cglib demo以及Enhancer源码解析

迈不过友情╰ 2022-03-10 06:17 577阅读 0赞

转载自：[https://www.jianshu.com/p/20203286ccd9][https_www.jianshu.com_p_20203286ccd9]

先通过demo演示效果，然后进行源码分析  
demo用Enhancer结合MethodInterceptor以及CallBackFilter完成

这里Enhancer类是CGLib中的一个字节码增强器，它可以方便的对你想要处理的类进行扩展

## 1.demo ##

拦截器1

package cglib;
    
    import net.sf.cglib.proxy.MethodInterceptor;
    import net.sf.cglib.proxy.MethodProxy;
    import java.lang.reflect.Method;
    
    public class CglibProxy implements MethodInterceptor {
    
        //实现MethodInterceptor接口，定义方法的拦截器
        @Override
        public Object intercept(Object o, Method method, Object[] objects,
                MethodProxy methodProxy) throws Throwable {
            System.out.println("pre");
            //通过代理类调用父类中的方法,即实体类方法
            Object result = methodProxy.invokeSuper(o, objects);
            System.out.println("after");
            return result;
        }
    }

拦截器2

package cglib;
    
    import net.sf.cglib.proxy.MethodInterceptor;
    import net.sf.cglib.proxy.MethodProxy;
    import java.lang.reflect.Method;
    
    public class CglibProxy2 implements MethodInterceptor {
    
        //实现MethodInterceptor接口，定义方法的拦截器
        @Override
        public Object intercept(Object o, Method method, Object[] objects,
                MethodProxy methodProxy) throws Throwable {
            System.out.println("pre1");
            //通过代理类调用父类中的方法,即实体类方法
            Object result = methodProxy.invokeSuper(o, objects);
            System.out.println("after1");
            return result;
        }
    }

回调过滤器CallbackFilter

package cglib;
    
    import net.sf.cglib.proxy.CallbackFilter;
    import java.lang.reflect.Method;
    
    public class filter implements CallbackFilter {
        @Override
        public int accept(Method method) {
            if(method.getName().equals("toString")) {
                return 1;
            }
            return 0;
        }
    }

测试类

package cglib;
    
    import net.sf.cglib.core.DebuggingClassWriter;
    import net.sf.cglib.proxy.Callback;
    import net.sf.cglib.proxy.Enhancer;
    
    public class CglibLearn {
        //定义委托类，可以不是接口
        static class serviceImpl {
            void say()
            {
                System.out.println("say");
            }
        }
    
        public static Object getProxyInstance(Object realSubject) {
            Enhancer enhancer = new Enhancer();
            //需要创建子类的类,即定义委托类
            enhancer.setSuperclass(realSubject.getClass());
            //设置两个CallBack以及CallbackFilter
            Callback[] callbacks=new Callback[2];
            callbacks[0]=new CglibProxy();
            callbacks[1]=new CglibProxy2();
            enhancer.setCallbacks(callbacks);
            enhancer.setCallbackFilter(new filter());
            //通过字节码技术动态创建子类实例
            return enhancer.create();
        }
    
        public static void main(String[] args) {
            //将sam,class文件写到硬盘
            System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, ".//");
            //通过生成子类的方式创建代理类
            serviceImpl impl = (serviceImpl)getProxyInstance(new serviceImpl());
            impl.say();
            impl.toString();
        }
    }

输出,自己想想就知道

## 2.源码分析 ##

看源码之前，最好先了解下callBack和callBackFilter是有什么作用，再看会带着问题看

直接进测试类的enhancer.create();探究这个代理对象是怎么生成的,下面按照几个注意的环节来讲，会经历整个创建过程

### 2.1根据代理类的配置作为组合Key ###

net.sf.cglib.proxy.Enhancer#create()
    net.sf.cglib.proxy.Enhancer#createHelper()
    
    private Object createHelper() {
            //进行有效性验证，比如有多个callBack却没有callBackFilter
            validate();
            if (superclass != null) {
                setNamePrefix(superclass.getName());
            } else if (interfaces != null) {
                setNamePrefix(interfaces[ReflectUtils.findPackageProtected(interfaces)].getName());
            }
            //先根据KEY_FACTORY 以当前代理类的配置信息 生成一个组合Key，再利用这个组合Key，进行create
            return super.create(KEY_FACTORY.newInstance((superclass != null) ? superclass.getName() : null,
                                                        ReflectUtils.getNames(interfaces),
                                                        filter,
                                                        callbackTypes,
                                                        useFactory,
                                                        interceptDuringConstruction,
                                                        serialVersionUID));
        }

