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Java互联网企业架构技术VIP课程【腾讯课堂每特】

设计模式的分类

Java互联网企业架构技术VIP课程【腾讯课堂每特】

课程内容

站在架构角度，基于装饰模式纯手写设计多级缓存框架

如何理解多级缓存框架设计
装饰模式与代理模式之间的区别
3.装饰模式如何在Mybatis、IO流运用
4.基于装饰设计多级缓存框架
5.自定义缓存注解，轻松搞定多级缓存问题

本节课需要知识：动态代理技术+Aop+装饰模式+Redis缓存概念

注意：因为该设计模式比较接近真实案例，需要有SpringBoot基础。

创建型模式

工厂方法模式、抽象工厂模式、单例模式、建造者模式、原型模式。

结构型模式

适配器模式、装饰器模式、代理模式、外观模式、桥接模式、组合模式、享元模式

行为模式

策略模式、模板方法模式、观察者模式、迭代子模式、责任链模式、命令模式、备忘录模式、状态模式、访问者模式、中介者模式、解释器模式。

彻底搞懂代理模式实现原理

什么是代理模式

代理模式主要对我们方法执行之前与之后实现增强

代理模式应用场景

日志的采集
权限控制
实现aop
Mybatis mapper
Spring的事务
全局捕获异常
Rpc远程调用接口
代理数据源

代理模式创建方式

静态代理

静态代理需要自己人工编写代理类代码

基于接口实现方式

public class OrderServiceProxy implements OrderService{
    private OrderService orderService;

    public OrderServiceProxy(OrderService orderService) {
        this.orderService = orderService;
    }

    public String addOrder(String userName, String userPwd) {
        System.out.println("使用静态代理类打印日志开始：userName:" + userName + "," + userPwd);
        String result = orderService.addOrder(userName, userPwd);
        System.out.println("使用静态代理类打印日志结束：userName:" + userName + "," + userPwd);
        return result;
    }
}

public interface OrderService {
    /**
     * 需要被代理的方法
     * @return
     */
     String addOrder(String userName,String userPwd);
}

public class Test001 {
    public static void main(String[] args) {
        OrderService orderService = new OrderServiceProxy(new OrderServiceImpl());
        orderService.addOrder("mayikt","123456");
    }
}

基于继承的实现方式

public class OrderServiceProxy extends OrderServiceImpl {
    private OrderService orderService;

    public OrderServiceProxy(OrderService orderService) {
        this.orderService = orderService;
    }

    public String addOrder(String userName, String userPwd) {
        System.out.println("使用静态代理类打印日志开始：userName:" + userName + "," + userPwd);
        String result = super.addOrder(userName, userPwd);
        System.out.println("使用静态代理类打印日志结束：userName:" + userName + "," + userPwd);
        return result;
    }
}

动态代理与静态代理的区别

动态代理不需要写代理类对象，通过程序自动生成，而静态代理需要我们自己写代理类对象。

动态代理

动态代理是在实现阶段不用关心代理类，而在运行阶段才指定哪一个对象。

动态代理类的源码是在程序运行期间由JVM根据反射等机制动态的生成。

Jdk动态代理

JDK动态代理的一般步骤如下：

1.创建被代理的接口和类；

2.实现InvocationHandler接口，对目标接口中声明的所有方法进行统一处理；

3.调用Proxy的静态方法，创建代理类并生成相应的代理对象；

实现原理：利用拦截器机制必须实现InvocationHandler接口中的invoke方法实现对

我们的目标方法增强。

public class JdkInvocationHandler implements InvocationHandler {
    /**
     * 目标对象
     */
    private Object target;

    public JdkInvocationHandler(Object target) {
        this.target = target;
    }

    /**
     * @param proxy 使用jdk程序生成的代理类
     * @param method 目标方法
     * @param args   方法需要传递的参数
     * @return
     */
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("使用Jdk动态代理打印日志开始" + args[0]);
        Object result = method.invoke(target, args);
        System.out.println("使用Jdk动态代理打印日志结束" + args[1]);
        return result;
    }

