RE|GoF23种设计模式-动态代理

蔚落 2022-10-01 05:55 118阅读 0赞

## 代理模式 ##

### 定义 ###

代理(Proxy)是一种设计模式,提供了对目标对象另外的访问方式;即通过代理对象访问目标对象.这样做的好处是:可以在目标对象实现的基础上,增强额外的功能操作,即扩展目标对象的功能。符合开闭原则。代理模式属于结构型 模式，有静态代理和动态代理。

## 静态代理 ##

需求：现在我们需要根据类型来分别把数据上传到不同Ftp服务。

/** * 数据的模型类 */
    public static class Data {
    
        private Integer type;
        private String name;
        private String sex;
    
        public Integer getType() {
            return type;
        }
    
        public void setType(Integer type) {
            this.type = type;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getSex() {
            return sex;
        }
    
        public void setSex(String sex) {
            this.sex = sex;
        }
    
    }
    
    
    public static interface IFTPService {
        void upload(Data data);
    }
    
    public static class FTPService implements IFTPService {
    
        @Override
        public void upload(Data data) {
            System.out.println("Data{" +
                    "type=" + data.getType() +
                    ", name='" + data.getName() + '\'' +
                    ", sex='" + data.getSex() + '\'' +
                    '}');
        }
    
    }
    
    public static class FTPServiceStaticProxy implements IFTPService {
    
        private IFTPService ftpService;
    
        // 静态代理 构造注入的方式赋值
        public FTPServiceStaticProxy(IFTPService ftpService) {
            this.ftpService = ftpService;
        }
    
        @Override
        public void upload(Data data) {
            before();
            if (data.getType() % 2 == 0) {
                System.out.println("上传到服务器 1");
                ftpService.upload(data);
            } else {
                System.out.println("上传到服务器 2");
                ftpService.upload(data);
            }
            after();
        }
    
        private void before(){
            System.out.println("Proxy before method.");
        }
        private void after(){
            System.out.println("Proxy after method.");
        }
    }
    
    
    public static void main(String[] args) {
        Data data = new Data();
        data.setName("Name Zhuang San");
        data.setSex("男");
        data.setType(1);
        new FTPServiceStaticProxy(new FTPService()).upload(data);
    
        Data data2 = new Data();
        data.setName("Name Wan Wu");
        data.setSex("男");
        data.setType(2);
        new FTPServiceStaticProxy(new FTPService()).upload(data);
    }
    
    复制代码

## 动态代理 ##

动态代理有以下特点:

1.  代理对象,不需要实现接口
2.  代理对象的生成,是利用JDK的API,动态的在内存中构建代理对象(需要我们指定创建代理对象/目标对象实现的接口的类型)
3.  动态代理也叫做: JDK代理,接口代理

### JDK 实现方式 ###

/** * 数据的模型类 */
    public static class Data {
    
        private Integer type;
        private String name;
        private String sex;
    
        public Integer getType() {
            return type;
        }
    
        public void setType(Integer type) {
            this.type = type;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getSex() {
            return sex;
        }
    
        public void setSex(String sex) {
            this.sex = sex;
        }
    
    }
    
    public static interface IFTPService {
        void upload(Data data);
    }
    
    public static class FTPService implements IFTPService {
    
        @Override
        public void upload(Data data) {
            System.out.println("Data{" +
                    "type=" + data.getType() +
                    ", name='" + data.getName() + '\'' +
                    ", sex='" + data.getSex() + '\'' +
                    '}');
        }
    
    }
    
    public static class JDKProxyFTPService implements InvocationHandler {
    
        private Object target;
    
        public Object upload(Object target) {
            this.target = target;
            Class<?> clazz = target.getClass();
            // 如何实现的代理？
            return Proxy.newProxyInstance(clazz.getClassLoader(), clazz.getInterfaces(), this);
        }
    
