一、搭建Spring源码环境
1.1 声明式事务
plugins {
id 'java'
}
group 'org.springframework'
version '5.0.21.BUILD-SNAPSHOT'
sourceCompatibility = 1.8
repositories {
mavenCentral()
}
dependencies {
compile project(':spring-context')
compile project(':spring-aspects')
compile project(':spring-tx')
compile project(':spring-jdbc')
testCompile group: 'junit', name: 'junit', version: '4.12'
compile group: 'mysql', name: 'mysql-connector-java', version: '5.1.6'
}
gradle依赖
配置步骤：
1.开启事务管理器
2.指定数据源
3.绑定事务管理器与数据源
// 代替xml配置类
@Configuration // 配置类
@ComponentScan(basePackages = "com.best") // 组件扫描
@EnableTransactionManagement // 开启事务管理
public class TxConfig {
// 创建数据库连接池，指定数据源
@Bean
public DataSource dataSource() {
DriverManagerDataSource dataSource = new DriverManagerDataSource();
dataSource.setDriverClassName("com.mysql.jdbc.Driver");
dataSource.setUrl("jdbc:mysql://localhost:3306/user_db?characterEncoding=utf8");
dataSource.setUsername("root");
dataSource.setPassword("root");
return dataSource;
}
// 创建JdbcTemplate对象
@Bean
public JdbcTemplate getJdbcTemplate(DataSource dataSource) {
//到IOC容器种根据类型找到dataSource
JdbcTemplate jdbcTemplate = new JdbcTemplate();
//注入dataSource
jdbcTemplate.setDataSource(dataSource);
return jdbcTemplate;
}
// 创建事务管理器，事务管理器与数据源绑定
@Bean
public DataSourceTransactionManager getDataSourceTransactionManager(DataSource dataSource) {
DataSourceTransactionManager transactionManager = new DataSourceTransactionManager();
transactionManager.setDataSource(dataSource);
return transactionManager;
}
}public interface UserDao {
//多钱
void addMoney();
//少钱
void reduceMoney();
}
@Repository
public class UserDaoImpl implements UserDao {
@Autowired
private JdbcTemplate jdbcTemplate;
//lucy转账100给mary
//少钱
@Override
public void reduceMoney() {
String sql = "update t_account set money=money-? where username=?";
jdbcTemplate.update(sql, 100, "lucy");
}
//多钱
@Override
public void addMoney() {
String sql = "update t_account set money=money+? where username=?";
jdbcTemplate.update(sql, 100, "mary");
}
}@Service
public class UserService {
//注入dao
@Autowired
private UserDao userDao;
//转账的方法
//@Transactional(rollbackFor = Exception.class)
public void accountMoney() {
try {
// 第一步 开启事务
// 第二步 进行业务操作
// lucy少100
userDao.reduceMoney();
// 模拟异常 NullPointerException
String str = null;
str.toLowerCase();
// mary多100
userDao.addMoney();
// 第三步 没有发送异常，提交事务
} catch (Exception e) {
// 第四步 出现异常，事务回滚
// TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();
e.printStackTrace();
}
}
} 
public class SpringTransactionExample {
private static String url = "jdbc:mysql://localhost:3306/spring_transaction?useSSL=false&characterEncoding=utf-8&autoReconnect=true";
private static String user = "root";
private static String password = "root";
public static void main(String[] args) {
// 获取数据源
final DataSource ds = new DriverManagerDataSource(url, user, password);
// 编程式事务
final TransactionTemplate template = new TransactionTemplate();
// 设置事务管理器
template.setTransactionManager(new DataSourceTransactionManager(ds));
template.execute(new TransactionCallback() {
@Override
public Object doInTransaction(TransactionStatus transactionStatus) {
Connection conn = DataSourceUtils.getConnection(ds);
Object savePoint = null;
try {
{
// 插入
PreparedStatement prepare = conn.prepareStatement("insert into person(id, name) values (?, ?)");
prepare.setString(1, "1");
prepare.setString(2, "1111");
prepare.executeUpdate();
}
// 设置保存点，回滚的化，不会回滚保存点之前的操作
savePoint = transactionStatus.createSavepoint();
{
// 插入
PreparedStatement prepare = conn.prepareStatement("insert into person(id, name) values (?, ?)");
prepare.setString(1, "2");
prepare.setString(2, "222");
prepare.executeUpdate();
}
{
// 更新
PreparedStatement prepare = conn.prepareStatement("update person set name = ? where id = ?");
prepare.setString(1, "jak");
prepare.setInt(2, 6);
prepare.executeUpdate();
// 模拟异常
int i = 1 / 0;
}
} catch (SQLException e) {
e.printStackTrace();
} catch (Exception e) {
System.out.println("更新失败");
if (savePoint != null) {
// 回滚到保存点
transactionStatus.rollbackToSavepoint(savePoint);
} else {
transactionStatus.setRollbackOnly();
}
}
return null;
}
});
}
}
Spring 事务操作、Spring事务分析
二、声明式事务源码分析
spring事务图解流程
申明式事务整体调用过程，可以抽出2条线：
1.使用代理模式，生成代理增强类。
2.根据代理事务管理配置类，配置事务的织入，在业务方法前后进行环绕增强，增加一些事务的相关操作。例如获取事务属性、提交事务、回滚事务。
过程如下图：
申明式事务使用@Transactional这种注解的方式，那么我们就从springboot 容器启动时的自动配置载入（spring boot容器启动详解）开始看。在/META-INF/spring.factories中配置文件中查找，如下图：
载入2个关于事务的自动配置类：
org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,
org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,
jta咱们就不看了，看一下TransactionAutoConfiguration这个自动配置类：
@Configuration
@ConditionalOnClass(PlatformTransactionManager.class)
@AutoConfigureAfter({ JtaAutoConfiguration.class, HibernateJpaAutoConfiguration.class,
DataSourceTransactionManagerAutoConfiguration.class,
Neo4jDataAutoConfiguration.class })
@EnableConfigurationProperties(TransactionProperties.class)
public class TransactionAutoConfiguration {
@Bean
@ConditionalOnMissingBean
public TransactionManagerCustomizers platformTransactionManagerCustomizers(
ObjectProvider cls, BeanDefinitionRegistry registry, @Nullable Object source) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
// 如果当前注册器包含internalAutoProxyCreator
if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
BeanDefinition apcDefinition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
if (!cls.getName().equals(apcDefinition.getBeanClassName())) {
// 如果当前类不是internalAutoProxyCreator
int currentPriority = findPriorityForClass(apcDefinition.getBeanClassName());
int requiredPriority = findPriorityForClass(cls);
// 如果下标大于已存在的内部自动代理构造器，index越小，优先级越高,
// InfrastructureAdvisorAutoProxyCreator index=0,requiredPriority最小，不进入
if (currentPriority < requiredPriority) {
apcDefinition.setBeanClassName(cls.getName());
}
}
// 直接返回
return null;
}
// 如果当前注册器不包含internalAutoProxyCreator，则把当前类作为根定义
RootBeanDefinition beanDefinition = new RootBeanDefinition(cls);
beanDefinition.setSource(source);
beanDefinition.getPropertyValues().add("order", Ordered.HIGHEST_PRECEDENCE);
beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition);
return beanDefinition;
}
private static int findPriorityForClass(Class clazz) {
return APC_PRIORITY_LIST.indexOf(clazz);
}
/**
* Stores the auto proxy creator classes in escalation order.