这里注意  
***KEY\_FACTORY 就是前两节讲到的根据KeyFactory，完成multi-value的一个Key***  
可以理解成这里如果代理类的配置，作为Key，一样的换就能利用缓存了，后面会讲到利用的缓存

private static final EnhancerKey KEY_FACTORY =
          (EnhancerKey)KeyFactory.create(EnhancerKey.class);
    
    public interface EnhancerKey {
            public Object newInstance(String type,
                                      String[] interfaces,
                                      CallbackFilter filter,
                                      Type[] callbackTypes,
                                      boolean useFactory,
                                      boolean interceptDuringConstruction,
                                      Long serialVersionUID);
        }

### 2.2 利用缓存完成根据Key获取Class信息，进而生成代理对象 ###

这一块代码比较简单，和之前jdk动态代理利用的缓存差不多,在KeyFactory那一节也讲过，还是列出来就行,看注释就够了

protected Object create(Object key) {
            try {
                //需要缓存的类
                Class gen = null;
                synchronized (source) {
                    ClassLoader loader = getClassLoader();
                    Map cache2 = null;
                    //根据来源区分,根据classLoader进行一级缓存
                    cache2 = (Map)source.cache.get(loader);
                    if (cache2 == null) {
                        cache2 = new HashMap();
                        cache2.put(NAME_KEY, new HashSet());
                        source.cache.put(loader, cache2);
                    } else if (useCache) {
                        //用缓存
                        Reference ref = (Reference)cache2.get(key);
                        gen = (Class) (( ref == null ) ? null : ref.get()); 
                    }
                    if (gen == null) {
                        Object save = CURRENT.get();
                        CURRENT.set(this);
                        try {
                            this.key = key;
                            if (attemptLoad) {
                                try {
                                    gen = loader.loadClass(getClassName());
                                } catch (ClassNotFoundException e) {
                                    // ignore
                                }
                            }
                            if (gen == null) {
                                //结合生成策略，得到类的字节码
                                byte[] b = strategy.generate(this);
                                String className = ClassNameReader.getClassName(new ClassReader(b));
                                getClassNameCache(loader).add(className);
                                //根据字节码生成类
                                gen = ReflectUtils.defineClass(className, b, loader);
                            }
                            if (useCache) {
                                //根据传入的key，进行二级缓存
                                cache2.put(key, new WeakReference(gen));
                            }
                            //根据类，生成实例
                            return firstInstance(gen);
                        } finally {
                            CURRENT.set(save);
                        }
                    }
                }
                return firstInstance(gen);
            } catch (RuntimeException e) {
                throw e;
            } catch (Error e) {
                throw e;
            } catch (Exception e) {
                throw new CodeGenerationException(e);
            }
        }

可以看出来，关注点集中在代理类的生成,即

byte[] b = strategy.generate(this);

### 2.3.代理类的生成 ###

继续跟进

net.sf.cglib.core.GeneratorStrategy#generate
    net.sf.cglib.core.DefaultGeneratorStrategy#generate
    net.sf.cglib.core.ClassGenerator#generateClass
    net.sf.cglib.proxy.Enhancer#generateClass