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            // 只让 upload 方法进入
            if (!"upload".equals(method.getName())) return method.invoke(target, args);
            before(args[0]);
            Object r = method.invoke(target, args);
            after();
            return r;
        }
    
        private void before(Object data){
            System.out.println("Proxy before method.");
            if (data instanceof Data) { // 判断是否属于 -- Data 模型
                Data d = (Data) data;
                if (d.getType() % 2 == 0)
                    System.out.println("上传到服务器 1");
                else
                    System.out.println("上传到服务器 2");
            }
        }
        private void after(){
            System.out.println("Proxy after method.");
        }
    
    
    }
    
    public static void main(String[] args) {
        IFTPService ftpService = (IFTPService) new JDKProxyFTPService().upload(new FTPService());
        Data data = new Data();
        data.setName("Name Zhuang San");
        data.setSex("男");
        data.setType(1);
        ftpService.upload(data);
    }
    
    复制代码

#### Proxy 是如何实现的呢？ ####

我们都知道 JDK Proxy 采用字节重组，重新生的对象来替代原始的对象以达到动态代理的目的。JDK Proxy 生成对象的步骤如下：

1.  拿到被代理对象的引用，并且获取到它的所有的接口，反射获取。
2.  JDK Proxy 类重新生成一个新的类、同时新的类要实现被代理类所有实现的所有的接口。
3.  动态生成 Java 代码，把新加的业务逻辑方法由一定的逻辑代码去调用（在代码中体现）。
4.  编译新生成的 Java 代码.class。
5.  再重新加载到 JVM 中运行。

public static void main(String[] args) throws IOException {
        //通过反编译工具可以查看源代码
        byte [] bytes = ProxyGenerator.generateProxyClass("$Proxy0", new Class[]{IFTPService.class});
        FileOutputStream os = new FileOutputStream("E://$Proxy0.class");
        os.write(bytes);
        os.close();
    }
    
    复制代码

使用反编译工具，得到java代码如下：

package com.reape.design.pattern.proxy;
    
    import java.lang.reflect.*;
    import com.reape.design.pattern.proxy.*;
    
    // 继承了Proxy类 接口我们的 JDKIFTPService
    public final class $Proxy0 extends Proxy implements JDKIFTPService {
        private static Method m1;
        private static Method m3;
        private static Method m2;
        private static Method m0;
    
        public $Proxy0(final InvocationHandler invocationHandler) {
            super(invocationHandler);
        }
    
        // 重写了 toString hashCode equals 指向了原来的地址
        public final boolean equals(final Object o) {
            try {
                return (boolean)super.h.invoke(this, $Proxy0.m1, new Object[] { o });
            }
            catch (Error | RuntimeException error) {
                throw new Error();
            }
            catch (Throwable t) {
                throw new UndeclaredThrowableException(t);
            }
        }
    
        public final void upload(final JDKData jdkData) {
            try {
                super.h.invoke(this, $Proxy0.m3, new Object[] { jdkData });
            }
            catch (Error | RuntimeException error) {
                throw new Error();
            }
            catch (Throwable t) {
                throw new UndeclaredThrowableException(t);
            }
        }
    
        public final String toString() {
            try {
                return (String)super.h.invoke(this, $Proxy0.m2, null);
            }
            catch (Error | RuntimeException error) {
                throw new Error();
            }
            catch (Throwable t) {
                throw new UndeclaredThrowableException(t);
            }
        }
    
        public final int hashCode() {
            try {
                return (int)super.h.invoke(this, $Proxy0.m0, null);
            }
            catch (Error | RuntimeException error) {
                throw new Error();
            }
            catch (Throwable t) {
                throw new UndeclaredThrowableException(t);
            }
        }
    
        static {
            try {
                $Proxy0.m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
                $Proxy0.m3 = Class.forName("com.reape.design.pattern.proxy.JDKIFTPService").getMethod("upload", Class.forName("com.reape.design.pattern.proxy.JDKData"));
                $Proxy0.m2 = Class.forName("java.lang.Object").getMethod("toString", (Class<?>[])new Class[0]);
                $Proxy0.m0 = Class.forName("java.lang.Object").getMethod("hashCode", (Class<?>[])new Class[0]);
            }
            catch (NoSuchMethodException ex) {
                throw new NoSuchMethodError(ex.getMessage());
            }
            catch (ClassNotFoundException ex2) {
                throw new NoClassDefFoundError(ex2.getMessage());
            }
        }
    }
    
