昨天遇到個問題，同一事務內，前一步插入成功的記錄，後面的查詢不到這條記錄，折騰了我好久，最後發現自己把工具類放錯包了 
。
剛好也順便看了下tx標籤配置方式下 事務的解析過程，參考地址：
http://michael-softtech.iteye.com/blog/monthblog/2010-11
首先關於spring事務的配置方式，相信大家都知道是有5種，但我們經常使用的應該就是基於註解和tx標籤配置攔截器兩種方式了，而我接觸過項目一直以來都是tx方法
雖說知道怎麼去配置，但一直以來沒有深究具體過程，正好借這個機會學習下。
<!-- 通知 -->
<tx:advice id="txAdvice" transaction-manager="transactionManager">
<tx:attributes>
<tx:method name="add*" propagation="REQUIRED"/>
<tx:method name="save*" propagation="REQUIRED"/>
<tx:method name="insert*" propagation="REQUIRED"/>
<tx:method name="update*" propagation="REQUIRED"/>
<tx:method name="find*" propagation="NOT_SUPPORTED" read-only="true"/>
<tx:method name="select*" propagation="NOT_SUPPORTED" read-only="true"/>
<tx:method name="get*" propagation="NOT_SUPPORTED" read-only="true"/>
<tx:method name="load*" propagation="NOT_SUPPORTED" read-only="true" />
<tx:method name="search*" propagation="NOT_SUPPORTED" read-only="true" />
</tx:attributes>
</tx:advice>
<!-- aop事務代理 -->
<aop:config>
<aop:advisor advice-ref="txAdvice" pointcut="execution(* cn.com.wp.**.serviceImpl.*.*(..))"/>
</aop:config>
spring xml標籤解析一般需要 BeanDefinitionParser ,NamespaceHandler tx對應的類爲 TxNamespaceHandler ，TxAdviceBeanDefinitionParser
查看TxNamespaceHandler 源碼
@Override
public void init() {
registerBeanDefinitionParser("advice", new TxAdviceBeanDefinitionParser());
registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
registerBeanDefinitionParser("jta-transaction-manager", new JtaTransactionManagerBeanDefinitionParser());
}可以看到在init初始化方法中 通過registerBeanDefinitionParser註冊了對 advice屬性的解析類 TxAdviceBeanDefinitionParser
雖說是這樣，但對於何時調用這個方法還是一頭霧水，而spring解析xml是通過DefaultNamespaceHandlerResolver入口
查看DefaultNamespaceHandlerResolver類 有個resolve方法，單詞意思很明確-> 解析
代碼如下：
@Override
public NamespaceHandler resolve(String namespaceUri) {
Map<String, Object> handlerMappings = getHandlerMappings();
Object handlerOrClassName = handlerMappings.get(namespaceUri);
if (handlerOrClassName == null) {
return null;
}
else if (handlerOrClassName instanceof NamespaceHandler) {
return (NamespaceHandler) handlerOrClassName;
}
else {
String className = (String) handlerOrClassName;
try {
Class<?> handlerClass = ClassUtils.forName(className, this.classLoader);
if (!NamespaceHandler.class.isAssignableFrom(handlerClass)) {
throw new FatalBeanException("Class [" + className + "] for namespace [" + namespaceUri +
"] does not implement the [" + NamespaceHandler.class.getName() + "] interface");
}
NamespaceHandler namespaceHandler = (NamespaceHandler) BeanUtils.instantiateClass(handlerClass);
namespaceHandler.init();
handlerMappings.put(namespaceUri, namespaceHandler);
return namespaceHandler;
}
catch (ClassNotFoundException ex) {
throw new FatalBeanException("NamespaceHandler class [" + className + "] for namespace [" +
namespaceUri + "] not found", ex);
}
catch (LinkageError err) {
throw new FatalBeanException("Invalid NamespaceHandler class [" + className + "] for namespace [" +
namespaceUri + "]: problem with handler class file or dependent class", err);
}
}
}
上面是之前畫的xmlWebApplicationContext加載bean的過程
可以看出resolve 以及parse的調用位置
查看 NamespaceHandler的實現類 NamespaceHandlerSupport 的parse方法
@Override
public BeanDefinition parse(Element element, ParserContext parserContext) {
