代理模式——动态代理（自己写一个）

来源：互联网发布：数控车床自动编程软件编辑：程序博客网时间：2024/05/22 16:52

思路

难点：proxy类，它的作用就是帮我们产生代理类。

将所有方法代码拼接成字符串。
将生成代理类的代码拼接成字符串（包含所有方法拼接成的字符串）。
将此字符串写入文件中、并使用JavaComplier对它进行编译。
将编译好的文件load进内存供我们使用，并返回代理实例。

Proxy代码：

public class Proxy {      public static Object newProxyInstance(Class intefc, InvocationHandler handle) throws Exception {          String rt = "\r\t" ;          String methodStr = "" ;                    // first we should realize all the methods of the interface          Method[] methods = intefc.getMethods();          for (Method m : methods) {              methodStr +="public void "+m.getName()+"(){"+rt+                          "    try{"+rt+                          "        Method method = "+intefc.getName()+".class.getMethod(\""+m.getName()+"\");" + rt +                          "        handle.invoke(this,method);" +rt+                          "    }catch(Exception ex){}" +rt+                          "}" ;                                    }          String clazzStr =  "package com.zdp.dynamicProxy;"+rt+                             "import java.lang.reflect.Method;"+rt+                             "public class $Proxy1 implements "+intefc.getName()+"{"+rt+                             "    private com.zdp.dynamicProxy.InvocationHandler handle ;"+rt+                             "    public $Proxy1(InvocationHandler handle){"+rt+                             "        this.handle=handle;"+rt+                             "    }"+rt+                             "    @Override"+rt+                              methodStr +rt+                             "}";                              // write to a java file   String uri = "D:/develop_environment/babasport/homework/src/com/zdp/dynamicProxy/$Proxy1.java";        File file = new File(uri) ;          FileWriter writer = null ;          try {              writer = new FileWriter(file);              writer.write(clazzStr) ;              writer.flush() ;          } catch (IOException e) {              e.printStackTrace();          }finally{              try {                  if(writer !=null){                      writer.close() ;                  }              } catch (IOException e) {                  e.printStackTrace();              }          }                    //load the java file, and then create an instance String url="D:/develop_environment/babasport/homework/src/";        URL[] urls = new URL[] {new URL("file:/" + url)};          URLClassLoader urlLoader = new URLClassLoader(urls);          Class c = urlLoader.loadClass("com.zdp.dynamicProxy.$Proxy1");                    //return the proxy instance          Constructor ctr = c.getConstructor(InvocationHandler.class);          Object proxyInstance = ctr.newInstance(handle);            return proxyInstance;      }  }

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