    /**
     * 生成代理类
     *
     * @param <T>
     * @return
     */
    public <T> T getProxy() {
        return (T) Proxy.newProxyInstance(target.getClass().getClassLoader(),
                target.getClass().getInterfaces(), this);
    }

}

public class JdkInvocationHandler implements InvocationHandler {
    /**
     * 目标对象
     */
    private Object target;

    public JdkInvocationHandler(Object target) {
        this.target = target;
    }

    /**
     * @param proxy 使用jdk程序生成的代理类
     * @param method 目标方法
     * @param args 方法需要传递的参数
     * @return
     */
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("使用Jdk动态代理打印日志开始" + args[0]);
        Object result = method.invoke(target, args);
        System.out.println("使用Jdk动态代理打印日志结束" + args[1]);
        return result;
    }

    public <T> T getProxy() {
        return (T) Proxy.newProxyInstance(target.getClass().getClassLoader(),
                target.getClass().getInterfaces(), this);
    }

}

JdkInvocationHandler jdkInvocationHandler = new JdkInvocationHandler(new OrderServiceImpl());
OrderServiceImpl orderService = jdkInvocationHandler.getProxy();
orderService.addOrder("mayikt", "meite");

加上该代码：

获取代理的生成的class文件

System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");

使用反编译工具该Pclass

注意：继承了Proxy类，实现了代理的接口，由于java不能多继承，这里已经继承了Proxy类了，不能再继承其他的类，所以JDK的动态代理不支持对实现类的代理，只支持接口的代理。

纯手写Jdk动态代理

思路分析：

定义InvocationHandler类回调方法
使用java反射技术获取接口下所有的方法，拼接 $Proxy0.java代码
在将$Proxy0.java编译成class文件，读取到内存中

public class $Proxy0 implements com.mayikt.service.OrderService {

    private MayiktJdkInvocationHandler h;
    private static Method m3;

    public $Proxy0(MayiktJdkInvocationHandler mayiktJdkInvocationHandler) {
        this.h = mayiktJdkInvocationHandler;
    }

    @Override
    public String addOrder(String ver1, String var2) {
        try {
            return (String) h.invoke(this, m3, new Object[]{ver1, var2});
        } catch (RuntimeException | Error var4) {
            throw var4;
        } catch (Throwable var5) {
            throw new UndeclaredThrowableException(var5);
        }
    }

    static {
        try {
            m3 = Class.forName("com.mayikt.service.OrderService").getMethod("addOrder", Class.forName("java.lang.String"), Class.forName("java.lang.String"));
        } catch (NoSuchMethodException var2) {
            throw new NoSuchMethodError(var2.getMessage());
        } catch (ClassNotFoundException var3) {
            throw new NoClassDefFoundError(var3.getMessage());
        }
    }
}

public class MyJdkInvocationHandler implements MayiktJdkInvocationHandler {
    /**
     * 目标对象
     */
    private Object target;

    public MyJdkInvocationHandler(Object target) {
        this.target = target;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("使用Jdk动态代理打印日志开始" + args[0]);
        Object result = method.invoke(target, args);
        System.out.println("使用Jdk动态代理打印日志结束" + args[1]);
        return result;
    }
    public <T> T getProxy() {
        return (T) new $Proxy0(this);
    }

}

MyJdkInvocationHandler myJdkInvocationHandler = new MyJdkInvocationHandler(new OrderServiceImpl());
OrderService orderService = myJdkInvocationHandler.getProxy();
orderService.addOrder("mayikt", "meite");

public class MyProxy {
    private static String rt = "\r\t";