    复制代码

#### 手写动态代理 ####

// 1. ClassLoader 自定义
    
    import java.io.ByteArrayOutputStream;
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.IOException;
    
    public class MyClassLoader extends ClassLoader{
    
        private File classPathFile;
    
        public MyClassLoader(){
            String classPath = MyClassLoader.class.getResource("").getPath();
            this.classPathFile = new File(classPath);
        }
        protected Class<?> findClass(String name) throws ClassNotFoundException {
            String className = MyClassLoader.class.getPackage().getName() + "." + name;
            if(classPathFile != null){
                File classFile = new File(classPathFile,name.replaceAll("\\.","/") + ".class");
                if(classFile.exists()){
                    FileInputStream in = null;
                    ByteArrayOutputStream out = null;
                    try{
                        in = new FileInputStream(classFile);
                        out = new ByteArrayOutputStream();
                        byte [] buff = new byte[1024];
                        int len;
                        while ((len = in.read(buff)) != -1){
                            out.write(buff,0,len);
                        }
                        return defineClass(className,out.toByteArray(),0,out.size());
                    }catch (Exception e){
                        e.printStackTrace();
                    }finally {
                        if(null != in){
                            try {
                                in.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                        if(out != null){
                            try {
                                out.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            }
            return null;
        }
    }
    
    // 2. 动态代理实现的接口类
    import java.lang.reflect.Method;
    
    /** * 动态代理实现的接口类 */
    public interface MyInvocationHandler {
    
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable;
    
    }
    
    
    3. 生成java文件编译为class写入jvm，动态代理 /** * 用来生成源代码的工具类 */ public class MyProxy {
    
    
        private static final String ln = "\r\n";
        private static final String t = "\t";
    
        public static Object newProxyInstance(MyClassLoader classLoader, Class<?> [] interfaces, MyInvocationHandler h){
            try {
                // 1.动态生成源代码文件
                String src = generateSrc(interfaces);
    
                //2、Java 文件输出磁盘
                String filePath = MyProxy.class.getResource("").getPath();
                System.out.println(filePath);
                File f = new File(filePath + "$Proxy0.java");
                FileWriter fw = null;
                fw = new FileWriter(f);
                fw.write(src);
                fw.flush();
                fw.close();
                //3、把生成的.java 文件编译成.class 文件
                JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
                StandardJavaFileManager manage = compiler.getStandardFileManager(null,null,null);
                Iterable iterable = manage.getJavaFileObjects(f);
                JavaCompiler.CompilationTask task =
                        compiler.getTask(null,manage,null,null,null, iterable);
                task.call();
                manage.close();
                //4、编译生成的.class 文件加载到 JVM 中来
                Class<Object> proxyClass = (Class<Object>) classLoader.findClass("$Proxy0");
                Constructor<Object> c = proxyClass.getConstructor(MyInvocationHandler.class);
    // f.delete();
                //5、返回字节码重组以后的新的代理对象
                return c.newInstance(h);
            } catch (IOException | InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException | ClassNotFoundException e) {
                e.printStackTrace();
            }
            return null;
        }
    
