MyBatis Plus執行流程與插件機制原理的深入淺析

發布時間：2020-11-04 15:51:01 來源：億速云閱讀：1267 作者：Leah 欄目：開發技術

這篇文章將為大家詳細講解有關MyBatis Plus執行流程與插件機制原理的深入淺析，文章內容質量較高，因此小編分享給大家做個參考，希望大家閱讀完這篇文章后對相關知識有一定的了解。

MyBatis Plus插件

MyBatis Plus提供了分頁插件PaginationInterceptor、執行分析插件SqlExplainInterceptor、性能分析插件PerformanceInterceptor以及樂觀鎖插件OptimisticLockerInterceptor。

Mybatis 通過插件 (Interceptor) 可以做到攔截四大對象相關方法的執行 ,根據需求完成相關數據的動態改變。

四大對象是：

Executor
StatementHandler
ParameterHandler
ResultSetHandler

四大對象的每個對象在創建時，都會執行interceptorChain.pluginAll()，會經過每個插件對象的 plugin()方法，目的是為當前的四大對象創建代理。代理對象就可以攔截到四大對象相關方法的執行，因為要執行四大對象的方法需要經過代理。

① xml下插件的配置

如下所示：

<bean id="sqlSessionFactoryBean" class="com.baomidou.mybatisplus.spring.MybatisSqlSessionFactoryBean">
<!-- 數據源 -->
<property name="dataSource" ref="dataSource">
</property>
<property name="configLocation" value="classpath:mybatis-config.xml">
</property>
<!-- 別名處理 --><property name="typeAliasesPackage" value="com.jane.mp.beans">
</property>
<!-- 注入全局MP策略配置 --><property name="globalConfig" ref="globalConfiguration">
</property>
<!-- 插件注冊 --><property name="plugins"><list><!-- 注冊分頁插件 -->
<bean class="com.baomidou.mybatisplus.plugins.PaginationInterceptor">
</bean>
<!-- 注冊執行分析插件 --><bean class="com.baomidou.mybatisplus.plugins.SqlExplainInterceptor">
<property name="stopProceed" value="true"></property></bean>
<!-- 注冊性能分析插件 -->
<bean class="com.baomidou.mybatisplus.plugins.PerformanceInterceptor"><property name="format" value="true">
</property>
<!-- <property name="maxTime" value="5"></property> --></bean>
<!-- 注冊樂觀鎖插件 -->
<bean class="com.baomidou.mybatisplus.plugins.OptimisticLockerInterceptor"></bean>
</list></property></bean>

② springboot下注冊插件

這里以分頁插件為例：

@Bean public PaginationInterceptor paginationInterceptor() 
{  
PaginationInterceptor paginationInterceptor = new PaginationInterceptor();  
// 設置請求的頁面大于最大頁后操作， true調回到首頁，false 繼續請求 默認false  
// paginationInterceptor.setOverflow(false); 
// 設置最大單頁限制數量，默認 500 條，-1 不受限制  
// paginationInterceptor.setLimit(500); 
// 開啟 count 的 join 優化,只針對部分 left join  
paginationInterceptor.setCountSqlParser(new JsqlParserCountOptimize(true)); 
return paginationInterceptor; 
}

③ SqlExplainInterceptor

SQL執行分析攔截器，全類名是com.baomidou.mybatisplus.plugins.SqlExplainInterceptor，只支持 MySQL5.6.3以上版本。

該插件的作用是分析 DELETE UPDATE語句 ,防止小白或者惡意進行DELETE UPDATE全表操作，不建議在生產環境中使用會造成性能下降，

在插件的底層通過SQL語句分析命令 Explain 分析當前的 SQL語句，根據結果集中的 Extra列來斷定當前是否全表操作。

④ 性能分析插件

性能分析攔截器，全類名是com.baomidou.mybatisplus.plugins.PerformanceInterceptor，用于輸出每條 SQL 語句及其執行時間。SQL性能執行分析 ,開發環境使用超過指定時間，停止運行。

