MyBatis学习笔记（一）

MyBatis

MyBatis项目结构：

<src/>
	<main/>
		<java/>
			<org.mybatis.example/>
				<mapper/>
					<InterfaceFile>UserMapper</InterfaceFile>
					<MapperConfigFile>UserMapper.xml</MapperConfigFile>
		<resources/>
			<MybatisConfigFile>mybatis-config.xml</MybatisConfigFile>
	<test/>
<MavenFile>pom.xml</MavenFile>

Maven配置

<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.7</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.23</version>
    </dependency>

</dependencies>
<build>
    <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>

MyBatis配置

db.properties：

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/learndemo?useSSL=true&useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true
username=pinpin
password=

mybatis-config.xml：

<?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"/>
    <typeAliases>
        <typeAlias type="cc.keqing.pojo.User" alias="User"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper class="cc.keqing.dao.UserMapper"/>
    </mappers>
</configuration>

示例程序

Mapper接口

package cc.keqing.mapper;

import cc.keqing.pojo.User;

import java.util.List;

public interface UserMapper {
    List<User> getUserList();
    User getUserById(int id);
}

接口配置文件

<?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">
<mapper namespace="cc.keqing.dao.UserMapper">
    <select id="getUserList" resultType="cc.keqing.pojo.User">
        select * from user
    </select>
    <select id="getUserById" resultType="cc.keqing.pojo.User">
        select * from user where id=#{id}
    </select>
</mapper>

测试程序

工具类

package cc.keqing.utils;

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 java.io.IOException;
import java.io.InputStream;

public class MyBatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        String resource = "mybatisConfig.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

测试类

package cc.keqing.dao;

import cc.keqing.pojo.User;
import cc.keqing.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserTest {
    @Test
    public void test() {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
//        User user = mapper.getUserById(1);
//        System.out.println(user);
        sqlSession.close();
    }
}

CRUD

public interface UserMapper {
    List<User> getUserList();
    User getUserById(int id);
    int insertUser(User user);
    int deleteUser(int id);
    int updateUser(User user);
}

<?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">
<mapper namespace="cc.keqing.dao.UserMapper">
    <select id="getUserList" resultType="cc.keqing.pojo.User">
        select * from user
    </select>
    <select id="getUserById" resultType="cc.keqing.pojo.User">
        select * from user where id = #{id}
    </select>
    <insert id="insertUser" parameterType="cc.keqing.pojo.User">
        insert into user (id, name, pwd) values (#{id}, #{name}, #{pwd})
    </insert>
    
    <delete id="deleteUser" parameterType="int">
        delete from user where id = #{id}
    </delete>
    
    <update id="updateUser" parameterType="cc.keqing.pojo.User">
        update user set name = #{name}, pwd = #{pwd} where id = #{id}
    </update>
</mapper>

@Test
public void updateUser() {
    SqlSession sqlSession = MyBatisUtils.getSqlSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    mapper.updateUser(new User(3, "admin", "admin"));
    //增删改需要提交事务
    sqlSession.commit();
    sqlSession.close();
}

Map

使用map作为参数，传递map中的key

配置解析

Alias 别名

通过typeAliases标签设置别名

<typeAliases>
    <package name="org.example.pojo"/>
</typeAliases>

或者

<typeAliases>
    <typeAlias type="cc.keqing.pojo.User" alias="User"/>
</typeAliases>

• 使用package设置别名，会扫描包下所有类，默认将所有类名的首字母小写形式设置为类的别名（如User设置别名为user）,除非该类使用注解@Alias("alias")手动设置了别名。
• 使用typeAlias设置别名