報錯日志
在搭建 spring 4.3 + mybatis 3.4 的開發(fā)框架時，啟動報錯
啟動報錯如下：
nested exception is java.sql.SQLException: ${jdbc.driver}
配置都是大同小異，唯一的區(qū)別是加了這個更便捷的配置
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.taro.dao"/>
<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
</bean>
有了這個配置就不需要再寫一大堆繁瑣的Dao配置，spring會自動為我們把這些 dao 寫入到 內(nèi)部維護的BeanDefinitions 中去。
解決方法
- 一.如果有配置 default-autowire 將這個配置去掉
- 二.spring 配置文件中org.mybatis.spring.SqlSessionFactoryBean 的命名不要命名成
sqlSessionFactory， 另外MapperScannerConfigurer中的sqlSessionFactoryBeanName也改成相應(yīng)的名字
正確的配置:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"
default-autowire="byName" default-lazy-init="true">
<!-- DataSource數(shù)據(jù) -->
<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
<property name="name" value="souchecar"/>
<property name="driverClassName" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
<property name="maxActive" value="20"/>
<property name="minIdle" value="2"/>
<property name="initialSize" value="2"/>
<property name="validationQuery" value="SELECT 1"/>
<property name="testOnBorrow" value="false"/>
<property name="testOnReturn" value="false"/>
<property name="testWhileIdle" value="true"/>
<property name="timeBetweenEvictionRunsMillis" value="60000"/>
<property name="minEvictableIdleTimeMillis" value="300000"/>
<property name="defaultAutoCommit" value="true"/>
<property name="removeAbandoned" value="true"/>
<property name="removeAbandonedTimeout" value="6000"/>
<property name="logAbandoned" value="true"/>
<property name="filters" value="stat"/>
</bean>
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="mapperLocations">
<list>
<value>classpath*:sqlmap/**/*.xml</value>
</list>
</property>
<property name="dataSource" ref="dataSource"/>
</bean>
<!-- DAO接口所在包名，Spring會自動查找其下的類 -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.taro.dao"/>
<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
</bean>
</beans>
分析原因
看報錯可知配置信息沒有加載進去
配置信息我是配置了的，配置沒有任何問題
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath*:*.properties</value>
</list>
</property>
</bean>
那么是什么原因呢，讓我們來看源碼
可知 PropertyPlaceholderConfigurer 是實現(xiàn)了 BeanFactoryPostProcessor 接口的
而 MapperScannerConfigurer 實現(xiàn)了 BeanDefinitionRegistryPostProcessor 接口
要想知道這幾個接口含義,以及是在spring 加載的哪個過程執(zhí)行的，還是得一步步的看源碼
- 回到spring最經(jīng)典的入口代碼
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 一,Prepare this context for refreshing.
prepareRefresh();
// 二,重啟容器,并載入BeanDefinitions
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 三,Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// 四,Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// 五,執(zhí)行BeanFactoryPostProcessor接口和BeanDefinitionRegistryPostProcessor接口的地方
invokeBeanFactoryPostProcessors(beanFactory);
// 六,Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// 七,Initialize message source for this context.
initMessageSource();
// 八,Initialize event multicaster for this context.
initApplicationEventMulticaster();
// 九,Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
- 我們重點來看第5步，進入invokeBeanFactoryPostProcessors方法
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
- invokeBeanFactoryPostProcessors
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// 先執(zhí)行 BeanDefinitionRegistryPostProcessors // processedBeans 存放已經(jīng)執(zhí)行過的 FactoryPostProcessor
Set<String> processedBeans = new HashSet<String>();
// 先判斷beanFactory 是不是 BeanDefinitionRegistry 類型
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();
// 把手動加入的 BeanFactoryPostProcessor 分類型分別放入regularPostProcessors ,registryProcessors 中
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
regularPostProcessors.add(postProcessor);
}
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// Separate between BeanDefinitionRegistryPostProcessors that implement
// PriorityOrdered, Ordered, and the rest.
// 下面的代碼會根據(jù)優(yōu)先級情況先后執(zhí)行 BeanDefinitionRegistryPostProcessor 和 BeanFactoryPostProcessors
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
// 先執(zhí)行實現(xiàn)了 PriorityOrdered （優(yōu)先執(zhí)行）的接口的BeanDefinitionRegistryPostProcessor.class
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// 再執(zhí)行 Ordered 類型的BeanDefinitionRegistryPostProcessor.class
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// 最后執(zhí)行 剩下的BeanDefinitionRegistryPostProcessor
boolean reiterate = true;
while (reiterate) {
reiterate = false;
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
// 執(zhí)行手動加入的
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// 直接執(zhí)行
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// 根據(jù)排序順序執(zhí)行 BeanFactoryPostProcessor ,前面已經(jīng)執(zhí)行過的BeanDefinitionRegistryPostProcessor 不會執(zhí)行
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
List<String> orderedPostProcessorNames = new ArrayList<String>();
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
for (String ppName : postProcessorNames) {
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();
}
超級長的一堆代碼,看著慌...
我們分幾步來分析
- BeanDefinitionRegistryPostProcessor 優(yōu)先執(zhí)行，執(zhí)行順序 實現(xiàn)了么接口PriorityOrdered
最優(yōu)先 Ordered其次 ,最后執(zhí)行普通的 BeanDefinitionRegistryPostProcessor - 再執(zhí)行手動加入的 BeanDefinitionRegistryPostProcessor 和BeanFactoryPostProcessor （由容器的 addBeanFactoryPostProcessor
方法加入的） - 之后執(zhí)行 BeanFactoryPostProcessor ,執(zhí)行順序與BeanDefinitionRegistryPostProcessor類似
現(xiàn)在我們再來分析原因
通過查看MapperScannerConfigurer源碼，可知其實現(xiàn)了BeanDefinitionRegistryPostProcessor接口，而PropertyPlaceholderConfigurer實現(xiàn)的是BeanFactoryPostProcessor接口。 那么這就說明MapperScannerConfigurer是優(yōu)先于PropertyPlaceholderConfigurer執(zhí)行的,那么要是MapperScannerConfigurer提前初始化了數(shù)據(jù)庫連接,而相關(guān)配置屬性還沒被替換,就會報這個錯了。
貌似問題找打了，可仔細一看，我MapperScannerConfigurer配置的注入屬性不是sqlSessionFactoryBeanName嗎（sqlSessionFactoryBeanName會在spring初始化完成后才會獲?。@可只是String 類型,怎么就提前去初始化了sqlSessionFactory 呢?
這就得從spring的依賴注入規(guī)則去分析了
首先，我配置的是自動注入 default-autowire="byName" 意思就是說就算我不配各種property Spring 也會自動根據(jù)Name去容器里找然后注入給我。那么問題就出在這里，因為MapperScannerConfigurer 里有SqlSessionFactory 類型的屬性，所以spring就自作主張給我們?nèi)ト萜骼镎腋鶕?jù)名字sqlSessionFactory去找這個類型的 BeanDefinition，因為我們配置的sqlSessionFactory 名字恰好也是 sqlSessionFactory，結(jié)果就給找到了,一找到就立馬調(diào)用getBean方法提前初始化sqlSessionFactory了,進而提前初始化了dataSource，導(dǎo)致了報錯！
所以解決方法就是上文提到的這兩種方式
Spring 系列
