全家福

image.png

被代理类准备

image.png
ImServiceImpl

  1. package com.xiang.service.impl;
  3. import com.xiang.service.ImService;
  5. public class ImServiceImpl implements ImService {
  6.     @Override
  7.     public void sendSms() {
  8.         System.out.println("我在发送消息");
  9.     }
  10. }

ImService

  1. package com.xiang.service;
  3. public interface ImService {
  4.     void sendSms();
  5. }

思路分析

参考静态代理，sendSms()方法里面的内容需要程序员自己定义，所以封装成接口（MyInvocationHandler），让程序员自己实现，People是目标对象，也需要程序员自己实现，所以此处删掉。

  1. public class ImProxy implements ImService{
  3.     private ImService imService;
  5.     StudentsProxy(ImService imService){
  6.          this.imService = imService;
  7.     }
  9.     @Override
  10.     public void sendSms(){
  11.         System.out.println("===> 方法增强前");
  12.         people.tuition();
  13.         System.out.println("===> 方法增强后");
  14.     }
  15. }

封装后

  1. package com.xiang.proxy;
  3. import com.xiang.proxy.handler.MyInvocationHandler;
  4. import com.xiang.service.ImService;
  6. import java.lang.reflect.Method;
  8. /**
  9.  * 动态代理生成的执行方法，本来是动态生成的，此处为了学习暂时手动自定义
  10.  */
  11. public class $Proxy0 implements ImService {
  13.     private MyInvocationHandler h;
  15.     public $Proxy0(MyInvocationHandler h){
  16.         this.h = h;
  17.     }
  19.     @Override
  20.     public void sendSms() {
  21.         try {
  22.             Method sendSms = ImService.class.getMethod("sendSms", new Class[]{});
  23.             h.invoke(h, sendSms, null);
  24.         } catch (Throwable throwable) {
  25.             throwable.printStackTrace();
  26.         }
  27.     }
  28. }

提出的公共接口
MyInvocationHandler

  1. public interface MyInvocationHandler {
  3.     /**
  4.      * 要实现的方法
  5.      * @param proxy 代理类
  6.      * @param method 被代理类
  7.      * @param args 被代理类的入参。
  8.      * @return
  9.      * @throws Throwable
  10.      */
  11.     Object invoke(Object proxy, Method method, Object[] args)
  12.             throws Throwable;
  14. }

动态代理类
ImProxy

  1. public class ImProxy implements MyInvocationHandler {
  3.     public Object objFactory;
  5.     public ImProxy(Object objFactory){
  6.         this.objFactory = objFactory;
  7.     }
  9.     @Override
  10.     public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
  11.         System.out.println("===> 方法增强前");
  12.         Object invoke = method.invoke(objFactory, args);
  13.         System.out.println("===> 方法增强后");
  14.         return invoke;
  15.     }
  16. }

结论

我们只需要动态生成$Proxy0即可。

原理思路

  1. 使用java语言组装$Proxy0.java源代码 获取实现的接口，使用java的反射技术获取该接口下面的所有方法。
  2. 将 $Proxy0.java 编异成 $Proxy0.class文件（JavaCompiler 类似于我们在命令行输入的javac）
  3. 通过classLoader加载到内存中。

