事务与异步脏数据问题

冷不防 2023-06-29 05:47 24阅读 0赞

# 1、事务未提交，异步获取不到数据 #

package com.spring.pro.service.impl;
    
    import java.util.concurrent.CompletableFuture;
    import java.util.concurrent.TimeUnit;
    
    import javax.annotation.Resource;
    
    import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
    import org.springframework.stereotype.Component;
    import org.springframework.transaction.annotation.Transactional;
    
    import com.alibaba.fastjson.JSON;
    import com.spring.pro.entity.User;
    import com.spring.pro.mapper.UserMapper;
    import com.spring.pro.service.UserService;
    
    import lombok.extern.slf4j.Slf4j;
    
    /**
     * @Title: UserServiceImpl.java
     * @ProjectName com.spring.pro.threadpool
     * @Description:
     * @author ybwei
     * @date 2020年1月10日 下午4:37:35
     */
    @Component("userService")
    @Slf4j
    public class UserServiceImpl implements UserService {
    
    	@Resource
    	private UserMapper userMapper;
    	@Resource(name = "taskExecutor")
    	private ThreadPoolTaskExecutor threadPoolTaskExecutor;
    
    	@Override
    	@Transactional
    	public void testTransactional() {
    		User user = new User();
    		user.setName("张三");
    		user.setAge(12);
    		userMapper.insertSelective(user);
    		// 异步
    		CompletableFuture.runAsync(() -> {
    			handleDb(user.getId());
    		}, threadPoolTaskExecutor);
    		try {
    			TimeUnit.SECONDS.sleep(1);// 休眠1秒，测试使用，保证异步执行时，事务未提交
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    		log.info("添加后user:{}", JSON.toJSONString(user));
    	}
    
    	private void handleDb(Long id) {
    		User user = userMapper.selectByPrimaryKey(id);
    		log.info("异步user:{}", JSON.toJSONString(user));
    	}
    
    }

打印日志如下

[INFO ] 2020-01-10 16:52:34.907 [taskExecutor-1] c.s.pro.service.impl.UserServiceImpl - 异步user:null
    [INFO ] 2020-01-10 16:52:35.659 [http-nio-8080-exec-5] c.s.pro.service.impl.UserServiceImpl - 添加后user:{"age":12,"id":47025,"name":"张三"}

因为事务还未提交，所以异步中获取user是空的。

# 2、事务已提交，获取数据库数据 #

异步中的user，我们想要的是事务提交后的数据

package com.spring.pro.service.impl;
    
    import java.util.concurrent.CompletableFuture;
    import java.util.concurrent.TimeUnit;
    
    import javax.annotation.Resource;
    
    import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
    import org.springframework.stereotype.Component;
    import org.springframework.transaction.annotation.Transactional;
    
    import com.alibaba.fastjson.JSON;
    import com.spring.pro.entity.User;
    import com.spring.pro.mapper.UserMapper;
    import com.spring.pro.service.UserService;
    
    import lombok.extern.slf4j.Slf4j;
    
    /**
     * @Title: UserServiceImpl.java
     * @ProjectName com.spring.pro.threadpool
     * @Description:
     * @author ybwei
     * @date 2020年1月10日 下午4:37:35
     */
    @Component("userService")
    @Slf4j
    public class UserServiceImpl implements UserService {
    
    	@Resource
    	private UserMapper userMapper;
    	@Resource(name = "taskExecutor")
    	private ThreadPoolTaskExecutor threadPoolTaskExecutor;
    
    	@Override
    	@Transactional
    	public void testTransactional() {
    		User user = new User();
    		user.setName("张三");
    		user.setAge(12);
    		userMapper.insertSelective(user);
    		// 异步
    		CompletableFuture.runAsync(() -> {
    			handleDb(user.getId());
    		}, threadPoolTaskExecutor);
    		log.info("添加后user:{}", JSON.toJSONString(user));
    	}
    
    	private void handleDb(Long id) {
    		try {
    			TimeUnit.SECONDS.sleep(1);// 休眠1秒，测试使用，保证异步执行时，事务已提交
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    		User user = userMapper.selectByPrimaryKey(id);
    		log.info("异步user:{}", JSON.toJSONString(user));
    	}
    
    }

打印日志如下：

[INFO ] 2020-01-10 16:57:14.862 [http-nio-8080-exec-7] c.s.pro.service.impl.UserServiceImpl - 添加后user:{"age":12,"id":47027,"name":"张三"}
    [INFO ] 2020-01-10 16:57:15.866 [taskExecutor-2] c.s.pro.service.impl.UserServiceImpl - 异步user:{"age":12,"createTime":1578646634000,"id":47027,"name":"张三","points":0,"status":0,"updateTime":1578646634000}

# 3、解决问题 #

第二步，休眠1秒，并不是解决问题的方案。

package com.spring.pro.service.impl;
    
    import java.util.concurrent.CompletableFuture;
    
    import javax.annotation.Resource;
    
    import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
    import org.springframework.stereotype.Component;
    import org.springframework.transaction.annotation.Transactional;
    import org.springframework.transaction.support.TransactionSynchronizationAdapter;
    import org.springframework.transaction.support.TransactionSynchronizationManager;
    
    import com.alibaba.fastjson.JSON;
    import com.spring.pro.entity.User;
    import com.spring.pro.mapper.UserMapper;
    import com.spring.pro.service.UserService;
    
    import lombok.extern.slf4j.Slf4j;
    
    /**
     * @Title: UserServiceImpl.java
     * @ProjectName com.spring.pro.threadpool
     * @Description:
     * @author ybwei
     * @date 2020年1月10日 下午4:37:35
     */
    @Component("userService")
    @Slf4j
    public class UserServiceImpl implements UserService {
    
    	@Resource
    	private UserMapper userMapper;
    	@Resource(name = "taskExecutor")
    	private ThreadPoolTaskExecutor threadPoolTaskExecutor;
    
    	@Override
    	@Transactional
    	public void testTransactional() {
    		User user = new User();
    		user.setName("张三");
    		user.setAge(12);
    		userMapper.insertSelective(user);
    		TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronizationAdapter() {
    			@Override
    			public void afterCommit() {
    				// 异步
    				CompletableFuture.runAsync(() -> {
    					handleDb(user.getId());
    				}, threadPoolTaskExecutor);
    			}
    		});
    		log.info("添加后user:{}", JSON.toJSONString(user));
    	}
    
    	private void handleDb(Long id) {
    		User user = userMapper.selectByPrimaryKey(id);
    		log.info("异步user:{}", JSON.toJSONString(user));
    	}
    
    }

TransactionSynchronizationManager.registerSynchronization可以保证事务提交后，才会执行afterCommit里面的异步方法。