使用自动生成java文件和自动编译的静态代理模式

落日映苍穹つ 2022-06-10 04:07 138阅读 0赞

public interface Moveable {
    	void move();//
    }

public class Car implements Moveable{
    	@Override
    	public void move() {
    		System.out.println("我是卡车,出发开往目的地...");
    	}
    }

//动态代理1
    public class Proxy {
    	public static Object newProxyInstance(Moveable move){
    		String rt="\r\n";
    		String src="package proxy1.dynamic;"+rt;
    			  src+="public class CarTimeProxy implements Moveable{"+rt;
    			  src+="	private Moveable move;"+rt;
    			  src+="	public CarTimeProxy(Moveable move){"+rt;
    			  src+="		this.move=move;"+rt;
    			  src+="	}"+rt;
    			  src+="	@Override"+rt;
    			  src+="	public void move(){"+rt;					  				
    			  src+="		System.out.println(\"开始记录时间:\");"+rt;
    			  src+="		long start=System.currentTimeMillis();"+rt;
    			  src+="		move.move();"+rt;
    			  src+="		System.out.println(\"共耗时:\"+(System.currentTimeMillis()-start));"+rt;
    			  src+="	}"+rt;
    			  src+="}"+rt;
    	  //创建java文件
    	  String filepath=System.getProperty("user.dir")+"/src/proxy1/dynamic";
    	  File file=new File(filepath+"/CarTimeProxy.java");
    	  try{
    		if(!file.exists()){
    			file.createNewFile();
    		}
    		FileWriter fw=new FileWriter(file);
    		fw.write(src);
    		fw.close();	
    	  }catch(Exception e){e.printStackTrace();}
    	  
    	  //编译
    		JavaCompiler javac=ToolProvider.getSystemJavaCompiler();
    		StandardJavaFileManager javafile=javac.getStandardFileManager(null, null, null);
    		String filename=filepath+"/CarTimeProxy.java";
    		Iterable units=javafile.getJavaFileObjects(filename);
    		CompilationTask t=javac.getTask(null, javafile, null, null, null, units);
    		t.call();
    		try {javafile.close();
    		} catch (IOException e) {e.printStackTrace();}
    		
    	 //把刚才在D:/下生成的class文件CarTimeProxy.class加载进内存并生成实例对象
    		URL[] urls;
    		Object obj=null;
    		try {
    			urls = new URL[]{new URL("file:///D:/Workspaces/base/bin/")};
    			URLClassLoader classload=new URLClassLoader(urls);
    			Class clazz=classload.loadClass("proxy1.dynamic.CarTimeProxy");
    			Constructor cons=clazz.getConstructor(Moveable.class);
    			obj=cons.newInstance(move);
    		} catch (Exception e) {
    			e.printStackTrace();
    		} 
    		return obj;
    	}
    }

public class Client {
    	public static void main(String[] args) throws ClassNotFoundException {
    		
    		Moveable move=new Car();
    		Moveable proxy=(Moveable) Proxy.newProxyInstance(move);
    		proxy.move();
    		/**
    		 * 运行结果:
    		 * 开始记录时间:
    		 * 我是卡车,出发开往目的地...
    		 * 共耗时:0
    		 */
    	}
    }