生于忧患，死于安乐

在UsersServiceImpl中有两个事务方法

• InsertUsers() 和InsertCuser() 都是被事务注解所申明的方法；且InsertUsers中调用了InsertCuser
• InsertUsers使用REQUIRED行为传播
• InsertCusers使用REQUIRES_NEW行为传播

package com.springboot.study.demo1.service.impl;

import com.springboot.study.demo1.entity.Cuser;
import com.springboot.study.demo1.entity.Users;
import com.springboot.study.demo1.service.CuserService;
import com.springboot.study.demo1.service.UsersService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.transaction.support.TransactionSynchronizationManager;

import java.util.List;
import java.util.Map;

/**
 * @program: springboot_study
 * @description:
 * @author: yinkai
 * @create: 2020-03-02 15:31
 */
@Service
public class UsersServiceImpl implements UsersService {
    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Autowired
    private UsersService usersService;

    @Transactional(propagation = Propagation.REQUIRED)
    @Override
    public void InsertUsers() {

        jdbcTemplate.update("INSERT INTO users(id,name, age, email) VALUES (?, ?, ?, ?);", 111, "InsertUsers", 24, "InsertUsers@qq.com");
        //打印事务id
        List<Map<String, Object>> maps = jdbcTemplate.queryForList("SELECT TRX_ID FROM INFORMATION_SCHEMA.INNODB_TRX WHERE TRX_MYSQL_THREAD_ID = CONNECTION_ID( );");
        System.out.println(maps + TransactionSynchronizationManager.getCurrentTransactionName());

        //调用本service中另一个方法
        usersService.InsertCuser();

    }

    @Transactional(propagation = Propagation.REQUIRES_NEW)
    @Override
    public void InsertCuser() {

        jdbcTemplate.update("INSERT INTO users(id,name, age, email) VALUES (?, ?, ?, ?);", 112, "InsertUsers", 24, "InsertUsers@qq.com");
        //打印事务id
        List<Map<String, Object>> maps = jdbcTemplate.queryForList("SELECT TRX_ID FROM INFORMATION_SCHEMA.INNODB_TRX WHERE TRX_MYSQL_THREAD_ID = CONNECTION_ID( );");
        System.out.println(maps + TransactionSynchronizationManager.getCurrentTransactionName());
    }
}

我们来看看执行日志，可以看到两者打印的事务id相同。使用的是同一个事务。这违背了REQUIRES_NEW传播行为的语义了！

image.png

理论上此时两个方法分别会开启自己的事务才对呀？为什么InsertCuser方法没有开启事务？

如果理解了spring实现申明式事务的原理就都明白了。我们都知道spring底层是使用动态代理来实现事务切面的。所以就必须走代理对象调用方法才能使方法增强生效!
注意看代码中是如何调用InsertCuser方法的：InsertCuser(cuser);这就相当于同过this调用本类方法 this.InsertCuser(cuser);

此处的this指向目标对象而不是代理对象，因此调用this.InsertCuser()将不会执行InsertCuser事务切面，即不会执行事务增强，因此b方法的事务定义@Transactional(propagation = Propagation.REQUIRES_NEW)将不会实施，即结果是InsertCuser和InsertUsers方法的事务定义是一样的。

所以只要得到usersService的代理对象就行了~

可以使用自我注入的方式解决这个问题

代码修改如下

在UsersService 类中再注入一个UsersService 实例，然后通过这个实例属性进行InsertCuser方法的调用。岂不美哉？

package com.springboot.study.demo1.service.impl;

import com.springboot.study.demo1.entity.Cuser;
import com.springboot.study.demo1.entity.Users;
import com.springboot.study.demo1.service.CuserService;
import com.springboot.study.demo1.service.UsersService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.transaction.support.TransactionSynchronizationManager;

import java.util.List;
import java.util.Map;

/**
 * @program: springboot_study
 * @description:
 * @author: yinkai
 * @create: 2020-03-02 15:31
 */
@Service
public class UsersServiceImpl implements UsersService {
    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Autowired
    private UsersService usersService;

    @Transactional(propagation = Propagation.REQUIRED)
    @Override
    public void InsertUsers() {

        jdbcTemplate.update("INSERT INTO users(id,name, age, email) VALUES (?, ?, ?, ?);", 111, "InsertUsers", 24, "InsertUsers@qq.com");
        //打印事务id
        List<Map<String, Object>> maps = jdbcTemplate.queryForList("SELECT TRX_ID FROM INFORMATION_SCHEMA.INNODB_TRX WHERE TRX_MYSQL_THREAD_ID = CONNECTION_ID( );");
        System.out.println(maps + TransactionSynchronizationManager.getCurrentTransactionName());

        //调用本service中另一个方法
        usersService.InsertCuser();

    }

    @Transactional(propagation = Propagation.REQUIRES_NEW)
    @Override
    public void InsertCuser() {

        jdbcTemplate.update("INSERT INTO users(id,name, age, email) VALUES (?, ?, ?, ?);", 112, "InsertUsers", 24, "InsertUsers@qq.com");
        //打印事务id
        List<Map<String, Object>> maps = jdbcTemplate.queryForList("SELECT TRX_ID FROM INFORMATION_SCHEMA.INNODB_TRX WHERE TRX_MYSQL_THREAD_ID = CONNECTION_ID( );");
        System.out.println(maps + TransactionSynchronizationManager.getCurrentTransactionName());
    }
}

执行如下，已经不是同一个事务了

image.png

还可以使用这种较为优雅的方式

 ((UsersService) AopContext.currentProxy())