动态代理---动态生成java文件并编译成class文件

[java]代码库

package com.cjb.proxy;

import java.io.File;
import java.io.FileWriter;
import java.lang.reflect.Constructor;
import java.net.URL;
import java.net.URLClassLoader;

import javax.tools.JavaCompiler;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import javax.tools.JavaCompiler.CompilationTask;


public class Test
{
 public static void main(String[] args) throws Exception
 {
  String rt = "\r\n";
  String source = "package com.cjb.proxy;" + ""+ rt
    + "public class Dealer implements Store"+ rt  + "{"+ rt  + "private Store s;" + rt +
    "public Dealer(Store s)"+ rt  + " {" + "  this.s = s;"+ rt
    + " }" + rt +

    " public void sell()" + " {"+ rt
    + "  System.out.println(\"price markup....\");"+ rt
    + "  s.sell();" + " }" + rt+
    "}";

  String fileName = System.getProperty("user.dir")//获取到项目的根路径
    + "/src/com/cjb/proxy/Dealer.java";
  File f = new File(fileName);
  FileWriter fw = new FileWriter(f);
  fw.write(source);
  fw.flush();
  fw.close();//这里只是产生一个JAVA文件,简单的IO操作

  // compile下面开始编译这个Store.java
  JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
  StandardJavaFileManager fileMgr = compiler.getStandardFileManager(null,
    null, null);
  Iterable units = fileMgr.getJavaFileObjects(fileName);
  CompilationTask t = compiler.getTask(null, fileMgr, null, null, null,
    units);
  t.call();
  fileMgr.close();

  // load into memory and create an instance
  URL[] urls = new URL[] { new URL("file:/"
    + System.getProperty("user.dir") + "/src") };
  URLClassLoader ul = new URLClassLoader(urls);
  Class c = ul.loadClass("com.cjb.proxy.Dealer");
  System.out.println(c);

//客户端调用

  Constructor ctr = c.getConstructor(Store.class);
  Store s = (Store)ctr.newInstance(new Supermarket());//这里看到,这个我们这个代理类必须实现Store的原因
  s.sell();
 }
}//源代码片段来自云代码http://yuncode.net