*/
private static final List targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);
// Adapt to TransactionAspectSupport's invokeWithinTransaction...
// 以事务的方式调用目标方法
// 调用TransactionAspectSupport的 invokeWithinTransaction方法
return invokeWithinTransaction(invocation.getMethod(), targetClass, invocation::proceed);
}如上图TransactionInterceptor复写MethodInterceptor接口的invoke方法，并在invoke方法中调用了父类TransactionAspectSupport的invokeWithinTransaction()方法，源码如下：
@Nullable
protected Object invokeWithinTransaction(Method method, @Nullable Class targetClass,
final InvocationCallback invocation) throws Throwable {
// If the transaction attribute is null, the method is non-transactional.
// 获取我们的事务属性源对象
TransactionAttributeSource tas = getTransactionAttributeSource();
// 通过事务属性源对象获取到当前方法的事务属性信息
// 如果transaction attribute为空,该方法就是非事务（非编程式事务)
final TransactionAttribute txAttr = (tas != null ? tas.getTransactionAttribute(method, targetClass) : null);
// 获取我们配置的事务管理器对象
final PlatformTransactionManager tm = determineTransactionManager(txAttr);
// 获取连接点的唯一标识 类名+方法名
final String joinpointIdentification = methodIdentification(method, targetClass, txAttr);
// 声明式事务处理：如果事务属性为空 或者 非回调偏向的事务管理器
if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) {
// Standard transaction demarcation with getTransaction and commit/rollback calls.
// 创建TransactionInfo
TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification);
Object retVal;
try {
// This is an around advice: Invoke the next interceptor in the chain.
// This will normally result in a target object being invoked.
// 这里就是一个环绕增强，在这个proceed前后可以自己定义增强实现
// 执行被增强方法
retVal = invocation.proceedWithInvocation();
}
catch (Throwable ex) {
// target invocation exception
// 异常回滚
// 根据事务定义的，该异常需要回滚就回滚，否则提交事务
completeTransactionAfterThrowing(txInfo, ex);
throw ex;
}
finally {
// 清除事务信息，恢复线程私有的老的事务信息
// 清空当前事务信息，重置为老的
cleanupTransactionInfo(txInfo);
}
// 成功后提交，会进行资源储量，连接释放，恢复挂起事务等操作
// 返回结果之前提交事务
commitTransactionAfterReturning(txInfo);
return retVal;
}
else {
// 编程式事务处理
Object result;
final ThrowableHolder throwableHolder = new ThrowableHolder();
// It's a CallbackPreferringPlatformTransactionManager: pass a TransactionCallback in.
try {
result = ((CallbackPreferringPlatformTransactionManager) tm).execute(txAttr, status -> {
TransactionInfo txInfo = prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
try {
return invocation.proceedWithInvocation();
}
catch (Throwable ex) {
if (txAttr.rollbackOn(ex)) {
// A RuntimeException: will lead to a rollback.
// 如果该异常需要回滚
if (ex instanceof RuntimeException) {
// 如果是运行时异常返回
throw (RuntimeException) ex;
}
else {
// 如果是其它异常都抛ThrowableHolderException
throw new ThrowableHolderException(ex);
}
}
// 如果不需要回滚
else {
// A normal return value: will lead to a commit.
// 定义异常，最终就直接提交事务了
throwableHolder.throwable = ex;
return null;
}
}
finally {
// 清空当前事务信息，重置为老的
cleanupTransactionInfo(txInfo);
}
});
}
catch (ThrowableHolderException ex) {
throw ex.getCause();
}
catch (TransactionSystemException ex2) {
// 上抛异常
if (throwableHolder.throwable != null) {
logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
ex2.initApplicationException(throwableHolder.throwable);
}
throw ex2;
}
catch (Throwable ex2) {
if (throwableHolder.throwable != null) {
logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
}
throw ex2;
}
// Check result state: It might indicate a Throwable to rethrow.
if (throwableHolder.throwable != null) {
throw throwableHolder.throwable;
}
return result;
}
}如上图，我们主要看第一个分支，申明式事务，核心流程如下：
1.createTransactionIfNecessary():如果有必要，创建事务
2.InvocationCallback的proceedWithInvocation()：InvocationCallback是父类的内部回调接口，子类中实现该接口供父类调用，子类TransactionInterceptor中invocation.proceed()。回调方法执行
3.异常回滚completeTransactionAfterThrowing()
1.createTransactionIfNecessary():
protected TransactionInfo createTransactionIfNecessary(@Nullable PlatformTransactionManager tm,
@Nullable TransactionAttribute txAttr, final String joinpointIdentification) {
// If no name specified, apply method identification as transaction name.
