JavaWeb学习--MyBatis框架增删改查案例与动态SQL

MyBatis框架增删改查案例与动态SQL

环境准备

开始之前先装一个mybatisx插件,方便跳转xml和接口方法,和生成对应id

查询

<!--UserMapper.xml-->

<?xml version="1.0" encoding="UTF-8" ?>

<!--sql映射文件-->
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<!--
namespace:名称空间
-->
<mapper namespace="BrandMapper">
    <!--id:唯一标识符 resulttype:POJO类类型-->
    <select id="selectAll" resultType="Brand">
        select *
        from tb_brand;
    </select>
</mapper>

//BrandMapper.class

import java.util.List;


public interface UserMapper {

    List<User> selectAll();
}

测试类

//测试类

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 org.junit.Test;

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

public class MyBatisTest {

    @Test
    public void testSelectAll() throws IOException {
        //1.加载mybatis的核心配置文件,获取sqlsessionfactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2.获取sqlsession对象,用它来执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //3.执行sql
        BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);

        //4.执行方法
        List<Brand> brands = brandMapper.selectAll();
        System.out.println(brands);

        //4.释放资源
        sqlSession.close();
    }
}

最后记得配置文件里加上

<!--加载SQL映射文件-->
<mapper resource="BrandMapper.xml"/>

<!--
    *参数占位符:
        1．#{}:会将其替换为?，为了防止SQL注入
        2．$:拼sql。会存在SQL注入问题
        3．使用时机:
               *参数传递的时候:#{}
               *表名或者列名不固定的情况下:$手会存在SQL注入问题
    -->
    <select id="selectById" resultMap="brandResultMap">
        select *
        from tb_brand where id = #{id};
    </select>

参数类型与转义字符的处理