spring boot事务管理

spring boot集成事务十分的简单，只需要在启动类上面增加@EnableTransactionManagement注解，然后在需要实现事务的方法上添加@Transactional注解就可以了。下面我们根据上一次的代码来演示下。

首先，我们修改下启动类

package com.example.demo;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@SpringBootApplication
@MapperScan(basePackages = ("com.example.demo.mapper"))
@EnableTransactionManagement//开启springboot事务的支持
public class DemoApplication extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(DemoApplication.class);
    }

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

}

在service中添加一个修改方法

package com.example.demo.service;

import com.example.demo.model.Student;

public interface GetStudentService {

    public Student getStudentInfo();

    public int update();
}

package com.example.demo.service.impl;

import com.example.demo.mapper.StudentMapper;
import com.example.demo.model.Student;
import com.example.demo.service.GetStudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
public class GetStudentServiceImpl implements GetStudentService {

    @Autowired
    private StudentMapper studentMapper;

    @Override
    public Student getStudentInfo() {
        Student student = studentMapper.selectByPrimaryKey("122528");
        return student;
    }

    @Transactional//增加事务注解
    @Override
    public int update(){
        Student student = new Student();
        student.setId("122528");
        student.setName("李四");
        int ret = studentMapper.updateByPrimaryKey(student);

        int i = 100/0; //触发异常，测试更新事件会不会回滚
        return ret;
    }
}

在上面的类中特意引发了异常，用于我们的测试。最后在controlle中添加对修改方法的调用。

package com.example.demo.controller;

import com.example.demo.model.Student;
import com.example.demo.service.GetStudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class GetStudentController {

    @Autowired
    private GetStudentService getStudentService;

    @RequestMapping("/getStudent")
    public String getStudent(){
        Student student = getStudentService.getStudentInfo();
        return "学号=" + student.getId() + ";姓名=" + student.getName();
    }

    @RequestMapping("/updateStudent")
    public String updateStudent(){
        getStudentService.update();
        return "success";
    }
}

数据库中原始的姓名是张三，现在将他改为李四，访问地址http://127.0.0.1:8088/demo/updateStudent，最终结果报了异常，然后查看数据库中的值，发现没有发生变化，因此我们的事务注解生效了。

---

在上面的操作过程中，我发现了一个问题，在controller中如果使用private GetStudentServiceImpl getStudentServiceImpl;启动的时候就会报错：

Description:

The bean 'getStudentServiceImpl' could not be injected as a 'com.example.demo.service.impl.GetStudentServiceImpl' because it is a JDK dynamic proxy that implements:
    com.example.demo.service.GetStudentService

Action:

Consider injecting the bean as one of its interfaces or forcing the use of CGLib-based proxies by setting proxyTargetClass=true on @EnableAsync and/or @EnableCaching.

Process finished with exit code 1

对此有两种解决方法，一种是我上面的，将代码中的引用由实现类改为接口类即可。另外一种是在开启事务的注解上增加属性。即@EnableTransactionManagement(proxyTargetClass = true)，开启CGLIB代理也能解决。

因为开启事务时，会自动开启动态代理，默认的是开启的jdk动态代理。详细解释地址：https://blog.csdn.net/huang_550/article/details/76492600。这块目前还不清楚什么原理，后面再细研究。

spring boot热部署配置，增加pom.xml依赖

 <!-- spring boot热部署插件-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>true</scope>
            <optional>true</optional>
        </dependency>