最终就是利用Enhancer来生成代理类,下面有详细的注释

public void generateClass(ClassVisitor v) throws Exception {
            Class sc = (superclass == null) ? Object.class : superclass;
            if (TypeUtils.isFinal(sc.getModifiers()))
                throw new IllegalArgumentException("Cannot subclass final class " + sc);
            List constructors = new ArrayList(Arrays.asList(sc.getDeclaredConstructors()));
            filterConstructors(sc, constructors);
            // Order is very important: must add superclass, then
            // its superclass chain, then each interface and
            // its superinterfaces.
            List actualMethods = new ArrayList();
            List interfaceMethods = new ArrayList();
            final Set forcePublic = new HashSet();
            /*
            根据规定的父类，生成需要的方法，参见 CglibLearn$serviceImpl$$EnhancerByCGLIB$$81852b18.class
            actualMethods记录所有经过过滤的方法
            interfaceMethods和forcePublic的size都为0
            */
            getMethods(sc, interfaces, actualMethods, interfaceMethods, forcePublic);
            for(int i=0;i<actualMethods.size();i++) {
                System.out.println("actualMethods is " + actualMethods.get(i));
            }
            /*
            把actualMethods中，非abstract,非native,非synchronized方法的修饰符全部变成final
            将转化后的方法信息MethodInfo列表 记录在methods中
             */
            List methods = CollectionUtils.transform(actualMethods, new Transformer() {
                public Object transform(Object value) {
                    Method method = (Method)value;
                    int modifiers = Constants.ACC_FINAL
                        | (method.getModifiers()
                           & ~Constants.ACC_ABSTRACT
                           & ~Constants.ACC_NATIVE
                           & ~Constants.ACC_SYNCHRONIZED);
                    if (forcePublic.contains(MethodWrapper.create(method))) {
                        modifiers = (modifiers & ~Constants.ACC_PROTECTED) | Constants.ACC_PUBLIC;
                    }
                    return ReflectUtils.getMethodInfo(method, modifiers);
                }
            });
            ClassEmitter e = new ClassEmitter(v);
            //开始生成代理类 继承指定的superClass
            e.begin_class(Constants.V1_2,
                          Constants.ACC_PUBLIC,
                          getClassName(),
                          Type.getType(sc),
                          (useFactory ?
                           TypeUtils.add(TypeUtils.getTypes(interfaces), FACTORY) :
                           TypeUtils.getTypes(interfaces)),
                          Constants.SOURCE_FILE);
            //将构造函数信息 记录在 constructorInfo 中
            List constructorInfo = CollectionUtils.transform(constructors, MethodInfoTransformer.getInstance());
            e.declare_field(Constants.ACC_PRIVATE, BOUND_FIELD, Type.BOOLEAN_TYPE, null);
            if (!interceptDuringConstruction) {
                e.declare_field(Constants.ACC_PRIVATE, CONSTRUCTED_FIELD, Type.BOOLEAN_TYPE, null);
            }
            e.declare_field(Constants.PRIVATE_FINAL_STATIC, THREAD_CALLBACKS_FIELD, THREAD_LOCAL, null);
            e.declare_field(Constants.PRIVATE_FINAL_STATIC, STATIC_CALLBACKS_FIELD, CALLBACK_ARRAY, null);
            if (serialVersionUID != null) {
                e.declare_field(Constants.PRIVATE_FINAL_STATIC, Constants.SUID_FIELD_NAME, Type.LONG_TYPE, serialVersionUID);
            }
            //声明field,是定义的callbackType，设置了几个callBack，这里就有几个field,名字为CGLIB$CALLBACK_xxx(为id)
            for (int i = 0; i < callbackTypes.length; i++) {
                e.declare_field(Constants.ACC_PRIVATE, getCallbackField(i), callbackTypes[i], null);
            }
            //根据methods,actualMethods生成方法，完成callBack，callBackFilter的处理
            emitMethods(e, methods, actualMethods);
            //生成构造函数
            emitConstructors(e, constructorInfo);
            //这几个暂时不清楚
            emitSetThreadCallbacks(e);
            emitSetStaticCallbacks(e);
            emitBindCallbacks(e);
    
            if (useFactory) {
                int[] keys = getCallbackKeys();
                emitNewInstanceCallbacks(e);
                emitNewInstanceCallback(e);
                emitNewInstanceMultiarg(e, constructorInfo);
                emitGetCallback(e, keys);
                emitSetCallback(e, keys);
                emitGetCallbacks(e);
                emitSetCallbacks(e);
            }
            e.end_class();
        }

备注，上面利用asm完成类的生成,主要步骤如下

***1.getMethods(sc, interfaces, actualMethods, interfaceMethods, forcePublic);***  
这个方法就是递归的将superClass的父类，父接口的函数全部记录在method中,  
然后过滤掉原有类的static方法，private方法,和superClass位于不同包的类中的方法(不知道何时会出现这种情况???),以及final方法

获取，并且过滤完之后，剩下的方法是

void cglib.CglibLearn$serviceImpl.say()
    protected void java.lang.Object.finalize() throws java.lang.Throwable
    public boolean java.lang.Object.equals(java.lang.Object)
    public java.lang.String java.lang.Object.toString()
    public native int java.lang.Object.hashCode()
    protected native java.lang.Object java.lang.Object.clone() throws java.lang.CloneNotSupportedException

***2.emitMethods***  
这个函数是用来生成代理类里面的methods，非常重要，列出源码如下

/*
            methods 是方法的信息列表, 每一个类型都是MethodInfo
            actualMethods 是真实的方法, 每一个类型都是Method
         */
        private void emitMethods(final ClassEmitter ce, List methods, List actualMethods) {
            /*
            根据callbackTypes得到对应的generator,跟进去看
            比如callbackType是MethodInterceptor.class,对应的generator就是MethodInterceptorGenerator.INSTANCE
             */
            CallbackGenerator[] generators = CallbackInfo.getGenerators(callbackTypes);
    
            Map groups = new HashMap();
            final Map indexes = new HashMap();
            final Map originalModifiers = new HashMap();
            final Map positions = CollectionUtils.getIndexMap(methods);
            final Map declToBridge = new HashMap();
    