// 如果还没有定义名字，把连接点的id定义成事务的名称
if (txAttr != null && txAttr.getName() == null) {
txAttr = new DelegatingTransactionAttribute(txAttr) {
@Override
public String getName() {
return joinpointIdentification;
}
};
}
TransactionStatus status = null;
if (txAttr != null) {
if (tm != null) {
// 根据事务属性获取事务TransactionStatus，大道归一，都是调用PlatformTransactionManager.getTransaction()
status = tm.getTransaction(txAttr);
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Skipping transactional joinpoint [" + joinpointIdentification +
"] because no transaction manager has been configured");
}
}
}
// prepareTransactionInfo(),构造一个TransactionInfo事务信息对象，绑定当前线程：ThreadLocal
return prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
}核心就是：
1）getTransaction()，根据事务属性获取事务TransactionStatus，大道归一，都是调用PlatformTransactionManager.getTransaction()。 2）prepareTransactionInfo(),构造一个TransactionInfo事务信息对象，绑定当前线程：ThreadLocal。
2.invocation.proceed()回调业务方法:
最终实现类是ReflectiveMethodInvocation，类图如下：
如上图，ReflectiveMethodInvocation类实现了ProxyMethodInvocation接口，但是ProxyMethodInvocation继承了3层接口...ProxyMethodInvocation->MethodInvocation->Invocation->Joinpoint
Joinpoint：连接点接口，定义了执行接口：Object proceed() throws Throwable; 执行当前连接点，并跳到拦截器链上的下一个拦截器。
Invocation：调用接口，继承自Joinpoint，定义了获取参数接口： Object[] getArguments();是一个带参数的、可被拦截器拦截的连接点。
MethodInvocation：方法调用接口，继承自Invocation，定义了获取方法接口：Method getMethod(); 是一个带参数的可被拦截的连接点方法。
ProxyMethodInvocation：代理方法调用接口，继承自MethodInvocation，定义了获取代理对象接口：Object getProxy();是一个由代理类执行的方法调用连接点方法。
ReflectiveMethodInvocation：实现了ProxyMethodInvocation接口，自然就实现了父类接口的的所有接口。获取代理类，获取方法，获取参数，用代理类执行这个方法并且自动跳到下一个连接点。
下面看一下proceed方法源码：
@Override
@Nullable
public Object proceed() throws Throwable {
// We start with an index of -1 and increment early.
// 从索引为-1的拦截器开始调用，并按序递增，如果拦截器链中的拦截器迭代调用完毕，开始调用target的函数，这个函数是通过反射机制完成的
// 具体实现在AopUtils.invokeJoinPointUsingReflection方法中
// 启动时索引为-1，唤醒连接点，后续递增
if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
return invokeJoinpoint();
}
// 获取下一个要执行的拦截器，沿着定义好的interceptorOrInterceptionAdvice链进行处理
Object interceptorOrInterceptionAdvice =
this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
// Evaluate dynamic method matcher here: static part will already have
// been evaluated and found to match.
// 这里对拦截器进行动态匹配的判断，这里是对pointcut触发进行匹配的地方，如果和定义的pointCut匹配，那么这个advice将会得到执行
// 这里进行动态方法匹配校验，静态的方法匹配早已经校验过了（MethodMatcher接口有两种典型：动态/静态校验）
InterceptorAndDynamicMethodMatcher dm =
(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {
return dm.interceptor.invoke(this);
}
else {
// Dynamic matching failed.
// Skip this interceptor and invoke the next in the chain.
// 如果不匹配，那么proceed会被递归调用，直到所有的拦截器都被运行过为止
// 动态匹配失败，跳过当前拦截，进入下一个（拦截器链）
return proceed();
}
}
else {
// It's an interceptor, so we just invoke it: The pointcut will have
// been evaluated statically before this object was constructed.
// 普通拦截器，直接调用拦截器，将this作为参数传递以保证当前实例中调用链的执行
return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
}
}咱们这里最终调用的是((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);就是TransactionInterceptor事务拦截器回调 目标业务方法
3.completeTransactionAfterThrowing()
最终调用AbstractPlatformTransactionManager的rollback()，提交事务commitTransactionAfterReturning()最终调用AbstractPlatformTransactionManager的commit()
protected void completeTransactionAfterThrowing(@Nullable TransactionInfo txInfo, Throwable ex) {
if (txInfo != null && txInfo.getTransactionStatus() != null) {
if (logger.isTraceEnabled()) {
logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() +
"] after exception: " + ex);
}
if (txInfo.transactionAttribute != null && txInfo.transactionAttribute.rollbackOn(ex)) {
try {
// 最终调用AbstractPlatformTransactionManager的rollback()
txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());
}
catch (TransactionSystemException ex2) {
logger.error("Application exception overridden by rollback exception", ex);
ex2.initApplicationException(ex);
throw ex2;
}
catch (RuntimeException | Error ex2) {
logger.error("Application exception overridden by rollback exception", ex);
throw ex2;
}
}
else {
// We don't roll back on this exception.