    public static Object newProxyInstance(JavaClassLoader classLoader, Class classInfo, MayiktInvocationHandler mayiktInvocationHandler) {
        try {
            // 1.拼接java代理代理源代码
            Method[] methods = classInfo.getMethods();
            String proxyClass = "package com.mayikt.service;" + rt
                    + "import java.lang.reflect.Method;" + rt
                    + "import com.mayikt.service.proxy.MayiktInvocationHandler;" + rt
                    + "import java.lang.reflect.UndeclaredThrowableException;" + rt
                    + "public class $Proxy0 implements " + classInfo.getName() + "{" + rt
                    + "MayiktInvocationHandler h;" + rt
                    + "public $Proxy0(MayiktInvocationHandler h)" + "{" + rt
                    + "this.h= h;" + rt + "}"
                    + getMethodString(methods, classInfo) + rt + "}";
            // 2.将该源代码写入到本地文件中
            String filename = "d:/code/$Proxy0.java";
            File f = new File(filename);
            FileWriter fw = new FileWriter(f);
            fw.write(proxyClass);
            fw.flush();
            fw.close();
            // 3.编译为class文件
            JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
            StandardJavaFileManager fileMgr = compiler.getStandardFileManager(null, null, null);
            Iterable units = fileMgr.getJavaFileObjects(filename);
            JavaCompiler.CompilationTask t = compiler.getTask(null, fileMgr, null, null, null, units);
            t.call();
            fileMgr.close();
            // 4.将class文件加入到内存中
            Class proxy0Class = classLoader.findClass("$Proxy0");
            //5.使用java反射机制给函数中赋值
            Constructor m = proxy0Class.getConstructor(MayiktInvocationHandler.class);
            Object object = m.newInstance(mayiktInvocationHandler);
            return object;
        } catch (Exception e) {
            return null;
        }
    }

    public static String getMethodString(Method[] methods, Class intf) {
        String proxyMe = "";

        for (Method method : methods) {
            Class<?>[] parameterTypes = method.getParameterTypes();
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < parameterTypes.length; i++) {
                sb.append(parameterTypes[i].getName() + " ver" + (i + 1));
                if (i < parameterTypes.length - 1) {
                    sb.append(" ,");
                }
            }
            String parameterStr = sb.toString();
            proxyMe = "public " + method.getReturnType().getName() + " " + method.getName() + " ( " + parameterStr + " ) { " +
                    "try {   Method m3 = Class.forName(\"com.mayikt.service.OrderService\").getMethod(\"addOrder\", Class.forName(\"java.lang.String\"), Class.forName(\"java.lang.String\"));" +
                    "return (String) h.invoke(this, m3, new Object[]{ver1, ver2}); } catch (RuntimeException | Error var4) { throw var4; } catch (Throwable var5) {   throw new UndeclaredThrowableException(var5); } " +
                    "" +
                    " } ";

        }
        return proxyMe;
    }

    public static void main(String[] args) {
        newProxyInstance(null, OrderService.class, null);
    }
}

public class JavaClassLoader extends ClassLoader {

    private File classPathFile;

    public JavaClassLoader(){
//        String classPath=JavaClassLoader.class.getResource("").getPath();
        String classPath="D:\\code";
        this.classPathFile=new File(classPath);
    }

    @Override
    public Class<?> findClass(String name) throws ClassNotFoundException {
        String className= JavaClassLoader.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(in!=null){
                      try {
                          in.close();
                      } catch (IOException e) {
                          e.printStackTrace();
                      }
                  }
                  if(out!=null){
                      try {
                          out.close();
                      } catch (IOException e) {
                          e.printStackTrace();
                      }
                  }
              }
          }
        }
        return null;
    }
}

public class MyJdkInvocationHandler implements MayiktJdkInvocationHandler {
    /**
     * 目标对象
     */
    private Object target;

    public MyJdkInvocationHandler(Object target) {
        this.target = target;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("使用Jdk动态代理打印日志开始" + args[0]);
        Object result = method.invoke(target, args);
        System.out.println("使用Jdk动态代理打印日志结束" + args[1]);
        return result;
    }

    public <T> T getProxy() {
        return (T) MyProxy.newProxyInstance(new JavaClassLoader(), target.getClass().getInterfaces()[0], this);
    }
}