            Iterator it1 = methods.iterator();
            Iterator it2 = (actualMethods != null) ? actualMethods.iterator() : null;
    
            while (it1.hasNext()) {
                MethodInfo method = (MethodInfo)it1.next();
                Method actualMethod = (it2 != null) ? (Method)it2.next() : null;
                /*
                根据定义的callBackFilter的accept值，判断由哪一个callBack来过滤当前方法
                filter这里默认是net.sf.cglib.proxy.Enhancer.ALL_ZERO,即accept永远返回0
                 */
                int index = filter.accept(actualMethod);
                if (index >= callbackTypes.length) {
                    throw new IllegalArgumentException("Callback filter returned an index that is too large: " + index);
                }
                originalModifiers.put(method, new Integer((actualMethod != null) ? actualMethod.getModifiers() : method.getModifiers()));
                //通过indexes这个map记录每个map该由第几个callBack来处理
                indexes.put(method, new Integer(index));
                //让这个callBack对应的generator 记录下来它要处理这个method
                List group = (List)groups.get(generators[index]);
                if (group == null) {
                    groups.put(generators[index], group = new ArrayList(methods.size()));
                }
                group.add(method);
                
                // Optimization: build up a map of Class -> bridge methods in class
                // so that we can look up all the bridge methods in one pass for a class.
                if (TypeUtils.isBridge(actualMethod.getModifiers())) {
                    Set bridges = (Set)declToBridge.get(actualMethod.getDeclaringClass());
                    if (bridges == null) {
                        bridges = new HashSet();
                        declToBridge.put(actualMethod.getDeclaringClass(), bridges);
                    }
                    bridges.add(method.getSignature());             
                }
            }
            
            final Map bridgeToTarget = new BridgeMethodResolver(declToBridge).resolveAll();
    
            Set seenGen = new HashSet();
            CodeEmitter se = ce.getStaticHook();
            se.new_instance(THREAD_LOCAL);
            se.dup();
            se.invoke_constructor(THREAD_LOCAL, CSTRUCT_NULL);
            se.putfield(THREAD_CALLBACKS_FIELD);
    
            final Object[] state = new Object[1];
            //下面context定义了如何根据callBack信息，来进行代码生成
            CallbackGenerator.Context context = new CallbackGenerator.Context() {
                public ClassLoader getClassLoader() {
                    return Enhancer.this.getClassLoader();
                }
                public int getOriginalModifiers(MethodInfo method) {
                    return ((Integer)originalModifiers.get(method)).intValue();
                }
                //根据method判断对应的callBack下标
                public int getIndex(MethodInfo method) {
                    return ((Integer)indexes.get(method)).intValue();
                }
                /*
                根据下标让当前method生成“调用对应callBack”的代码
                这也表现出来一个method只有一个callBack
                 */
                public void emitCallback(CodeEmitter e, int index) {
                    emitCurrentCallback(e, index);
                }
                public Signature getImplSignature(MethodInfo method) {
                    return rename(method.getSignature(), ((Integer)positions.get(method)).intValue());
                }
                public void emitInvoke(CodeEmitter e, MethodInfo method) {
                    // If this is a bridge and we know the target was called from invokespecial,
                    // then we need to invoke_virtual w/ the bridge target instead of doing
                    // a super, because super may itself be using super, which would bypass
                    // any proxies on the target.
                    Signature bridgeTarget = (Signature)bridgeToTarget.get(method.getSignature());
                    if (bridgeTarget != null) {
                        // TODO: this assumes that the target has wider or the same type
                        // parameters than the current.  
                        // In reality this should always be true because otherwise we wouldn't
                        // have had a bridge doing an invokespecial.
                        // If it isn't true, we would need to checkcast each argument
                        // against the target's argument types
                        e.invoke_virtual_this(bridgeTarget);
                        
                        Type retType = method.getSignature().getReturnType();                    
                        // Not necessary to cast if the target & bridge have
                        // the same return type. 
                        // (This conveniently includes void and primitive types,
                        // which would fail if casted.  It's not possible to 
                        // covariant from boxed to unbox (or vice versa), so no having
                        // to box/unbox for bridges).
                        // TODO: It also isn't necessary to checkcast if the return is
                        // assignable from the target.  (This would happen if a subclass
                        // used covariant returns to narrow the return type within a bridge
                        // method.)
                        if (!retType.equals(bridgeTarget.getReturnType())) {
                            e.checkcast(retType);
                        }
                    } else {
                        e.super_invoke(method.getSignature());
                    }
                }
                public CodeEmitter beginMethod(ClassEmitter ce, MethodInfo method) {
                    CodeEmitter e = EmitUtils.begin_method(ce, method);
                    if (!interceptDuringConstruction &&
                        !TypeUtils.isAbstract(method.getModifiers())) {
                        Label constructed = e.make_label();
                        e.load_this();
                        e.getfield(CONSTRUCTED_FIELD);
                        e.if_jump(e.NE, constructed);
                        e.load_this();
                        e.load_args();
                        e.super_invoke();
                        e.return_value();
                        e.mark(constructed);
                    }
                    return e;
                }
            };
            for (int i = 0; i < callbackTypes.length; i++) {
                CallbackGenerator gen = generators[i];
                if (!seenGen.contains(gen)) {
                    seenGen.add(gen);
                    /*
                    每个callBack对应的generator要处理的列表为fmethods
                    下面将每个method对应的callBack调用关系，生成代码
                     */
                    final List fmethods = (List)groups.get(gen);
                    if (fmethods != null) {
                        try {
                            gen.generate(ce, context, fmethods);
                            gen.generateStatic(se, context, fmethods);
                        } catch (RuntimeException x) {
                            throw x;
                        } catch (Exception x) {
                            throw new CodeGenerationException(x);
                        }
                    }
                }
            }
            se.return_value();
            se.end_method();
        }

