回调

1. 同步回调

• Callback

public interface Callback {

    void onSuccess(String result);

    void onFail(String result);
}

• Server

public class Server {

    private static Map<String, String> map = new HashMap<>();

    static {
        map.put("1", "111");
        map.put("2", "222");
    }

    public void query(String id, Callback callback) throws InterruptedException {
        TimeUnit.SECONDS.sleep(10);
        if (map.containsKey(id)) {
            callback.onSuccess(map.get(id));
        } else {
            callback.onFail("no result for query");
        }
    }
}

• Client

public class Client {
    public static void main(String[] args) throws InterruptedException {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-hh HH:mm:ss");

        Server server = new Server();
        Callback callback = new Callback() {
            @Override
            public void onSuccess(String result) {
                System.out.println(format.format(new Date()) + " Success: " + result);
            }

            @Override
            public void onFail(String result) {
                System.out.println(format.format(new Date()) + " Fail: " + result);
            }
        };

        System.out.println(format.format(new Date()) + " begin query...");
        server.query("1", callback);
        System.out.println(format.format(new Date()) + " finished");
    }
}

• 运行结果

2020-10-11 11:32:51 begin query...
2020-10-11 11:33:01 Success: 111
2020-10-11 11:33:01 finished

2. 异步回调

• Callback
  同上

• Server
  同上

• Client

public class Client {
    public static void main(String[] args) {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-hh HH:mm:ss");

        Server server = new Server();
        Callback callback = new Callback() {
            @Override
            public void onSuccess(String result) {
                System.out.println(format.format(new Date()) + " Success: " + result);
            }

            @Override
            public void onFail(String result) {
                System.out.println(format.format(new Date()) + " Fail: " + result);
            }
        };

        System.out.println(format.format(new Date()) + " begin query...");

        new Thread(() -> {
            try {
                server.query("1", callback);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }).start();

        System.out.println(format.format(new Date()) + " do something else...");
    }
}

• 运行结果

2020-10-11 11:36:08 begin query...
2020-10-11 11:36:08 do something else...
2020-10-11 11:36:18 Success: 111