Java-馬士兵設計模式學習筆記-代理模式--動態代理 修改成可以代理任意接口

一、概述

1.目標：把Proxy修改成可以代理任意接口及其任意方法

2.思路：

(1)代理任意接口：把接口類型作為參數傳給Proxy的newProxyInstance(Class interfze)

(2)代理任意方法：用interfze.getMethods()取出所有方法，拼接實現方法的字符串

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二、代碼

1.Movable.java

2.Tank.java

3.Proxy.java

4.Client.java

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1.Movable.java

package proxy;

public interface Movable {
    public void move();
    public void stop();
}

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2.Tank.java

package proxy;

import java.util.Random;

public class Tank implements Movable {

    @Override
    public void move() {
        System.out.println("Tank moving.......");
        try {
            Thread.sleep(new Random().nextInt(2000));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void stop() {
        System.out.println("Tank stopping.......");
        
    }

}

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3.Proxy.java

package proxy;

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

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

public class Proxy {

    public static Object newProxyInstance(Class interfze) throws Exception {
        
        String rt = "\n\r";
        
        //拼接"實現接口方法"的字符串
        String methodStr = "";
        for(Method m: interfze.getMethods() ){
            
            //取出方法的修飾符和返回值類型
            String [] parts = m.toString().replace("abstract ", "").split("\\.");
            String [] parts2 = parts[0].split(" ");
            
            methodStr +=
            "@Override" + rt +
            parts2[0]+" "+parts2[1]+" "+m.getName()+"() {" + rt +
                "System.out.println(\"Time Proxy start...........\");" + rt +
                "long start = System.currentTimeMillis();" + rt +
                "m." + m.getName() + "();" + rt +
                "long end = System.currentTimeMillis();" + rt +
                "System.out.println(\"花費時間：\"+(end - start));" + rt +
                "System.out.println(\"Time Proxy end...........\");" + rt +
            "}" ;
        }
        
        
        //動態代理文件的源碼
        String str = 
        "package proxy;" + rt +

        "public class TankTimeProxy implements " + interfze.getName() + " {"+rt+

            "private " + interfze.getName() + " m;" + rt +
            
            "public TankTimeProxy(" + interfze.getName() + " m) {" + rt +
                "this.m = m;" + rt +
            "}" + rt +

            methodStr + rt +

        "}" ;
        
        //把源碼寫到java文件里
        File file = new File(System.getProperty("user.dir")+"/src/proxy/TankTimeProxy.java");
        FileWriter fw = new FileWriter(file);
        fw.write(str);
        fw.flush();
        fw.close();
        
        //編譯源碼，生成class,注意編譯環境要換成jdk才有compiler,單純的jre沒有compiler，會空指針錯誤
        JavaCompiler jc = ToolProvider.getSystemJavaCompiler();
        
        //文件管事器
        StandardJavaFileManager fileMgr = jc.getStandardFileManager(null, null, null);
        
        //編譯單元
        Iterable units = fileMgr.getJavaFileObjects(file);
        
        //編譯任務
        CompilationTask t = jc.getTask(null, fileMgr, null, null, null, units);
        
        //編譯
        t.call();    
        fileMgr.close();
        
        //把類load到內存里
        URL[] urls = new URL[] {new URL("file:/"+System.getProperty("user.dir")+"/src/proxy/TankTimeProxy.class")};
        URLClassLoader uc = new URLClassLoader(urls);
        Class c = uc.loadClass("proxy.TankTimeProxy");
        
        //生成實例
        //return c.newInstance(); //c.newInstance()會調用無參數的Construtor，若類沒有無參的Constructor時會出錯
        Constructor ctr = c.getConstructor(interfze);
        return ctr.newInstance(new Tank());
    }
}

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4.Client.java

package proxy;

import java.io.IOException;

import org.junit.Test;

public class Client {

    @Test
    public void testProxy() throws Exception{
        
        Movable m = (Movable)Proxy.newProxyInstance(Movable.class);
        m.move();
        m.stop();
        
    }
}

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三、運行結果