spring整合mybatis详解

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前言

本篇主要讲怎么使用spring整合mybatis

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一、实现步骤

spring的特点是IOC和AOP，IOC是控制反转，即创建对象。整合spring和mybatis正是使用了spring的这种特点。我们可以使用spring创建如下对象，来整和mybatis。

• 数据库的连接对象
• 创建SqlSessionFactory
• 创建SqlSession对象
• 获得Mapper的代理对象

实现步骤:

• 准备数据酷
• 创建java-maven项目
• 导入依赖
  • spring
  • mybatis
  • 数据库驱动
  • spring整合mybatis的单独依赖
  • spring-jdbc,对Dao层的支持
• 配置文件
  • applicationContext.xml [重点]
    • 加载数据配置文件
    • 配置数据源
    • 创建SqlSessionFactory
    • 配置Mapper扫描器
  • mybatis-config.xml
  • db.properties
  • log4j.properties
• 类文件
  • User
  • UserService
  • UserServiceImpl
  • UserMapper.java
  • UserMapper.xml
• 测试

创建maven，数据库和实体类、前几篇已经记录过不在进行一一演示。

在maven的基础上导入依赖

<dependencies>
   	    
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-contextartifactId>
            <version>5.1.6.RELEASEversion>
        dependency>
		
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-aspectsartifactId>
            <version>5.1.6.RELEASEversion>
        dependency>
        
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-jdbcartifactId>
            <version>5.1.6.RELEASEversion>
        dependency>
        
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.5.7version>
        dependency>
	    
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>5.1.47version>
        dependency>
        
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatis-springartifactId>
            <version>1.3.1version>
        dependency>
		
        <dependency>
            <groupId>log4jgroupId>
            <artifactId>log4jartifactId>
            <version>1.2.17version>
        dependency>
    dependencies>

    <build>
        <resources>
            <resource>
                <directory>src/main/javadirectory>
                <includes>
                    <include>*.xmlinclude>
                    <include>**/*.xmlinclude>
                includes>
                <filtering>truefiltering>
            resource>
        resources>
    build>

编写配置文件applicationContext.xml

<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"
       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">

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

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

    
    <bean id="dataSource" class="org.apache.ibatis.datasource.pooled.PooledDataSource">
        <property name="driver" value="${jdbc.driver}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
    bean>


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

        
        <property name="typeAliasesPackage" value="com.lzl.model"/>

    bean>

    
    <bean id="mapperScannerConfigurer" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.lzl.mapper"/>
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/>
    bean>
beans>

编写mybatis-config.xml配置

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

<configuration>
    
configuration>

db.properties 数据源配置

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/库名?useSSL=false
jdbc.username=用户名
jdbc.password=密码

log4j.properties日志配置

log4j.rootLogger=error
log4j.logger.com.qf.mapper=debug,stdout

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

服务层的实现

public interface UserService {
    User findUserById(int id);
}

@Service
public class UserServiceImpl implements UserService {

    // 设置Dao属性
    @Autowired // 自动注入Mapper
    private UserMapper userMapper;

    @Override
    public User findUserById(int id) {
        User user = userMapper.findUserById(id);
        return user;
    }
}

持久层的实现

public interface UserMapper {
    User findUserById(int id);
}

DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.qf.mapper.UserMapper">

    <select id="findUserById" parameterType="int" resultType="User">
        select * from user where id = #{id}
    select>

mapper>

测试类编写

public class TestSpringMybatis {

    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService service = context.getBean("userServiceImpl", UserService.class);

        User user = service.findUserById(51);
        System.out.println(user);
    }
}

至此已经将spring和mybatis整合完毕

二、使用mybatis-config.xml

上述整合步骤中，将所有的mybatis配置文件中的内容全部整合到了applicationContext.xml中。我们还可以使用另外一种方式来进行整和
这里仅作一种配置别名使用mybatis-config.xml演示

<configuration>
    
    
    <typeAliases>
        <package name="com.qf.model"/>
    typeAliases>
    
configuration>

在applicationContext.xml中加载该配置

  
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        
        <property name="configLocation" value="classpath:mybatis-config.xml"/>

        
        <property name="dataSource" ref="dataSource"/>

        
        
    bean>

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出现的BUG

整合完毕以后，log4j日志不显示。原因在于整合mybatis后,mybatis自己无法确定到底使用哪一个日志框架.所以,需要在mybatis的全局配置文件中,指定日志的实现方案为log4j。

<configuration>
    

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