIB$BIND_CALLBACKS(this);
        var10000 = this.CGLIB$CALLBACK_0;
    }

    if (var10000 != null) {
        Object var3 = var10000.intercept(this, CGLIB$add$0$Method, new Object[]{new Integer(var1), new Integer(var2)}, CGLIB$add$0$Proxy);
        return var3 == null ? 0 : ((Number)var3).intValue();
    } else {
        return super.add(var1, var2);
    }
}

我们先关注两个对象 CGLIB$add$0$Method 和 CGLIB$add$0$Proxy，这两个变量的赋值都在静态方法 CGLIB$STATICHOOK1() 中，这个方法在静态代码块中被调用，也就是说当代理类的class文件被加载到内存中时便已经执行了。

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public class Calculator$$EnhancerByCGLIB$$345a285a extends Calculator implements Factory {    
	...
    static {
        CGLIB$STATICHOOK1();
    }
}

CGLIB$add$0$Method

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static void CGLIB$STATICHOOK1() {
    CGLIB$THREAD_CALLBACKS = new ThreadLocal();
    CGLIB$emptyArgs = new Object[0];
    Class var0 = Class.forName("com.eitan.proxy.cglib.Calculator$$EnhancerByCGLIB$$345a285a");
    Class var1;
    Method[] var10000 = ReflectUtils.findMethods(new String[]{"add", "(II)I", "sub", "(II)I", "mult", "(II)I", "div", "(II)I"}, (var1 = Class.forName("com.eitan.proxy.cglib.Calculator")).getDeclaredMethods());
    CGLIB$add$0$Method = var10000[0];
    CGLIB$add$0$Proxy = MethodProxy.create(var1, var0, "(II)I", "add", "CGLIB$add$0");
    CGLIB$sub$1$Method = var10000[1];
    CGLIB$sub$1$Proxy = MethodProxy.create(var1, var0, "(II)I", "sub", "CGLIB$sub$1");
    CGLIB$mult$2$Method = var10000[2];
    CGLIB$mult$2$Proxy = MethodProxy.create(var1, var0, "(II)I", "mult", "CGLIB$mult$2");
    CGLIB$div$3$Method = var10000[3];
    CGLIB$div$3$Proxy = MethodProxy.create(var1, var0, "(II)I", "div", "CGLIB$div$3");
    ...
}

可以看出，该成员变量是通过 var1 = Class.forName(“com.eitan.proxy.cglib.Calculator”)).getDeclaredMethods() 拿到被代理类的所有 Method 方法对象，然后按顺序依次赋值 CGLIB$add$0$Method = var10000[0] ，因此变量 CGLIB$add$0$Method 就代表被代理对象的 add方法的 Method 对象。

CGLIB$add$0$Proxy

这是 CGLIB 框架里的 MethodProxy 类的对象，通过 MethodProxy.create(var1, var0, “(II)I”, “add”, “CGLIB$add$0”) 方法构建。其中 var1 为被代理对象的class对象 var1 = Class.forName(“com.eitan.proxy.cglib.Calculator”)，var0 为代理对象的class对象 Class var0 = Class.forName(“com.eitan.proxy.cglib.Calculator$$EnhancerByCGLIB$$345a285a”) 。

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public static MethodProxy create(Class c1, Class c2, String desc, String name1, String name2) {
	MethodProxy proxy = new MethodProxy();
       // name1 = "add"
	proxy.sig1 = new Signature(name1, desc);
       // name2 = "CGLIB$add$0"
	proxy.sig2 = new Signature(name2, desc);
	proxy.createInfo = new CreateInfo(c1, c2);
	return proxy;
}

其中 name1 = “add”，name2 = “CGLIB$add$0” 是两个方法名：

  • add 方法：代理对象对原方法的增强，在其中调用了 MethodInterceptor 的 intercept 方法
  • CGLIB$add$0：直接调用父类的 add 方法，也就是直接调用被代理对象的 add 方法

methodProxy.invokeSuper(o, objects)

当我们知道了 MethodInterceptor 的 intercept 方法的入参代表何值之后，我们将注意力放在自定义的 MethodInceptor 子类。

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public class MyCglib implements MethodInterceptor {
    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("调用cglib动态代理");
        return methodProxy.invokeSuper(o, objects);
    }
}

