Spring-Mybatis整合 | 原理分析

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▌环境搭建

步骤：

导入相关jar包

• junit
• mybatis
• mysql
• spring
• aop织入
• mybatis-spring

环境搭建：

    <dependencies>
        
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.12version>
        dependency>
        
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>8.0.28version>
        dependency>
        
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.5.2version>
        dependency>
        
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-webmvcartifactId>
            <version>5.2.0.RELEASEversion>
        dependency>
        
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-jdbcartifactId>
            <version>5.1.9.RELEASEversion>
        dependency>
        
        <dependency>
            <groupId>org.aspectjgroupId>
            <artifactId>aspectjweaverartifactId>
            <version>1.9.4version>
        dependency>
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatis-springartifactId>
            <version>2.0.2version>
        dependency>
    dependencies>

▌Mybatis流程回顾

• 编写实体类

package com.wei.pojo;

import lombok.Data;

@Data
public class User {
    private int id;
    private String name;
    private String pwd;
}

• 编写核心配置文件

DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">


<configuration>

    
    

    <settings>
        
        <setting name="logImpl" value="LOG4J"/>
    settings>


    <typeAliases>
        <package name="com.wei.pojo.User"/>
    typeAliases>



    
    <environments default="development">
        <environment id="development">
            
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            dataSource>
        environment>
    environments>

    <mappers>
        <mapper class="com.wei.Mapper.UserMapper"/>
    mappers>



configuration>

• 编写接口

package com.wei.Mapper;

import com.wei.pojo.User;

import java.util.List;

public interface UserMapper {
    public List<User> selectUser();
}

• 编写Mapper映射文件

DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">


<mapper namespace="com.wei.Mapper.UserMapper">

    
    <select id="selectUser" resultType="com.wei.pojo.User">
        select * from mybatis.user;
    select>

mapper>

• 测试

import com.wei.Mapper.UserMapper;
import com.wei.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MyTest {

   @Test
    public void test() throws IOException {
       String resources = "mybatis-config.xml";
       //读取mybatis-config.xml主配置文件
      InputStream in = Resources.getResourceAsStream(resources);
      SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(in);
       SqlSession sqlSession = sessionFactory.openSession(true);

       UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      List<User> userList = mapper.selectUser();

      for (User user : userList) {
         System.out.println(user);
      }

      sqlSession.close();
   }
}

▌Mybatis-Spring整合

SqlSessionTemplate方式

• 要和 Spring 一起使用 MyBatis，需要在 Spring 应用上下文中定义至少两样东西：一个 SqlSessionFactory 和至少一个数据映射器类。
• 在 MyBatis-Spring 中，可使用 SqlSessionFactoryBean来创建 SqlSessionFactory。 要配置这个工厂 bean，只需要把下面代码放在 Spring 的 XML 配置文件中
• 在基础的 MyBatis 用法中，是通过 SqlSessionFactoryBuilder 来创建 SqlSessionFactory 的。而在 MyBatis-Spring 中，则使用 SqlSessionFactoryBean 来创建

• 编写UserMapper接口类

package com.wei.Mapper;

import com.wei.pojo.User;

import java.util.List;

public interface UserMapper {
    public List<User> selectUser();
}

• UserMapper.xml映射文件

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

<!--namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.wei.Mapper.UserMapper">

    <!--select查询语句查询全部用户-->
    <select id="selectUser" resultType="com.wei.pojo.User">
        select * from mybatis.user;
    </select>

</mapper>

• UserMapperImpl实现类，接口增加实现类

package com.wei.Mapper;

import com.wei.pojo.User;
import org.mybatis.spring.SqlSessionTemplate;

import java.util.List;

public class UserMapperImpl implements UserMapper{


    //以前来有操作使用SqlSession执行，现在所有操作在SqlSessionTemplate
    private SqlSessionTemplate sqlSession;

    public void setSqlSession(SqlSessionTemplate sqlSession) {
        this.sqlSession = sqlSession;
    }

    public List<User> selectUser(){
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        return mapper.selectUser();
    }
}

• User接口

package com.wei.pojo;

import lombok.Data;

@Data
public class User {
    private int id;
    private String name;
    private String pwd;
}

• Mybatis-config.xml核心配置文件

DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">


<configuration>

    
    

    <settings>
        
        <setting name="logImpl" value="LOG4J"/>
    settings>


    <typeAliases>
        <package name="com.wei.pojo"/>
    typeAliases>

    
    <environments default="development">
        <environment id="development">
            
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            dataSource>
        environment>
    environments>




configuration>

• log4j.properties资源包

log4j.properties
#将等级为DEBUG的日志信息输出到console和file两个目的地
log4j.rootLogger=DEBUG,console,file

