錯誤示例，同一個類中使用非同步方法：

package com.xqnode.learning.controller;

import com.fasterxml.jackson.core.JsonProcessingException;
import org.springframework.scheduling.annotation.Async;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import
 
 org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

@RestController
@RequestMapping("/test")
public class TestController {

    @GetMapping("/async")
    public Map<Object, Object> test() throws InterruptedException, JsonProcessingException {
        System.out.println("接收到請求。。。"
 
);
        task();
        Map<Object, Object> map = new HashMap<>();
        System.out.println("請求結束。。。");
        map.put("msg", "操作成功");
        map.put("code", "0");
        return map;
    }

    @Async
    void task() throws InterruptedException {
        TimeUnit.SECONDS.sleep(5);
        System.out.println("執行緒任務執行結束。。。"
 
);
    }
}

來分析下錯誤的原因：
當我使用postman呼叫該介面的時候發現，我預想中的立即返回並沒有發生。後來查詢資料發現，我在同一個controller中呼叫，在介面方法中呼叫了非同步方法。這是不會生效的。

正確示例：

package com.xqnode.learning.controller;

import com.xqnode.learning.service.AsyncService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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.HashMap;
import java.util.Map;

@RestController
@RequestMapping("/test")
public class TestController {

    private static final Logger LOG = LoggerFactory.getLogger(TestController.class);

    @Autowired
    private AsyncService asyncService;

    @GetMapping("/async")
    public Map<Object, Object> test() throws InterruptedException {
        LOG.info("接收到請求。。。");
        asyncService.task();
        Map<Object, Object> map = new HashMap<>();
        LOG.info("請求結束。。。");
        map.put("msg", "操作成功");
        map.put("code", "0");
        return map;
    }
}

將非同步呼叫放到service中：

package com.xqnode.learning.service;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;

import java.util.concurrent.TimeUnit;

@Service
public class AsyncService {

    private static final Logger LOG = LoggerFactory.getLogger(AsyncService.class);


    @Async("asyncExecutor")
    public void task() throws InterruptedException {

        TimeUnit.SECONDS.sleep(5);
        LOG.info("執行緒任務執行結束。。。");
    }
}

這時候再重啟專案請求該介面，就會發現介面可以立即返回值。而task任務是非同步執行的，5秒之後才會列印結果：