IDEA初步使用MyBatis

Posted 2020-11-27 rollupbytian

学习链接：https://www.bilibili.com/video/BV1gs411j7kA?p=2

1.建立java文件

2.加载类路径。mybatis.jar 和 数据库驱动jar

File->Project Structure->Modules->Dependencies->右侧加号->1.jar
3.在数据库中建立一张person表 id name age
在src中 建立一个person类
4.通过配置文件将类和表对应起来，在person所在的那个类里面
建立一个 personMapper.xml文件
1）personMapper.xml所在的路径 没有.xml
通过id值 返回值类型 然后里面需要传入的参数的类型
5.在src下面直接建立 conf.xml文件

这里需要用到新建xml文件： 参考链接 https://blog.csdn.net/nba_linshuhao/article/details/82735770?depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-1&utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-1

里面有那个url username password mapper 里面是映射文件的路径
这里需要将数据库的链接包导入进来
4.测试类TestMyBatis文件
加载conf.xml文件 配置文件 为了访问数据库

然后通过id进行访问

testMyBatis
package org.student.entity;

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.Reader;

public class testMyBatis {
    public static void main(String[] args) throws IOException {
        //加载MyBatis配置文件（为了访问数据库）
        Reader reader = Resources.getResourceAsReader("conf.xml") ;
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader) ;
        //session - connection


        SqlSession session = sessionFactory.openSession() ;
        String statement = "org.student.entity.personMapper.queryPersonById" ;
        Person person = session.selectOne( statement,4 ) ;
        System.out.println(person);
        session.close();

    }
}

配置文件
conf.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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!-- 配置数据库信息 -->
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:MySQL://localhost:3306/hotel?&amp;useSSL=false&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!-- 加载映射文件 -->
        <mapper resource="org/student/entity/personMapper.xml"/>
    </mappers>
</configuration>

personMapper.xml
<?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="org.student.entity.personMapper">
    <select id="queryPersonById" resultType="org.student.entity.Person"  parameterType="int">
        select * from person where  id = #{id} 
    </select>
</mapper>

person类
package org.student.entity;

public class Person {
    private int id;
    private String name;
    private int age;
    public Person() {

    }
    public Person(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return this.id+","+this.name+","+this.age ;
    }

}