当代理对象执行 add(1, 1) 方法时，最终将调用该对象的 intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) 方法。从代理对象的class文件可以分析出这个方法的各个入参的实际含义：

  • Object o：代理对象
  • Method method：被代理类所执行方法的Method对象
  • Object[] objects：所执行方法的入参
  • MethodProxy methodProxy：cglib包下的类，包含了代理类和被代理类的class对象以及两个方法名 add 和 CGLIB$add$0

为什么methodProxy.invokeSuper(o, objects)方法会调用被代理对象的方法呢？

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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();
	}
}

init()

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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();
                   // 生成被代理类的 FastClass 对象
				fci.f1 = helper(ci, ci.c1);
                   // 生成代理类的 FastClass 对象
				fci.f2 = helper(ci, ci.c2);
                   // 即调用被代理类的 FastClass 对象找出 sig1 包含的方法名 add 的下标
				fci.i1 = fci.f1.getIndex(sig1);
                   // 即调用代理类的 FastClass 对象找出 sig2 包含的方法名 CGLIB$add$0 的下标
				fci.i2 = fci.f2.getIndex(sig2);
				fastClassInfo = fci;
				createInfo = null;
			}
		}
	}
}

fci.f2.invoke(fci.i2, obj, args);

调用代理类的 FastClass 对象的 invoke(fci.i2, obj, args) 方法，其中：

  • fci.i2：调用代理类的 FastClass 对象的 fci.f2.getIndex(sig2) 找出的索引
  • obj：methodProxy.invokeSuper(o, objects) 传入的对象 o，这里也就是代理对象
  • args：要调用的方法参数

Calculator$$EnhancerByCGLIB$$345a285a$$FastClassByCGLIB$$cfb242b8d代理对象的FastClass

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public class Calculator$$EnhancerByCGLIB$$345a285a$$FastClassByCGLIB$$cfb242b8 extends FastClass {
    public Calculator$$EnhancerByCGLIB$$345a285a$$FastClassByCGLIB$$cfb242b8(Class var1) {
        super(var1);
    }

    public int getIndex(Signature var1) {
        String var10000 = var1.toString();
        switch(var10000.hashCode()) {
        case -2131682232:
            if (var10000.equals("sub(II)I")) {
                return 8;
            }
            break;
        case -1870561232:
            if (var10000.equals("CGLIB$findMethodProxy(Lorg/springframework/cglib/core/Signature;)Lorg/springframework/cglib/proxy/MethodProxy;")) {
                return 17;
            }
            break;
        case -1860420502:
            if (var10000.equals("CGLIB$clone$7()Ljava/lang/Object;")) {
                return 22;
            }
            break;
        case -1745842178:
            if (var10000.equals("setCallbacks([Lorg/springframework/cglib/proxy/Callback;)V")) {
                return 10;
            }
            break;
        case -1641413109:
            if (var10000.equals("newInstance([Lorg/springframework/cglib/proxy/Callback;)Ljava/lang/Object;")) {
                return 5;
            }
            break;
        case -1457535688:
            if (var10000.equals("CGLIB$STATICHOOK1()V")) {
                return 25;
            }
            break;
        case -1411753352:
            if (var10000.equals("CGLIB$hashCode$6()I")) {
                return 20;
            }
            break;
        case -1287932281:
            if (var10000.equals("add(II)I")) {
                return 0;
            }
            break;
        case -1267343528:
            if (var10000.equals("mult(II)I")) {
                return 15;
            }
            break;
        case -1034266769:
            if (var10000.equals("CGLIB$SET_STATIC_CALLBACKS([Lorg/springframework/cglib/proxy/Callback;)V")) {
                return 14;
            }
            break;
        case -1025895669:
            if (var10000.equals("CGLIB$SET_THREAD_CALLBACKS([Lorg/springframework/cglib/proxy/Callback;)V")) {
                return 13;
            }
            break;
        case -988317324:
            if (var10000.equals("newInstance([Ljava/lang/Class;[Ljava/lang/Object;[Lorg/springframework/cglib/proxy/Callback;)Ljava/lang/Object;")) {
                return 6;
            }
            break;
        case -984241474:
            if (var10000.equals("CGLIB$add$0(II)I")) {
                return 26;
            }
            break;
        case -974181657:
            if (var10000.equals("CGLIB$mult$2(II)I")) {
                return 23;
            }
            break;
        case -629417301:
            if (var10000.equals("CGLIB$div$3(II)I")) {
                return 24;
            }
            break;
        case -508378822:
            if (var10000.equals("clone()Ljava/lang/Object;")) {
                return 4;
            }
            break;
        case -50496290:
            if (var10000.equals("CGLIB$sub$1(II)I")) {
                return 21;
            }
            break;
        case 303407255:
            if (var10000.equals("div(II)I")) {
                return 16;
            }
            break;
        case 593200387:
            if (var10000.equals("CGLIB$equals$4(Ljava/lang/Object;)Z")) {
                return 18;
            }
            break;
        case 610042816:
            if (var10000.equals("newInstance(Lorg/springframework/cglib/proxy/Callback;)Ljava/lang/Object;")) {
                return 7;
            }
            break;
        case 1132856532:
            if (var10000.equals("getCallbacks()[Lorg/springframework/cglib/proxy/Callback;")) {
                return 12;
            }
            break;
        case 1246779367:
            if (var10000.equals("setCallback(ILorg/springframework/cglib/proxy/Callback;)V")) {
                return 9;
            }
            break;
        case 1364367423:
            if (var10000.equals("getCallback(I)Lorg/springframework/cglib/proxy/Callback;")) {
                return 11;
            }
            break;
        case 1826985398:
            if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
                return 1;
            }
            break;
        case 1913648695:
            if (var10000.equals("toString()Ljava/lang/String;")) {
                return 2;
            }
            break;
        case 1940521675:
            if (var10000.equals("CGLIB$toString$5()Ljava/lang/String;")) {
                return 19;
            }
            break;
        case 1984935277:
            if (var10000.equals("hashCode()I")) {
                return 3;
            }
        }