// Will still roll back if TransactionStatus.isRollbackOnly() is true.
try {
// 最终调用AbstractPlatformTransactionManager的commit()
txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
}
catch (TransactionSystemException ex2) {
logger.error("Application exception overridden by commit exception", ex);
ex2.initApplicationException(ex);
throw ex2;
}
catch (RuntimeException | Error ex2) {
logger.error("Application exception overridden by commit exception", ex);
throw ex2;
}
}
}
}总结：
可见不管是编程式事务，还是声明式事务，最终源码都是调用事务管理器的PlatformTransactionManager接口的3个方法：
- getTransaction
- commit
- rollback
下一节我们就来看看这个事务管理如何实现这3个方法。
事务核心源码
先看下核心类图：
如上提所示，PlatformTransactionManager顶级接口定义了最核心的事务管理方法，下面一层是AbstractPlatformTransactionManager抽象类，实现了PlatformTransactionManager接口的方法并定义了一些抽象方法，供子类拓展。最后下面一层是2个经典事务管理器：
1.DataSourceTransactionmanager,即JDBC单数据库事务管理器，基于Connection实现，
2.JtaTransactionManager,即多数据库事务管理器（又叫做分布式事务管理器），其实现了JTA规范，使用XA协议进行两阶段提交。
我们这里只看基于JDBC connection的DataSourceTransactionmanager源码。
在这之前先大概看下事务属性
事务接口架构
Spring事务属性
Spring事务状态
PlatformTransactionManager接口
public interface PlatformTransactionManager {
// 获取事务状态
TransactionStatus getTransaction(TransactionDefinition definition) throws TransactionException;
// 事务提交
void commit(TransactionStatus status) throws TransactionException;
// 事务回滚
void rollback(TransactionStatus status) throws TransactionException;
}1.getTransaction获取事务
AbstractPlatformTransactionManager实现了getTransaction()方法如下：
AbstractPlatformTransactionManger#getTransaction
@Override
public final TransactionStatus getTransaction(@Nullable TransactionDefinition definition) throws TransactionException {
Object transaction = doGetTransaction();
// Cache debug flag to avoid repeated checks.
boolean debugEnabled = logger.isDebugEnabled();
if (definition == null) {
// Use defaults if no transaction definition given.
definition = new DefaultTransactionDefinition();
}
// 如果当前已经存在事务
if (isExistingTransaction(transaction)) {
// Existing transaction found -> check propagation behavior to find out how to behave.
// 根据不同传播机制不同处理
return handleExistingTransaction(definition, transaction, debugEnabled);
}
// Check definition settings for new transaction.
// 超时不能小于默认值
if (definition.getTimeout() < TransactionDefinition.TIMEOUT_DEFAULT) {
throw new InvalidTimeoutException("Invalid transaction timeout", definition.getTimeout());
}
// No existing transaction found -> check propagation behavior to find out how to proceed.
// 当前不存在事务，传播机制=mandatory（支持当前事务，没事务报错），报错
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_MANDATORY) {
throw new IllegalTransactionStateException(
"No existing transaction found for transaction marked with propagation 'mandatory'");
}
// 当前不存在事务，传播机制=required/required_new/nested，这三种情况，需要新开启事务，且加上事务同步
else if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRED ||
definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW ||
definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) {
SuspendedResourcesHolder suspendedResources = suspend(null);
if (debugEnabled) {
logger.debug("Creating new transaction with name [" + definition.getName() + "]: " + definition);
}
try {
// 是否需要新开启同步 // 开启
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
DefaultTransactionStatus status = newTransactionStatus(
definition, transaction, true, newSynchronization, debugEnabled, suspendedResources);
// 开启新事务
doBegin(transaction, definition);
// 准备同步
prepareSynchronization(status, definition);
return status;
}
catch (RuntimeException | Error ex) {
resume(null, suspendedResources);
throw ex;
}
}
else {
// Create "empty" transaction: no actual transaction, but potentially synchronization.
// 当前不存在事务，且传播机制=propagation_supports/propagation_not_supported/propagation_never，
// 这三种情况，创建“空”事务:没有实际事务，但可能是同步。
// 警告：有隔离级别但是并没有定义实际的事务初始化
if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT && logger.isWarnEnabled()) {
logger.warn("Custom isolation level specified but no actual transaction initiated; " +
"isolation level will effectively be ignored: " + definition);
}
boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS);
return prepareTransactionStatus(definition, null, true, newSynchronization, debugEnabled, null);
}
}
如上图，源码分成了2条处理线，
1.当前已存在事务：isExistingTransaction()判断是否存在事务，存在事务handleExistingTransaction()根据不同传播机制不同处理
2.当前不存在事务: 不同传播机制不同处理
handleExistingTransaction()源码如下：
AbstractPlatformTransactionManager#handleExistingTransaction
private TransactionStatus handleExistingTransaction(
TransactionDefinition definition, Object transaction, boolean debugEnabled)
throws TransactionException {
// 1.never（不支持当前事务;如果当前事务存在，抛出异常）报错
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NEVER) {
throw new IllegalTransactionStateException(
"Existing transaction found for transaction marked with propagation 'never'");
}
// 2.not_supported（不支持当前事务，现有同步将被挂起）挂起当前事务
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NOT_SUPPORTED) {
if (debugEnabled) {
logger.debug("Suspending current transaction");
}
Object suspendedResources = suspend(transaction);
boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS);
return prepareTransactionStatus(
definition, null, false, newSynchronization, debugEnabled, suspendedResources);
}
// 3.requires_new挂起当前事务，创建新事务
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW) {
if (debugEnabled) {
logger.debug("Suspending current transaction, creating new transaction with name [" +
definition.getName() + "]");
}
// 挂起当前事务
SuspendedResourcesHolder suspendedResources = suspend(transaction);
try {
// 创建新事务
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
DefaultTransactionStatus status = newTransactionStatus(
definition, transaction, true, newSynchronization, debugEnabled, suspendedResources);
doBegin(transaction, definition);
prepareSynchronization(status, definition);
return status;
}
catch (RuntimeException | Error beginEx) {
resumeAfterBeginException(transaction, suspendedResources, beginEx);
throw beginEx;
}
}
// 4.nested嵌套事务
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) {
if (!isNestedTransactionAllowed()) {
throw new NestedTransactionNotSupportedException(
"Transaction manager does not allow nested transactions by default - " +
"specify 'nestedTransactionAllowed' property with value 'true'");
}
if (debugEnabled) {
logger.debug("Creating nested transaction with name [" + definition.getName() + "]");
}
// 是否支持保存点：非JTA事务走这个分支。AbstractPlatformTransactionManager默认是true，JtaTransactionManager复写了该方法false，
// DataSourceTransactionManager没有复写，还是true
if (useSavepointForNestedTransaction()) {
// Create savepoint within existing Spring-managed transaction,
// through the SavepointManager API implemented by TransactionStatus.
