mybatis 缓存 + spring 整合详解

@Test
    // 测试自动映射
    public void testAutoMapping() throws IOException {
        // 2.获取sqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        // 3.获取对应mapper
        TUserMapper mapper = sqlSession.getMapper(TUserMapper.class);
        // 4.执行查询语句并返回结果
        TUser user = mapper.selectByPrimaryKey(1);
        TUser user2 = mapper.selectByPrimaryKey(1);
        TUser user3 = mapper.selectByPrimaryKey(1);
        TUser user4 = mapper.selectByPrimaryKey(1);
        System.out.println(user == user4);
    }

2020-10-22 19:45:46.216 [main] DEBUG c.e.mybatis.mapper.TUserMapper.selectByPrimaryKey - <== Total: 1
true

一级缓存 是 sqlSession的， 一级 缓存是线程级别的

优先从 二级缓存【线程共享缓存】 查找，然后再查找一级缓存【线程独享】， 没有，然后再查找数据库

 

 控制台上 出现 cache Hit  的 就是 二级缓存了，mybatis 会自己统计缓存命中率

 多个 mapper 可以通过 配置 cache-ref  配置同一个缓存数据源

使用二级缓存，容易脏读，没有提交的数据被回滚了，你就用了没有提交的脏数据，一般用专业的第三方缓存根据在业务层控制

 

使用 mybatis-spring 整合在一起

 

mybatis 的异常 封装到了 spring 的 DataAccessException

    <!-- 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="typeAliasesPackage" value="com.enjoylearning.mybatis.entity" />
        <property name="mapperLocations" value="classpath*:sqlmapper/*.xml" />
    </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.enjoylearning.mybatis.mapper" />
    </bean>

总结：

    <!-- 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="typeAliasesPackage" value="com.enjoylearning.mybatis.entity" />
        <property name="mapperLocations" value="classpath*:sqlmapper/*.xml" />
    </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.enjoylearning.mybatis.mapper" />
    </bean>



    <!-- (事务管理)transaction manager -->
    <bean id="transactionManager"
        class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
        <qualifier value="transactionManager" />
    </bean>

    <tx:annotation-driven transaction-manager="transactionManager" />


    <context:component-scan base-package="com.*">
    </context:component-scan>

还需要 添加一个 mybatis-config.xml 配置 mybatis 部分配置

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    
    <properties resource="db.properties"/>
    
    <settings>
        
        
        <setting name="mapUnderscoreToCamelCase" value="true" />
        
        
    
    </settings>

    <!-- 别名定义 -->
    
    <typeAliases>
        <package name="com.enjoylearning.mybatis.entity"/>
    </typeAliases>


    <!--配置environment环境 -->
    <environments default="development">
        <!-- 环境配置1，每个SqlSessionFactory对应一个环境 -->
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="UNPOOLED">
                <property name="driver" value="${jdbc_driver}" />
                <property name="url" value="${jdbc_url}" />
                <property name="username" value="${jdbc_username}" />
                <property name="password" value="${jdbc_password}" />
            </dataSource>
        </environment>


    </environments>

    <!-- 映射文件，mapper的配置文件 -->
    <mappers>
        <!--直接映射到相应的mapper文件 -->
        <mapper resource="sqlmapper/TUserMapper.xml" />
        <mapper resource="sqlmapper/TJobHistoryMapper.xml" /> 
        <!-- <mapper class="com.enjoylearning.mybatis.mapper.TJobHistoryAnnoMapper"/> -->
    </mappers>

</configuration>  

完整整合配置：

<?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:c="http://www.springframework.org/schema/c"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:cache="http://www.springframework.org/schema/cache" 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.xsd
                        http://www.springframework.org/schema/context 
                        http://www.springframework.org/schema/context/spring-context-4.3.xsd
                        http://www.springframework.org/schema/cache
                        http://www.springframework.org/schema/cache/spring-cache.xsd
                        http://www.springframework.org/schema/tx 
                          http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
                          http://www.springframework.org/schema/aop
                        http://www.springframework.org/schema/aop/spring-aop-4.2.xsd">

    <context:property-placeholder location="classpath:db.properties"
        ignore-unresolvable="true" />

    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"
        init-method="init" destroy-method="close">
        <!-- 基本属性 url、user、password -->
        <property name="driverClassName" value="${jdbc_driver}" />
        <property name="url" value="${jdbc_url}" />
        <property name="username" value="${jdbc_username}" />
        <property name="password" value="${jdbc_password}" />

        <!-- 配置初始化大小、最小、最大 -->
        <property name="initialSize" value="1" />
        <property name="minIdle" value="1" />
        <property name="maxActive" value="20" />

        <!-- 配置获取连接等待超时的时间 -->
        <property name="maxWait" value="60000" />

        <!-- 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒 -->
        <property name="timeBetweenEvictionRunsMillis" value="60000" />

        <!-- 配置一个连接在池中最小生存的时间，单位是毫秒 -->
        <property name="minEvictableIdleTimeMillis" value="300000" />

        <property name="validationQuery" value="SELECT 'x'" />
        <property name="testWhileIdle" value="true" />
        <property name="testOnBorrow" value="false" />
        <property name="testOnReturn" value="false" />

        <!-- 打开PSCache，并且指定每个连接上PSCache的大小 -->
        <property name="poolPreparedStatements" value="true" />
        <property name="maxPoolPreparedStatementPerConnectionSize"
            value="20" />
        <!-- 配置监控统计拦截的filters -->
        <property name="filters" value="stat" />
    </bean>


    <!-- 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="typeAliasesPackage" value="com.enjoylearning.mybatis.entity" />
        <property name="mapperLocations" value="classpath*:sqlmapper/*.xml" />
    </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.enjoylearning.mybatis.mapper" />
    </bean>



    <!-- (事务管理)transaction manager -->
    <bean id="transactionManager"
        class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
        <qualifier value="transactionManager" />
    </bean>

    <tx:annotation-driven transaction-manager="transactionManager" />


    <context:component-scan base-package="com.*">
    </context:component-scan>

</beans>