CGLIB动态代理

利用asm字节码技术，生成子类实现对目标方法实现增强

实现方式

Maven依赖

<dependencies>
    <dependency>
        <groupId>cglib</groupId>
        <artifactId>cglib</artifactId>
        <version>3.2.12</version>
    </dependency>
</dependencies>

核心代码

public class CglibMethodInterceptor implements MethodInterceptor {
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        System.out.println("<<<<<日志收集开始...>>>>>>>");
        Object reuslt = proxy.invokeSuper(obj, args);
        System.out.println("<<<<<日志收集结束...>>>>>>>");
        return reuslt;
    }
}

System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "D:\\code");
CglibMethodInterceptor cglibMethodInterceptor = new CglibMethodInterceptor();
Enhancer enhancer = new Enhancer();
// 设置代理类的付类
enhancer.setSuperclass(MemberServiceImpl.class);
// 设置回调对象
enhancer.setCallback(cglibMethodInterceptor);
// 创建代理对象
MemberServiceImpl orderServiceImpl = (MemberServiceImpl) enhancer.create();
orderServiceImpl.getMember();

Cglib动态代理底层源码分析

Cglib依赖于ASM字节码技术，直接生成class文件，在采用类加载器读取到程序中，

使用fastclass对被代理类的方法建立索引文件不需要依赖于反射查找到目标方法，所以效率比Jdk动态代理要高。

public class OrderServiceImpl$$EnhancerByCGLIB$$1dd3a71c extends OrderServiceImpl {

    static void CGLIB$STATICHOOK1() throws ClassNotFoundException {
        Method amethod[];
        Method amethod1[];
        CGLIB$THREAD_CALLBACKS = new ThreadLocal();
        CGLIB$emptyArgs = new Object[0];
        Class class1 = Class.forName("com.mayikt.service.impl.OrderServiceImpl$$EnhancerByCGLIB$$1dd3a71c");
        Class class2;
        amethod = ReflectUtils.findMethods(new String[]{
                "addOrder", "(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;"
        }, (class2 = Class.forName("com.mayikt.service.impl.OrderServiceImpl")).getDeclaredMethods());
        Method[] _tmp = amethod;
        CGLIB$addOrder$0$Method = amethod[0];
        CGLIB$addOrder$0$Proxy = MethodProxy.create(class2, class1, "(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;", "addOrder", "CGLIB$addOrder$0");
        amethod1 = ReflectUtils.findMethods(new String[]{
                "equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"
        }, (class2 = Class.forName("java.lang.Object")).getDeclaredMethods());
        Method[] _tmp1 = amethod1;
        CGLIB$equals$1$Method = amethod1[0];
        CGLIB$equals$1$Proxy = MethodProxy.create(class2, class1, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$1");
        CGLIB$toString$2$Method = amethod1[1];
        CGLIB$toString$2$Proxy = MethodProxy.create(class2, class1, "()Ljava/lang/String;", "toString", "CGLIB$toString$2");
        CGLIB$hashCode$3$Method = amethod1[2];
        CGLIB$hashCode$3$Proxy = MethodProxy.create(class2, class1, "()I", "hashCode", "CGLIB$hashCode$3");
        CGLIB$clone$4$Method = amethod1[3];
        CGLIB$clone$4$Proxy = MethodProxy.create(class2, class1, "()Ljava/lang/Object;", "clone", "CGLIB$clone$4");
    }

    final String CGLIB$addOrder$0(String s, String s1) {
        return super.addOrder(s, s1);
    }

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

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

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

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

    public final String addOrder(String paramString1, String paramString2) {
        MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
        if (tmp4_1 == null) {