// Usually uses JDBC 3.0 savepoints. Never activates Spring synchronization.
DefaultTransactionStatus status =
prepareTransactionStatus(definition, transaction, false, false, debugEnabled, null);
// 创建保存点
status.createAndHoldSavepoint();
return status;
}
else {
// Nested transaction through nested begin and commit/rollback calls.
// Usually only for JTA: Spring synchronization might get activated here
// in case of a pre-existing JTA transaction.
// JTA事务走这个分支，创建新事务
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
DefaultTransactionStatus status = newTransactionStatus(
definition, transaction, true, newSynchronization, debugEnabled, null);
doBegin(transaction, definition);
prepareSynchronization(status, definition);
return status;
}
}如上图，当前线程已存在事务情况下，新的不同隔离级别处理情况：
1.NERVER：不支持当前事务;如果当前事务存在，抛出异常:"Existing transaction found for transaction marked with propagation 'never'" 2.NOT_SUPPORTED：不支持当前事务，现有同步将被挂起:suspend() 3.REQUIRES_NEW挂起当前事务，创建新事务:
1)suspend()
2)doBegin() 4.NESTED嵌套事务
1）非JTA事务：createAndHoldSavepoint()创建JDBC3.0保存点，不需要同步
2) JTA事务：开启新事务，doBegin()+prepareSynchronization()需要同步
这里有几个核心方法：挂起当前事务suspend()、开启新事务doBegin()。
suspend()源码如下：
AbstractPlatformTransactionManager#suspend
@Nullable
protected final SuspendedResourcesHolder suspend(@Nullable Object transaction) throws TransactionException {
// 1.当前存在同步
if (TransactionSynchronizationManager.isSynchronizationActive()) {
List suspendedSynchronizations = doSuspendSynchronization();
try {
Object suspendedResources = null;
if (transaction != null) {
// 事务不为空，挂起事务
suspendedResources = doSuspend(transaction);
}
// 解除绑定当前事务各种属性：名称、只读、隔离级别、是否是真实的事务.
String name = TransactionSynchronizationManager.getCurrentTransactionName();
TransactionSynchronizationManager.setCurrentTransactionName(null);
boolean readOnly = TransactionSynchronizationManager.isCurrentTransactionReadOnly();
TransactionSynchronizationManager.setCurrentTransactionReadOnly(false);
Integer isolationLevel = TransactionSynchronizationManager.getCurrentTransactionIsolationLevel();
TransactionSynchronizationManager.setCurrentTransactionIsolationLevel(null);
boolean wasActive = TransactionSynchronizationManager.isActualTransactionActive();
TransactionSynchronizationManager.setActualTransactionActive(false);
return new SuspendedResourcesHolder(
suspendedResources, suspendedSynchronizations, name, readOnly, isolationLevel, wasActive);
}
catch (RuntimeException | Error ex) {
// doSuspend failed - original transaction is still active...
doResumeSynchronization(suspendedSynchronizations);
throw ex;
}
}
// 2.没有同步，但事务不为空，挂起事务
else if (transaction != null) {
// Transaction active but no synchronization active.
Object suspendedResources = doSuspend(transaction);
return new SuspendedResourcesHolder(suspendedResources);
}
// 3.没有同步，但事务为空，什么都不用做
else {
// Neither transaction nor synchronization active.
return null;
}
}doSuspend(),挂起事务，AbstractPlatformTransactionManager抽象类doSuspend()会报错：不支持挂起，如果具体事务执行器支持就复写doSuspend()，DataSourceTransactionManager实现如下：
DataSourceTransactionManager#doSuspend
protected Object doSuspend(Object transaction) throws TransactionException {
// AbstractPlatformTransactionManager抽象类doSuspend()会报错：不支持挂起，如果具体事务执行器支持就复写doSuspend()
throw new TransactionSuspensionNotSupportedException(
"Transaction manager [" + getClass().getName() + "] does not support transaction suspension");
}
@Override
protected Object doSuspend(Object transaction) {
DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
// 把当前事务的connectionHolder数据库连接持有者清空。
txObject.setConnectionHolder(null);
// 当前线程解绑datasource
return TransactionSynchronizationManager.unbindResource(obtainDataSource());
}挂起DataSourceTransactionManager事务的核心操作就是：
1.把当前事务的connectionHolder数据库连接持有者清空。
2.当前线程解绑datasource.其实就是ThreadLocal移除对应变量（TransactionSynchronizationManager类中定义的private static final ThreadLocal resources = new NamedThreadLocal("Transactional resources");）
TransactionSynchronizationManager事务同步管理器，该类维护了多个线程本地变量ThreadLocal，如下图：
public abstract class TransactionSynchronizationManager {
private static final Log logger = LogFactory.getLog(TransactionSynchronizationManager.class);
// 事务资源：map 两种数据对。
// 1.会话工厂和会话k=SqlSessionFactory v=SqlSessionHolder
// 2.数据源和连接k=DataSource v=ConnectionHolder
private static final ThreadLocal resources =
new NamedThreadLocal("Transactional resources");
// 事务同步
private static final ThreadLocal synchronizations =
new NamedThreadLocal("Transaction synchronizations");
// 当前事务名称
private static final ThreadLocal currentTransactionName =
new NamedThreadLocal("Current transaction name");
// 当前事务的只读属性
private static final ThreadLocal currentTransactionReadOnly =
new NamedThreadLocal("Current transaction read-only status");
// 当前事务的隔离级别
private static final ThreadLocal currentTransactionIsolationLevel =
new NamedThreadLocal("Current transaction isolation level");
// 是否存在事务
private static final ThreadLocal actualTransactionActive =
new NamedThreadLocal("Actual transaction active");
...