⑤ 樂觀鎖插件

全類名是com.baomidou.mybatisplus.plugins.OptimisticLockerInterceptor。如果想實現如下需求 : 當要更新一條記錄的時候，希望這條記錄沒有被別人更新，就可以使用該插件進行判斷。

樂觀鎖的實現原理(@Version 用于注解實體字段，必須要有) :

取出記錄時，獲取當前 version
更新時，帶上這個version
執行更新時，set version = yourVersion+1 where version = yourVersion
如果 version不對，就更新失敗

【2】獲取sqlSessionFactoryBean

如下圖所示，在系統啟動時會初始化定義的bean。DefaultListableBeanFactory.preInstantiateSingletons方法中會從beanDefinitionNames中獲取bean name然后依次創建。

這里可以看到RootBeanDefinition是com.baomidou.mybatisplus.spring.MybatisSqlSessionFactoryBean。

MyBatis Plus執行流程與插件機制原理的深入淺析

① 獲取bean的過程中bean屬性

如下所示，在getBean過程中可以看到bean的屬性：

MyBatis Plus執行流程與插件機制原理的深入淺析

② createBean

第一次獲取bean的時候會走到AbstractAutowireCapableBeanFactory.createBean進行bean的創建。

 /** 創建一個bean實例，為bean實例設置屬性值，調用post-processors-bean后置處理器 */@Overrideprotected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) 
 throws BeanCreationException 
 {//...暫時忽略其他代碼 
 try {// 這里會首先觸發BeanPostProcessors ，如果這里能獲取到bean則直接返回，不再走doCreateBean 
 Object bean = resolveBeforeInstantiation(beanName, mbdToUse); 
 if (bean != null)
 { 
 return bean; 
 } }//...暫時忽略其他代碼

在AbstractAutowireCapableBeanFactory.resolveBeforeInstantiation中就會分別執行bean后置處理器的前置和后置方法。

protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) 
{ Object bean = null; 
if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved))
{ 
// Make sure bean class is actually resolved at this point. 
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors())
{  
Class<&#63;> targetType = determineTargetType(beanName, mbd);  
if (targetType != null) {  
bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);  
if (bean != null)
{   
bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);  
}  
} 
} 
mbd.beforeInstantiationResolved = (bean != null); 
} 
return bean;
}

執行后置處理器的前置方法如下所示：

MyBatis Plus執行流程與插件機制原理的深入淺析

③ doCreateBean

AbstractAutowireCapableBeanFactory.doCreateBean是創建bean的核心方法，這會為bean屬性賦值并會觸發bean后置處理器、InitializingBean以及自定init方法等。

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) throws BeanCreationException 
{
// Instantiate the bean.--實例化beanBeanWrapper instanceWrapper = null;if (mbd.isSingleton()) { instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);}if (instanceWrapper == null) 
{//獲取bean的包裝對象-這里很重要 instanceWrapper = createBeanInstance(beanName, mbd, args);}final Object bean = (instanceWrapper != null &#63; instanceWrapper.getWrappedInstance() : null);Class<&#63;> beanType = (instanceWrapper != null &#63; instanceWrapper.getWrappedClass() : null);mbd.resolvedTargetType = beanType;
// Allow post-processors to modify the merged bean definition.synchronized (mbd.postProcessingLock) 
{ if (!mbd.postProcessed)
 { try {//調用MergedBeanDefinitionPostProcessors的postProcessMergedBeanDefinition方法  applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); 
} catch (Throwable ex) 
{ 
 throw new BeanCreationException(mbd.getResourceDescription(), beanName,   "Post-processing of merged bean definition failed", ex); 
} mbd.postProcessed = true; }}//...//這里暫時忽略其他代碼
// Initialize the bean instance.--初始化bean實例Object exposedObject = bean;try {//如下方法很重要 populateBean(beanName, mbd, instanceWrapper); if (exposedObject != null) 
{ 
 exposedObject = initializeBean(beanName, exposedObject, mbd); 
}}//...

