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【1】MyBatis Plus插件

MyBatis Plus提供了分頁(yè)插件PaginationInterceptor、執(zhí)行分析插件SqlExplainInterceptor、性能分析插件PerformanceInterceptor以及樂(lè)觀鎖插件OptimisticLockerInterceptor。

Mybatis 通過(guò)插件 (Interceptor) 可以做到攔截四大對(duì)象相關(guān)方法的執(zhí)行 ,根據(jù)需求完成相關(guān)數(shù)據(jù)的動(dòng)態(tài)改變。

四大對(duì)象是：

Executor
StatementHandler
ParameterHandler
ResultSetHandler

四大對(duì)象的每個(gè)對(duì)象在創(chuàng)建時(shí)，都會(huì)執(zhí)行interceptorChain.pluginAll()，會(huì)經(jīng)過(guò)每個(gè)插件對(duì)象的?plugin()方法，目的是為當(dāng)前的四大對(duì)象創(chuàng)建代理。代理對(duì)象就可以攔截到四大對(duì)象相關(guān)方法的執(zhí)行，因?yàn)橐獔?zhí)行四大對(duì)象的方法需要經(jīng)過(guò)代理。

① xml下插件的配置

如下所示：

"sqlSessionFactoryBean" class="com.baomidou.mybatisplus.spring.MybatisSqlSessionFactoryBean"><property name="dataSource" ref="dataSource">property><property name="configLocation" value="classpath:mybatis-config.xml">property><property name="typeAliasesPackage" value="com.jane.mp.beans">property><property name="globalConfig" ref="globalConfiguration">property><property name="plugins"><list><bean class="com.baomidou.mybatisplus.plugins.PaginationInterceptor">bean><bean class="com.baomidou.mybatisplus.plugins.SqlExplainInterceptor"><property name="stopProceed" value="true">property>bean><bean class="com.baomidou.mybatisplus.plugins.PerformanceInterceptor"><property name="format" value="true">property>bean><bean class="com.baomidou.mybatisplus.plugins.OptimisticLockerInterceptor">bean>list>property>bean>

② springboot下注冊(cè)插件

這里以分頁(yè)插件為例：

@Bean public PaginationInterceptor paginationInterceptor() {     PaginationInterceptor paginationInterceptor = new PaginationInterceptor();     // 設(shè)置請(qǐng)求的頁(yè)面大于最大頁(yè)后操作， true調(diào)回到首頁(yè)，false 繼續(xù)請(qǐng)求  默認(rèn)false     // paginationInterceptor.setOverflow(false);     // 設(shè)置最大單頁(yè)限制數(shù)量，默認(rèn) 500 條，-1 不受限制     // paginationInterceptor.setLimit(500);     // 開(kāi)啟 count 的 join 優(yōu)化,只針對(duì)部分 left join     paginationInterceptor.setCountSqlParser(new JsqlParserCountOptimize(true));     return paginationInterceptor;?}

③ SqlExplainInterceptor

SQL執(zhí)行分析攔截器，全類(lèi)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(yǔ)句 ,防止小白或者惡意進(jìn)行DELETE UPDATE全表操作，不建議在生產(chǎn)環(huán)境中使用會(huì)造成性能下降，

在插件的底層通過(guò)SQL語(yǔ)句分析命令?Explain?分析當(dāng)前的 SQL語(yǔ)句，根據(jù)結(jié)果集中的?Extra列來(lái)斷定當(dāng)前是否全表操作。

④ 性能分析插件

性能分析攔截器，全類(lèi)名是com.baomidou.mybatisplus.plugins.PerformanceInterceptor，用于輸出每條 SQL 語(yǔ)句及其執(zhí)行時(shí)間。SQL性能執(zhí)行分析 ,開(kāi)發(fā)環(huán)境使用超過(guò)指定時(shí)間，停止運(yùn)行。

⑤ 樂(lè)觀鎖插件

全類(lèi)名是com.baomidou.mybatisplus.plugins.OptimisticLockerInterceptor。如果想實(shí)現(xiàn)如下需求 : 當(dāng)要更新一條記錄的時(shí)候，希望這條記錄沒(méi)有被別人更新，就可以使用該插件進(jìn)行判斷。

樂(lè)觀鎖的實(shí)現(xiàn)原理(@Version 用于注解實(shí)體字段，必須要有) :

