Spring-tx-TransactionInfo

该类是每层事务的抽象，并且是一个链表结构，一个节点表示一层事务，这链表（这多层事务）对应着同一个TransactionInterceptor和同一个PlatformTransactionManager

由于该类是一个protected修饰的TransactionAspectSupport的内部类，所以如果自己想查看执行事务时候，当前事务的属性，应该通过反射机制调用currentTransactionInfo方法才可以，本文后续会有调试代码

该类是TransactionAspectSupport类的内部类，有下面几个属性

@Nullable
private final PlatformTransactionManager transactionManager;
@Nullable
private final TransactionAttribute transactionAttribute;

private final String joinpointIdentification;
@Nullable
private TransactionStatus transactionStatus;
@Nullable
private TransactionInfo oldTransactionInfo;

其中transactionManager，transactionAttribute，transactionStatus，都已经介绍过，本文着重阐述joinpointIdentification和oldTransactionInfo

一：joinpointIdentification
要执行事务的方法的全限定名，字符串形式
二：oldTransactionInfo
表示在哪个事务中开启的事务，比如A事务里有事务B，那么此时就有两个TransactionInfo，后一个TransactionInfo（B）包含着一个前一个TransactionInfo（A）的引用，这个指针用oldTransactionInfo属性来表示

下面是证明oldTransactionInfo过程，不爱看的不看
创建第一个事务类Create1

@Component
public class Creater1 {
    
    
	@Autowired
	JdbcTemplate jdbcTemplate;
	@Autowired
	Creater2 creater2;

	@Transactional(rollbackFor = Exception.class)
	public void create() throws Exception {
    
    
		jdbcTemplate.update("insert into t1(value) values ('爱1次马银霜')");
		Class<TransactionAspectSupport> clazz = TransactionAspectSupport.class;
		Method m = clazz.getDeclaredMethod("currentTransactionInfo");
		m.setAccessible(true);
		Object o = m.invoke(clazz);
		System.out.println(o);// 将断点打到这里观察oldTransactionInfo属性
		creater2.create();
	}
}

创建第二个事务类Create2，用来在Create1中嵌套

@Component
public class Creater2 {
    
    
	@Autowired
	JdbcTemplate jdbcTemplate;
	@Transactional(rollbackFor = Exception.class, propagation = Propagation.REQUIRED)
	public void create() throws Exception {
    
    
		jdbcTemplate.update("insert into t1(value) values ('爱2次马银霜')");
		Class<TransactionAspectSupport> clazz = TransactionAspectSupport.class;
		Method m = clazz.getDeclaredMethod("currentTransactionInfo");
		m.setAccessible(true);
		Object o = m.invoke(clazz);// 将断点打到这里观察oldTransactionInfo属性
		System.out.println(o);
	}
}

创建Main方法，并且运行，查看断点处，可发现oldTransactionInfo的值，正好一个事务对应一个info

@Configuration
@EnableTransactionManagement
public class TestMain {
    
    

	@Bean
	public DataSource dataSource() {
    
    
		HikariDataSource ds = new HikariDataSource();
		ds.setJdbcUrl("jdbc:mysql://localhost:3306/swttest?serverTimezone=UTC&&useSSL=false");
		ds.setUsername("root");
		ds.setPassword("123456");
		return ds;
	}

	@Bean
	public JdbcTemplate jdbcTemplate() {
    
    
		JdbcTemplate jdbc = new JdbcTemplate();
		jdbc.setDataSource(dataSource());
		return jdbc;
	}

	@Bean
	public PlatformTransactionManager platformTransactionManager() {
    
    
		DataSourceTransactionManager manager = new DataSourceTransactionManager(dataSource());
		return manager;
	}

	public static void main(String[] args) throws Throwable {
    
    
		// 依赖容器的话必须要开启@EnableTransactionManagement注解，表示告诉spring我要使用事务
		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(
				"基础包名");
		Creater1 tt = ctx.getBean(Creater1.class);
		tt.create();
	}
}