高效开发：Java中Future的使用（Future代表的是异步执行的结果）

1、Future是java 1.5引入的一个interface，可以方便的用于异步结果的获取。

2、Future代表的是异步执行的结果，意思是当异步执行结束之后，返回的结果将会保存在Future中。

那么我们什么时候会用到Future呢？ 一般来说，当我们执行一个长时间运行的任务时，使用Future就可以让我们暂时去处理其他的任务，等长任务执行完毕再返回其结果。

经常会使用到Future的场景有：1. 计算密集场景。2. 处理大数据量。3. 远程方法调用等，都是耗时比较长的需要等待的任务。

上代码例子：Controller层

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import java.util.concurrent.Future;/**      * 首页异步请求统计接口      *      * @return      */     @RequestMapping(value = "/getAssetAsyncComponent", method = { RequestMethod.GET })     public BaseResult getAssetAsyncComponent() throws Exception {           RequestAttributes requestAttributes = RequestContextHolder.currentRequestAttributes();           long currentTimeMillis = System.currentTimeMillis();           Future<Map<String, Object>> countAssetInfoByAssetType = assetMgrAsyncComponentTask                 .countAssetInfoByAssetType(requestAttributes);         Future<Map<String, Object>> getCountUnAsset = assetMgrAsyncComponentTask.getCountUnAsset(requestAttributes);         Future<Map<String, Object>> getAssetFoundTaskTop = assetMgrAsyncComponentTask                 .getAssetFoundTaskTop(requestAttributes);         Future<Map<String, Object>> listBusinessHomePage = assetMgrAsyncComponentTask                 .listBusinessHomePage(requestAttributes);         Future<Map<String, Object>> getTop5Business = assetMgrAsyncComponentTask.getTop5Business(requestAttributes);           for (;;) {             if (countAssetInfoByAssetType.isDone() && getCountUnAsset.isDone() && getAssetFoundTaskTop.isDone()                     && listBusinessHomePage.isDone() && getTop5Business.isDone()) {                 // 5个任务都调用完成，退出循环等待                 break;             }             Thread.sleep(300);         }           Map<String, Object> map = new HashMap<String, Object>();         map.put("countAssetInfoByAssetType", countAssetInfoByAssetType.get());         map.put("getCountUnAsset", getCountUnAsset.get());         map.put("getAssetFoundTaskTop", getAssetFoundTaskTop.get());         map.put("listBusinessHomePage", listBusinessHomePage.get());         map.put("getTop5Business", getTop5Business.get());           long currentTimeMillis1 = System.currentTimeMillis();         System.out.println("首页 第一次请求的时候  异步获取全部的数据 task任务总耗时:" + (currentTimeMillis1 - currentTimeMillis) + "ms");           return new BaseResult(map);     }

　　下一层加注解异步@Async即可

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import org.springframework.scheduling.annotation.AsyncResult;@Async     public Future<Map<String, Object>> countAssetInfoByAssetType(RequestAttributes requestAttributes) {         Map<String, Object> resultsMap = new HashMap<String, Object>();         long begin = System.currentTimeMillis();         try {             RequestContextHolder.setRequestAttributes(requestAttributes, true);             BaseResult baseResult = assetInfoQueryService.countAssetInfoByAssetType();             resultsMap = (Map<String, Object>) baseResult.getData();         } catch (Exception e) {             resultsMap.put("error", "countAssetInfoByAssetType 接口异常");         }         long end = System.currentTimeMillis();         System.out.println("countAssetInfoByAssetType 接口 耗时(秒)=" + (end - begin) / 1000.0);         return new AsyncResult<Map<String, Object>>(resultsMap);     }

　　也可以去看 https://blog.51cto.com/u_15287666/2976131 此博主的文章