起因：
项目期间由于一次异常回滚问题，发现自己在事务知识方面知识的遗漏，趁着这次机会，做了几次rollbackFor的测试。
测试：
现在有两个事务，事务oute包含事务Inner。事务A回滚规则是当事务抛出TestException，其中TestException继承RunTimeException。事务B的回滚规则是事务抛RuntimeException。事务的传播方式都是使用的默认，即 Propagation.REQUIRED。如以下代码：
1 @Override
2 @Transactional(rollbackFor = TestException.class)
3 public void transOuter() {
4 productMapper.updateOrderQuantityPessimistic(product_code1);
5 ((ProductService) AopContext.currentProxy()).transInner();
6 }
7
8 @Transactional(rollbackFor = Exception.class)
9 public void transInner() {
10 productMapper.updateOrderQuantityPessimistic(product_code);
11 if (true) {
12 throw new RuntimeException();
13 }
14 }
以下为TestException的代码。
1 public class TestException extends RuntimeException {
2
3 public TestException(String message) {
4 super(message);
5 }
6 }
一开始按照自己对事务的理解， 默认的传播属性之下。事务B启动的时候，会默认使用事务A的rollbackFor来进行回滚，所以该代码运行时候。程序不会回滚。
然而测试，测试完之后发现事务A、B都进行了回滚。
看着测试结果产生了疑问。难道是以innner的rollBack为准？接着进行测试。
1 @Override
2 @Transactional(rollbackFor = Exception.class)
3 public void transOuter() {
4 productMapper.updateOrderQuantityPessimistic(product_code1);
5 ((ProductService) AopContext.currentProxy()).transInner();
6 }
7
8 @Transactional(rollbackFor = TestException.class)
9 public void transInner() {
10 productMapper.updateOrderQuantityPessimistic(product_code);
11 if (true) {
12 throw new RuntimeException();
13 }
14 }
再次测试，测试完之后发现事务A、B依然进行了回滚。
感觉自己对事务的理解还是太浅薄了，是时候debug一波源码。
分析源码：
查看 org.springframework.transaction.interceptor.TransactionAspectSupport 类的 invokeWithinTransaction方法。该方法是事务执行的主要方法，这里我们主要看第20行的事务捕捉那一块。completeTransactionAfterThrowing的方法。
1 protected Object invokeWithinTransaction(Method method, Class<?> targetClass, final InvocationCallback invocation)
2 throws Throwable {
3
4 // If the transaction attribute is null, the method is non-transactional.
5 final TransactionAttribute txAttr = getTransactionAttributeSource().getTransactionAttribute(method, targetClass);
6 final PlatformTransactionManager tm = determineTransactionManager(txAttr);
7 final String joinpointIdentification = methodIdentification(method, targetClass);
8
9 if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) {
10 // Standard transaction demarcation with getTransaction and commit/rollback calls.
11 TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification);
12 Object retVal = null;
13 try {
14 // This is an around advice: Invoke the next interceptor in the chain.
15 // This will normally result in a target object being invoked.
16 retVal = invocation.proceedWithInvocation();
17 }
18 catch (Throwable ex) {
19 // 事务异常捕捉主要在这边获取
20 completeTransactionAfterThrowing(txInfo, ex);
21 throw ex;
22 }
23 finally {
24 cleanupTransactionInfo(txInfo);
25 }
26 commitTransactionAfterReturning(txInfo);
27 return retVal;
28 }
29
30 else {
31 // It‘s a CallbackPreferringPlatformTransactionManager: pass a TransactionCallback in.
32 try {
33 Object result = ((CallbackPreferringPlatformTransactionManager) tm).execute(txAttr,
34 new TransactionCallback<Object>() {
35 @Override
36 public Object doInTransaction(TransactionStatus status) {
37 TransactionInfo txInfo = prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
38 try {
39 return invocation.proceedWithInvocation();
40 }
41 catch (Throwable ex) {
42 if (txAttr.rollbackOn(ex)) {
43 // A RuntimeException: will lead to a rollback.
44 if (ex instanceof RuntimeException) {
45 throw (RuntimeException) ex;
46 }
47 else {
48 throw new ThrowableHolderException(ex);
49 }
50 }
51 else {
52 // A normal return value: will lead to a commit.
53 return new ThrowableHolder(ex);
54 }
55 }
56 finally {
57 cleanupTransactionInfo(txInfo);
58 }
59 }
60 });
61
62 // Check result: It might indicate a Throwable to rethrow.
