08-事务源码解析

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

<!-- 注册数据源 -->
<bean id="dataSource" class="...">
    <property name="" value=""/>
</bean>

<!-- 注册事务管理器 -->
<bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
    <property name="dataSource" ref="dataSource" />
</bean>

<!-- 开启事务注解 -->
<tx:annotation-driven transaction-manager="txManager" />

@EnableTransactionManagement//重要
@Configuration
public class TxConfig {

    @Bean
    public DataSource dataSource() {
        ComboPooledDataSource dataSource = new ComboPooledDataSource();
        dataSource.setUser("...");
        dataSource.setPassword("...");
        dataSource.setDriverClass("...");
        dataSource.setJdbcUrl("...");
        return dataSource;
    }
  
    //重要
    @Bean
    public PlatformTransactionManager platformTransactionManager() {
        return new DataSourceTransactionManager(dataSource());//放入数据源
    }
}

public interface PlatformTransactionManager {
    //获取一个Transaction
    TransactionStatus getTransaction(TransactionDefinition var1) throws TransactionException;
    //提交事务
    void commit(TransactionStatus var1) throws TransactionException;
    //回滚事务
    void rollback(TransactionStatus var1) throws TransactionException;
}

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

@Configuration
//在类路径下有这个类存在PlatformTransactionManager时，这个配置类才会生效
//而前面我们已经引入了spring-boot-starter-jdbc，那自然是存在了
@ConditionalOnClass({ JdbcTemplate.class, PlatformTransactionManager.class })
@AutoConfigureOrder(Ordered.LOWEST_PRECEDENCE)
@EnableConfigurationProperties(DataSourceProperties.class)
public class DataSourceTransactionManagerAutoConfiguration {

    @Configuration
    @ConditionalOnSingleCandidate(DataSource.class)
    static class DataSourceTransactionManagerConfiguration {

        private final DataSource dataSource;

        private final TransactionManagerCustomizers transactionManagerCustomizers;

        DataSourceTransactionManagerConfiguration(DataSource dataSource,
                ObjectProvider<TransactionManagerCustomizers> transactionManagerCustomizers) {
            this.dataSource = dataSource;
            this.transactionManagerCustomizers = transactionManagerCustomizers
                    .getIfAvailable();
        }

        @Bean
        //没有当Spring容器中不存在PlatformTransactionManager这个对象时，创建DataSourceTransactionManager
        //也就是如果我们自定义了DataSourceTransactionManager并注入Spring容器，这里将不会执行
        @ConditionalOnMissingBean(PlatformTransactionManager.class)
        public DataSourceTransactionManager transactionManager(DataSourceProperties properties) {
            //创建DataSourceTransactionManager注入Spring容器，并且把dataSource传进去
            DataSourceTransactionManager transactionManager = new DataSourceTransactionManager(this.dataSource);
            if (this.transactionManagerCustomizers != null) {
                this.transactionManagerCustomizers.customize(transactionManager);
            }
            return transactionManager;
        }

    }

}

@Configuration
//和DataSourceTransactionManagerAutoConfiguration中是一样的
//引入了spring-boot-starter-jdbc，那自然是存在了PlatformTransactionManager
@ConditionalOnClass({PlatformTransactionManager.class})
//这个自动配置类必须要在DataSourceTransactionManagerAutoConfiguration这个自动配置类之后才能生效
//也就是前面我们已经往Spring容器中注入了DataSourceTransactionManager这个对象才执行这个配置类
@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
        //重点：通过 @EnableTransactionManagement注解开启事务
        //可以看到和我们自己使用@EnableTransactionManagement是一样的
        @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() {
            }
        }
    }

    @Configuration
    @ConditionalOnSingleCandidate(PlatformTransactionManager.class)
    public static class TransactionTemplateConfiguration {
        private final PlatformTransactionManager transactionManager;

        public TransactionTemplateConfiguration(PlatformTransactionManager transactionManager) {
            this.transactionManager = transactionManager;
        }

        @Bean
        @ConditionalOnMissingBean
        public TransactionTemplate transactionTemplate() {
            return new TransactionTemplate(this.transactionManager);
        }
    }
}

<dependency>
  <groupId>org.mybatis.spring.boot</groupId>
  <artifactId>mybatis-spring-boot-starter</artifactId>
  <version>1.3.0</version>
</dependency>