}DataSourceTransactionManager#doBegin
@Override
protected void doBegin(Object transaction, TransactionDefinition definition) {
DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
Connection con = null;
try {
// 如果事务还没有connection或者connection在事务同步状态，重置新的connectionHolder
if (!txObject.hasConnectionHolder() ||
txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
Connection newCon = obtainDataSource().getConnection();
if (logger.isDebugEnabled()) {
logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
}
// 重置新的connectionHolder
txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
}
//设置新的连接为事务同步中
txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
con = txObject.getConnectionHolder().getConnection();
// conn设置事务隔离级别,只读
Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
txObject.setPreviousIsolationLevel(previousIsolationLevel);
// Switch to manual commit if necessary. This is very expensive in some JDBC drivers,
// so we don't want to do it unnecessarily (for example if we've explicitly
// configured the connection pool to set it already).
// 如果是自动提交切换到手动提交
if (con.getAutoCommit()) {
txObject.setMustRestoreAutoCommit(true);
if (logger.isDebugEnabled()) {
logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
}
con.setAutoCommit(false);
}
// 如果只读，执行sql设置事务只读
prepareTransactionalConnection(con, definition);
// 设置connection持有者的事务开启状态
txObject.getConnectionHolder().setTransactionActive(true);
int timeout = determineTimeout(definition);
if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
// 设置超时秒数
txObject.getConnectionHolder().setTimeoutInSeconds(timeout);
}
// Bind the connection holder to the thread.
// 绑定connection持有者到当前线程
if (txObject.isNewConnectionHolder()) {
TransactionSynchronizationManager.bindResource(obtainDataSource(), txObject.getConnectionHolder());
}
}
catch (Throwable ex) {
if (txObject.isNewConnectionHolder()) {
DataSourceUtils.releaseConnection(con, obtainDataSource());
txObject.setConnectionHolder(null, false);
}
throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
}
}如上图，开启新事务的准备工作doBegin()的核心操作就是：
1.DataSourceTransactionObject“数据源事务对象”，设置ConnectionHolder，再给ConnectionHolder设置各种属性：自动提交、超时、事务开启、隔离级别。
2.给当前线程绑定一个线程本地变量，key=DataSource数据源 v=ConnectionHolder数据库连接。
2.commit提交事务
一、讲解源码之前先看一下资源管理类：
SqlSessionSynchronization是SqlSessionUtils的一个内部类，继承自TransactionSynchronizationAdapter抽象类，实现了事务同步接口TransactionSynchronization。
类图如下：
TransactionSynchronization接口定义了事务操作时的对应资源的（JDBC事务那么就是SqlSessionSynchronization）管理方法：
1 // 挂起事务
2 void suspend();
3
4 // 唤醒事务
4 void resume();
5
6 void flush();
7
8 // 提交事务前
9 void beforeCommit(boolean readOnly);
10
11 // 提交事务完成前
12 void beforeCompletion();
13
14 // 提交事务后
15 void afterCommit();
16
17 // 提交事务完成后
18 void afterCompletion(int status);后续很多都是使用这些接口管理事务。
二、 commit提交事务
AbstractPlatformTransactionManager的commit源码如下：
AbstractPlatformTransactionManger#commit
@Override
public final void commit(TransactionStatus status) throws TransactionException {
// 如果事务已完结，报错，无法再次提交
if (status.isCompleted()) {
throw new IllegalTransactionStateException(
"Transaction is already completed - do not call commit or rollback more than once per transaction");
}
DefaultTransactionStatus defStatus = (DefaultTransactionStatus) status;
// 如果事务明确标记为回滚
if (defStatus.isLocalRollbackOnly()) {
if (defStatus.isDebug()) {
logger.debug("Transactional code has requested rollback");
}
// 执行回滚
processRollback(defStatus, false);
return;
}
// 如果不需要全局回滚时提交 且 全局回滚
if (!shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {
if (defStatus.isDebug()) {
logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");
}
// 执行回滚
processRollback(defStatus, true);
return;
}
// 执行提交事务
processCommit(defStatus);
}
如上图，各种判断：
- 1.如果事务明确标记为本地回滚，-》执行回滚
- 2.如果不需要全局回滚时提交 且 全局回滚-》执行回滚
- 3.提交事务，核心方法processCommit()
processCommit如下：
private void processCommit(DefaultTransactionStatus status) throws TransactionException {
try {
boolean beforeCompletionInvoked = false;
try {
boolean unexpectedRollback = false;
// 3个前置操作
prepareForCommit(status);
triggerBeforeCommit(status);
triggerBeforeCompletion(status);
// 3个前置操作已调用
beforeCompletionInvoked = true;
//1.有保存点，即嵌套事务
if (status.hasSavepoint()) {
if (status.isDebug()) {
logger.debug("Releasing transaction savepoint");
}
unexpectedRollback = status.isGlobalRollbackOnly();
// 释放保存点
status.releaseHeldSavepoint();
}
// 2.新事务
else if (status.isNewTransaction()) {
if (status.isDebug()) {
logger.debug("Initiating transaction commit");
}
unexpectedRollback = status.isGlobalRollbackOnly();
// 调用事务处理器提交事务
doCommit(status);
}
else if (isFailEarlyOnGlobalRollbackOnly()) {
unexpectedRollback = status.isGlobalRollbackOnly();
}
// Throw UnexpectedRollbackException if we have a global rollback-only
// marker but still didn't get a corresponding exception from commit.