        return -1;
    }

    public int getIndex(String var1, Class[] var2) {
        switch(var1.hashCode()) {
        case -1776922004:
            if (var1.equals("toString")) {
                switch(var2.length) {
                case 0:
                    return 2;
                }
            }
            break;
        case -1295482945:
            if (var1.equals("equals")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("java.lang.Object")) {
                        return 1;
                    }
                }
            }
            break;
        case -1053468136:
            if (var1.equals("getCallbacks")) {
                switch(var2.length) {
                case 0:
                    return 12;
                }
            }
            break;
        case -124978606:
            if (var1.equals("CGLIB$equals$4")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("java.lang.Object")) {
                        return 18;
                    }
                }
            }
            break;
        case -60403779:
            if (var1.equals("CGLIB$SET_STATIC_CALLBACKS")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("[Lorg.springframework.cglib.proxy.Callback;")) {
                        return 14;
                    }
                }
            }
            break;
        case -29025552:
            if (var1.equals("CGLIB$hashCode$6")) {
                switch(var2.length) {
                case 0:
                    return 20;
                }
            }
            break;
        case 96417:
            if (var1.equals("add")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 0;
                    }
                }
            }
            break;
        case 99473:
            if (var1.equals("div")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 16;
                    }
                }
            }
            break;
        case 114240:
            if (var1.equals("sub")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 8;
                    }
                }
            }
            break;
        case 3363120:
            if (var1.equals("mult")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 15;
                    }
                }
            }
            break;
        case 85179481:
            if (var1.equals("CGLIB$SET_THREAD_CALLBACKS")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("[Lorg.springframework.cglib.proxy.Callback;")) {
                        return 13;
                    }
                }
            }
            break;
        case 94756189:
            if (var1.equals("clone")) {
                switch(var2.length) {
                case 0:
                    return 4;
                }
            }
            break;
        case 147696667:
            if (var1.equals("hashCode")) {
                switch(var2.length) {
                case 0:
                    return 3;
                }
            }
            break;
        case 161998109:
            if (var1.equals("CGLIB$STATICHOOK1")) {
                switch(var2.length) {
                case 0:
                    return 25;
                }
            }
            break;
        case 357484609:
            if (var1.equals("CGLIB$mult$2")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 23;
                    }
                }
            }
            break;
        case 495524492:
            if (var1.equals("setCallbacks")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("[Lorg.springframework.cglib.proxy.Callback;")) {
                        return 10;
                    }
                }
            }
            break;
        case 1108311562:
            if (var1.equals("CGLIB$add$0")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 26;
                    }
                }
            }
            break;
        case 1111248381:
            if (var1.equals("CGLIB$div$3")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 24;
                    }
                }
            }
            break;
        case 1125439466:
            if (var1.equals("CGLIB$sub$1")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 21;
                    }
                }
            }
            break;
        case 1154623345:
            if (var1.equals("CGLIB$findMethodProxy")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("org.springframework.cglib.core.Signature")) {
                        return 17;
                    }
                }
            }
            break;
        case 1543336192:
            if (var1.equals("CGLIB$toString$5")) {
                switch(var2.length) {
                case 0:
                    return 19;
                }
            }
            break;
        case 1811874389:
            if (var1.equals("newInstance")) {
                switch(var2.length) {
                case 1:
                    String var10001 = var2[0].getName();
                    switch(var10001.hashCode()) {
                    case -1997738671:
                        if (var10001.equals("[Lorg.springframework.cglib.proxy.Callback;")) {
                            return 5;
                        }
                        break;
                    case 1364160985:
                        if (var10001.equals("org.springframework.cglib.proxy.Callback")) {
                            return 7;
                        }
                    }
                case 2:
                default:
                    break;
                case 3:
                    if (var2[0].getName().equals("[Ljava.lang.Class;") && var2[1].getName().equals("[Ljava.lang.Object;") && var2[2].getName().equals("[Lorg.springframework.cglib.proxy.Callback;")) {
                        return 6;
                    }
                }
            }
            break;
        case 1817099975:
            if (var1.equals("setCallback")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("org.springframework.cglib.proxy.Callback")) {
                        return 9;
                    }
                }
            }
            break;
        case 1905679803:
            if (var1.equals("getCallback")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("int")) {
                        return 11;
                    }
                }
            }
            break;
        case 1951977613:
            if (var1.equals("CGLIB$clone$7")) {
                switch(var2.length) {
                case 0:
                    return 22;
                }
            }
        }