④ populateBean

顧名思義，為bean實例屬性賦值。

AbstractAutowireCapableBeanFactory.populateBean

protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {//獲取屬性值列表PropertyValues pvs = mbd.getPropertyValues();
//...該種符號表示暫時忽略其他代碼
//在為bean屬性賦值前，給InstantiationAwareBeanPostProcessors 機會修改bean的狀態//應用場景如支持字段注入boolean continueWithPropertyPopulation = true;
//循環調用InstantiationAwareBeanPostProcessors 的postProcessAfterInstantiation方法if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) {  InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;  if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {  continueWithPropertyPopulation = false;  break;  } } }}
if (!continueWithPropertyPopulation) { return;}//解析autowire注解字段，進行主動注入if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME || mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
 // Add property values based on autowire by name if applicable. if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) { autowireByName(beanName, mbd, bw, newPvs); }
 // Add property values based on autowire by type if applicable. if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { autowireByType(beanName, mbd, bw, newPvs); }
 pvs = newPvs;}boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);//循環調用InstantiationAwareBeanPostProcessors 的postProcessPropertyValues方法if (hasInstAwareBpps || needsDepCheck) { PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching); if (hasInstAwareBpps) { for (BeanPostProcessor bp : getBeanPostProcessors()) {  if (bp instanceof InstantiationAwareBeanPostProcessor) {  InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;  pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);  if (pvs == null) {   return;  }  } } } if (needsDepCheck) { checkDependencies(beanName, mbd, filteredPds, pvs); }}//在這里為屬性賦值，會進行類型轉換，這里注意關鍵詞deep copy//如果是引用類型且bean沒有存在，則會進行bean的創建過程applyPropertyValues(beanName, mbd, bw, pvs);}

如下圖所示在創建sqlSessionFactoryBean過程中會創建其屬性globalConfiguration對象：

MyBatis Plus執行流程與插件機制原理的深入淺析

如下圖所示在創建sqlSessionFactoryBean過程中(從左側的方法順序就可以看出來)會創建其屬性PaginationInterceptor對象：

MyBatis Plus執行流程與插件機制原理的深入淺析

如下圖所示在創建sqlSessionFactoryBean過程中(從左側的方法順序就可以看出來)會創建其屬性SqlExplainInterceptor對象：

MyBatis Plus執行流程與插件機制原理的深入淺析

如下圖所示在創建sqlSessionFactoryBean過程中(從左側的方法順序就可以看出來)會創建其屬性PerformanceInterceptor對象：

MyBatis Plus執行流程與插件機制原理的深入淺析

如下圖所示在創建sqlSessionFactoryBean過程中(從左側的方法順序就可以看出來)會創建其屬性OptimisticLockerInterceptor對象：

MyBatis Plus執行流程與插件機制原理的深入淺析

⑤ initializeBean

AbstractAutowireCapableBeanFactory.initializeBean源碼如下：

protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd)
{ 
if (System.getSecurityManager() != null) 
{ 
AccessController.doPrivileged(new PrivilegedAction<Object>() 
{ 
@Override  public Object run() 
{  
invokeAwareMethods(beanName, bean);  
return null; 
} 
}, getAccessControlContext()); } else { //調用意識/通知方法 invokeAwareMethods(beanName, bean); 
}
 Object wrappedBean = bean; 
 if (mbd == null || !mbd.isSynthetic())
 { //調用bean后置處理器的前置方法 
 wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName); 
 } //調用初始化方法 
 try { 
 invokeInitMethods(beanName, wrappedBean, mbd); 
 } catch (Throwable ex) 
 { 
 throw new BeanCreationException(  
 (mbd != null &#63; mbd.getResourceDescription() : null),  
 beanName, "Invocation of init method failed", ex); 
 }