        private static String generateSrc(Class<?>[] interfaces){
            // interfaces ---> 需要实现的接口的类
            StringBuilder sb = new StringBuilder();
            sb.append("package com.reape.design.pattern.proxy.handwriting;" + ln);
            sb.append("import java.lang.reflect.*;" + ln);
            sb.append("public class $Proxy0 implements").append(interfacesToString(interfaces));
            sb.append(" {").append(ln);
            sb.append(t + "private com.reape.design.pattern.proxy.handwriting.MyInvocationHandler h;" + ln);
            sb.append(t + "public $Proxy0(com.reape.design.pattern.proxy.handwriting.MyInvocationHandler h) { " + ln);
            sb.append(t + t + "this.h = h;" + ln);
            sb.append(t + "}" + ln);
            for (Class<?> anInterface : interfaces) {
                for (Method m : anInterface.getMethods()) {
                    Class<?>[] params = m.getParameterTypes();
                    Class<?> result = m.getReturnType();
                    sb.append(t + "public final ")
                            .append(resultToString(result))
                            .append(" ")
                            .append(m.getName())
                            .append("(")
                            .append(paramsToString(params))
                            .append(") {").append(ln);
                    sb.append(t + t + "try {" + ln);
                    sb.append(t + t + t)
                            .append(returnToString(result))
                            .append("h.invoke(this, " + "Class.forName(\"")
    // .append(anInterface.getName())
                            .append("com.reape.design.pattern.proxy.JDKFTPService")
                            .append("\")")
                            .append(".getMethod(").append("\"").append(m.getName()).append("\"").append(", ")
                            .append(paramsFormNameToString(params))
                            .append(")").append(", new Object[]{ p0 });").append(ln);
                    sb.append(t + t + "}" + ln);
                    sb.append(t + t + "catch(Error | RuntimeException error) { error.printStackTrace();" + ln);
                    sb.append(t + t + t + "throw new Error();" + ln);
                    sb.append(t + t + "}" + ln);
                    sb.append(t + t + "catch (Throwable t) {" + ln);
                    sb.append(t + t + t + "throw new UndeclaredThrowableException(t);" + ln);
                    sb.append(t + t + "}" + ln);
                    sb.append(t + "}" + ln);
                }
            }
            sb.append("}" + ln);
            return sb.toString();
        }
    
        /** * 接口类数组转 String * @param interfaces 接口类数组 * @return 字符串 */
        private static String interfacesToString(Class<?>[] interfaces) {
            if (interfaces.length < 1) return "";
            StringBuilder sb = new StringBuilder();
            for (Class<?> anInterface : interfaces) {
                sb.append(" ").append(anInterface.getName()).append(",");
            }
            return sb.substring(0, sb.length() - 1);
        }
    
    
        private static String paramsToString(Class<?>[] params) {
            if (params.length < 1) return "";
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < params.length; i++) {
                sb.append(params[i].getName()).append(" ").append("p").append(i).append(", ");
            }
            return sb.substring(0, sb.length() - 2);
        }
    
        private static String paramsFormNameToString(Class<?>[] params) {
            if (params.length < 1) return "";
            StringBuilder sb = new StringBuilder();
            for (Class<?> param : params) {
                sb.append("Class.forName(\"").append(param.getName()).append("\"), ");
            }
            return sb.substring(0, sb.length() - 2);
        }
    
    
        private static String resultToString(Class<?> result) {
            String name = result.getName();
            return "void".equals(name) ? "void" : name;
        }
    
        private static String returnToString(Class<?> result) {
            String name = result.getName();
            return "void".equals(name) ? "" : "return (" + name + ") ";
        }
    
    }
    
    // 4.测试
    
    
    
    public class Test implements MyInvocationHandler {
    
        private Object target;
    
        public Object get(Object target) {
            this.target = target;
            Class<?> clazz = target.getClass();
            return MyProxy.newProxyInstance(new MyClassLoader(), clazz.getInterfaces(), this);
        }
    
        private void before(Object data){
            System.out.println(data);
            System.out.println("Proxy before method.");
        }
        private void after(){
            System.out.println("Proxy after method.");
        }
    
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            // 只让 upload 方法进入
            if (!"upload".equals(method.getName())) return method.invoke(target, args);
            before(args[0]);
            Object r = method.invoke(target, args);
            after();
            return r;
        }
    
    
        public static void main(String[] args) {
            JDKIFTPService ftpService = (JDKIFTPService) new Test().get(new JDKFTPService());
            JDKData data = new JDKData();
            data.setName("Name Zhuang San");
            data.setSex("男");
            data.setType(1);
            ftpService.upload(data);
        }
    