#控制台输出的相关设置
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.Target=System.out
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=【%c】-%m%n

#文件输出的相关配置
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=./log/wei.log
log4j.appender.file.MaxFileSize=10mb
log4j.appender.file.Threshold=DEBUG
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=【%p】[%d{yy-MM-dd}【%c】%m%n

#日志输出级别
log4j.logger.org.mybatis=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

• ​ spring-dao.xml（将sqlSessionFactory等bean注入到spring框架中，来管理持久层中的操作）

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">


    
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8"/>
        <property name="username" value="root"/>
        <property name="password" value="root"/>
    bean>

    
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        
        <property name="dataSource" ref="dataSource"/>
        

        
        <property name="configLocation" value="classpath:mybatis-config.xml"/>
        <property name="mapperLocations" value="classpath:com/wei/Mapper/*.xml"/>
    bean>

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

    
    <bean id="userMpaaer" class="com.wei.Mapper.UserMapperImpl">
        <property name="sqlSession" ref="sqlSession"/>
    bean>
beans>

• ​ ApplicationContext.xml（配置Spring框架所需的信息）

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">


    
    <import resource="spring-dao.xml"/>

    
    <bean id="userMpaaer" class="com.wei.Mapper.UserMapperImpl">
        <property name="sqlSession" ref="sqlSession"/>
    bean>
beans>

• 测试

import com.wei.Mapper.UserMapper;
import com.wei.pojo.User;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import java.io.IOException;


public class MyTest {

   @Test
    public void test() throws IOException {
       //解析beans.xml文件，生成管理相应的Bean对象
       ApplicationContext context = new ClassPathXmlApplicationContext("ApplicationContext.xml");
//       UserMapper userMpaaer = context.getBean("userMpaaer", UserMapper.class);
       UserMapper userMpaaer = (UserMapper) context.getBean("userMpaaer");

       for (User user: userMpaaer.selectUser()){
           System.out.println(user);
       }
   }
}

SqlSessionTemplate分析

SqlSessionTemplate 是 MyBatis-Spring 的核心。作为 SqlSession 的一个实现，这意味着可以使用它无缝代替你代码中已经在使用的 SqlSession。 SqlSessionTemplate 是线程安全的，可以被多个 DAO 或映射器所共享使用

• 使用 SqlSessionFactory 作为构造方法的参数来创建 SqlSessionTemplate 对象

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

@Configuration
public class MyBatisConfig {
  @Bean
  public SqlSessionTemplate sqlSession() throws Exception {
    return new SqlSessionTemplate(sqlSessionFactory());
  }
}

• 现在，这个 bean 就可以直接注入到你的 DAO bean 中了。你需要在你的 bean 中添加一个 SqlSession 属性，就像下面这样：

public class UserDaoImpl implements UserDao {

  private SqlSession sqlSession;

  public void setSqlSession(SqlSession sqlSession) {
    this.sqlSession = sqlSession;
  }

  public User getUser(String userId) {
    return sqlSession.selectOne("org.mybatis.spring.sample.mapper.UserMapper.getUser", userId);
  }
}

• 注入Spring：按下面这样，注入 SqlSessionTemplate

<bean id="userDao" class="org.mybatis.spring.sample.dao.UserDaoImpl">
  <property name="sqlSession" ref="sqlSession" />
bean>

• SqlSessionTemplate 还有一个接收 ExecutorType 参数的构造方法。这允许你使用如下 Spring 配置来批量创建对象，例如批量创建一些 SqlSession：

<bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
  <constructor-arg index="0" ref="sqlSessionFactory" />
  <constructor-arg index="1" value="BATCH" />
bean>

@Configuration
public class MyBatisConfig {
  @Bean
  public SqlSessionTemplate sqlSession() throws Exception {
    return new SqlSessionTemplate(sqlSessionFactory(), ExecutorType.BATCH);
  }
}

• 现在所有的映射语句可以进行批量操作了，可以在 DAO 中编写如下的代码

public class UserService {
  private final SqlSession sqlSession;
  public UserService(SqlSession sqlSession) {
    this.sqlSession = sqlSession;
  }
  public void insertUsers(List<User> users) {
    for (User user : users) {
      sqlSession.insert("org.mybatis.spring.sample.mapper.UserMapper.insertUser", user);
    }
  }
}