AbstractAutowireCapableBeanFactory.invokeInitMethods方法源碼如下：

protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd) 
throws Throwable {
 boolean isInitializingBean = (bean instanceof InitializingBean); 
 if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) 
 { 
 if (logger.isDebugEnabled()) 
 {  
 logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'"); 
 } 
 //調用InitializingBean.afterPropertiesSet 
 if (System.getSecurityManager() != null)
 {  
 try {  
 AccessController.doPrivileged(new PrivilegedExceptionAction<Object>()
 {  
 @Override   public Object run() throws Exception 
 {   
 ((InitializingBean) bean).afterPropertiesSet();   
 return null;  
 }  }, getAccessControlContext()); 
 }  
 catch (PrivilegedActionException pae) 
 {  
 throw pae.getException(); 
 } } else {  ((InitializingBean) bean).afterPropertiesSet(); 
 } }//調用自定義初始化方法 if (mbd != null)
 { 
 String initMethodName = mbd.getInitMethodName(); 
 if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&  
 !mbd.isExternallyManagedInitMethod(initMethodName))
 {  
 invokeCustomInitMethod(beanName, bean, mbd); 
 } 
 }}

如下圖所示，MybatisSqlSessionFactoryBean同樣實現了InitializingBean接口。那么我們就需要注意其afterPropertiesSet方法了。

MyBatis Plus執行流程與插件機制原理的深入淺析

⑥ MybatisSqlSessionFactoryBean.afterPropertiesSet

如下所示，代碼很簡短只是創建了sqlSessionFactory。

@Overridepublic void afterPropertiesSet() throws Exception
{ 
notNull(dataSource, "Property 'dataSource' is required"); //sqlSessionFactoryBuilder在populateBean的applyPropertyValues過程中已經存在！ 
notNull(sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required"); 
state((configuration == null && configLocation == null) || !(configuration != null && configLocation != null),  
"Property 'configuration' and 'configLocation' can not specified with together");
 this.sqlSessionFactory = buildSqlSessionFactory();
 }

進入afterPropertiesSet()方法前MybatisSqlSessionFactoryBean如下所示：

MyBatis Plus執行流程與插件機制原理的深入淺析

我們看一下sqlSessionFactory，這是一段很長的過程：

protected SqlSessionFactory buildSqlSessionFactory() throws Exception
{ 
Configuration configuration; // TODO 加載自定義 MybatisXmlConfigBuilder 
MybatisXMLConfigBuilder xmlConfigBuilder = null; 
if (this.configuration != null) 
{  
configuration = this.configuration;  
if (configuration.getVariables() == null) 
{  
 configuration.setVariables(this.configurationProperties);  
 } else if (this.configurationProperties != null)
 {  
 configuration.getVariables().putAll(this.configurationProperties);  
 } 
 } else if (this.configLocation != null) { //通常如果配置了configLocation會從這里創建MybatisXMLConfigBuilder， //其構造方法又創建了MybatisConfiguration 
 xmlConfigBuilder = new MybatisXMLConfigBuilder(this.configLocation.getInputStream(), null, this.configurationProperties);  
 configuration = xmlConfigBuilder.getConfiguration(); } else {  
 if (LOGGER.isDebugEnabled()) {   
 LOGGER.debug("Property 'configuration' or 'configLocation' not specified, using default MyBatis Configuration");  
 }  
 // TODO 使用自定義配置  
 configuration = new MybatisConfiguration();  
 if (this.configurationProperties != null)
 {  
 configuration.setVariables(this.configurationProperties);  
 } }
 if (this.objectFactory != null)
 {  
 configuration.setObjectFactory(this.objectFactory); 
 }
 if (this.objectWrapperFactory != null)
 {  
 configuration.setObjectWrapperFactory(this.objectWrapperFactory); 
 }
 if (this.vfs != null) {  configuration.setVfsImpl(this.vfs); 
 }
 if (hasLength(this.typeAliasesPackage))
 {  
 // TODO 支持自定義通配符 
 String[] typeAliasPackageArray; 
 if (typeAliasesPackage.contains("*") && !typeAliasesPackage.contains(",")   
 && !typeAliasesPackage.contains(";")) 
 {   
 typeAliasPackageArray = PackageHelper.convertTypeAliasesPackage(typeAliasesPackage);  
 } else {   typeAliasPackageArray = tokenizeToStringArray(this.typeAliasesPackage,  
  ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);  
  }  
  if (typeAliasPackageArray == null) {   
  throw new MybatisPlusException("not find typeAliasesPackage:" + typeAliasesPackage);  
  }  for (String packageToScan : typeAliasPackageArray) 
  {   
  configuration.getTypeAliasRegistry().registerAliases(packageToScan,   
  typeAliasesSuperType == null &#63; Object.class : typeAliasesSuperType);   
  if (LOGGER.isDebugEnabled())
  {    
  LOGGER.debug("Scanned package: '" + packageToScan + "' for aliases");  
  }  
  } 
  }