    }
    
    // 上面的代码写考虑的不是很完整
    // 有很多判断的地方没有判断以及重写 toString ，equals 等
    
    // java的代理是编译为class文件然后写入的到jvm节约的了内存消耗，但是跟cglib对比还是差很远
    // cglib是字节码操作
    
    复制代码

### CGLib实现 ###

// 导入jar包
    // 1. asm.jar
    // 2. cglib.jar
    
    
    public class JDKData {
        private Integer type;
        private String name;
        private String sex;
    
        public Integer getType() {
            return type;
        }
    
        public void setType(Integer type) {
            this.type = type;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getSex() {
            return sex;
        }
    
        public void setSex(String sex) {
            this.sex = sex;
        }
    }
    
    
    public class JDKFTPService implements JDKIFTPService {
    
        @Override
        public void upload(JDKData data) {
            System.out.println("Data{" +
                    "type=" + data.getType() +
                    ", name='" + data.getName() + '\'' +
                    ", sex='" + data.getSex() + '\'' +
                    '}');
        }
    }
    
    
    
    
    public class CglibJDK implements MethodInterceptor {
    
        public Object getInstance(Class<?> clazz) throws Exception{
            Enhancer enhancer = new Enhancer();
            //要把哪个设置为即将生成的新类父类
            enhancer.setSuperclass(clazz);
            enhancer.setCallback(this);
            return enhancer.create();
        }
    
        @Override
        public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
            //业务的增强
            before(objects[0]);
            Object obj = methodProxy.invokeSuper(o,objects);
            after();
            return obj;
        }
    
    
        private void before(Object data){
            System.out.println("Proxy before method.");
            System.out.println(data);
            if (data instanceof JDKData) { // 判断是否属于 -- Data 模型
                JDKData d = (JDKData) data;
                if (d.getType() % 2 == 0)
                    System.out.println("上传到服务器 1");
                else
                    System.out.println("上传到服务器 2");
            }
        }
        private void after(){
            System.out.println("Proxy after method.");
        }
    }
    
    
    // 测试
    public static void main(String[] args) {
        try {
            JDKFTPService obj = (JDKFTPService) new CglibJDK().getInstance(JDKFTPService.class);
            JDKData data = new JDKData();
            data.setName("Name Zhuang San");
            data.setSex("男");
            data.setType(1);
            obj.upload(data);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    // 编译得到class文件
    
    package com.reape.design.pattern.proxy.cglib;
    
    import net.sf.cglib.reflect.*;
    import net.sf.cglib.core.*;
    import net.sf.cglib.proxy.*;
    import java.lang.reflect.*;
    
    public class JDKFTPService$$EnhancerByCGLIB$$5a7831ef$$FastClassByCGLIB$$5a694231 extends FastClass {
        public JDKFTPService$$EnhancerByCGLIB$$5a7831ef$$FastClassByCGLIB$$5a694231(final Class clazz) {
            super(clazz);
        }
        