这里的主要工作如下

int index = filter.accept(actualMethod); 这里是判断当前method是由哪一个callBack来处理
    
    ...
    定义如何根据callBack信息，来进行代码生成
    CallbackGenerator.Context context = new CallbackGenerator.Context(){xxx}
    ...
    
    每个callBack对应的generator要处理的列表为fmethods
    下面将每个method对应的callBack调用关系，生成代码
    final List fmethods = (List)groups.get(gen);

### 2.4.代理类的结果 ###

本地生成了文件

![Image 1][]

image.png

其中，CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b文件的细节在intellij并没有显示完全，用  
[http://www.javadecompilers.com/result][http_www.javadecompilers.com_result] 去decompile一下，可以看到细节,一定要展示出来，方便理解代理类创建的过程

/*
     * Decompiled with CFR 0_118.
     * 
     * Could not load the following classes:
     *  cglib.CglibLearn
     *  cglib.CglibLearn$serviceImpl
     *  net.sf.cglib.core.ReflectUtils
     *  net.sf.cglib.core.Signature
     *  net.sf.cglib.proxy.Callback
     *  net.sf.cglib.proxy.Factory
     *  net.sf.cglib.proxy.MethodInterceptor
     *  net.sf.cglib.proxy.MethodProxy
     */
    package cglib;
    
    import cglib.CglibLearn;
    import java.lang.reflect.Method;
    import net.sf.cglib.core.ReflectUtils;
    import net.sf.cglib.core.Signature;
    import net.sf.cglib.proxy.Callback;
    import net.sf.cglib.proxy.Factory;
    import net.sf.cglib.proxy.MethodInterceptor;
    import net.sf.cglib.proxy.MethodProxy;
    
    public class CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b
    extends CglibLearn.serviceImpl
    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 MethodInterceptor CGLIB$CALLBACK_1;
        private static final Method CGLIB$say$0$Method;
        private static final MethodProxy CGLIB$say$0$Proxy;
        private static final Object[] CGLIB$emptyArgs;
        private static final Method CGLIB$finalize$1$Method;
        private static final MethodProxy CGLIB$finalize$1$Proxy;
        private static final Method CGLIB$equals$2$Method;
        private static final MethodProxy CGLIB$equals$2$Proxy;
        private static final Method CGLIB$toString$3$Method;
        private static final MethodProxy CGLIB$toString$3$Proxy;
        private static final Method CGLIB$hashCode$4$Method;
        private static final MethodProxy CGLIB$hashCode$4$Proxy;
        private static final Method CGLIB$clone$5$Method;
        private static final MethodProxy CGLIB$clone$5$Proxy;
    
        static void CGLIB$STATICHOOK1() {
            CGLIB$THREAD_CALLBACKS = new ThreadLocal();
            CGLIB$emptyArgs = new Object[0];
            Class class_ = Class.forName("cglib.CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b");
            Class class_2 = Class.forName("java.lang.Object");
            Method[] arrmethod = ReflectUtils.findMethods((String[])new String[]{"finalize", "()V", "equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (Method[])class_2.getDeclaredMethods());
            CGLIB$finalize$1$Method = arrmethod[0];
            CGLIB$finalize$1$Proxy = MethodProxy.create(class_2, class_, (String)"()V", (String)"finalize", (String)"CGLIB$finalize$1");
            CGLIB$equals$2$Method = arrmethod[1];
            CGLIB$equals$2$Proxy = MethodProxy.create(class_2, class_, (String)"(Ljava/lang/Object;)Z", (String)"equals", (String)"CGLIB$equals$2");
            CGLIB$toString$3$Method = arrmethod[2];
            CGLIB$toString$3$Proxy = MethodProxy.create(class_2, class_, (String)"()Ljava/lang/String;", (String)"toString", (String)"CGLIB$toString$3");
            CGLIB$hashCode$4$Method = arrmethod[3];
            CGLIB$hashCode$4$Proxy = MethodProxy.create(class_2, class_, (String)"()I", (String)"hashCode", (String)"CGLIB$hashCode$4");
            CGLIB$clone$5$Method = arrmethod[4];
            CGLIB$clone$5$Proxy = MethodProxy.create(class_2, class_, (String)"()Ljava/lang/Object;", (String)"clone", (String)"CGLIB$clone$5");
            class_2 = Class.forName("cglib.CglibLearn$serviceImpl");
            CGLIB$say$0$Method = ReflectUtils.findMethods((String[])new String[]{"say", "()V"}, (Method[])class_2.getDeclaredMethods())[0];
            CGLIB$say$0$Proxy = MethodProxy.create(class_2, class_, (String)"()V", (String)"say", (String)"CGLIB$say$0");
        }
    