return findParserForElement(element, parserContext).parse(element, parserContext);
}private BeanDefinitionParser findParserForElement(Element element, ParserContext parserContext) {
String localName = parserContext.getDelegate().getLocalName(element);
BeanDefinitionParser parser = this.parsers.get(localName);
if (parser == null) {
parserContext.getReaderContext().fatal(
"Cannot locate BeanDefinitionParser for element [" + localName + "]", element);
}
return parser;
}
查看對應的parse方法，在其祖父類 AbstractBeanDefinitionParser中
@Override
public final BeanDefinition parse(Element element, ParserContext parserContext) {
AbstractBeanDefinition definition = parseInternal(element, parserContext);
if (definition != null && !parserContext.isNested()) {
try {
String id = resolveId(element, definition, parserContext);
if (!StringUtils.hasText(id)) {
parserContext.getReaderContext().error(
"Id is required for element '" + parserContext.getDelegate().getLocalName(element)
+ "' when used as a top-level tag", element);
}
String[] aliases = null;
if (shouldParseNameAsAliases()) {
String name = element.getAttribute(NAME_ATTRIBUTE);
if (StringUtils.hasLength(name)) {
aliases = StringUtils.trimArrayElements(StringUtils.commaDelimitedListToStringArray(name));
}
}
BeanDefinitionHolder holder = new BeanDefinitionHolder(definition, id, aliases);
registerBeanDefinition(holder, parserContext.getRegistry());
if (shouldFireEvents()) {
BeanComponentDefinition componentDefinition = new BeanComponentDefinition(holder);
postProcessComponentDefinition(componentDefinition);
parserContext.registerComponent(componentDefinition);
}
}
catch (BeanDefinitionStoreException ex) {
parserContext.getReaderContext().error(ex.getMessage(), element);
return null;
}
}
return definition;
}查看對應代碼
@Override
protected final AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition();
String parentName = getParentName(element);
if (parentName != null) {
builder.getRawBeanDefinition().setParentName(parentName);
}
<span style="white-space:pre"> </span>//獲取bean的類型
Class<?> beanClass = getBeanClass(element);
if (beanClass != null) {
builder.getRawBeanDefinition().setBeanClass(beanClass);
}
else {
String beanClassName = getBeanClassName(element);
if (beanClassName != null) {
builder.getRawBeanDefinition().setBeanClassName(beanClassName);
}
}
builder.getRawBeanDefinition().setSource(parserContext.extractSource(element));
if (parserContext.isNested()) {
// Inner bean definition must receive same scope as containing bean.
builder.setScope(parserContext.getContainingBeanDefinition().getScope());
}
if (parserContext.isDefaultLazyInit()) {
// Default-lazy-init applies to custom bean definitions as well.
builder.setLazyInit(true);
}
doParse(element, parserContext, builder);
return builder.getBeanDefinition();
}@Override
protected Class<?> getBeanClass(Element element) {
return TransactionInterceptor.class;
}TransactionInterceptor 類的定義
public class TransactionInterceptor extends TransactionAspectSupport implements MethodInterceptor, Serializable {查看invoke方法
@Override
public Object invoke(final MethodInvocation invocation) throws Throwable {
// Work out the target class: may be {@code null}.
// The TransactionAttributeSource should be passed the target class
// as well as the method, which may be from an interface.