 // TODO 自定義枚舉類掃描處理 
 if (hasLength(this.typeEnumsPackage))
 {  
 Set<Class> classes = null;  
 if (typeEnumsPackage.contains("*") && !typeEnumsPackage.contains(",")  
 && !typeEnumsPackage.contains(";")) 
 {  
 classes = PackageHelper.scanTypePackage(typeEnumsPackage);  
 } else {   String[] typeEnumsPackageArray = tokenizeToStringArray(this.typeEnumsPackage,   
 ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);   
 if (typeEnumsPackageArray == null) 
 {   
 throw new MybatisPlusException("not find typeEnumsPackage:" + typeEnumsPackage);   
 }  
 classes = new HashSet<Class>();   
 for (String typePackage : typeEnumsPackageArray)
 {    
 classes.addAll(PackageHelper.scanTypePackage(typePackage));  
 }  
 }  // 取得類型轉換注冊器  
 TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();  
 for (Class cls : classes) {   if (cls.isEnum()) {    if (IEnum.class.isAssignableFrom(cls)) {   
 typeHandlerRegistry.register(cls.getName(), com.baomidou.mybatisplus.handlers.EnumTypeHandler.class.getCanonicalName());    } else {     
 // 使用原生 EnumOrdinalTypeHandler     typeHandlerRegistry.register(cls.getName(), org.apache.ibatis.type.EnumOrdinalTypeHandler.class.getCanonicalName());   
 }  
 }  } }
 if (!isEmpty(this.typeAliases)) { 