        final void CGLIB$say$0() {
            super.say();
        }
    
        final void say() {
            MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
            if (methodInterceptor == null) {
                CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BIND_CALLBACKS((Object)this);
                methodInterceptor = this.CGLIB$CALLBACK_0;
            }
            if (methodInterceptor != null) {
                Object object = methodInterceptor.intercept((Object)this, CGLIB$say$0$Method, CGLIB$emptyArgs, CGLIB$say$0$Proxy);
                return;
            }
            super.say();
        }
    
        final void CGLIB$finalize$1() throws Throwable {
            super.finalize();
        }
    
        protected final void finalize() throws Throwable {
            MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
            if (methodInterceptor == null) {
                CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BIND_CALLBACKS((Object)this);
                methodInterceptor = this.CGLIB$CALLBACK_0;
            }
            if (methodInterceptor != null) {
                Object object = methodInterceptor.intercept((Object)this, CGLIB$finalize$1$Method, CGLIB$emptyArgs, CGLIB$finalize$1$Proxy);
                return;
            }
            super.finalize();
        }
    
        final boolean CGLIB$equals$2(Object object) {
            return super.equals(object);
        }
    
        public final boolean equals(Object object) {
            MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
            if (methodInterceptor == null) {
                CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BIND_CALLBACKS((Object)this);
                methodInterceptor = this.CGLIB$CALLBACK_0;
            }
            if (methodInterceptor != null) {
                Object object2 = methodInterceptor.intercept((Object)this, CGLIB$equals$2$Method, new Object[]{object}, CGLIB$equals$2$Proxy);
                return object2 == null ? false : (Boolean)object2;
            }
            return super.equals(object);
        }
    
        final String CGLIB$toString$3() {
            return super.toString();
        }
    
        public final String toString() {
            MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_1;
            if (methodInterceptor == null) {
                CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BIND_CALLBACKS((Object)this);
                methodInterceptor = this.CGLIB$CALLBACK_1;
            }
            if (methodInterceptor != null) {
                return (String)methodInterceptor.intercept((Object)this, CGLIB$toString$3$Method, CGLIB$emptyArgs, CGLIB$toString$3$Proxy);
            }
            return super.toString();
        }
    
        final int CGLIB$hashCode$4() {
            return super.hashCode();
        }
    
        public final int hashCode() {
            MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
            if (methodInterceptor == null) {
                CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BIND_CALLBACKS((Object)this);
                methodInterceptor = this.CGLIB$CALLBACK_0;
            }
            if (methodInterceptor != null) {
                Object object = methodInterceptor.intercept((Object)this, CGLIB$hashCode$4$Method, CGLIB$emptyArgs, CGLIB$hashCode$4$Proxy);
                return object == null ? 0 : ((Number)object).intValue();
            }
            return super.hashCode();
        }
    
        final Object CGLIB$clone$5() throws CloneNotSupportedException {
            return super.clone();
        }
    
        protected final Object clone() throws CloneNotSupportedException {
            MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
            if (methodInterceptor == null) {
                CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BIND_CALLBACKS((Object)this);
                methodInterceptor = this.CGLIB$CALLBACK_0;
            }
            if (methodInterceptor != null) {
                return methodInterceptor.intercept((Object)this, CGLIB$clone$5$Method, CGLIB$emptyArgs, CGLIB$clone$5$Proxy);
            }
            return super.clone();
        }
    
