MyBatis学习（二）------完成简单的CRUD操作

一、使用MyBatis对表执行CRUD操作

1. 首先在UsersMapper接口中编写相应的方法

package mybatis.Mapper;

import mybatis.pojo.Users;

import java.util.List;
public interface UsersMapper {
    //查询表中数据
    public List<Users> getAll();
    public Users getById(int id);
    public List<Users> getByUserName(String name);
    //对表进行CRUD操作
    //增加用户
    public int save(Users u);
    //根据主键ID删除用户
    public int delete(Integer id);
    //更新用户
    public int update(Users u);
}

2. 完成UsersMapper.xml文件内具体方法内容的编写

<?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">

<!--
1、Mapper.xml文件中的namespace与mapper接口的类路径相同。
2、Mapper接口方法名和Mapper.xml中定义的每个statement的id相同
3、Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql 的parameterType的类型相同
4、Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同
5、接口与xml文件必同名，而且在同一个路径下
-->
<mapper namespace="mybatis.Mapper.UsersMapper">
    <sql id="allcolumn">
        id,username,age
    </sql>
    <select id="getAll" resultType="mybatis.pojo.Users">
        select <include refid="allcolumn"></include>
        from users
    </select>

    <select id="getById" parameterType="int" resultType="mybatis.pojo.Users">
        select <include refid="allcolumn"></include>
        from users where id=#{id}
    </select>
    <select id="getByUserName" parameterType="string" resultType="mybatis.pojo.Users">
        select <include refid="allcolumn"></include>
        from users
        where username like '%${value}%'
    </select>
    <!--增加用户-->
    <insert id="save"  parameterType="mybatis.pojo.Users">
        insert into users(username, age) values (#{username},#{age})
    </insert>
    <!--删除用户-->
    <delete id="delete" parameterType="int">
        delete from users where id=#{id}
    </delete>
    <!--更新用户-->
    <update id="update" parameterType="mybatis.pojo.Users">
        update users set username=#{username},age=#{age}
        where id=#{id}
    </update>
</mapper>

3. 编写测试类代码

package mybatis.Test;

import mybatis.Mapper.UsersMapper;
import mybatis.pojo.Users;
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 org.junit.Before;
import org.junit.Test;

import java.io.InputStream;
import java.util.Date;
import java.util.List;

public class MyTest {
    //创建连接对象
    SqlSession sqlSession;
    //创建UsersMapper对象
    UsersMapper usersMapper;

    @Before
    public void setSession() throws Exception{
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSessionFactory factory=new SqlSessionFactoryBuilder().build(inputStream);
        sqlSession=factory.openSession();
        usersMapper=sqlSession.getMapper(UsersMapper.class);
    }
    @Test
    public void testgetAll(){
        List<Users> ulist = usersMapper.getAll();
        for (Users u:ulist){
            System.out.println(u);
        }
        sqlSession.close();
    }

    @Test
    public void testGetById(){
        Users u=usersMapper.getById(1);
        System.out.println(u);
        sqlSession.close();
    }
    @Test
    public  void testfindUsersByName(){
        List<Users> ulist = usersMapper.getByUserName("三");
        for(Users u:ulist){
            System.out.println(u);
        }
        sqlSession.close();
    }
    @Test
    public void testSave(){
        Users u=new Users();
        u.setUsername("王五");
        u.setAge(15);
        int num=usersMapper.save(u);
        sqlSession.commit();
        sqlSession.close();
        System.out.println(num);
    }
    @Test
    public void testDelete(){

        int num=usersMapper.delete(1);
        sqlSession.commit();
        sqlSession.close();
        System.out.println(num);
    }
    @Test
    public void testUpdate(){
        Users u=new Users();
        u.setUsername("赵六");
        u.setAge(12);
        u.setId(5);
        int num=usersMapper.update(u);
        sqlSession.commit();
        sqlSession.close();
        System.out.println(num);
    }
}

4. 运行结果