第一个mybatis程序

搭建数据库

CREATE DATABASE `mybatis`;

USE `mybatis`;

CREATE TABLE `user`(
`id` INT(20) NOT NULL PRIMARY KEY,
`name` VARCHAR(30) DEFAULT NULL,
`pwd` VARCHAR(30) DEFAULT NULL
)ENGINE=INNODB DEFAULT CHARSET=utf8mb4;

INSERT INTO `user`(`id`,`name`,`pwd`) VALUES
(1,'狂神','123456'),
(2,'张三','123456'),
(3,'李四','123890')

搭建模块

 

 

创建一个模块

 

 

 编写mybatis-config.xml配置文件

<?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">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3307/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="org/mybatis/example/BlogMapper.xml"/>
    </mappers>
</configuration>

编写mybatis工具类

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;

//sqlSessionFactory --> sqlSession
public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            //使用Mybatis获取sqlSessionFactory
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

编写代码

实体类

 

 

 

 

 

 测试代码

 

 

 

 就是每个Mapper都需要在mybatis-config.xml中注册

 

 

 

 

 

 若注册后发生初始化异常失败错误，找不到Mapper文件，原因可能如下：

 

 

 

 

public class UserMapperTest {
    @Test
public void test(){
        //第一步获得SqlSession对象
SqlSession sqlSession = MybatisUtils.getSqlSession();
//执行SQL
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = userMapper.getUserList();

        for (User user : userList) {
            System.out.println(user);
}
        //关闭SqlSession
sqlSession.close();
}
}