SpringMVC4+MyBatis+SQL Server2014 基于SqlSession实现读写分离（也可以实现主从分离）

前言

    上篇文章我觉的使用拦截器虽然方便快捷，但是在使用读串还是写串上你无法控制，我更希望我们像jdbc那样可以手动控制我使用读写串，那么这篇则在sqlsession的基础上实现读写分离， 这种方式则需要手动实现daoImpl。

项目结构

开发环境

  SpringMVC+MyBatis+SQL Server2014

实现读写分离

1、关键点是springmvc-servlet.xml中的配置，datasource、sqlsessionfactory、sqlsession

<?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:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:tx="http://www.springframework.org/schema/tx"
       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.xsd
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc.xsd
       http://www.springframework.org/schema/tx
       http://www.springframework.org/schema/tx/spring-tx.xsd">

    <!--从配置文件加载数据库信息-->
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations" value="classpath:config/jdbc.properties"/>
        <property name="fileEncoding" value="UTF-8"/>
    </bean>

    <!--配置数据源，这里使用Spring默认-->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${sqlserver.driver}"/>
        <property name="url" value="${sqlserver.url}"/>
        <property name="username" value="${sqlserver.username}"/>
        <property name="password" value="${sqlserver.password}"/>
    </bean>


    <!--配置sqlSessionFactory-->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="configLocation" value="classpath:springmvc-mybatis.xml"/>
        <property name="dataSource" ref="dataSource"/>
    </bean>

    <!--master-->
    <bean id="masterSqlSession" class="org.mybatis.spring.SqlSessionTemplate">
        <constructor-arg index="0" ref="sqlSessionFactory"/>
    </bean>

    <!--slave-->
    <bean id="slaveSqlSession" class="org.mybatis.spring.SqlSessionTemplate">
        <constructor-arg index="0" ref="sqlSessionFactory"/>
    </bean>

    <!--事务管理器 -->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"/>
    </bean>

    <!-- 使用注解事务，需要在Service方法中添加Transactional注解属性 -->
    <tx:annotation-driven transaction-manager="transactionManager"/>

    <!--扫描Mapper-->
    <!--<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">-->
        <!--<property name="basePackage" value="com.autohome.dao"/>-->
    <!--</bean>-->

    <!--启用最新的注解器、映射器-->
    <mvc:annotation-driven/>


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

    <!--jsp视图解析器-->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/views/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

</beans>

2、UserMapper.xml。 namespace不再和dao的包名保持一致

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="mapper.UserDao">
    <select id="listAllUser" resultType="User">
        select * from t_userinfo
    </select>

    <select id="listPagedUser"   resultType="User">
        select top ${pageSize} * from t_userinfo where id not in (select top (${pageSize} * (${pageIndex} -1)) id from t_userinfo)
    </select>

    <select id="count" resultType="int">
        select count(*) from t_userinfo
    </select>

    <insert id="insertUser" parameterType="User">
        insert into t_userinfo(name,address) VALUES (#{name},#{address})
    </insert>

    <update id="updateUser" parameterType="User">
        UPDATE  t_userinfo set name=#{name},address=#{address} where id=#{id}
    </update>

    <delete id="deleteUser" parameterType="int">
        DELETE FROM t_userinfo where id=#{id}
    </delete>

    <select id="getUserById" resultType="User" parameterType="int">
        select * from t_userinfo where id=#{id}
    </select>

</mapper>

3、UserDao 接口、UserDao实现

public interface UserDao {
    List<User> listAllUser();
    int insertUser(User user);
    User getUserById(int id);
}

@Repository("userDaoImpl")
public class UserDaoImpl implements UserDao {

    @Autowired
    private SqlSession masterSqlSession;

    @Autowired
    private SqlSession slaveSqlSession;


    public List<User> listAllUser() {
        System.out.println("===========slave==========");
        return slaveSqlSession.selectList("mapper.UserDao.listAllUser");
    }

    public int insertUser(User user) {
        System.out.println("===========master==========");
        return masterSqlSession.insert("mapper.UserDao.insertUser",user);
    }

    public User getUserById(int id) {
        System.out.println("===========slave==========");
        return slaveSqlSession.selectOne("mapper.UserDao.getUserById",id);
    }
}

4、Serivce

@Service
public class UserService {

    @Autowired
    @Qualifier("userDaoImpl")
    UserDao userDao;

    public List<User> listAllUser() {

        return userDao.listAllUser();
    }

    @Transactional
    public int insertUser(User user) {
        return userDao.insertUser(user);
    }

    public User getUserById(int id) {
        return userDao.getUserById(id);
    }


}

　　

总结

     在controller中调用service方法时则可以看出当前方法使用的连接串，而且不用去关心sqlsession的打开关闭问题。

补充

     一开始只站在demo的角度去想sqlsession主从分离或者读写分离，从实际应用角度的话从datasource就要分开，并且使用不同的读写连接串。那么针对如上的配置就是需要配置read-datasource、write-datasource、readsqlsessionfactory、writesqlsessionfactory、readsqlsession、writesqlsession。