1.Callable

1) Runnable, which performs an independent task but does not return a value. If you want a return value after the task is completed, you can use the callable interface;

2) Callable is a paradigm with type parameters. Its type parameter method is expressed as the value returned by the method call () instead of run (), and it must be used ExecutorService.submint () method.

difference:

1. Callable, which accepts a generic type and returns a value of this type in the call() method; however, runnable’s run() method has no return value;
2. Callable, whose call() method can throw an exception, while runnable’s run() method does not.

2. Business scenario:

In HTTP requests, the business processing process takes a long time, such as large queries, remote calls and other scenarios. The main thread that receives HTTP requests will be occupied all the time, and the number of threads in Tomcat thread pool is limited. Therefore, the number of HTTP requests accepted per unit time will decrease.

3. Code examples

1）controller

package com.liuxd.controller;

import com.liuxd.entity.Responses;
import com.liuxd.service.BusinessService;
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.RestController;

import java.util.concurrent.Callable;

@Slf4j
@RestController
public class AsyncCallableController {

    @Autowired
    private BusinessService businessService;

    @GetMapping(value = "/getData")
    public Callable<Responses<String>> getData() {

        log.info("HTTP request received...");

        Callable<Responses<String>> data = (() -> {
            return businessService.getData();
        });

        log.info("The task of the receiving HTTP request thread has been completed, exit!");

        return data;
    }

}

2) service

package com.liuxd.service;

import com.liuxd.entity.Responses;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;

@Slf4j
@Service
public class BusinessService {

    public Responses<String> getData(){

        log.info("Call the service method and start the execution...");

        try {
            Thread.sleep(2500L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        log.info("Call service method, end of execution!");

        return new Responses<>(0,"Done","SUCCESS");

    }

}

3) Print results