@Transactional 的使用

@Transactional 使用注意点

• @Transactional 注解只能应用到 public 方法或者类上才有效
• 首先开启 @EnableTransactionManagement，但是Spring Boot已经默认开启 @EnableTransactionManagement 。

Spring Boot 如何默认开启@EnableTransactionManagement

查看类 TransactionAutoConfiguration

org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration      

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package org.springframework.boot.autoconfigure.transaction;

import java.util.Collection;
import java.util.stream.Collectors;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
import org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration;
...

@Configuration
@ConditionalOnClass({PlatformTransactionManager.class})
@AutoConfigureAfter({JtaAutoConfiguration.class, HibernateJpaAutoConfiguration.class, DataSourceTransactionManagerAutoConfiguration.class, Neo4jDataAutoConfiguration.class})
@EnableConfigurationProperties({TransactionProperties.class})
public class TransactionAutoConfiguration {
    public TransactionAutoConfiguration() {
    }

...

    @Configuration
    @ConditionalOnBean({PlatformTransactionManager.class})
    @ConditionalOnMissingBean({AbstractTransactionManagementConfiguration.class})
    public static class EnableTransactionManagementConfiguration {
        public EnableTransactionManagementConfiguration() {
        }

        @Configuration
        @EnableTransactionManagement(
            proxyTargetClass = true
        )
        @ConditionalOnProperty(
            prefix = "spring.aop",
            name = {"proxy-target-class"},
            havingValue = "true",
            matchIfMissing = true
        )
        public static class CglibAutoProxyConfiguration {
            public CglibAutoProxyConfiguration() {
            }
        }

        @Configuration
        @EnableTransactionManagement(
            proxyTargetClass = false
        )
        @ConditionalOnProperty(
            prefix = "spring.aop",
            name = {"proxy-target-class"},
            havingValue = "false",
            matchIfMissing = false
        )
        public static class JdkDynamicAutoProxyConfiguration {
            public JdkDynamicAutoProxyConfiguration() {
            }
        }
    }

...
}      

Spring Boot 引入了一个事务自动配置类 TransactionAutoConfiguration。该类已经默认添加EnableTransactionManagement

@Transactional 的简单使用

1) 只需在方法加上 @Transactional 注解

@Override
@Transactional
public String testTransactional(boolean flag){
    testMapper.insert(Test);
    if (flag) {
        throw new RuntimeException("run time error");
    }
    return "成功";
}      

flag = true。该事务没有提交 commit，因为遇到 RuntimeException 异常该事务进行了回滚，数据库中插入数据失败。

@Transactional(propagation = Propagation.REQUIRED, rollbackFor = Exception.class)
@Override
public String save(ProductModuleConfig productModuleConfig){
    testMapper.insert(Test);
    try {
        String a = null;
        boolean equals = a.equals("2");
    } catch (Exception e) {
        e.printStackTrace();
    }
    return "成功";
}      

• save 方法无 @Transactional 注解

• save 方法有 @Transactional 注解