爲何多線程、junit 中沒法使用spring 依賴注入？

時間 2019-11-12

標籤爲何多線程 junit 沒法使用 spring 依賴注入欄目 Java 简体版

原文原文鏈接

　　爲何多線程、junit 中沒法使用spring 依賴注入？這個問題，其實體現了，咱們對spring已依賴太深，以致於不想本身寫實例了。那麼究竟是爲何在多線程和junit單元測試中不能使用依賴注入呢？java

1、爲何多線程下spring的依賴注入失效了呢？spring

　　答：由於spring爲了考慮安全性問題，在多線程狀況下，不支持直接使用 @Resouce 註解方式進行直接的bean注入，那麼也就是說，若是在多線程調用該注入實例化的變量時，將會報NullPointerException 。json

　　解決辦法：多線程狀況下，經過調用的service進行傳入須要操做的bean變量，而多線程只是將前臺工做轉移到後臺。以下：api

# CalculateServiceImpl.java 服務實現，傳入須要調用的bean

    package com.xx.op.user;
    
    import com.xx.note.dubbo.dto.CertificateApplyDto;
    import com.xx.con.dubbo.api.ContractRemoteService;
    import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    import javax.annotation.Resource;
    
    public class CalculateServiceImpl implements CalculateService {
    
        private Logger logger = LoggerFactory.getLogger(this.getClass());
        
        @Resource(name = "threadPoolTaskExecutor")
        private ThreadPoolTaskExecutor threadPoolTaskExecutor;
        
        @Resource                // 默認name可寫可不寫
        private ContractRemoteService contractRemoteService;
        
        @Override
        public void doSth(String userId) throws Exception
            CertificateApplyDto certificateApplyDto = new CertificateApplyDto();
            certificateApplyDto.setBorrowNid(userId);
            SignContractThread signContractThread = new SignContractThread(contractRemoteService, certificateApplyDto);
            threadPoolTaskExecutor.execute(signContractThread);                //異步簽署協議
        }
    }

# SignContractThread.java 異步實現調用安全

    package com.xx.cc.common.async;

    import com.alibaba.fastjson.JSON;
    import com.dianping.cat.message.Event;
    import com.xx.framework.dto.ResponseEntity;
    import com.xx.no.dubbo.dto.CertificateApplyDto;
    import com.xx.con.dubbo.api.ContractRemoteService;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;

    public class SignContractThread implements Runnable {
        private Logger logger = LoggerFactory.getLogger(this.getClass());

        /**
         * 沒法使用依賴注入實現多純種的bean, 從外部傳入方式
         */
        private ContractRemoteService contractRemoteService;

        private CertificateApplyDto certificateApplyDto;

        public SignContractThread(ContractRemoteService contractRemoteService, CertificateApplyDto certificateApplyDto) {
            this.contractRemoteService = contractRemoteService;
            this.certificateApplyDto = certificateApplyDto;
        }

        @Override
        public void run() {
            String requestParamJson = JSON.toJSONString(this.doSSt);
            logger.debug("===========>>>>> 異步調用, 參數： {} ==============>>>>>>>>>", requestParamJson);
            try {
                ResponseEntity responseEntity = contractRemoteService.doSSt(certificateApplyDto);
                logger.debug("<<<<<<<<<<=========== 異步調用，method:doSSt，返回結果：{}", responseEntity);
                EE.logEvent("Monitor_signContract", "asyncSignContractResult", Event.SUCCESS, JSON.toJSONString(responseEntity));
            } catch (Exception e) {
                logger.error("==-------===異步調用，發生異常，請求參數: {}, 異常-{}", requestParamJson, e););
                throw new RuntimeException("異步調用_doSSt，發生異常", e);
            } finally {
                // ... 調用完畢
            }
        }
    }

　　這樣，經過傳入外部依賴注入的bean，線程進行調用，便可避免線程沒法注入bean的問題了。固然了，你可能還會想到使用 getBean的方法獲取，其實也是能夠的，不過應該有必定的危險性，由於至關於你得再次將applicationContext裏的東西再實例化一遍。服務器

2、junit中沒法使用依賴注入的問題？mybatis

　　答：由於junit通常會走最小化的方式，而非每次都要將整個框架的東西載入，從而減小加載時間。固然，若是確實須要，這個問題，其實目前在高版本的junit中，已經不存在了，經過加載 SpringJUnit4ClassRunner，便可進行注入值。多線程

　　解決方案1：使用高版本的junit進行測試，以下：app

    
    package com.xx.mybatis3spring3intg.junit;

    import java.util.List;

    import com.xx.mybatis3spring.bean.User;
    import com.xx.mybatis3spring.service.UserService;
    
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.test.context.ContextConfiguration;
    import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    
    @RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration({"/config/application*.xml"})
    public class UserServiceTest {
        
        @Resource
        private UserService userService;
        
        @Test
        public void c1() {
            List<User> userList = userService.query(new User());
            System.out.println(userList);
        }

    }

　　解決方案2：經過getBean的方式獲取須要的bean，由於僅僅是單元測試，加載資源稍微多些也沒有關係。框架

    package com.xx.c.order;

    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationCoimport com.xx.c.service.order.OrderService;

    public class OrderServiceTest {
        private static ApplicationContext context=new ClassPathXmlApplicationContext("applicationContext.xml");
        private static OrderService orderService = (OrderService)context.getBean("orderService");
        private static Object getBean(String name) {
            if (context == null) {
                context = new ClassPathXmlApplicationContext("applicationContext.xml");
            }
            return context.getBean(name);
        }
        public static void main(String[] args) {
            String borrowNid = "11111111111";
            com.xx.c.dubboapi.biz.OutApiManager service = (com.xx.c.dubboapi.biz.OutApiManager)getBean("outApiManagerImpl");
            System.out.println("========"+service.getWang(borrowNid));
            System.out.println("========"+service.getRepayList("111111111111111111"));
       }    
    }