Future模式

package net.jcip.examples;

import java.util.*;
import java.util.concurrent.*;
import static net.jcip.examples.LaunderThrowable.launderThrowable;

/**
 * FutureRenderer
 * <p/>
 * Waiting for image download with \Future
 *
 * @author Brian Goetz and Tim Peierls
 */
public abstract class FutureRenderer {
    private final ExecutorService executor = Executors.newCachedThreadPool();

    void renderPage(CharSequence source) {
        final List<ImageInfo> imageInfos = scanForImageInfo(source);
        Callable<List<ImageData>> task =
                new Callable<List<ImageData>>() {
                    public List<ImageData> call() {
                        List<ImageData> result = new ArrayList<ImageData>();
                        for (ImageInfo imageInfo : imageInfos)
                            result.add(imageInfo.downloadImage());
                        return result;
                    }
                };

        Future<List<ImageData>> future = executor.submit(task);
        renderText(source);

        try {
            List<ImageData> imageData = future.get();
            for (ImageData data : imageData)
                renderImage(data);
        } catch (InterruptedException e) {
            // Re-assert the thread's interrupted status
            Thread.currentThread().interrupt();
            // We don't need the result, so cancel the task too
            future.cancel(true);
        } catch (ExecutionException e) {
            throw launderThrowable(e.getCause());
        }
    }

    interface ImageData {
    }

    interface ImageInfo {
        ImageData downloadImage();
    }

    abstract void renderText(CharSequence s);

    abstract List<ImageInfo> scanForImageInfo(CharSequence s);

    abstract void renderImage(ImageData i);
}

簡單實現

package Future.Sample;

public class RealData implements Data {
    private final String content;
    public RealData(int count, char c) {
        System.out.println("        making RealData(" + count + ", " + c + ") BEGIN");
        char[] buffer = new char[count];
        for (int i = 0; i < count; i++) {
            buffer[i] = c;
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
            }
        }
        System.out.println("        making RealData(" + count + ", " + c + ") END");
        this.content = new String(buffer);
    }
    public String getContent() {
        return content;
    }
}

package Future.Sample;

public class FutureData implements Data {
    private RealData realdata = null;
    private boolean ready = false;
    public synchronized void setRealData(RealData realdata) {
        if (ready) {                        
            return;     // balk
        }
        this.realdata = realdata;
        this.ready = true;
        notifyAll();
    }
    public synchronized String getContent() {
        while (!ready) {
            try {
                wait();
            } catch (InterruptedException e) {
            }
        }
        return realdata.getContent();
    }
}

package Future.Sample;

public class Host {
public Data request(final int count, final char c) {
System.out.println(" request(" + count + ", " + c + “) BEGIN”);

    // (1) ����FutureData��ʵ��
    final FutureData future = new FutureData();

    // (2) Ϊ�˽���RealData��ʵ�壬�����µ��߳�
    new Thread() {                                      
        public void run() {                             
            RealData realdata = new RealData(count, c);
            future.setRealData(realdata);
        }                                               
    }.start();                                          

    System.out.println("    request(" + count + ", " + c + ") END");

    // (3) ȡ��FutureDataʵ�壬��Ϊ����ֵ�^��
    return future;
}

}

package Future.Sample;

public class Main {
    public static void main(String[] args) {
        System.out.println("main BEGIN");
        Host host = new Host();
        Data data1 = host.request(10, 'A');
        Data data2 = host.request(20, 'B');
        Data data3 = host.request(30, 'C');

        System.out.println("main otherJob BEGIN");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
        }
        System.out.println("main otherJob END");

        System.out.println("data1 = " + data1.getContent());
        System.out.println("data2 = " + data2.getContent());
        System.out.println("data3 = " + data3.getContent());
        System.out.println("main END");
    }
}

複製鏈接，在瀏覽器打開
tomcat源碼解析
https://study.163.com/course/introduction/1209535854.htm

Springmvc源碼解析
https://study.163.com/course/introduction/1209536851.htm