取出記錄時(shí)，獲取當(dāng)前 version
更新時(shí)，帶上這個(gè)version
執(zhí)行更新時(shí)，set version = yourVersion+1 where version = yourVersion
如果 version不對(duì)，就更新失敗

【2】獲取sqlSessionFactoryBean

如下圖所示，在系統(tǒng)啟動(dòng)時(shí)會(huì)初始化定義的bean。DefaultListableBeanFactory.preInstantiateSingletons方法中會(huì)從beanDefinitionNames中獲取bean name然后依次創(chuàng)建。

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

① 獲取bean的過(guò)程中bean屬性

如下所示，在getBean過(guò)程中可以看到bean的屬性：

② createBean

第一次獲取bean的時(shí)候會(huì)走到AbstractAutowireCapableBeanFactory.createBean進(jìn)行bean的創(chuàng)建。

 /** 創(chuàng)建一個(gè)bean實(shí)例，為bean實(shí)例設(shè)置屬性值，調(diào)用post-processors-bean后置處理器 */@Overrideprotected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {//...暫時(shí)忽略其他代碼  try {// 這里會(huì)首先觸發(fā)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(shí)忽略其他代碼
//如果上面沒(méi)有獲取到bean，則會(huì)走doCreateBean--這也是創(chuàng)建bean的核心過(guò)程  Object beanInstance = doCreateBean(beanName, mbdToUse, args);//...暫時(shí)忽略其他代碼  return beanInstance;}

在AbstractAutowireCapableBeanFactory.resolveBeforeInstantiation中就會(huì)分別執(zhí)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 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(zhí)行后置處理器的前置方法如下所示：

③ doCreateBean

AbstractAutowireCapableBeanFactory.doCreateBean是創(chuàng)建bean的核心方法，這會(huì)為bean屬性賦值并會(huì)觸發(fā)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(shí)例化beanBeanWrapper instanceWrapper = null;if (mbd.isSingleton()) {  instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);}if (instanceWrapper == null) {//獲取bean的包裝對(duì)象-這里很重要  instanceWrapper = createBeanInstance(beanName, mbd, args);}final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);Class beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);mbd.resolvedTargetType = beanType;
// Allow post-processors to modify the merged bean definition.synchronized (mbd.postProcessingLock) {  if (!mbd.postProcessed) {    try {//調(diào)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(shí)忽略其他代碼
// Initialize the bean instance.--初始化bean實(shí)例Object exposedObject = bean;try {//如下方法很重要  populateBean(beanName, mbd, instanceWrapper);  if (exposedObject != null) {    exposedObject = initializeBean(beanName, exposedObject, mbd);  }}//...
// Register bean as disposable.try {  registerDisposableBeanIfNecessary(beanName, bean, mbd);}//...return exposedObject;}

④ populateBean

顧名思義，為bean實(shí)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(hào)表示暫時(shí)忽略其他代碼
//在為bean屬性賦值前，給InstantiationAwareBeanPostProcessors 機(jī)會(huì)修改bean的狀態(tài)//應(yīng)用場(chǎng)景如支持字段注入boolean continueWithPropertyPopulation = true;
//循環(huán)調(diào)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(jìn)行主動(dòng)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(huán)調(diào)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(huì)進(jìn)行類(lèi)型轉(zhuǎn)換，這里注意關(guān)鍵詞deep copy//如果是引用類(lèi)型且bean沒(méi)有存在，則會(huì)進(jìn)行bean的創(chuàng)建過(guò)程applyPropertyValues(beanName, mbd, bw, pvs);}

如下圖所示在創(chuàng)建sqlSessionFactoryBean過(guò)程中會(huì)創(chuàng)建其屬性globalConfiguration對(duì)象：

如下圖所示在創(chuàng)建sqlSessionFactoryBean過(guò)程中(從左側(cè)的方法順序就可以看出來(lái))會(huì)創(chuàng)建其屬性PaginationInterceptor對(duì)象：

如下圖所示在創(chuàng)建sqlSessionFactoryBean過(guò)程中(從左側(cè)的方法順序就可以看出來(lái))會(huì)創(chuàng)建其屬性SqlExplainInterceptor對(duì)象：

如下圖所示在創(chuàng)建sqlSessionFactoryBean過(guò)程中(從左側(cè)的方法順序就可以看出來(lái))會(huì)創(chuàng)建其屬性PerformanceInterceptor對(duì)象：

如下圖所示在創(chuàng)建sqlSessionFactoryBean過(guò)程中(從左側(cè)的方法順序就可以看出來(lái))會(huì)創(chuàng)建其屬性OptimisticLockerInterceptor對(duì)象：

