Mybatis与SpringMVC整合 源码分析

       之前项目中使用过SSM框架，但一直没有拿出时间进行深入的研究。

    本文主要针对持久层框架Mybatis以及与SpringMVC的整合进行源码分析。

      1.整合需要的Jar

   Mybatis与Spring整合的主要jar包有两个：mybatis-3.4.0.jar和mybatis-spring-1.3.0.jar

    Maven的pom.xml配置文件：      

<!-- mybatis --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.4.0</version></dependency><dependency><groupId>org.mybatis</groupId><artifactId>mybatis-spring</artifactId><version>1.3.0</version></dependency> 

     2.SpringMVC配置文件

   Mybatis与SpringMVC的整合是在spring-mybatis.xml配置文件中进行声明。配置文件结构如下：

  

     其中spring-mvc.xml是SpringMVC的配置文件。

     spring-mybatis.xml的配置内容如下：

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"xmlns:tx="http://www.springframework.org/schema/tx"xmlns:aop="http://www.springframework.org/schema/aop"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsdhttp://www.springframework.org/schema/context            http://www.springframework.org/schema/context/spring-context-3.1.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.1.xsdhttp://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.1.xsd"><!--自动扫描含有@Service将其注入为bean --><context:component-scan base-package="com.*.service" use-default-filters="false">    <context:include-filter type="annotation"              expression="org.springframework.stereotype.Service" />    </context:component-scan>      <!--引入配置属性文件 --><bean id="propertyConfigurer"          class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">          <property name="location" value="classpath:config/jdbc.properties" />      </bean> <!-- 配置数据源 使用的是Druid数据源 --><bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"          destroy-method="close">          <property name="driverClassName" value="${driver}" />          <property name="url" value="${url}" />          <property name="username" value="${username}" />          <property name="password" value="${password}" />          <!-- 初始化连接大小 -->          <property name="initialSize" value="${initialSize}"></property>          <!-- 连接池最大数量 -->          <property name="maxActive" value="${maxActive}"></property>          <!-- 连接池最大空闲 -->          <property name="maxIdle" value="${maxIdle}"></property>          <!-- 连接池最小空闲 -->          <property name="minIdle" value="${minIdle}"></property>          <!-- 获取连接最大等待时间 -->          <property name="maxWait" value="${maxWait}"></property>      </bean>         <!-- weblogic推荐使用jndi连接池 -->    <!--     <bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean">         <property name="jndiName">             <value>java:comp/env/jdbc/myDatasource</value>         </property>     </bean>     --> <span style="color:#ff0000;"><strong><!-- spring和MyBatis完美整合，不需要mybatis的配置映射文件 --><bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"><property name="dataSource" ref="dataSource" /><property name="configLocation" value="classpath:mybatis/mybatis-config.xml" /><!-- 自动扫描entity目录, 省掉Configuration.xml里的手工配置 --><property name="mapperLocations" value="classpath*:com/**/mapping/*.xml" /></bean><bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate"><constructor-arg index="0" ref="sqlSessionFactory" /></bean> <!-- DAO接口所在包名，Spring会自动查找其下的类 --><bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"><property name="basePackage" value="com.*.dao" /><property name="sqlSessionTemplateBeanName" value="sqlSession" /></bean></strong></span><!-- 配置事务管理器 --><bean id="transactionManager"class="org.springframework.jdbc.datasource.DataSourceTransactionManager"><property name="dataSource" ref="dataSource" /></bean><!-- 注解方式配置事物 --><!-- <tx:annotation-driven transaction-manager="transactionManager" /> --><!-- 拦截器方式配置事物 --><tx:advice id="transactionAdvice" transaction-manager="transactionManager"><tx:attributes><tx:method name="insert*" propagation="REQUIRED" /><tx:method name="update*" propagation="REQUIRED" /><tx:method name="delete*" propagation="REQUIRED" /><tx:method name="get*" propagation="SUPPORTS" read-only="true"/><tx:method name="find*" propagation="SUPPORTS" read-only="true" /><tx:method name="select*" propagation="SUPPORTS" read-only="true" /></tx:attributes></tx:advice><!-- Spring aop事务管理 --><aop:config><aop:pointcut id="transactionPointcut"expression="execution(* com..service.impl.*Impl.*(..))" /><aop:advisor pointcut-ref="transactionPointcut"advice-ref="transactionAdvice" /></aop:config></beans>

    Mybatis与Spring整合部分是红色字体标注的内容。

    SqlSessionFactoryBean：datasource、configuration和*mapper.xml的配置信息都会注入到其中。

       部分源码：

   <span style="font-size:18px;"><span style="color:#ff0000;">private Resource configLocation;</span>  private Configuration configuration;  <span style="color:#ff0000;">private Resource[] mapperLocations;  private DataSource dataSource;</span>  private TransactionFactory transactionFactory;  private Properties configurationProperties;  private SqlSessionFactoryBuilder sqlSessionFactoryBuilder;  private SqlSessionFactory sqlSessionFactory;  private String environment;  private boolean failFast;  private Interceptor[] plugins;  private TypeHandler<?>[] typeHandlers;  private String typeHandlersPackage;  private Class<?>[] typeAliases;  private String typeAliasesPackage;  private Class<?> typeAliasesSuperType;  private DatabaseIdProvider databaseIdProvider;  private Class<? extends VFS> vfs;  private Cache cache;  private ObjectFactory objectFactory;  private ObjectWrapperFactory objectWrapperFactory;</span>

         SqlSessionTemplate：实现了SqlSession接口，是Mybatis与数据库进行交互的主要类。

    部分源码：

 public SqlSessionTemplate(<span style="color:#ff0000;">SqlSessionFactory sqlSessionFactory</span>)  {    this(sqlSessionFactory, sqlSessionFactory.getConfiguration().getDefaultExecutorType());  }  public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType)  {    this(sqlSessionFactory, executorType,       new MyBatisExceptionTranslator(sqlSessionFactory.getConfiguration      ().getEnvironment().getDataSource(), true));  }  public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType, PersistenceExceptionTranslator exceptionTranslator)  {    Assert.notNull(sqlSessionFactory, "Property 'sqlSessionFactory' is required");    Assert.notNull(executorType, "Property 'executorType' is required");    this.sqlSessionFactory = sqlSessionFactory;    this.executorType = executorType;    this.exceptionTranslator = exceptionTranslator;    this.<strong><span style="color:#ff0000;">sqlSessionProxy</span></strong> = ((DisposableBean)Proxy.newProxyInstance(SqlSessionFactory.class.getClassLoader      (), new Class[] { DisposableBean.class }, new SqlSessionInterceptor(this, null)));  }

       可以看出SqlSessionTempalte利用SqlSessionFactory，也就是上文配置的SqlSessionFactoryBean，最终生成了SqlSession的实例化对象sqlSessionProxy，使用的生成方式是Java Proxy机制。

<span style="font-size:24px;">     <span style="color:#ff0000;"><strong>MapperScannerConfigurer：用来自动扫描basePackage目录下的Mapper接口，将每个Mapper接口进行封装生成MapperFactoryBean的实例。</strong></span></span>

       至此，Mybatis与SpringMVC已经整合完成。