Mybatis 第一个程序
第一步：连接数据库
注意testconnection会出错，因为时区问题
将时区改为Asia/Shanghai

第二步：配置mybatis-config.xml配置文件
官方文档里有说明示例

<?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:3306/mybatis?useSSL=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="******(不给看)"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/lonzo/dao/UserMapper.xml"/>
    </mappers>
</configuration>

第三步：编写mybatisUtils工具类
通过xml配置文件得到sqlsessionfactory,然后用factory来创建sqlsession实例

package com.lonzo.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 {
        try {

            String  resource ="mybatis-config.xml";
            InputStream inputStream;
            inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

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

}

第四步：创建实体类

package com.lonzo.pojo;

public class User {
    private int id;
    private String name;
    private String pwd;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    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;
    }
}

第五步：创建Mapper接口和实现Mapper接口的配置xml文件

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

<?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">
<!--namespace:命名空间，绑定一个对应的Mapper接口-->
<mapper namespace="com.lonzo.dao.UserMapperr">  这里名字写错了...出错  是Mapper,多了个r
    <select id="getUserList" resultType="com.lonzo.pojo.User">-- 注意这里的属性值
        select * from user
    </select>
</mapper>

第六步：Junit测试

package com.ball.dao;

import com.ball.pojo.User;
import com.ball.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {
    @Test

    public void test(){
        //获得sqlsession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }

}

出错：Maven静态资源过滤问题

在xml中写入：

  <!--在build中配置resource，来防止资源导出失败的问题-->
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>

    </build>

以后最好都用上，防止出错，因为可能经常会出现这问题