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。