注意，只需要在希望语句执行的方法与 SqlSessionTemplate 中的默认设置不同时使用这种配置。

这种配置的弊端在于，当调用这个方法时，不能存在使用不同 ExecutorType 的进行中的事务。要么确保对不同 ExecutorType 的 SqlSessionTemplate 的调用处在不同的事务中，要么完全不使用事务

configLocation & mapperLocations分析

• Spring-dao.xml中

<property name="configLocation" value="classpath:mybatis-config.xml"/>
<property name="mapperLocations" value="classpath:com/wei/Mapper/*.xml"/>

• configLocation ：即mybatis-config.xml核心配置文件

当你需要使用mybatis-config.xml 配置文件的时候你就需要配置config-location，config-location的作用是确定mybatis-config.xml文件位置

• mapperLocations：dao接口类的映射文件

mapper-locations是用来注册所写的xxxmapper.xml映射文件

SqlSessionDaoSupport方式

• 创建User类

package com.wei.pojo;

import lombok.Data;

@Data
public class User {
    private int id;
    private String name;
    private String pwd;
}

• UserMapper接口

package com.wei.Mapper;

import com.wei.pojo.User;

import java.util.List;

public interface UserMapper {
    public List<User> selectUser();
}

• UserMapper.xml映射文件

DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">


<mapper namespace="com.wei.Mapper.UserMapper">

    
    <select id="selectUser" resultType="com.wei.pojo.User">
        select * from mybatis.user;
    select>

mapper>

• Spring-dao.xml(配置、整合Mybatis)

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">


    
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8"/>
        <property name="username" value="root"/>
        <property name="password" value="root"/>
    bean>

    
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        
        <property name="dataSource" ref="dataSource"/>
        

        
        <property name="configLocation" value="classpath:mybatis-config.xml"/>
        <property name="mapperLocations" value="classpath:com/wei/Mapper/*.xml"/>
    bean>
beans>

• UserMapperImpl实现类，注入到spring中(applicationContext.xml)

package com.wei.Mapper;

import com.wei.pojo.User;
import org.mybatis.spring.support.SqlSessionDaoSupport;

import java.util.List;

public class UserMapperImpl2 extends SqlSessionDaoSupport implements UserMapper{

    @Override
    public List<User> selectUser() {
//        SqlSession sqlSession = getSqlSession();
//        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        return getSqlSession().getMapper(UserMapper.class).selectUser();
    }
}

• applicationContext.xml(配置Spring框架所需的信息)

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">


    
    <import resource="spring-dao.xml"/>

    
    <bean id="userMpaaer" class="com.wei.Mapper.UserMapperImpl">
        <property name="sqlSession" ref="sqlSession"/>
    bean>

    <bean id="userMapper2" class="com.wei.Mapper.UserMapperImpl2">
        <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
    bean>
beans>

• MyTest测试类

import com.wei.Mapper.UserMapper;
import com.wei.pojo.User;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import java.io.IOException;


public class MyTest {

   @Test
    public void test() throws IOException {
       //解析beans.xml文件，生成管理相应的Bean对象
       ApplicationContext context = new ClassPathXmlApplicationContext("ApplicationContext.xml");
//       UserMapper userMpaaer = context.getBean("userMpaaer", UserMapper.class);
       UserMapper userMpaaer = (UserMapper) context.getBean("userMpaaer");

       for (User user: userMpaaer.selectUser()){
           System.out.println(user);
       }
   }
}

SqlSessionDaoSupport分析

SqlSessionDaoSupport 是一个抽象的支持类，用来为你提供 SqlSession。调用 getSqlSession() 方法你会得到一个 SqlSessionTemplate，之后可以用于执行 SQL 方法，就像下面这样:

public class UserDaoImpl extends SqlSessionDaoSupport implements UserDao {
  public User getUser(String userId) {
    return getSqlSession().selectOne("org.mybatis.spring.sample.mapper.UserMapper.getUser", userId);
  }
}

在这个类里面，通常更倾向于使用 MapperFactoryBean，因为它不需要额外的代码。但是，如果你需要在 DAO 中做其它非 MyBatis 的工作或需要一个非抽象的实现类，那么这个类就很有用了。

SqlSessionDaoSupport 需要通过属性设置一个 sqlSessionFactory 或 SqlSessionTemplate。如果两个属性都被设置了，那么 SqlSessionFactory 将被忽略。

假设类 UserMapperImpl 是 SqlSessionDaoSupport 的子类，可以编写如下的 Spring 配置来执行设置：

<bean id="userDao" class="org.mybatis.spring.sample.dao.UserDaoImpl">
  <property name="sqlSessionFactory" ref="sqlSessionFactory" />
bean>

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