java中的动态代理----自己手动实现

代码使用了common-io，需要其jar

1 接口

public interface Pruduct {
    void selling();
}

 2 书籍类

public class Book implements Pruduct {
    @Override
    public void selling() {
        try {
            Thread.sleep(1000);
            System.out.println("books selling.....");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

 3 定义日志类

public class LogTranService{

    public static void before(){

        System.out.println("begin log...");
    }

    public static void after(){
        System.out.println("finish log...");
    }

}

 4 定义时间类

public class TimeTranService {
    static long bgn;

    public static void before(){
        bgn = System.currentTimeMillis();
        System.out.println("begin time...  " + bgn);
    }
    public static void after(){
        long end = System.currentTimeMillis();
        System.out.println("end time...  " + (end-bgn));
    }

}

 5 定义InvocationHander 

import java.lang.reflect.Method;

public interface InvocationHander {
    public void invoke(Object o,Method m);
}

import java.lang.reflect.Method;
public class ProxyHander implements InvocationHander {

    private Object target;
    public ProxyHander(Object target) {
        this.target = target;
    }
    @Override
    public void invoke(Object o, Method m) {
        try {
            TimeTranService.before();
            LogTranService.before();
            m.invoke(target);
            LogTranService.after();
            TimeTranService.after();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 6 代理类

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;

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

import org.apache.commons.io.FileUtils;
public class Proxy {
    /*
     * 空的构造函数
     */
    private Proxy(){
    }
    /*
     * 返回代理类
     */
    public static Object newProxyInstance(Class inter,InvocationHander h){
        String proxyClassName = "$Proxy3";
        String packageName  = inter.getPackage().getName();
        String InHanderPackage = h.getClass().getPackage().getName();
        String rt = "
";// 换行
        String methodCode = "";
        for (Method method:inter.getMethods()) {
            methodCode+="   @Override"+rt+

            "   public void "+ method.getName()+"() {"+rt+
            "       try{"+rt+
            "           Method method  = "+inter.getName()+".class.getMethod(""
            +           method.getName()+   "");"+rt+
            "           h.invoke(this,method);      "+rt+
            "       }catch(Exception e ){" +rt+
            "           e.printStackTrace();" +rt+
            "       }"+rt+
            "   }";
        }
        /*
         * 总的java代码
         */
        String javaCode=
        "package  "+packageName+";"+rt+
        "import "+InHanderPackage+".InvocationHander;"+rt+

        "import java.lang.reflect.Method;"+rt+
        "public class "+proxyClassName+" implements "+inter.getName()+" {"+rt+
        "   public "+proxyClassName+"("+InHanderPackage+".InvocationHander h) {"+rt+
        "       super();"+rt+
        "       this.h = h;"+rt+
        "   }"+rt+
        "   private "+InHanderPackage+".InvocationHander h;"+rt+
        methodCode+rt+
        "}";
        /*
         *  生成java文件
         */
        // 生成文件路径
        String filename =  System.getProperty("user.dir")+"/bin/"+packageName+"/"+proxyClassName+".java";
        File file = new File(filename);
        try {
            System.out.println(filename);
            FileUtils.writeStringToFile(file, javaCode);// commons-io这个框架可以放很方便的操作文件
        } catch (IOException e) {
            e.printStackTrace();
        }


        // 编译  拿到编译器
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        // 文件管理
        StandardJavaFileManager fileMgr = compiler.getStandardFileManager(null, null, null);
        //获取文件
        Iterable units = fileMgr.getJavaFileObjects(filename);

        // 编译任务
        CompilationTask t  = compiler.getTask(null, fileMgr, null, null, null, units);
        // call进行编译
        t.call();
        try {
            fileMgr.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        // load到内存
        ClassLoader cl = ClassLoader.getSystemClassLoader();
        try {
            Class c = cl.loadClass(packageName+"."+proxyClassName);
            Constructor ctr = c.getConstructor(InvocationHander.class);
            System.out.println("代理类的名字为："+c.getName()+"===========");
            return ctr.newInstance(h);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}

 7 测试

public class Client {
    public static void main(String[] args) {
        Book book = new Book();
        InvocationHander h = new ProxyHander(book);
        Pruduct m = (Pruduct)Proxy.newProxyInstance(Pruduct.class,h);
        m.selling();
    }
}