        public int getIndex(final Signature signature) {
            final String string = signature.toString();
            switch (string.hashCode()) {
                case -2055565910: {
                    if (string.equals("CGLIB$SET_THREAD_CALLBACKS([Lnet/sf/cglib/proxy/Callback;)V")) {
                        return 12;
                    }
                    break;
                }
                case -1882565338: {
                    if (string.equals("CGLIB$equals$1(Ljava/lang/Object;)Z")) {
                        return 15;
                    }
                    break;
                }
                case -1457535688: {
                    if (string.equals("CGLIB$STATICHOOK1()V")) {
                        return 19;
                    }
                    break;
                }
                case -1411842725: {
                    if (string.equals("CGLIB$hashCode$3()I")) {
                        return 18;
                    }
                    break;
                }
                case -894172689: {
                    if (string.equals("newInstance(Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
                        return 6;
                    }
                    break;
                }
                case -623122092: {
                    if (string.equals("CGLIB$findMethodProxy(Lnet/sf/cglib/core/Signature;)Lnet/sf/cglib/proxy/MethodProxy;")) {
                        return 20;
                    }
                    break;
                }
                case -508378822: {
                    if (string.equals("clone()Ljava/lang/Object;")) {
                        return 3;
                    }
                    break;
                }
                case -419626537: {
                    if (string.equals("setCallbacks([Lnet/sf/cglib/proxy/Callback;)V")) {
                        return 11;
                    }
                    break;
                }
                case 560567118: {
                    if (string.equals("setCallback(ILnet/sf/cglib/proxy/Callback;)V")) {
                        return 7;
                    }
                    break;
                }
                case 773140094: {
                    if (string.equals("CGLIB$upload$0(Lcom/reape/design/pattern/proxy/cglib/JDKData;)V")) {
                        return 14;
                    }
                    break;
                }
                case 811063227: {
                    if (string.equals("newInstance([Ljava/lang/Class;[Ljava/lang/Object;[Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
                        return 5;
                    }
                    break;
                }
                case 840180909: {
                    if (string.equals("upload(Lcom/reape/design/pattern/proxy/cglib/JDKData;)V")) {
                        return 8;
                    }
                    break;
                }
                case 973717575: {
                    if (string.equals("getCallbacks()[Lnet/sf/cglib/proxy/Callback;")) {
                        return 10;
                    }
                    break;
                }
                case 1221173700: {
                    if (string.equals("newInstance([Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
                        return 4;
                    }
                    break;
                }
                case 1230699260: {
                    if (string.equals("getCallback(I)Lnet/sf/cglib/proxy/Callback;")) {
                        return 9;
                    }
                    break;
                }
                case 1306468936: {
                    if (string.equals("CGLIB$toString$2()Ljava/lang/String;")) {
                        return 16;
                    }
                    break;
                }
                case 1584330438: {
                    if (string.equals("CGLIB$SET_STATIC_CALLBACKS([Lnet/sf/cglib/proxy/Callback;)V")) {
                        return 13;
                    }
                    break;
                }
                case 1800494055: {
                    if (string.equals("CGLIB$clone$4()Ljava/lang/Object;")) {
                        return 17;
                    }
                    break;
                }
                case 1826985398: {
                    if (string.equals("equals(Ljava/lang/Object;)Z")) {
                        return 0;
                    }
                    break;
                }
                case 1913648695: {
                    if (string.equals("toString()Ljava/lang/String;")) {
                        return 1;
                    }
                    break;
                }
                case 1984935277: {
                    if (string.equals("hashCode()I")) {
                        return 2;
                    }
                    break;
                }
            }
            return -1;
        }
        
        public int getIndex(final String s, final Class[] array) {
            Label_1103: {
                switch (s.hashCode()) {
                    case -1776922004: {
                        if (!s.equals("toString")) {
                            break;
                        }
                        switch (array.length) {
                            case 0: {
                                return 1;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case -1295482945: {
                        if (!s.equals("equals")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                if (array[0].getName().equals("java.lang.Object")) {
                                    return 0;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case -1053468136: {
                        if (!s.equals("getCallbacks")) {
                            break;
                        }
                        switch (array.length) {
                            case 0: {
                                return 10;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case -838595071: {
                        if (!s.equals("upload")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                if (array[0].getName().equals("com.reape.design.pattern.proxy.cglib.JDKData")) {
                                    return 8;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case -124978609: {
                        if (!s.equals("CGLIB$equals$1")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                if (array[0].getName().equals("java.lang.Object")) {
                                    return 15;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case -60403779: {
                        if (!s.equals("CGLIB$SET_STATIC_CALLBACKS")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                if (array[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
                                    return 13;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case -29025555: {
                        if (!s.equals("CGLIB$hashCode$3")) {
                            break;
                        }
                        switch (array.length) {
                            case 0: {
                                return 18;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 85179481: {
                        if (!s.equals("CGLIB$SET_THREAD_CALLBACKS")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                if (array[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
                                    return 12;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 94756189: {
                        if (!s.equals("clone")) {
                            break;
                        }
                        switch (array.length) {
                            case 0: {
                                return 3;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 147696667: {
                        if (!s.equals("hashCode")) {
                            break;
                        }
                        switch (array.length) {
                            case 0: {
                                return 2;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 161998109: {
                        if (!s.equals("CGLIB$STATICHOOK1")) {
                            break;
                        }
                        switch (array.length) {
                            case 0: {
                                return 19;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 495524492: {
                        if (!s.equals("setCallbacks")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                if (array[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
                                    return 11;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 857604112: {
                        if (!s.equals("CGLIB$upload$0")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                if (array[0].getName().equals("com.reape.design.pattern.proxy.cglib.JDKData")) {
                                    return 14;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 1154623345: {
                        if (!s.equals("CGLIB$findMethodProxy")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                if (array[0].getName().equals("net.sf.cglib.core.Signature")) {
                                    return 20;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 1543336189: {
                        if (!s.equals("CGLIB$toString$2")) {
                            break;
                        }
                        switch (array.length) {
                            case 0: {
                                return 16;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 1811874389: {
                        if (!s.equals("newInstance")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                final String name = array[0].getName();
                                switch (name.hashCode()) {
                                    case -845341380: {
                                        if (name.equals("net.sf.cglib.proxy.Callback")) {
                                            return 6;
                                        }
                                        break;
                                    }
                                    case 1730110032: {
                                        if (name.equals("[Lnet.sf.cglib.proxy.Callback;")) {
                                            return 4;
                                        }
                                        break;
                                    }
                                }
                                break Label_1103;
                            }
                            case 3: {
                                if (array[0].getName().equals("[Ljava.lang.Class;") && array[1].getName().equals("[Ljava.lang.Object;") && array[2].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
                                    return 5;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 1817099975: {
                        if (!s.equals("setCallback")) {
                            break;
                        }
                        switch (array.length) {
                            case 2: {
                                if (array[0].getName().equals("int") && array[1].getName().equals("net.sf.cglib.proxy.Callback")) {
                                    return 7;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 1905679803: {
                        if (!s.equals("getCallback")) {
                            break;
                        }
                        switch (array.length) {
                            case 1: {
                                if (array[0].getName().equals("int")) {
                                    return 9;
                                }
                                break Label_1103;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                    case 1951977610: {
                        if (!s.equals("CGLIB$clone$4")) {
                            break;
                        }
                        switch (array.length) {
                            case 0: {
                                return 17;
                            }
                            default: {
                                break Label_1103;
                            }
                        }
                        break;
                    }
                }
            }
            return -1;
        }
        