Class<?> targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);
// Adapt to TransactionAspectSupport's invokeWithinTransaction...
return invokeWithinTransaction(invocation.getMethod(), targetClass, new InvocationCallback() {
@Override
public Object proceedWithInvocation() throws Throwable {
return invocation.proceed();
}
});
}代碼如下：
protected Object invokeWithinTransaction(Method method, Class<?> targetClass, final InvocationCallback invocation)
throws Throwable {
// If the transaction attribute is null, the method is non-transactional.
final TransactionAttribute txAttr = getTransactionAttributeSource().getTransactionAttribute(method, targetClass);
final PlatformTransactionManager tm = determineTransactionManager(txAttr);
final String joinpointIdentification = methodIdentification(method, targetClass);
if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) {
// Standard transaction demarcation with getTransaction and commit/rollback calls.
TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification);
Object retVal = null;
try {
// This is an around advice: Invoke the next interceptor in the chain.
// This will normally result in a target object being invoked.
retVal = invocation.proceedWithInvocation();
}
catch (Throwable ex) {
// target invocation exception
completeTransactionAfterThrowing(txInfo, ex);
throw ex;
}
finally {
cleanupTransactionInfo(txInfo);
}
commitTransactionAfterReturning(txInfo);
return retVal;
}
else {
// It's a CallbackPreferringPlatformTransactionManager: pass a TransactionCallback in.
try {
Object result = ((CallbackPreferringPlatformTransactionManager) tm).execute(txAttr,
new TransactionCallback<Object>() {
@Override
public Object doInTransaction(TransactionStatus 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.
if (ex instanceof RuntimeException) {
throw (RuntimeException) ex;
}
else {
throw new ThrowableHolderException(ex);
}
}
else {
// A normal return value: will lead to a commit.
return new ThrowableHolder(ex);
}
}
finally {
cleanupTransactionInfo(txInfo);
}
}
});
// Check result: It might indicate a Throwable to rethrow.
if (result instanceof ThrowableHolder) {
throw ((ThrowableHolder) result).getThrowable();
}
else {
return result;
}
}
catch (ThrowableHolderException ex) {
throw ex.getCause();
}
}
}我自己理解就是查看當前執行方法是否滿足tx:method中配置的方法
其中TransactionAtrributeSource的一個實現類NameMatchTransactionAttributeSource的getTransactionAttribute方法爲
@Override
public TransactionAttribute getTransactionAttribute(Method method, Class<?> targetClass) {
if (!ClassUtils.isUserLevelMethod(method)) {
return null;
}
// Look for direct name match.
String methodName = method.getName();
TransactionAttribute attr = this.nameMap.get(methodName);
if (attr == null) {
// Look for most specific name match.
String bestNameMatch = null;
for (String mappedName : this.nameMap.keySet()) {
if (isMatch(methodName, mappedName) &&
(bestNameMatch == null || bestNameMatch.length() <= mappedName.length())) {
attr = this.nameMap.get(mappedName);
bestNameMatch = mappedName;
}
}
}
return attr;
}protected boolean isMatch(String methodName, String mappedName) {
return PatternMatchUtils.simpleMatch(mappedName, methodName);
}public static boolean simpleMatch(String pattern, String str)
{
if ((pattern == null) || (str == null)) {
return false;
}
int firstIndex = pattern.indexOf('*');
if (firstIndex == -1) {
return pattern.equals(str);
}
if (firstIndex == 0) {
if (pattern.length() == 1) {
return true;
}
int nextIndex = pattern.indexOf('*', firstIndex + 1);
if (nextIndex == -1) {
return str.endsWith(pattern.substring(1));
}
String part = pattern.substring(1, nextIndex);
if ("".equals(part)) {
return simpleMatch(pattern.substring(nextIndex), str);
}
int partIndex = str.indexOf(part);
while (partIndex != -1) {
if (simpleMatch(pattern.substring(nextIndex), str.substring(partIndex + part.length()))) {
return true;
}
partIndex = str.indexOf(part, partIndex + 1);
}
return false;
}spring AOP的是基於method的 所以這裏決定了method是否需要開啓事務
整個過程就是這樣，解析出advice對應的bean TransactionInterceptor 然後通過配置AOP pointcut 來指定切面位置
