SpringBoot设置事务管理

　　关于事务就不介绍了，前面在研究spring的时候就已经研究过了，参考:https://www.cnblogs.com/qlqwjy/p/7296493.html

　　这里直接研究springboot中事务的开启以及测试方法。

　　在Spring Boot中推荐使用@Transactional注解来申明事务。

首先需要导入依赖：

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>

　　当引入jdbc依赖之后，Spring Boot会自动默认分别注入DataSourceTransactionManager或JpaTransactionManager，所以我们不需要任何额外配置就可以用@Transactional注解进行事务的使用。

　　

　　在Service中添加@Transactional注解：

===================测试事务效果===========

Service层代码:

package cn.qlq.service.impl.user;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import cn.qlq.bean.user.User;import cn.qlq.mapper.user.UserMapper;
import cn.qlq.service.user.UserService;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;

    @Override
    public void addUser(User user) {
        userMapper.insert(user);
        int i = 1 / 0;
    }

}

(1)测试未添加事务

　　数据库原来记录:

测试添加后查看日志:(插入数据之后报异常)

2019-02-21 16:25:20.983  INFO 20960 --- [nio-8088-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring FrameworkServlet 'dispatcherServlet'
2019-02-21 16:25:20.984  INFO 20960 --- [nio-8088-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization started
2019-02-21 16:25:21.004  INFO 20960 --- [nio-8088-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in 20 ms
2019-02-21 16:25:21.047  INFO 20960 --- [nio-8088-exec-1] cn.qlq.action.UserController             : user -> User [id=null, username=2, password=2, userfullname=2, createtime=Thu Feb 21 16:25:21 CST 2019, isdeleted=null, sex=女, address=2]
2019-02-21 16:25:21.320 DEBUG 20960 --- [nio-8088-exec-1] cn.qlq.mapper.user.UserMapper.insert     : ==>  Preparing: insert into user (id, username, password, userfullname, createtime, isdeleted, sex, address) values (?, ?, ?, ?, ?, ?, ?, ?) 
2019-02-21 16:25:21.335 DEBUG 20960 --- [nio-8088-exec-1] cn.qlq.mapper.user.UserMapper.insert     : ==> Parameters: null, 2(String), 2(String), 2(String), 2019-02-21(Date), null, 女(String), 2(String)
2019-02-21 16:25:21.674 DEBUG 20960 --- [nio-8088-exec-1] cn.qlq.mapper.user.UserMapper.insert     : <==    Updates: 1
java.lang.ArithmeticException: / by zero
    at cn.qlq.service.impl.user.UserServiceImpl.addUser(UserServiceImpl.java:27)
    at cn.qlq.action.UserController.addUser(UserController.java:31)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:798)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1434)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
2019-02-21 16:25:21.763  WARN 20960 --- [nio-8088-exec-1] .m.m.a.ExceptionHandlerExceptionResolver : Resolved exception caused by Handler execution: java.lang.ArithmeticException: / by zero

 查看数据库:(数据增加，没有事务回滚)

(2)测试添加事务

只需在类加上@Transactional注解就可以了。

测试查看日志同上面一样，但是事务进行回滚了，只是没有打出日志。(下次提交发现id会跳过本次提交的值)

查看数据库记录:

补充：原理理解

　　在再次使用事务的时候发现其回滚没有打印日志，于是就想的研究一下原理。

　　其自动配置是在springboot-autoconfig-xxx.jar中。入口类是：DataSourceTransactionManagerAutoConfiguration

（1）查看DataSourceTransactionManagerAutoConfiguration源码：

/** <a href="http://www.cpupk.com/decompiler">Eclipse Class Decompiler</a> plugin, Copyright (c) 2017 Chen Chao. */
package org.springframework.boot.autoconfigure.jdbc;

import javax.sql.DataSource;

import org.springframework.beans.factory.ObjectProvider;
import org.springframework.boot.autoconfigure.AutoConfigureOrder;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
import org.springframework.boot.autoconfigure.transaction.TransactionManagerCustomizers;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.PlatformTransactionManager;

/**
 * {@link EnableAutoConfiguration Auto-configuration} for
 * {@link DataSourceTransactionManager}.
 *
 * @author Dave Syer
 * @author Stephane Nicoll
 * @author Andy Wilkinson
 * @author Kazuki Shimizu
 * @since 1.0.0
 */
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ JdbcTemplate.class, PlatformTransactionManager.class })
@AutoConfigureOrder(Ordered.LOWEST_PRECEDENCE)
@EnableConfigurationProperties(DataSourceProperties.class)
public class DataSourceTransactionManagerAutoConfiguration {

    @Configuration(proxyBeanMethods = false)
    @ConditionalOnSingleCandidate(DataSource.class)
    static class DataSourceTransactionManagerConfiguration {

        @Bean
        @ConditionalOnMissingBean(PlatformTransactionManager.class)
        DataSourceTransactionManager transactionManager(DataSource dataSource,
                ObjectProvider<TransactionManagerCustomizers> transactionManagerCustomizers) {
            DataSourceTransactionManager transactionManager = new DataSourceTransactionManager(dataSource);
            transactionManagerCustomizers.ifAvailable((customizers) -> customizers.customize(transactionManager));
            return transactionManager;
        }

    }

}

ConditionalOnClass表示在当前类路径下存在对应的类。

第一步：去掉上面的pom配置，并且去掉JPA等配置，发现不存在PlatformTransactionManager类。(没有这个class类，但是没报错是因为是class文件不会再次编译)

如果需要我们自己写判断可以用name判断，值是包全路径。源码如下：

@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnClassCondition.class)
public @interface ConditionalOnClass {

    Class<?>[] value() default {};

    String[] name() default {};

}

第二部：加上上面的pom配置发现在当前工程的classpath环境中可以找到上面类。

　　也可以在反编译的class文件中加断点测试，如果类路径有上面两个类会进入断点创建transactionManager对象；如果不存在不会进入断点。

在我们需要设置自己的事务管理器的时候可以重新返回一个PlatformTransactionManager对象，这些经常在使用动态数据源的时候需要设置自己的事务管理器，如下：

    @Bean
    public PlatformTransactionManager transactionManager() {
        // 配置事务管理, 使用事务时在方法头部添加@Transactional注解即可
        return new DataSourceTransactionManager(dynamicDataSource());
    }

 (2)