黑马程序员MyBatis总结（一、Mybatis快速入门）

本文为自我学习使用，如转载需本人同意

什么是Mybatis

1.表现层：页面展示
2.业务层：业务流程
3.持久层：持久化数据

JDBC的缺点和MyBatis简化

实例

1.配置xml文件

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

    <properties resource="sqlConfig.properties"/>
    <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?serverTimezone=UTC&characterEncoding=utf-8"/>
                <property name="username" value="${database.username}"/>
                <property name="password" value="1234"/>
            dataSource>
        environment>
    environments>
    <mappers>
        
        <mapper resource="CountryMapper.xml"/>
    mappers>
configuration>
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配置映射文件

DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="user">
    
    <select id="selectAll" resultType="Country">
        select * from sup_country
    select>
mapper>
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配置properties文件

database.driver=com.mysql.cj.jdbc.Driver
database.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&characterEncoding=utf-8
database.username=root
database.password=1234
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properties文件里不要加引号

配置实体（返回结果类型）

package entity;

import java.time.LocalDateTime;

public class Country {
    private Integer id;
    private String countryName;
    private String englishName;
    private String creator;
    private String modifier;
    private LocalDateTime createTime;
    private LocalDateTime updateTime;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getCountryName() {
        return countryName;
    }

    public void setCountryName(String countryName) {
        this.countryName = countryName;
    }

    public String getEnglishName() {
        return englishName;
    }

    public void setEnglishName(String englishName) {
        this.englishName = englishName;
    }

    public String getCreator() {
        return creator;
    }

    public void setCreator(String creator) {
        this.creator = creator;
    }

    public String getModifier() {
        return modifier;
    }

    public void setModifier(String modifier) {
        this.modifier = modifier;
    }

    public LocalDateTime getCreateTime() {
        return createTime;
    }

    public void setCreateTime(LocalDateTime create_time) {
        this.createTime = create_time;
    }

    public LocalDateTime getUpdateTime() {
        return updateTime;
    }

    public void setUpdateTime(LocalDateTime updateTime) {
        this.updateTime = updateTime;
    }

    @Override
    public String toString() {
        return "com.entity.Country{" +
                "id=" + id +
                ", countryName='" + countryName + '\'' +
                ", englishName='" + englishName + '\'' +
                ", creatot='" + creator + '\'' +
                ", modifier='" + modifier + '\'' +
                ", create_time=" + createTime +
                ", updateTime=" + updateTime +
                '}';
    }
}


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主类建立工厂获取sqlSession对象执行语句

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;

/**
 * Mybatis 快速入门
 */

public class app {
    public static void main(String[] args) throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        System.out.println(sqlSession.selectList("user.selectAll"));
    }

}

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案例2 使用代理

修改了下结构

1.定义sql同名文件Mapper接口，并将Mapper接口和SQL映射文件放置在同一目录下

注意：在resource文件中新建包不能使用点.，必须使用/
namespace为mapper接口文件

<?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.CountryMapper">
    <!--设置语句-->
    <select id="selectAll" resultType="Country">
        select * from sup_country
    </select>
</mapper>
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2.设置SQL映射文件的namespace属性为Mapper接口全限定名称

3.在Mapper接口中定义方法

方法名就是sql映射文件中的sql语句id，并保持参数类型和返回值类型一致

package mapper;
import entity.Country;

import java.util.List;

public interface CountryMapper {
    List<Country> selectAll();
}


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4.修改mybatis配置xml

扫描包mapper，这能获取mapper包下的所有xml文件（不会扫描mapper接口，mapper接口是在namespace="mapper.CountryMapper"加载的），可以简化代码。

不能重复扫描，比如我们把上面图片代码的注释解除，那就会重复扫描CountryMapper.xml。这是不被允许的：

5.编码

1.通过SqlSession的getMapper方法获取Mapper接口代理对象

2.调用对应方法完成sql的执行

mybatis核心配置文件