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(diào)用意識(shí)/通知方法    invokeAwareMethods(beanName, bean);  }
  Object wrappedBean = bean;  if (mbd == null || !mbd.isSynthetic()) {  //調(diào)用bean后置處理器的前置方法    wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);  }  //調(diào)用初始化方法  try {    invokeInitMethods(beanName, wrappedBean, mbd);  }  catch (Throwable ex) {    throw new BeanCreationException(        (mbd != null ? mbd.getResourceDescription() : null),        beanName, "Invocation of init method failed", ex);  }
  if (mbd == null || !mbd.isSynthetic()) {  //  //調(diào)用bean后置處理器的后置方法    wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);  }  return wrappedBean;}

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(diào)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(diào)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(shí)現(xiàn)了InitializingBean接口。那么我們就需要注意其afterPropertiesSet方法了。

⑥ MybatisSqlSessionFactoryBean.afterPropertiesSet

如下所示，代碼很簡(jiǎn)短只是創(chuàng)建了sqlSessionFactory。

@Overridepublic void afterPropertiesSet() throws Exception {    notNull(dataSource, "Property 'dataSource' is required"); //sqlSessionFactoryBuilder在populateBean的applyPropertyValues過(guò)程中已經(jīng)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(jìn)入afterPropertiesSet()方法前MybatisSqlSessionFactoryBean如下所示：

我們看一下sqlSessionFactory，這是一段很長(zhǎng)的過(guò)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(huì)從這里創(chuàng)建MybatisXMLConfigBuilder， //其構(gòu)造方法又創(chuàng)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 ? Object.class : typeAliasesSuperType);            if (LOGGER.isDebugEnabled()) {                LOGGER.debug("Scanned package: '" + packageToScan + "' for aliases");            }        }    }
    // TODO 自定義枚舉類(lèi)掃描處理    if (hasLength(this.typeEnumsPackage)) {        Set 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();            for (String typePackage : typeEnumsPackageArray) {                classes.addAll(PackageHelper.scanTypePackage(typePackage));            }        }        // 取得類(lèi)型轉(zhuǎn)換注冊(cè)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 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 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(shè)置元數(shù)據(jù)相關(guān)    GlobalConfigUtils.setMetaData(dataSource, globalConfig);    SqlSessionFactory sqlSessionFactory = this.sqlSessionFactoryBuilder.build(configuration);    // TODO SqlRunner    SqlRunner.FACTORY = sqlSessionFactory;    // TODO 緩存 sqlSessionFactory    globalConfig.setSqlSessionFactory(sqlSessionFactory);    // TODO 設(shè)置全局參數(shù)屬性    globalConfig.signGlobalConfig(sqlSessionFactory);    if (!isEmpty(this.mapperLocations)) {        if (globalConfig.isRefresh()) {            //TODO 設(shè)置自動(dòng)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(duì)象
獲取Configuration對(duì)象-MybatisConfiguration
配置對(duì)象Configuration添加插件configuration.addInterceptor(plugin);
xmlConfigBuilder.parse()對(duì)configuration做進(jìn)一步處理
獲取SpringManagedTransactionFactory用來(lái)創(chuàng)建SpringManagedTransaction
獲取一個(gè)DefaultSqlSessionFactory實(shí)例對(duì)象
globalConfig.setSqlSessionFactory(sqlSessionFactory)中會(huì)創(chuàng)建MybatisSqlSessionTemplate
解析mapperLocation對(duì)應(yīng)的一個(gè)個(gè)mapper配置文件，使用助手builderAssistant的addMappedStatement方法將一個(gè)個(gè)結(jié)點(diǎn)添加配置對(duì)象中
其他屬性設(shè)置等等

也就是說(shuō)，在MybatisSqlSessionFactoryBean.afterPropertiesSet方法執(zhí)行結(jié)束后，SqlSessionFactory、SqlSessionTemplate、Configuration等都已存在！

【3】查詢(xún)執(zhí)行流程分析

示例代碼如下：

List?emps?=?employeeMapper.selectPage(page,?null);

如下圖所示，此時(shí)我們獲取到的employeeMapper其實(shí)是個(gè)代理對(duì)象：

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本文鏈接：

https://janus.blog.csdn.net/article/details/108441600

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MyBatis Plus插件機(jī)制與執(zhí)行流程原理分析