Mybatis基础：crud操作

<mapper namespace="com.king.dao.UserMapper">

 <select id="getUserList" resultType="com.king.pojo.User">

package com.king.pojo;

//实体类
public class User {
    private int id;
    private String name;
    private String pwd;

    public User() {
    }

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

    public String getPwd() {
        return pwd;
    }

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

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

package com.king.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;

//工厂模式是为了生产产品的，当前就是sqlSessionFactory生产sqlSession
//sqlSessionFactory--->sqlSession
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            //使用Mybatis第一步，获取sqlSessionFacter对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。
    // SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。
    //你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句
    public static SqlSession getSqlSession(){

        return sqlSessionFactory.openSession();
    }

}

package com.king.dao;

import com.king.pojo.User;

import java.util.List;

//官方文档中Mapper代替了Dao
public interface UserMapper {
    //查询全部用户
    List<User> getUserList();

    //根据id查询用户
    User getUserById(int Id);

    //插入用户
    int addUser(User user);

    //修改用户
    int updateUser(User user);

    //删除
    int deleteUser(int id);
}

<?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=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.king.dao.UserMapper">

    <!--select查询语句-->
    <!--绑定方法--><!--给返回值类型resultType，引入对应的实体类中-->
    <select id="getUserList" resultType="com.king.pojo.User" >
       select * from mybatis.user
   </select>

    <select id="getUserById" parameterType="int" resultType="com.king.pojo.User">
       select * from mybatis.user where id = #{id}
   </select>

    <!--对象属性可以直接取出来-->
    <insert id="addUser" parameterType="com.king.pojo.User" >
       insert into mybatis.user (id,`name`,pwd) VALUES(#{id},#{name},#{pwd})
   </insert>

    <!--对象属性可以直接取出来-->
    <update id="updateUser" parameterType="com.king.pojo.User" >
       UPDATE mybatis.user SET `name`=#{name},pwd=#{pwd} WHERE id=#{id}
   </update>

    <delete id="deleteUser" parameterType="int" >
       DELETE from mybatis.user  WHERE id=#{id}
   </delete>


</mapper>

<?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">

<!--核心配置文件-->
<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;serverTimezone=UTC&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <!--每一个mapper.xml（dao层实现类）都需要在Mybatis核心配置文件中注册-->
    <mappers>
        <mapper resource="com/king/dao/UserMapper.xml"/>
    </mappers>

</configuration>

package com.king.dao;

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

import java.util.List;

public class UserDaoTest {
    @Test
    public void test(){
        //第一步：获得SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();


        //方式一：getMapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = userMapper.getUserList();

        for (User user : userList) {
            System.out.println(user);
        }


        //关闭SqlSession
        sqlSession.close();
    }



    @Test
    public void getUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user= mapper.getUserById(1);
        System.out.println(user);

        sqlSession.close();
    }


    //注意：增删改需要提交事务
    @Test
    public void addUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int user = mapper.addUser(new User(5, "姚悠", "00001111"));
        if (user>0){
            System.out.println("插入成功");
            //提交事务
            sqlSession.commit();
        }

        sqlSession.close();

    }

    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int user = mapper.updateUser(new User(1, "老刘", "111222"));
        if (user>0){
            System.out.println("修改成功");
            sqlSession.commit();
        }

        sqlSession.close();
    }


    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int user = mapper.deleteUser(1);
        if (user>0){
            System.out.println("删除成功");
            sqlSession.commit();
        }

        sqlSession.close();

    }

}