使用CompletableFuture实现业务服务的异步调用实战代码

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假如我有一个订单相关的统计接口，需要返回3样数据：今日订单数、今日交易额、总交易额。

一般的我们的做法是串行调用3个函数，把调用返回的结果返回给调用者，这3次调用时串行执行的，如果每个调用耗时1秒的话，3次调用总耗时就是3秒。

这种做法效率非常低，因为3次调用之间无所谓先后顺序，所以采用并行执行效率会更好。比如使用线程池ExecutorService实现异步调用。

其实Java8提供了一个非常牛逼的CompletableFuture类，也可以实现异步化：

 import lombok.extern.slf4j.Slf4j;

 import org.springframework.stereotype.Service;

 import java.util.concurrent.CompletableFuture;

 import java.util.concurrent.TimeUnit;

 @Slf4j

 @Service

 public class OrderService {

     /**

      * 今日订单数

      *

      * @return

      */

     public CompletableFuture<String> todayOrderCount() {

         return CompletableFuture.supplyAsync(() -> this.getTodayOrderCount());

     }

     public CompletableFuture<String> todayTurnover() {

         return CompletableFuture.supplyAsync(() -> this.getTodayTurnover());

     }

     public CompletableFuture<String> totalTurnover() {

         return CompletableFuture.supplyAsync(() -> this.getTotalTurnover());

     }

     private String getTodayOrderCount() {

         System.out.println(">>>>>>> 查询今日订单数:" + Thread.currentThread().getName());

         try {

             TimeUnit.SECONDS.sleep(1);

         } catch (InterruptedException e) {

             e.printStackTrace();

         }

         return "50";

     }

     /**

      * 今日交易额

      *

      * @return

      */

     private String getTodayTurnover() {

         System.out.println(">>>>>>> 查询今日交易额:" + Thread.currentThread().getName());

         try {

             TimeUnit.SECONDS.sleep(1);

         } catch (InterruptedException e) {

             e.printStackTrace();

         }

         return "200";

     }

     /**

      * 总交易额

      *

      * @return

      */

     private String getTotalTurnover() {

         System.out.println(">>>>>>> 查询总交易额:" + Thread.currentThread().getName());

         try {

             TimeUnit.SECONDS.sleep(1);

         } catch (InterruptedException e) {

             e.printStackTrace();

         }

         return "800";

     }

 }

 import com.alibaba.fastjson.JSONObject;

 import com.example.sb.service.test.impl.OrderService;

 import lombok.extern.slf4j.Slf4j;

 import org.springframework.beans.factory.annotation.Autowired;

 import org.springframework.web.bind.annotation.GetMapping;

 import org.springframework.web.bind.annotation.RequestMapping;

 import org.springframework.web.bind.annotation.RestController;

 import java.util.concurrent.CompletableFuture;

 @Slf4j

 @RestController

 @RequestMapping("/order")

 public class OrderController {

     @Autowired

     private OrderService orderService;

     @GetMapping("/report")

     public JSONObject report() {

         long start = System.currentTimeMillis();

         JSONObject json = orderReport();

         System.out.println("耗时:" + (System.currentTimeMillis() - start));

         return json;

     }

     private JSONObject orderReport() {

         CompletableFuture<String> todayOrderCountFuture = orderService.todayOrderCount();

         CompletableFuture<String> todayTurnoverFuture = orderService.todayTurnover();

         CompletableFuture<String> totalTurnoverFuture = orderService.totalTurnover();

         JSONObject json = new JSONObject();

         todayOrderCountFuture.whenComplete((v, t) -> {

             json.put("todayOrderCountFuture", v);

         });

         todayTurnoverFuture.whenComplete((v, t) -> {

             json.put("todayTurnoverFuture", v);

         });

         totalTurnoverFuture.whenComplete((v, t) -> {

             json.put("totalTurnoverFuture", v);

         });

         CompletableFuture.allOf(todayOrderCountFuture, todayTurnoverFuture, totalTurnoverFuture)

                 .thenRun(() -> System.out.println("完成！！！！"))

                 .join();

         return json;

     }

 }