        public int getIndex(final Class[] array) {
            switch (array.length) {
                case 0: {
                    return 0;
                }
                default: {
                    return -1;
                }
            }
        }
        
        public Object invoke(final int n, final Object o, final Object[] array) throws InvocationTargetException {
            final JDKFTPService$$EnhancerByCGLIB$$5a7831ef jdkftpService$$EnhancerByCGLIB$$5a7831ef = (JDKFTPService$$EnhancerByCGLIB$$5a7831ef)o;
            try {
                switch (n) {
                    case 0: {
                        return new Boolean(jdkftpService$$EnhancerByCGLIB$$5a7831ef.equals(array[0]));
                    }
                    case 1: {
                        return jdkftpService$$EnhancerByCGLIB$$5a7831ef.toString();
                    }
                    case 2: {
                        return new Integer(jdkftpService$$EnhancerByCGLIB$$5a7831ef.hashCode());
                    }
                    case 3: {
                        return jdkftpService$$EnhancerByCGLIB$$5a7831ef.clone();
                    }
                    case 4: {
                        return jdkftpService$$EnhancerByCGLIB$$5a7831ef.newInstance((Callback[])array[0]);
                    }
                    case 5: {
                        return jdkftpService$$EnhancerByCGLIB$$5a7831ef.newInstance((Class[])array[0], (Object[])array[1], (Callback[])array[2]);
                    }
                    case 6: {
                        return jdkftpService$$EnhancerByCGLIB$$5a7831ef.newInstance((Callback)array[0]);
                    }
                    case 7: {
                        jdkftpService$$EnhancerByCGLIB$$5a7831ef.setCallback(((Number)array[0]).intValue(), (Callback)array[1]);
                        return null;
                    }
                    case 8: {
                        jdkftpService$$EnhancerByCGLIB$$5a7831ef.upload((JDKData)array[0]);
                        return null;
                    }
                    case 9: {
                        return jdkftpService$$EnhancerByCGLIB$$5a7831ef.getCallback(((Number)array[0]).intValue());
                    }
                    case 10: {
                        return jdkftpService$$EnhancerByCGLIB$$5a7831ef.getCallbacks();
                    }
                    case 11: {
                        jdkftpService$$EnhancerByCGLIB$$5a7831ef.setCallbacks((Callback[])array[0]);
                        return null;
                    }
                    case 12: {
                        JDKFTPService$$EnhancerByCGLIB$$5a7831ef.CGLIB$SET_THREAD_CALLBACKS((Callback[])array[0]);
                        return null;
                    }
                    case 13: {
                        JDKFTPService$$EnhancerByCGLIB$$5a7831ef.CGLIB$SET_STATIC_CALLBACKS((Callback[])array[0]);
                        return null;
                    }
                    case 14: {
                        jdkftpService$$EnhancerByCGLIB$$5a7831ef.CGLIB$upload$0((JDKData)array[0]);
                        return null;
                    }
                    case 15: {
                        return new Boolean(jdkftpService$$EnhancerByCGLIB$$5a7831ef.CGLIB$equals$1(array[0]));
                    }
                    case 16: {
                        return jdkftpService$$EnhancerByCGLIB$$5a7831ef.CGLIB$toString$2();
                    }
                    case 17: {
                        return jdkftpService$$EnhancerByCGLIB$$5a7831ef.CGLIB$clone$4();
                    }
                    case 18: {
                        return new Integer(jdkftpService$$EnhancerByCGLIB$$5a7831ef.CGLIB$hashCode$3());
                    }
                    case 19: {
                        JDKFTPService$$EnhancerByCGLIB$$5a7831ef.CGLIB$STATICHOOK1();
                        return null;
                    }
                    case 20: {
                        return JDKFTPService$$EnhancerByCGLIB$$5a7831ef.CGLIB$findMethodProxy((Signature)array[0]);
                    }
                }
            }
            catch (Throwable t) {
                throw new InvocationTargetException(t);
            }
            throw new IllegalArgumentException("Cannot find matching method/constructor");
        }
        