        public static MethodProxy CGLIB$findMethodProxy(Signature signature) {
            String string = signature.toString();
            switch (string.hashCode()) {
                case -1574182249: {
                    if (!string.equals("finalize()V")) break;
                    return CGLIB$finalize$1$Proxy;
                }
                case -909388886: {
                    if (!string.equals("say()V")) break;
                    return CGLIB$say$0$Proxy;
                }
                case -508378822: {
                    if (!string.equals("clone()Ljava/lang/Object;")) break;
                    return CGLIB$clone$5$Proxy;
                }
                case 1826985398: {
                    if (!string.equals("equals(Ljava/lang/Object;)Z")) break;
                    return CGLIB$equals$2$Proxy;
                }
                case 1913648695: {
                    if (!string.equals("toString()Ljava/lang/String;")) break;
                    return CGLIB$toString$3$Proxy;
                }
                case 1984935277: {
                    if (!string.equals("hashCode()I")) break;
                    return CGLIB$hashCode$4$Proxy;
                }
            }
            return null;
        }
    
        public CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b() {
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b = this;
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BIND_CALLBACKS((Object)cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b);
        }
    
        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$BIND_CALLBACKS(Object object) {
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b = (CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b)((Object)object);
            if (!cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BOUND) {
                cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BOUND = true;
                Object t = CGLIB$THREAD_CALLBACKS.get();
                if (t != null || (v312 = CGLIB$STATIC_CALLBACKS) != null) {
                    Callback[] arrcallback = (Callback[])t;
                    CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b2 = cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b;
                    cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b2.CGLIB$CALLBACK_1 = (MethodInterceptor)arrcallback[1];
                    cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b2.CGLIB$CALLBACK_0 = (MethodInterceptor)arrcallback[0];
                }
            }
        }
    
        public Object newInstance(Callback[] arrcallback) {
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$SET_THREAD_CALLBACKS(arrcallback);
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$SET_THREAD_CALLBACKS(null);
            return new CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b();
        }
    
        public Object newInstance(Callback callback) {
            throw new IllegalStateException("More than one callback object required");
        }
    
        /*
         * Unable to fully structure code
         * Enabled aggressive block sorting
         * Lifted jumps to return sites
         */
        public Object newInstance(Class[] var1_1, Object[] var2_2, Callback[] var3_3) {
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$SET_THREAD_CALLBACKS(var3_3);
            switch (var1_1.length) {
                case 0: {
                    ** break;
                }
            }
            throw new IllegalArgumentException("Constructor not found");
    lbl6: // 1 sources:
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$SET_THREAD_CALLBACKS(null);
            return new CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b();
        }
    
        public Callback getCallback(int n) {
            MethodInterceptor methodInterceptor;
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BIND_CALLBACKS((Object)this);
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b = this;
            switch (n) {
                case 0: {
                    methodInterceptor = cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$CALLBACK_0;
                    break;
                }
                case 1: {
                    methodInterceptor = cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$CALLBACK_1;
                    break;
                }
                default: {
                    methodInterceptor = null;
                }
            }
            return methodInterceptor;
        }
    
        public void setCallback(int n, Callback callback) {
            switch (n) {
                case 0: {
                    this.CGLIB$CALLBACK_0 = (MethodInterceptor)callback;
                    break;
                }
                case 1: {
                    this.CGLIB$CALLBACK_1 = (MethodInterceptor)callback;
                    break;
                }
            }
        }
    
        public Callback[] getCallbacks() {
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$BIND_CALLBACKS((Object)this);
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b = this;
            return new Callback[]{this.CGLIB$CALLBACK_0, this.CGLIB$CALLBACK_1};
        }
    
        public void setCallbacks(Callback[] arrcallback) {
            Callback[] arrcallback2 = arrcallback;
            this.CGLIB$CALLBACK_0 = (MethodInterceptor)arrcallback2[0];
            Callback[] arrcallback3 = arrcallback2;
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b cglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b = this;
            this.CGLIB$CALLBACK_1 = (MethodInterceptor)arrcallback2[1];
        }
    
        static {
            CglibLearn$serviceImpl$$EnhancerByCGLIB$$4e65f4b.CGLIB$STATICHOOK1();
        }
    }

## 3.测试类的结果分析 ##

自己的demo中  
cglib.CglibProxy\#intercept和cglib.CglibProxy2\#intercept是如何工作的，即调用  
impl.say();的时候  
***拦截器是如何拦截的***

参照上面得到的decompile文件

final void say() {
            MethodInterceptor methodInterceptor = this.CGLIB$CALLBACK_0;
            if (methodInterceptor == null) {
                CGLIB$BIND_CALLBACKS(this);
                methodInterceptor = this.CGLIB$CALLBACK_0;
            }
            if (methodInterceptor != null) {
                methodInterceptor.intercept(this, CGLIB$say$0$Method, CGLIB$emptyArgs, CGLIB$say$0$Proxy);
            } else {
                say();
            }
        }

很容易看出来了，  
另外比较一下

![Image 1][]

image.png

这里就是CGLIB$CALLBACK\_1了，这个是怎么办到的?

