Furure的簡單介紹和使用
阿新 • • 發佈：2017-07-15
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引子：
上圖是兩個系統交互的情況，現在我想將對外系統的調用做成異步實現，那麽就需要考慮兩個問題：
主線程可以得到異步線程的結果，在得到結果之後再進行operation-4 ?主線程如何得到異步線程結果？ ?主線程在得到異步線程的結果之前是否可以不等待？可以使用Future模式來實現。
Future模式在請求發生時返回一個Future對象給發起請求的客戶端，然後由一個新的線程執行真正的異步業務處理，當客戶端需要異步處理的結果時，通過返回給客戶端的Future對象的get()方法獲取異步處理結果！
JDK的Future模式：Java.util.concurrent.future.Future接口
/**
* A <tt>Future</tt> represents the result of an asynchronous
* computation. Methods are provided to check if the computation is
* complete, to wait for its completion, and to retrieve the result of
* the computation. The result can only be retrieved using method
* <tt>get</tt> when the computation has completed, blocking if
* necessary until it is ready. Cancellation is performed by the
* <tt>cancel</tt> method. Additional methods are provided to
* determine if the task completed normally or was cancelled. Once a
* computation has completed, the computation cannot be cancelled.
* If you would like to use a <tt>Future</tt> for the sake
* of cancellability but not provide a usable result, you can
* declare types of the form {
對應的任務接口是：java.util.concurrent.Callable
/**
* A task that returns a result and may throw an exception.
* Implementors define a single method with no arguments called
* <tt>call</tt>.
*
* <p>The <tt>Callable</tt> interface is similar to {@link
* java.lang.Runnable}, in that both are designed for classes whose
* instances are potentially executed by another thread. A
* <tt>Runnable</tt>, however, does not return a result and cannot
* throw a checked exception.
*
* <p> The {@link Executors} class contains utility methods to
* convert from other common forms to <tt>Callable</tt> classes.
*
* @see Executor
* @since 1.5
* @author Doug Lea
* @param <V> the result type of method <tt>call</tt>
*/
public interface Callable<V> {
/**
* Computes a result, or throws an exception if unable to do so.
*
* @return computed result
* @throws Exception if unable to compute a result
*/
V call() throws Exception;
}
把javaDoc上的代碼摘抄出來看下~
public interface ArchiveSearcher {
String search(String target);
}
public class App {
ExecutorService executor = ;
ArchiveSearcher searcher =
void showSearch(final String target)
throws InterruptedException {
Future<String> future = executor.submit(new Callable<String>() {
public String call() {
return searcher.search(target);
}
});
displayOtherThings(); // do other things while searching
try {
displayText(future.get()); // use future
} catch (ExecutionException ex) {
cleanup();
return;
}
}
}
簡單實用介紹：
/**
* 異步任務
*/
public class AsynchronousTask implements Callable<String> {
private String data;
public AsynchronousTask(String data) {
this.data = data;
}
public String call() throws Exception {
try {
System.out.println(Thread.currentThread().getName() + "AsynchronousTask start...");
//模擬異步任務的處理
Thread.sleep(1000);
System.out.println((Thread.currentThread().getName() + "AsynchronousTask end..."));
} catch (Exception ex) {
ex.printStackTrace();
}
//返回異步任務的處理結果
return "hello future";
}
}
public class FutureTest {
public static void main(String[] args) throws Exception {
ExecutorService executor = Executors.newFixedThreadPool(10);
//進行異步任務處理
Future<String> submit = executor.submit(new AsynchronousTask("futire test"));
System.out.println(Thread.currentThread().getName() + "FutureTest start");
//這裏使用sleep方法表示對其他業務邏輯的處理
//與此同時異步任務也在執行，從而充分利用了等待時間
Thread.sleep(100);
System.out.println(Thread.currentThread().getName() + "FutureTest end");
//submit.get()獲取異步執行結果
//如果異步任務call沒有執行完成，則依然會等待
System.out.println("數據" + submit.get());
}
}
Furure的簡單介紹和使用