// 3.非新事务，且全局回滚失败，但是提交时没有得到异常，抛出异常
if (unexpectedRollback) {
throw new UnexpectedRollbackException(
"Transaction silently rolled back because it has been marked as rollback-only");
}
}
catch (UnexpectedRollbackException ex) {
// can only be caused by doCommit
// 触发完成后事务同步，状态为回滚
triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
throw ex;
}
// 事务异常
catch (TransactionException ex) {
// can only be caused by doCommit
// 提交失败回滚
if (isRollbackOnCommitFailure()) {
doRollbackOnCommitException(status, ex);
}
else {
// 触发完成后回调，事务同步状态为未知
triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
}
throw ex;
}
// 运行时异常
catch (RuntimeException | Error ex) {
if (!beforeCompletionInvoked) {
// 如果3个前置步骤未完成，调用前置的最后一步操作
triggerBeforeCompletion(status);
}
// 提交异常回滚
doRollbackOnCommitException(status, ex);
throw ex;
}
// Trigger afterCommit callbacks, with an exception thrown there
// propagated to callers but the transaction still considered as committed.
try {
triggerAfterCommit(status);
}
finally {
triggerAfterCompletion(status, TransactionSynchronization.STATUS_COMMITTED);
}
}
finally {
cleanupAfterCompletion(status);
}
}如上图，commit事务时，有6个核心操作，分别是3个前置操作，3个后置操作，如下：
1.prepareForCommit(status);源码是空的，没有拓展目前。
2.triggerBeforeCommit(status); 提交前触发操作
AbstractPlatformTransactionManger#triggerBeforeCommit
protected final void triggerBeforeCommit(DefaultTransactionStatus status) {
if (status.isNewSynchronization()) {
if (status.isDebug()) {
logger.trace("Triggering beforeCommit synchronization");
}
TransactionSynchronizationUtils.triggerBeforeCommit(status.isReadOnly());
}
}
public static void triggerBeforeCommit(boolean readOnly) {
for (TransactionSynchronization synchronization : TransactionSynchronizationManager.getSynchronizations()) {
synchronization.beforeCommit(readOnly);
}
}如上图，TransactionSynchronizationManager类定义了多个ThreadLocal（线程本地变量），其中一个用以保存当前线程的事务同步：
遍历事务同步器，把每个事务同步器都执行“提交前”操作
比如咱们用的jdbc事务，那么最终就是SqlSessionUtils.beforeCommit()->this.holder.getSqlSession().commit();提交会话。
(源码由于是spring管理事务，最终不会执行事务提交，例如是DefaultSqlSession：执行清除缓存、重置状态操作)
3.triggerBeforeCompletion(status)：完成前触发操作
如果是jdbc事务，那么最终就是，SqlSessionUtils.beforeCompletion->TransactionSynchronizationManager.unbindResource(sessionFactory); 解绑当前线程的会话工厂
this.holder.getSqlSession().close();关闭会话。(源码由于是spring管理事务，最终不会执行事务close操作，例如是DefaultSqlSession，也会执行各种清除收尾操作)
protected final void triggerBeforeCompletion(DefaultTransactionStatus status) {
if (status.isNewSynchronization()) {
if (status.isDebug()) {
logger.trace("Triggering beforeCompletion synchronization");
}
TransactionSynchronizationUtils.triggerBeforeCompletion();
}
}
public static void triggerBeforeCompletion() {
for (TransactionSynchronization synchronization : TransactionSynchronizationManager.getSynchronizations()) {
try {
synchronization.beforeCompletion();
}
catch (Throwable tsex) {
logger.error("TransactionSynchronization.beforeCompletion threw exception", tsex);
}
}
}4.triggerAfterCommit(status)：提交事务后触发操作。
TransactionSynchronizationUtils.triggerAfterCommit();->TransactionSynchronizationUtils.invokeAfterCommit
如下：
private void triggerAfterCommit(DefaultTransactionStatus status) {
if (status.isNewSynchronization()) {
if (status.isDebug()) {
logger.trace("Triggering afterCommit synchronization");
}
TransactionSynchronizationUtils.triggerAfterCommit();
}
}
public static void triggerAfterCommit() {
invokeAfterCommit(TransactionSynchronizationManager.getSynchronizations());
}
public static void invokeAfterCommit(@Nullable List synchronizations) {
if (synchronizations != null) {
for (TransactionSynchronization synchronization : synchronizations) {
synchronization.afterCommit();
}
}
}一顿找，最后在TransactionSynchronizationAdapter中复写过，并且是空的....SqlSessionSynchronization继承了TransactionSynchronizationAdapter但是没有复写这个方法
5. triggerAfterCompletion(status, TransactionSynchronization.STATUS_COMMITTED);
TransactionSynchronizationUtils.invokeAfterCompletion,如下：
private void triggerAfterCompletion(DefaultTransactionStatus status, int completionStatus) {
if (status.isNewSynchronization()) {
List synchronizations = TransactionSynchronizationManager.getSynchronizations();
TransactionSynchronizationManager.clearSynchronization();
if (!status.hasTransaction() || status.isNewTransaction()) {
if (status.isDebug()) {
logger.trace("Triggering afterCompletion synchronization");
}
invokeAfterCompletion(synchronizations, completionStatus);
}
else if (!synchronizations.isEmpty()) {
registerAfterCompletionWithExistingTransaction(status.getTransaction(), synchronizations);
}
}
}
public static void invokeAfterCompletion(@Nullable List synchronizations,
int completionStatus) {
if (synchronizations != null) {
for (TransactionSynchronization synchronization : synchronizations) {
try {
synchronization.afterCompletion(completionStatus);
}
catch (Throwable tsex) {
logger.error("TransactionSynchronization.afterCompletion threw exception", tsex);
}
}
}
}afterCompletion：对于JDBC事务来说，最终：
1）如果会话任然活着，关闭会话，
2）重置各种属性：SQL会话同步器（SqlSessionSynchronization）的SQL会话持有者（SqlSessionHolder）的referenceCount引用计数、synchronizedWithTransaction同步事务、rollbackOnly只回滚、deadline超时时间点。
6.cleanupAfterCompletion(status);
1）设置事务状态为已完成。
2) 如果是新的事务同步，解绑当前线程绑定的数据库资源，重置数据库连接
3）如果存在挂起的事务（嵌套事务），唤醒挂起的老事务的各种资源：数据库资源、同步器。
private void cleanupAfterCompletion(DefaultTransactionStatus status) {
// 设置事务状态完成
status.setCompleted();
// 如果是新的同步，清空当前线程绑定的除了资源外的全部线程本地变量：
// 包括事务同步器、事务名称、只读属性、隔离级别、真实的事务激活状态
if (status.isNewSynchronization()) {
TransactionSynchronizationManager.clear();
}
// 如果是新的事务同步
if (status.isNewTransaction()) {
doCleanupAfterCompletion(status.getTransaction());
}// 如果存在挂起的资源
if (status.getSuspendedResources() != null) {
if (status.isDebug()) {
logger.debug("Resuming suspended transaction after completion of inner transaction");
}
// 唤醒挂起的事务和资源（重新绑定之前挂起的数据库资源，唤醒同步器，注册同步器到TransactionSynchronizationManager）
Object transaction = (status.hasTransaction() ? status.getTransaction() : null);
resume(transaction, (SuspendedResourcesHolder) status.getSuspendedResources());
}
}对于DataSourceTransactionManager，doCleanupAfterCompletion源码如下：
@Override
protected void doCleanupAfterCompletion(Object transaction) {
DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
// Remove the connection holder from the thread, if exposed.
