Future 模式

• 该模式核心思想是异步调用。

Future 异步调用模式

public class Main {
    public static void main(String[] args) {
        Client client  = new Client() ;
        
        Data data = client.request("name");
        System.out.println("请求完毕");
        try {
            Thread.sleep(2000);
        } catch (Exception e) {
        }
        
        System.out.println("数据  = " + data.getResult());
    }
}

public class Client {
    public Data request(final String queryStr){
        final FutureData future = new FutureData() ;
        new Thread(){
            public void run() {
                RealData realData = new RealData(queryStr);
                future.setRealData(realData);
            }   ;
        }.start();  
        return future ;
    }   
}

public class RealData implements Data {
    protected  final String result ;
    public RealData(String result) {
        super();
        StringBuffer buffer =new StringBuffer();
        for(int i = 0 ; i < 10 ; i++){
            buffer.append(result+" ");
            try {
                Thread.sleep(100);
            } catch (Exception e) {     
            }
        }   
        this.result = buffer.toString();
    }
    @Override
    public String getResult() {
        return result;
    }
}

public interface Data {
    public String getResult();
}

public class FutureData implements Data {
    protected boolean isReady = false ;
    protected RealData  realData = null ;
    public synchronized  void setRealData(RealData realData) {
        if(isReady){
            return ;
        }
        this.realData = realData;
        isReady = true ;
        notifyAll();
    }
    @Override
    public synchronized String getResult() {
        while(!isReady){
            try {
                wait();
            } catch (Exception e) {
            }
        }
        return realData.result; 
    }
}

jdk 中的Future 模式

内置实现Future

public class FurureMain {

    public static void main(String[] args)  throws Exception{
        //构造任务
        FutureTask<String> future = new FutureTask<String>( new RealDataCall("a"));
        ExecutorService executor =Executors.newFixedThreadPool(1);
        executor.submit(future);
        System.out.println("请求完毕");
        try {   
            Thread.sleep(2000);
        } catch (Exception e) {
            // TODO: handle exception
        }   
        System.out.println("数据= ： "+ future.get());
    }   
}

public class RealDataCall implements Callable<String> {
    private String para ;
    public RealDataCall(String para) {
        super();
        this.para = para;
    }
    @Override
    public String call() throws Exception {
        StringBuffer buffer =new StringBuffer();
        for(int i = 0 ; i < 10 ; i++){
            buffer.append(para+" ");
            try {
                Thread.sleep(100);
            } catch (Exception e) {         
            }
        }
        return buffer.toString();
    }
}

1. 在这里面我们首先创建FutureTask对象实例， 表示该任务是有返回值的。
2. 第二步 使用Callable 产生数据。
3. 提交任务到线程池。 作为任务的简单提交。用get把结果查出来