        return -1;
    }

    public int getIndex(Class[] var1) {
        switch(var1.length) {
        case 0:
            return 0;
        default:
            return -1;
        }
    }

    public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
        345a285a var10000 = (345a285a)var2;
        int var10001 = var1;

        try {
            switch(var10001) {
            case 0:
                return new Integer(var10000.add(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 1:
                return new Boolean(var10000.equals(var3[0]));
            case 2:
                return var10000.toString();
            case 3:
                return new Integer(var10000.hashCode());
            case 4:
                return var10000.clone();
            case 5:
                return var10000.newInstance((Callback[])var3[0]);
            case 6:
                return var10000.newInstance((Class[])var3[0], (Object[])var3[1], (Callback[])var3[2]);
            case 7:
                return var10000.newInstance((Callback)var3[0]);
            case 8:
                return new Integer(var10000.sub(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 9:
                var10000.setCallback(((Number)var3[0]).intValue(), (Callback)var3[1]);
                return null;
            case 10:
                var10000.setCallbacks((Callback[])var3[0]);
                return null;
            case 11:
                return var10000.getCallback(((Number)var3[0]).intValue());
            case 12:
                return var10000.getCallbacks();
            case 13:
                345a285a.CGLIB$SET_THREAD_CALLBACKS((Callback[])var3[0]);
                return null;
            case 14:
                345a285a.CGLIB$SET_STATIC_CALLBACKS((Callback[])var3[0]);
                return null;
            case 15:
                return new Integer(var10000.mult(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 16:
                return new Integer(var10000.div(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 17:
                return 345a285a.CGLIB$findMethodProxy((Signature)var3[0]);
            case 18:
                return new Boolean(var10000.CGLIB$equals$4(var3[0]));
            case 19:
                return var10000.CGLIB$toString$5();
            case 20:
                return new Integer(var10000.CGLIB$hashCode$6());
            case 21:
                return new Integer(var10000.CGLIB$sub$1(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 22:
                return var10000.CGLIB$clone$7();
            case 23:
                return new Integer(var10000.CGLIB$mult$2(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 24:
                return new Integer(var10000.CGLIB$div$3(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 25:
                345a285a.CGLIB$STATICHOOK1();
                return null;
            case 26:
                return new Integer(var10000.CGLIB$add$0(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            }
        } catch (Throwable var4) {
            throw new InvocationTargetException(var4);
        }