其实在之前讲net.sf.cglib.proxy.Enhancer\#emitMethods时候就说了

net.sf.cglib.proxy.CallbackGenerator.Context\#getIndex  
配合net.sf.cglib.proxy.MethodInterceptorGenerator\#generate里面

context.emitCallback(e, context.getIndex(method));

完成了每个method知道自己对应的callBack是第几个

另外，拦截器拦截时，

Object result = methodProxy.invokeSuper(o, objects);

***invokeSuper是干吗的***  
这在下一节FastClass会讲

## 4.思考 ##

### 4.1 CallbackFilter 和 CallBack有什么关系 ###

一个method只能有一个CallBack(不定义也会有默认的)  
CallBackFilter就是完成一个mapping的过程，比如  
a,b method 用 A callBack  
c,d method 用 B callBack  
源码里也有体现出来一个method对应一个callBack

### 4.2 method与callBack之间的对应的关系是如何实现的 ###

net.sf.cglib.proxy.Enhancer\#emitMethods中  
每个method通过 int index = filter.accept(actualMethod); 知道当前method由第几个callBack处理  
然后由net.sf.cglib.proxy.MethodInterceptorGenerator\#generate

context.emitCallback(e, context.getIndex(method));

将这种对应关系写到类中去

### 4.3 Enhancer如何根据callBack,callBackFilter完成代理类class文件的定义 ###

net.sf.cglib.proxy.Enhancer\#generateClass  
主要是  
net.sf.cglib.proxy.Enhancer\#getMethods(java.lang.Class, java.lang.Class\[\], java.util.List, java.util.List, java.util.Set)  
net.sf.cglib.proxy.Enhancer\#emitMethods

### 4.4 与jdk动态代理区别 ###

这里cglib底层是用的asm，而jdk动态代理没有

### 4.5 Enhancer的"enhance"体现在哪 ###

个人理解，可能并不准确  
1.完成callBack以及callBackFilter等的aop处理  
2.完成代理类say()的调用 转发给 方法代理即CGLIB$say$0$Proxy

methodInterceptor.intercept(this, CGLIB$say$0$Method, CGLIB$emptyArgs, CGLIB$say$0$Proxy);
    //其中
    CGLIB$say$0$Proxy = MethodProxy.create(cls2, cls, "()V", "say", "CGLIB$say$0");

最终将cls2的say方法转发给cls的CGLIB$say$0方法(并不是上文列出来的CGLIB$say$0)，这个和fastClass相关，下一节再讲。

## 4.6 CGLIB$STATICHOOK1()作用 ##

创建各种方法代理即MethodProxy,在下一节和fastClass一起讲

## 5.备注 ##

### net.sf.cglib.proxy.Enhancer\#generateClass还有一些emit其他细节，目前没有涉及到，没有看 ###

## 6.问题 ##

findMethodProxy作用是啥，没有看到调用

## 7.refer ##

[http://javadox.com/cglib/cglib/2.2/net/sf/cglib/proxy/Enhancer.html\#generateClass(org.objectweb.asm.ClassVisitor)][http_javadox.com_cglib_cglib_2.2_net_sf_cglib_proxy_Enhancer.html_generateClass_org.objectweb.asm.ClassVisitor]  
[http://cglib.sourceforge.net/apidocs/][http_cglib.sourceforge.net_apidocs]  
[http://www.cnblogs.com/cruze/p/3865180.html][http_www.cnblogs.com_cruze_p_3865180.html]

作者：赤子心\_d709  
链接：https://www.jianshu.com/p/20203286ccd9  
来源：简书  
简书著作权归作者所有，任何形式的转载都请联系作者获得授权并注明出处。

[https_www.jianshu.com_p_20203286ccd9]: https://www.jianshu.com/p/20203286ccd9
[Image 1]: 
[http_www.javadecompilers.com_result]: https://link.jianshu.com?t=http://www.javadecompilers.com/result
[http_javadox.com_cglib_cglib_2.2_net_sf_cglib_proxy_Enhancer.html_generateClass_org.objectweb.asm.ClassVisitor]: https://link.jianshu.com?t=http://javadox.com/cglib/cglib/2.2/net/sf/cglib/proxy/Enhancer.html#generateClass%28org.objectweb.asm.ClassVisitor%29
[http_cglib.sourceforge.net_apidocs]: https://link.jianshu.com?t=http://cglib.sourceforge.net/apidocs/
[http_www.cnblogs.com_cruze_p_3865180.html]: https://link.jianshu.com?t=http://www.cnblogs.com/cruze/p/3865180.html