        public Object newInstance(final int n, final Object[] array) throws InvocationTargetException {
            try {
                switch (n) {
                    case 0: {
                        return new JDKFTPService$$EnhancerByCGLIB$$5a7831ef();
                    }
                }
            }
            catch (Throwable t) {
                throw new InvocationTargetException(t);
            }
            throw new IllegalArgumentException("Cannot find matching method/constructor");
        }
        
        public int getMaxIndex() {
            return 20;
        }
    }
    
    // 里面使用 extends FastClass
    // 子类重写父类的方法
    // 父类方法不能是final
    
    复制代码

#### CGLib 和 JDK 动态代理对比 ####

1.  JDK 动态代理是实现了被代理对象的接口，CGLib 是继承了被代理对象。
2.  JDK 和 CGLib 都是在运行期生成字节码，JDK 是直接写 Class 字节码，CGLib 使用 ASM 框架写 Class 字节码，Cglib 代理实现更复杂，生成代理类比 JDK 效率低。
3.  JDK 调用代理方法，是通过反射机制调用，CGLib 是通过 FastClass 机制直接调用方法， CGLib 执行效率更高。

#### 静态代理和动态的本质区别 ####

1.  静态代理只能通过手动完成代理操作，如果被代理类增加新的方法，代理类需要同步 新增，违背开闭原则。
2.  动态代理采用在运行时动态生成代码的方式，取消了对被代理类的扩展限制，遵循开 闭原则。
3.  若动态代理要对目标类的增强逻辑扩展，结合策略模式，只需要新增策略类便可完成， 无需修改代理类的代码。 代理模式的优缺点 使用代理模式具有以下几个优点：

*  代理模式能将代理对象与真实被调用的目标对象分离。
 *  一定程度上降低了系统的耦合度，扩展性好。
 *  可以起到保护目标对象的作用。
 *  可以对目标对象的功能增强。

当然，代理模式也是有缺点的：

1.  代理模式会造成系统设计中类的数量增加。
2.  在客户端和目标对象增加一个代理对象，会造成请求处理速度变慢。
3.  增加了系统的复杂度。

#### 执行速度 ####

ASM > javassist > 手写的（java -> class -> 加载）

转载于:https://juejin.im/post/5ce20b9ae51d4510843bb48e