Future+Callable异步查询

秒速五厘米 2023-06-27 08:58 6阅读 0赞

## Future+Callable异步查询 ##

*  Future (java.util.concurrent)  
    表示异步计算的结果。提供了检查计算是否完成的方法，以等待计算的完成，并获取计算的结果。
 *  Callable (java.util.concurrent)  
    Callable类似于Runnable，两者都是为那些其实例可能被另一个线程执行的类设计的。两者的区别是：Runnable不会反会返回结果，无法抛出经过检查的异常；Callable可以有返回值，返回值可以被Future拿到，能够抛出经过检查的异常。
    
        /** * 异步回调： * Future * Callable<T> */
        public class AsynchronousCallback { 
        
            public static void main(String[] args) { 
                String[] addresss = { "北京市","上海市"};
        
                List<Future<List<UserEntity>>> futureList = new ArrayList<>();
                for (String address: addresss) { 
                    futureList.add(ThreadPoolExecutorFactory.executor.submit(new TaskCallable(address)));
                }
        
                List<UserEntity> users = new ArrayList<>();
                for (Future<List<UserEntity>> user: futureList) { 
                    try { 
                    	//获取future中的返回值
                        List<UserEntity> list = user.get();
                        if (!CollectionUtils.isEmpty(list)){ 
                            users.addAll(list);
                        }
                    } catch (InterruptedException e) { 
                        e.printStackTrace();
                    } catch (ExecutionException e) { 
                        e.printStackTrace();
                    }
                }
                System.out.println(users);
            }
        }
 *  实现Callable， call方法中调用查询数据接口
    
        class TaskCallable implements Callable<List<UserEntity>> { 
        
            private String address;
        
            public TaskCallable(String address) { 
                this.address = address;
            }
        
            @Override
            public List<UserEntity> call() throws InterruptedException { 
                System.out.println(address);
                UserServiceImpl userService = new UserServiceImpl();
                List<UserEntity> userServiceById = userService.findById(address);
                return userServiceById;
            }
        }
 *  返回结果
    
        北京市
        上海市
        [UserEntity{ id=1, username='小红', sex='女', age=18, address='北京市'}, UserEntity{ id=2, username='小刚', sex='男', age=18, address='北京市'}, UserEntity{ id=3, username='小青', sex='女', age=18, address='北京市'}, UserEntity{ id=4, username='小率', sex='男', age=18, address='北京市'}, UserEntity{ id=4, username='小率', sex='男', age=18, address='北京市'}, UserEntity{ id=6, username='小1', sex='女', age=18, address='上海市'}, UserEntity{ id=7, username='小2', sex='男', age=18, address='上海市'}, UserEntity{ id=8, username='小3', sex='女', age=18, address='上海市'}, UserEntity{ id=9, username='小4', sex='男', age=18, address='上海市'}, UserEntity{ id=10, username='小5', sex='男', age=18, address='上海市'}]