// 如果是最新的连接持有者，解绑当前线程绑定的
if (txObject.isNewConnectionHolder()) {
TransactionSynchronizationManager.unbindResource(obtainDataSource());
}
// Reset connection.
// 重置数据库连接（隔离级别、只读）
Connection con = txObject.getConnectionHolder().getConnection();
try {
if (txObject.isMustRestoreAutoCommit()) {
con.setAutoCommit(true);
}
DataSourceUtils.resetConnectionAfterTransaction(con, txObject.getPreviousIsolationLevel());
}
catch (Throwable ex) {
logger.debug("Could not reset JDBC Connection after transaction", ex);
}
if (txObject.isNewConnectionHolder()) {
if (logger.isDebugEnabled()) {
logger.debug("Releasing JDBC Connection [" + con + "] after transaction");
}
// 资源引用计数-1，关闭数据库连接
DataSourceUtils.releaseConnection(con, this.dataSource);
}
// 重置连接持有者的全部属性
txObject.getConnectionHolder().clear();
}
AbstractPlatformTransactionManager中rollback源码如下：
@Override
public final void rollback(TransactionStatus status) throws TransactionException {
if (status.isCompleted()) {
throw new IllegalTransactionStateException(
"Transaction is already completed - do not call commit or rollback more than once per transaction");
}
DefaultTransactionStatus defStatus = (DefaultTransactionStatus) status;
processRollback(defStatus, false);
}processRollback
private void processRollback(DefaultTransactionStatus status, boolean unexpected) {
try {
boolean unexpectedRollback = unexpected;
try {
// 解绑当前线程绑定的会话工厂，并关闭会话
triggerBeforeCompletion(status);
// 1.如果有保存点，即嵌套式事务
if (status.hasSavepoint()) {
if (status.isDebug()) {
logger.debug("Rolling back transaction to savepoint");
}
// 回滚到保存点
status.rollbackToHeldSavepoint();
}
// 2.如果就是一个简单事务
else if (status.isNewTransaction()) {
if (status.isDebug()) {
logger.debug("Initiating transaction rollback");
}
// 回滚核心方法
doRollback(status);
}
else {
// Participating in larger transaction
// 3.当前存在事务且没有保存点，即加入当前事务的
if (status.hasTransaction()) {
// 如果已经标记为回滚 或 当加入事务失败时全局回滚（默认true）
if (status.isLocalRollbackOnly() || isGlobalRollbackOnParticipationFailure()) {
if (status.isDebug()) {
// debug时会打印：加入事务失败-标记已存在事务为回滚
logger.debug("Participating transaction failed - marking existing transaction as rollback-only");
}
// 设置当前connectionHolder：当加入一个已存在事务时回滚
doSetRollbackOnly(status);
}
else {
if (status.isDebug()) {
logger.debug("Participating transaction failed - letting transaction originator decide on rollback");
}
}
}
else {
logger.debug("Should roll back transaction but cannot - no transaction available");
}
// Unexpected rollback only matters here if we're asked to fail early
if (!isFailEarlyOnGlobalRollbackOnly()) {
unexpectedRollback = false;
}
}
}
catch (RuntimeException | Error ex) {
// 关闭会话，重置SqlSessionHolder属性
triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
throw ex;
}
triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
// Raise UnexpectedRollbackException if we had a global rollback-only marker
if (unexpectedRollback) {
throw new UnexpectedRollbackException(
"Transaction rolled back because it has been marked as rollback-only");
}
}
finally {
// 解绑当前线程
cleanupAfterCompletion(status);
}
}如上图，有几个公共方法和提交事务时一致，就不再重复。
这里主要看doRollback，DataSourceTransactionManager的doRollback()源码如下：
@Override
protected void doRollback(DefaultTransactionStatus status) {
DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
Connection con = txObject.getConnectionHolder().getConnection();
if (status.isDebug()) {
logger.debug("Rolling back JDBC transaction on Connection [" + con + "]");
}
try {
con.rollback();
}
catch (SQLException ex) {
throw new TransactionSystemException("Could not roll back JDBC transaction", ex);
}
}好吧，一点不复杂，就是Connection的rollback.
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