 for (Class<&#63;> typeAlias : this.typeAliases) 
 {   
 configuration.getTypeAliasRegistry().registerAlias(typeAlias);   
 if (LOGGER.isDebugEnabled())
 {  
 LOGGER.debug("Registered type alias: '" + typeAlias + "'");  
 }  
 } }
 if (!isEmpty(this.plugins)) 
 {  
 for (Interceptor plugin : this.plugins)
 {   
 configuration.addInterceptor(plugin);   
 if (LOGGER.isDebugEnabled()) 
 {    
 LOGGER.debug("Registered plugin: '" + plugin + "'");   
 }  
 } 
 }
 if (hasLength(this.typeHandlersPackage))
 {  
 String[] typeHandlersPackageArray = tokenizeToStringArray(this.typeHandlersPackage,  
 ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);  
 for (String packageToScan : typeHandlersPackageArray)
{  
 configuration.getTypeHandlerRegistry().register(packageToScan);   
 if (LOGGER.isDebugEnabled()) {    
 LOGGER.debug("Scanned package: '" + packageToScan + "' for type handlers");   
 }  
 } 
 }
 if (!isEmpty(this.typeHandlers))
 {  
 for (TypeHandler<&#63;> typeHandler : this.typeHandlers)
 {  
 configuration.getTypeHandlerRegistry().register(typeHandler);  
 if (LOGGER.isDebugEnabled()) 
 {    
 LOGGER.debug("Registered type handler: '" + typeHandler + "'");   
 }  } }
 if (this.databaseIdProvider != null) {//fix #64 set databaseId before parse mapper xmls  
 try {   configuration.setDatabaseId(this.databaseIdProvider.getDatabaseId(this.dataSource));  
 } catch (SQLException e) {   
 throw new NestedIOException("Failed getting a databaseId", e); 
 } 
 }
 if (this.cache != null)
 {  
 configuration.addCache(this.cache); 
 }
 if (xmlConfigBuilder != null) 
 {  
 try 
 {   
 xmlConfigBuilder.parse();
   if (LOGGER.isDebugEnabled())
	 {   
	 LOGGER.debug("Parsed configuration file: '" + this.configLocation + "'");   
	 }  } catch (Exception ex) 
	 {   
	 throw new NestedIOException("Failed to parse config resource: " + this.configLocation, ex);  
	 } finally {   
	 ErrorContext.instance().reset();  
	 }
	 }
 if (this.transactionFactory == null)
 {  this.transactionFactory = new SpringManagedTransactionFactory(); 
 }
 configuration.setEnvironment(new Environment(this.environment, this.transactionFactory, this.dataSource)); 
 // 設置元數據相關 
 GlobalConfigUtils.setMetaData(dataSource, globalConfig); SqlSessionFactory sqlSessionFactory = this.sqlSessionFactoryBuilder.build(configuration); 
 // TODO SqlRunner 
 SqlRunner.FACTORY = sqlSessionFactory; // TODO 緩存 sqlSessionFactory globalConfig.setSqlSessionFactory(sqlSessionFactory); // TODO 設置全局參數屬性 
 globalConfig.signGlobalConfig(sqlSessionFactory); 
 if (!isEmpty(this.mapperLocations)) {  
 if (globalConfig.isRefresh()) {   
 //TODO 設置自動刷新配置 減少配置   
 new MybatisMapperRefresh(this.mapperLocations, sqlSessionFactory, 2,    
 2, true);  }  
 for (Resource mapperLocation : this.mapperLocations)
 {  
 if (mapperLocation == null) {  
 continue;   
 }
   try {    
	 // TODO 這里也換了噢噢噢噢  
	 XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(),     
	 configuration, mapperLocation.toString(), configuration.getSqlFragments());    
	 xmlMapperBuilder.parse();   
	 } catch (Exception e) {   
	 throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", e);   
 } finally {    
 ErrorContext.instance().reset();   
 }
   if (LOGGER.isDebugEnabled())
	 {    
	 LOGGER.debug("Parsed mapper file: '" + mapperLocation + "'");  
	 } 
	 } 
	 } 
	 else { 
	 if (LOGGER.isDebugEnabled())
	 {  
	 LOGGER.debug("Property 'mapperLocations' was not specified or no matching resources found");  
	 } 
	 } 
	 return sqlSessionFactory;
	 }

上面代碼主要做了如下事情：

獲取MybatisXMLConfigBuilder對象
獲取Configuration對象-MybatisConfiguration
配置對象Configuration添加插件configuration.addInterceptor(plugin);
xmlConfigBuilder.parse()對configuration做進一步處理
獲取SpringManagedTransactionFactory用來創建SpringManagedTransaction
獲取一個DefaultSqlSessionFactory實例對象
globalConfig.setSqlSessionFactory(sqlSessionFactory)中會創建MybatisSqlSessionTemplate
解析mapperLocation對應的一個個mapper配置文件，使用助手builderAssistant的addMappedStatement方法將一個個結點添加配置對象中
其他屬性設置等等

也就是說，在MybatisSqlSessionFactoryBean.afterPropertiesSet方法執行結束后，SqlSessionFactory、SqlSessionTemplate、Configuration等都已存在！

【3】查詢執行流程分析

示例代碼如下：

List<Employee > emps = employeeMapper.selectPage(page, null);

如下圖所示，此時我們獲取到的employeeMapper其實是個代理對象：

MyBatis Plus執行流程與插件機制原理的深入淺析

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