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

    public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
        345a285a var10000 = new 345a285a;
        345a285a var10001 = var10000;
        int var10002 = var1;

        try {
            switch(var10002) {
            case 0:
                var10001.<init>();
                return var10000;
            }
        } catch (Throwable var3) {
            throw new InvocationTargetException(var3);
        }

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

    public int getMaxIndex() {
        return 26;
    }
}

Calculator$$FastClassByCGLIB$$9bbbb4ed被代理对象的FastClass

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public class Calculator$$FastClassByCGLIB$$9bbbb4ed extends FastClass {
    public Calculator$$FastClassByCGLIB$$9bbbb4ed(Class var1) {
        super(var1);
    }

    public int getIndex(Signature var1) {
        String var10000 = var1.toString();
        switch(var10000.hashCode()) {
        case -2131682232:
            if (var10000.equals("sub(II)I")) {
                return 1;
            }
            break;
        case -1287932281:
            if (var10000.equals("add(II)I")) {
                return 0;
            }
            break;
        case -1267343528:
            if (var10000.equals("mult(II)I")) {
                return 2;
            }
            break;
        case 303407255:
            if (var10000.equals("div(II)I")) {
                return 3;
            }
            break;
        case 1826985398:
            if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
                return 4;
            }
            break;
        case 1913648695:
            if (var10000.equals("toString()Ljava/lang/String;")) {
                return 5;
            }
            break;
        case 1984935277:
            if (var10000.equals("hashCode()I")) {
                return 6;
            }
        }

        return -1;
    }

    public int getIndex(String var1, Class[] var2) {
        switch(var1.hashCode()) {
        case -1776922004:
            if (var1.equals("toString")) {
                switch(var2.length) {
                case 0:
                    return 5;
                }
            }
            break;
        case -1295482945:
            if (var1.equals("equals")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("java.lang.Object")) {
                        return 4;
                    }
                }
            }
            break;
        case 96417:
            if (var1.equals("add")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 0;
                    }
                }
            }
            break;
        case 99473:
            if (var1.equals("div")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 3;
                    }
                }
            }
            break;
        case 114240:
            if (var1.equals("sub")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 1;
                    }
                }
            }
            break;
        case 3363120:
            if (var1.equals("mult")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("int")) {
                        return 2;
                    }
                }
            }
            break;
        case 147696667:
            if (var1.equals("hashCode")) {
                switch(var2.length) {
                case 0:
                    return 6;
                }
            }
        }

        return -1;
    }

    public int getIndex(Class[] var1) {
        switch(var1.length) {
        case 0:
            return 0;
        default:
            return -1;
        }
    }

    public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
        Calculator var10000 = (Calculator)var2;
        int var10001 = var1;

        try {
            switch(var10001) {
            case 0:
                return new Integer(var10000.add(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 1:
                return new Integer(var10000.sub(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 2:
                return new Integer(var10000.mult(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 3:
                return new Integer(var10000.div(((Number)var3[0]).intValue(), ((Number)var3[1]).intValue()));
            case 4:
                return new Boolean(var10000.equals(var3[0]));
            case 5:
                return var10000.toString();
            case 6:
                return new Integer(var10000.hashCode());
            }
        } catch (Throwable var4) {
            throw new InvocationTargetException(var4);
        }

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

    public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
        Calculator var10000 = new Calculator;
        Calculator var10001 = var10000;
        int var10002 = var1;

        try {
            switch(var10002) {
            case 0:
                var10001.<init>();
                return var10000;
            }
        } catch (Throwable var3) {
            throw new InvocationTargetException(var3);
        }

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

    public int getMaxIndex() {
        return 6;
    }
}

所以，fci.f2.invoke(fci.i2, obj, args) 实际上会通过方法的索引 fci.i2 找出对应相应执行的方法，再通过传入的对象直接调用该方法达成目的。总结一句，FastClass 类将目标类的所有方法建立索引，且通过方法名可以找出对应下标，在代码里直接对传入对象进行方法调用，避免了使用反射造成的性能消耗。