            CGLIB$BIND_CALLBACKS(this);
        }
        try {
            MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
            if (tmp17_14 != null) {
                return (String) tmp17_14.intercept(this, CGLIB$addOrder$0$Method, new Object[]{paramString1, paramString2}, CGLIB$addOrder$0$Proxy);
            }
        } catch (Throwable throwable) {
            throwable.printStackTrace();
        }
        return super.addOrder(paramString1, paramString2);
    }

    public Object newInstance(Callback acallback[]) {
        CGLIB$SET_THREAD_CALLBACKS(acallback);
        CGLIB$SET_THREAD_CALLBACKS(null);
        return new OrderServiceImpl$$EnhancerByCGLIB$$1dd3a71c();
    }

    public Object newInstance(Callback callback) {
        CGLIB$SET_THREAD_CALLBACKS(new Callback[]{
                callback
        });
        CGLIB$SET_THREAD_CALLBACKS(null);
        return new OrderServiceImpl$$EnhancerByCGLIB$$1dd3a71c();
    }

    public void setCallback(int i, Callback callback) {
        switch (i) {
            case 0: // '\0'
                CGLIB$CALLBACK_0 = (MethodInterceptor) callback;
                break;
        }
    }

    private boolean CGLIB$BOUND;
    public static Object CGLIB$FACTORY_DATA;
    private static ThreadLocal CGLIB$THREAD_CALLBACKS = null;
    private static final Callback CGLIB$STATIC_CALLBACKS[] = null;
    private MethodInterceptor CGLIB$CALLBACK_0;
    private static Object CGLIB$CALLBACK_FILTER;
    private static Method CGLIB$addOrder$0$Method = null;
    private static MethodProxy CGLIB$addOrder$0$Proxy = null;
    private static Object[] CGLIB$emptyArgs = null;
    private static Method CGLIB$equals$1$Method = null;
    private static MethodProxy CGLIB$equals$1$Proxy = null;
    private static Method CGLIB$toString$2$Method = null;
    private static MethodProxy CGLIB$toString$2$Proxy = null;
    private static Method CGLIB$hashCode$3$Method = null;
    private static MethodProxy CGLIB$hashCode$3$Proxy = null;
    private static Method CGLIB$clone$4$Method = null;
    private static MethodProxy CGLIB$clone$4$Proxy = null;

    static {
        try {
            CGLIB$STATICHOOK1();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public OrderServiceImpl$$EnhancerByCGLIB$$1dd3a71c() {
        CGLIB$BIND_CALLBACKS(this);
    }

    private void CGLIB$BIND_CALLBACKS(OrderServiceImpl$$EnhancerByCGLIB$$1dd3a71c orderServiceImpl$$EnhancerByCGLIB$$1dd3a71c) {
    }
}

FastClass机制

public class MayiktFastclass {

    /**
     * 根据索引查找到目标方法
     *
     * @param index
     * @param obj
     * @param args
     * @return
     */
    public static Object invoke(int index, Object obj, Object[] args) {
        OrderServiceImpl orderService = (OrderServiceImpl) obj;
        switch (index) {
            case 1:
                return orderService.addOrder(String.valueOf(args[0]), String.valueOf(args[1]));
        }
        return null;
    }

    /**
     * 根据签名简历索引文件
     *
     * @param sign
     * @return
     */
    public static int getIndex(String sign) {
        switch (sign.hashCode()) {
            case 1763340254:
                return 1;
            case 20:
                return 2;
        }
        return -1;
    }

    public static void main(String[] args) {
        System.out.println("addOrder()String,String".hashCode());
        Object result = invoke(getIndex("addOrder()String,String"), new OrderServiceImpl(), new String[]{"mayikt", "meite"});
    }
}

Jdk与Cglib动态代理的区别

Jdk动态代理利用反射技术生成匿名的代理类走InvokeHandler回调方法实现增强，同时也是一种基于接口的方式实现代理。
Cglib动态代理利用asm字节码技术生成一个子类覆盖其中的方法实现增强，同时采用fastClass机制对整个代理类建立索引比反射效率要高
在Spring中如果需要被代理的对象如果实现了接口采用Jdk动态代理，没有实现接口则使用Cglib动态代理。.

出处：https://www.cnblogs.com/itit9696/p/15130080.html

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