MyProxy

  1. package com.xiang.proxy;
  3. import com.xiang.proxy.handler.MyInvocationHandler;
  4. import com.xiang.proxy.handler.impl.ImProxy;
  5. import com.xiang.service.ImService;
  6. import com.xiang.service.impl.ImServiceImpl;
  8. import javax.tools.JavaCompiler;
  9. import javax.tools.JavaFileObject;
  10. import javax.tools.StandardJavaFileManager;
  11. import javax.tools.ToolProvider;
  12. import java.io.File;
  13. import java.io.FileWriter;
  14. import java.io.IOException;
  15. import java.lang.reflect.Constructor;
  16. import java.lang.reflect.Method;
  19. public class MyProxy{
  21.     private final static String PATH = "d:/code/"; //保存文件路径
  22.     private final static String CLASS_NAME = "$Proxy1"; //类名
  24.     public static Object newProxyInstance(MyClassLoader loader,
  25.                                           Class<?> interfaces,
  26.                                           MyInvocationHandler h){
  27.         //1. 获取要生成的代码String对象
  28.         String proxyClass = getProxyClass(interfaces);
  29.         //2.写入本地文件
  30.         String filename = PATH+CLASS_NAME+".java";//文件写入地址
  31.         whiteFile(proxyClass,filename);
  32.         //3. 将 $Proxy0.java 编异成 $Proxy0.class文件（JavaCompiler 类似于我们在命令行输入的javac）
  33.         compiler(filename);
  34.         //3. 通过classLoader加载到内存中。
  35.         try {
  36.             Class<?> clazz = loader.findClass(CLASS_NAME);
  37.             //构造函数入参对象。
  38.             Constructor<?> constructor = clazz.getConstructor(MyInvocationHandler.class);
  39.             return constructor.newInstance(h);
  40.         } catch (Exception e) {
  41.             e.printStackTrace();
  42.             return null;
  43.         }
  44.     }
  46.     /**
  47.      * 获取拼接代理对象
  48.      * @return
  49.      */
  50.     public static String getProxyClass(Class<?> interfaces){
  51.         Method[] methods = interfaces.getMethods();
  52.         StringBuilder stringBuilder = new StringBuilder();
  53.         stringBuilder.append("package com.xiang.proxy;");
  54.         stringBuilder.append("import com.xiang.proxy.handler.MyInvocationHandler;");
  55.         stringBuilder.append("import java.lang.reflect.Method;");
  57.         stringBuilder.append("public class "+CLASS_NAME+" implements "+interfaces.getName()+" {\n" );
  58.         stringBuilder.append(" private MyInvocationHandler h;\n" );
  59.         stringBuilder.append(" public "+CLASS_NAME+"(MyInvocationHandler h){\n" );
  60.         stringBuilder.append("  this.h = h;\n" );
  61.         stringBuilder.append(" }\n" );
  63.         stringBuilder.append(mothods(methods,interfaces));
  64.         stringBuilder.append("}");
  65.         return stringBuilder.toString();
  66.     }
  68.     /**
  69.      * 拼接方法
  70.      * @param methods
  71.      * @param interfaces
  72.      * @return
  73.      */
  74.     public static String mothods(Method[] methods,Class<?> interfaces){
  76.         StringBuilder stringBuilder = new StringBuilder();
  77.         for (Method method : methods) {
  78.             stringBuilder.append("@Override\n");
  79.             //此处偷懒，都没有返回值
  80.             stringBuilder.append("public void "+method.getName()+"() {\n" );
  81.             stringBuilder.append("try {\n" );
  82.             stringBuilder.append(" Method mothodName = "+interfaces.getName()+".class.getMethod(\""+method.getName()+"\", new Class[]{});\n" );
  83.             stringBuilder.append(" h.invoke(h, mothodName, null);\n" );
  84.             stringBuilder.append(" } catch (Throwable throwable) {\n" );
  85.             stringBuilder.append(" throwable.printStackTrace();\n" );
  86.             stringBuilder.append(" }\n" );
  87.             stringBuilder.append("}" );
  88.             stringBuilder.append(" " );
  89.         }
  91.         return stringBuilder.toString();
  92.     }
  94.     /**
  95.      * 文件写入本地
  96.      */
  97.     public static void whiteFile(String fileStirng,String filename){
  98.         File file = new File(filename);
  99.         try {
  100.             FileWriter fw = new FileWriter(file);
  101.             fw.write(fileStirng);
  102.             fw.flush();
  103.             fw.close();
  104.         } catch (IOException e) {
  105.             e.printStackTrace();
  106.         }
  107.     }
  109.     public static void compiler(String filename){
  110.         JavaCompiler javaCompiler = ToolProvider.getSystemJavaCompiler();
  111.         StandardJavaFileManager fileManager = javaCompiler.getStandardFileManager(null, null, null);
  112.         Iterable<? extends JavaFileObject> iterable = fileManager.getJavaFileObjects(filename);
  113.         JavaCompiler.CompilationTask task = javaCompiler.getTask(null, fileManager, null, null, null, iterable);
  114.         task.call();
  115.         try {
  116.             fileManager.close();
  117.         } catch (IOException e) {
  118.             e.printStackTrace();
  119.         }
  120.     }
  121. }
  1. package com.xiang.proxy;
  3. import java.io.ByteArrayOutputStream;
  4. import java.io.File;
  5. import java.io.FileInputStream;
  6. import java.io.IOException;
  8. public class MyClassLoader extends ClassLoader{
  9.     private File classPathFile;
  11.     public MyClassLoader(){
  12.         this.classPathFile = new File("D:\\code");
  13.     }
  15.     @Override
  16.     public Class<?> findClass(String name) throws ClassNotFoundException {
  18.         String className = MyClassLoader.class.getPackage().getName() + "." + name;
  20.         if(classPathFile != null){
  21.             File classFile = new File(classPathFile,name.replaceAll("\\.","/") + ".class");
  22.             if(classFile.exists()){
  23.                 FileInputStream in = null;
  24.                 ByteArrayOutputStream out = null;
  26.                 try{
  27.                     in = new FileInputStream(classFile);
  28.                     out = new ByteArrayOutputStream();
  29.                     byte [] buff = new byte[1024];
  30.                     int len;
  31.                     while ((len = in.read(buff)) != -1){
  32.                         out.write(buff,0,len);
  33.                     }
  34.                     return  defineClass(className,out.toByteArray(),0,out.size());
  35.                 }catch (Exception e){
  36.                     e.printStackTrace();
  37.                 }finally {
  38.                     if(null != in){
  39.                         try {
  40.                             in.close();
  41.                         } catch (IOException e) {
  42.                             e.printStackTrace();
  43.                         }
  44.                     }
  46.                     if(out != null){
  47.                         try {
  48.                             out.close();
  49.                         } catch (IOException e) {
  50.                             e.printStackTrace();
  51.                         }
  52.                     }
  53.                 }
  54.             }
  56.         }
  57.         return null;
  58.     }
  59. }

代码测试

  1. public static void main(String[] args) {
  2.     ImService imService = (ImService) newProxyInstance(new MyClassLoader(), ImService.class, new ImProxy(new ImServiceImpl()));
  3.     imService.sendSms();
  4. }