63 if (result instanceof ThrowableHolder) {
64 throw ((ThrowableHolder) result).getThrowable();
65 }
66 else {
67 return result;
68 }
69 }
70 catch (ThrowableHolderException ex) {
71 throw ex.getCause();
72 }
73 }
74 }
这边显示当事务的rollbackFor为TestException，而抛出的异常为RunTimeException时候。跟我们的transInner一致。接着往下看 completeTransactionAfterThrowing 方法。主要看第8行，第8行对事务进行判断，是否对该抛出的异常进行回滚。
1 protected void completeTransactionAfterThrowing(TransactionAspectSupport.TransactionInfo txInfo, Throwable ex) {
2 if (txInfo != null && txInfo.hasTransaction()) {
3 if (logger.isTraceEnabled()) {
4 logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() +
5 "] after exception: " + ex);
6 }
7 //这里主要判断事务捕获了异常以后，是否进行回滚
8 if (txInfo.transactionAttribute.rollbackOn(ex)) {
9 try {
10 txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());
11 }
12 catch (TransactionSystemException ex2) {
13 logger.error("Application exception overridden by rollback exception", ex);
14 ex2.initApplicationException(ex);
15 throw ex2;
16 }
17 catch (RuntimeException ex2) {
18 logger.error("Application exception overridden by rollback exception", ex);
19 throw ex2;
20 }
21 catch (Error err) {
22 logger.error("Application exception overridden by rollback error", ex);
23 throw err;
24 }
25 }
26 else {
27 // We don‘t roll back on this exception.
28 // Will still roll back if TransactionStatus.isRollbackOnly() is true.
29 try {
30 txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
31 }
32 catch (TransactionSystemException ex2) {
33 logger.error("Application exception overridden by commit exception", ex);
34 ex2.initApplicationException(ex);
35 throw ex2;
36 }
37 catch (RuntimeException ex2) {
38 logger.error("Application exception overridden by commit exception", ex);
39 throw ex2;
40 }
41 catch (Error err) {
42 logger.error("Application exception overridden by commit error", ex);
43 throw err;
44 }
45 }
46 }
47 }
再深入点进去看，看到第11行，这边获取该异常的深度。跳转到片段二进行代码查看。
1 public boolean rollbackOn(Throwable ex) {
2 if (logger.isTraceEnabled()) {
3 logger.trace("Applying rules to determine whether transaction should rollback on " + ex);
4 }
5
6 RollbackRuleAttribute winner = null;
7 int deepest = Integer.MAX_VALUE;
8
9 if (this.rollbackRules != null) {
10 for (RollbackRuleAttribute rule : this.rollbackRules) {
11 //获取异常的深度?
12 int depth = rule.getDepth(ex);
13 if (depth >= 0 && depth < deepest) {
14 deepest = depth;
15 winner = rule;
16 }
17 }
18 }
19
20 if (logger.isTraceEnabled()) {
21 logger.trace("Winning rollback rule is: " + winner);
22 }
23
24 // User superclass behavior (rollback on unchecked) if no rule matches.
25 if (winner == null) {
26 logger.trace("No relevant rollback rule found: applying default rules");
27 //如果depth为-1之后，父类的回滚方式
28 return super.rollbackOn(ex);
29 }
30
31 return !(winner instanceof NoRollbackRuleAttribute);
32 }
根据深度代码查看，rollbackFor和抛出异常ex不一致，返回-1。再回去看上面的代码片段，当返回-1之后，代码走到第28行。进行父类的回滚方法。
1 private int getDepth(Class<?> exceptionClass, int depth) {
2 if (exceptionClass.getName().contains(this.exceptionName)) {
3 // Found it!
4 return depth;
5 }
6 // If we‘ve gone as far as we can go and haven‘t found it...
7 //此处RuntimeException 跟TestException不一致，返回-1
8 if (exceptionClass == Throwable.class) {
9 return -1;
10 }
11 return getDepth(exceptionClass.getSuperclass(), depth + 1);
12 }
以下是父类的代码是否回滚判断方法，有没有很眼熟，只要抛出的异常的是RunTimeExcpetion或者Error则进行回滚。
1 public boolean rollbackOn(Throwable ex) {
2 return (ex instanceof RuntimeException || ex instanceof Error);
3 }
总结
根据上面的代码，我们可以推断出以下几个结论：
1、当我们抛出的异常为RunTime及其子类或者Error和其子类的时候。不论rollbackFor的异常是啥，都会进行事务的回滚。
2、当我们抛出的异常不是RunTime及其子类或者Error和其子类的时候，必须根据rollbackfor进行回滚。比如rollbackfor=RuntimeException，而抛出IOException时候，事务是不进行回滚的。
3、当我们抛出的异常不是RunTime及其子类或者Error和其子类的时候，如果嵌套事务中，只要有一个rollbackfor允许回滚，则整个事务回滚。
经过测试，上述的结论也没发现什么问题。
原文地址：https://www.cnblogs.com/null-qige/p/9243720.html
时间： 2024-10-23 05:41:47