MyBatis2(增删改查)
作者：互联网
查询所有数据
首先在数据库里新建一个表
-- 删除tb_brand表
drop table if exists tb_brand;
-- 创建tb_brand表
create table tb_brand
(
-- id 主键
id int primary key auto_increment,
-- 品牌名称
brand_name varchar(20),
-- 企业名称
company_name varchar(20),
-- 排序字段
ordered int,
-- 描述信息
description varchar(100),
-- 状态：0：禁用 1：启用
status int
);
-- 添加数据
insert into tb_brand (brand_name, company_name, ordered, description, status)
values ('三只松鼠', '三只松鼠股份有限公司', 5, '好吃不上火', 0),
('华为', '华为技术有限公司', 100, '华为致力于把数字世界带入每个人、每个家庭、每个组织，构建万物互联的智能世界', 1),
('小米', '小米科技有限公司', 50, 'are you ok', 1);
IDEA添加插件mybatisx
在file setting里的plugins里搜索下载即可
然后创建对应的接口和映射文件，还有实体类brand
在test下的文件里建立对应的测试文件
注意mybatis-config.xml，这是我的全局配置文件
<?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>
<typeAliases>
<package name="pojo"/>
</typeAliases>
<!--
environments：配置数据库连接环境信息。可以配置多个environment，通过default属性切换不同的environment
-->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<!--数据库连接信息-->
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="111111"/>
</dataSource>
</environment>
<environment id="test">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<!--数据库连接信息-->
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="111111"/>
</dataSource>
</environment>
</environments>
<mappers>
<!-- 加载sql映射文件
<mapper resource="mapper/UserMapper.xml"/>
<mapper resource="mapper/BrandMapper.xml"/>-->
<!--Mapper代理方式-->
<package name="mapper"/>
</mappers>
</configuration>
这种方法可以加载你该包下所有的映射文件，就不要一个个文件添加。
你的包含实体类的文件夹
brand.java
package pojo;
public class brand {
// id 主键
private Integer id;
// 品牌名称
private String brandName;
// 企业名称
private String companyName;
// 排序字段
private Integer ordered;
// 描述信息
private String description;
// 状态：0：禁用 1：启用
private Integer status;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getBrandName() {
return brandName;
}
public void setBrandName(String brandName) {
this.brandName = brandName;
}
public String getCompanyName() {
return companyName;
}
public void setCompanyName(String companyName) {
this.companyName = companyName;
}
public Integer getOrdered() {
return ordered;
}
public void setOrdered(Integer ordered) {
this.ordered = ordered;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public Integer getStatus() {
return status;
}
public void setStatus(Integer status) {
this.status = status;
}
@Override
public String toString() {
return "brand{" +
"id=" + id +
", brandName='" + brandName + '\'' +
", companyName='" + companyName + '\'' +
", ordered=" + ordered +
", description='" + description + '\'' +
", status=" + status +
'}';
}
}
BrandMapper.xml
<?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:名称空间,必须是对应接口的全限定名
-->
<mapper namespace="mapper.BrandMapper">
<!--
数据库的姓名是brand_name,实体类的姓名是brandName。即数据库表的字段名称和实体类属性名称不一样，
则不能自动封装，需要手动封装。
* 起别名，但是每次查询都要起一次
* resultMap
-->
<resultMap id="brandResultMap" type="brand">
<!--
id：完成主键字段的映射
column：表的列名
property：实体类的属性名
result：完成一般字段的映射
column：表的列名
property：实体类的属性名
-->
<result column="brand_name" property="brandName"/>
<result column="company_name" property="companyName"/>
</resultMap>
<select id="selectAll" resultMap="brandResultMap">
select * from tb_brand;
</select>
<!--<select id="selectAll" resultType="pojo.brand">
select *
from tb_brand;
</select>-->
</mapper>
BrandMapper.java
```bash
package mapper;
import pojo.brand;
import java.util.List;
public interface BrandMapper {
//查询所有
List<brand> selectAll();
}
myBatisTest,java
package demoTest;
import mapper.BrandMapper;
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 pojo.brand;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class myBatisTest {
@Test
public void testSelectAll() throws IOException {
//1. 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
SqlSession sqlSession = sqlSessionFactory.openSession();
//3. 获取Mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
//4. 执行方法
List<brand> brands = brandMapper.selectAll();
System.out.println(brands);
//5. 释放资源
sqlSession.close();
}
}
点击运行可以实现所有数据查询。
根据id进行查询
BrandMapper.java
//根据id进行查询
List<brand> selectById(int id);
BrandMapper.xml
<select id="selectById" resultMap="brandResultMap">
select * from tb_brand where id = #{id};
</select>
其中关于那个sql语句
参数占位符：
#{}
会将其替换为 ?，为了防止SQL注入，
${}
不常用，会存在参数注入问题
使用时机：
* 参数传递的时候：#{}
* 表名或者列名不固定的情况下：${} 会存在SQL注入问题
* 参数类型：parameterType：可以省略
* 特殊字符处理：
1. 转义字符：<(<)
2. CDATA区:
<select id="selectById" resultMap="brandResultMap">
select *
from tb_brand
where id
<![CDATA[
<
]]>
#{id};
</select>
myBatisTest.java
@Test
public void testSelectById() throws IOException {
int id = 1;
//1. 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
SqlSession sqlSession = sqlSessionFactory.openSession();
//3. 获取Mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
//4. 执行方法
List<brand> brands = brandMapper.selectById(id);
System.out.println(brands);
//5. 释放资源
sqlSession.close();
}
条件查询
多条件满足查询
1、接口方法参数使用 @Param 方式调用的方法
BrandMapper.java
List<brand> selectByCondition(@Param("status") int status,
@Param("companyName") String companyName, @Param("brandName") String
brandName);
BrandMapper.xml
<!--条件查询-->
<select id="selectByCondition" resultMap="brandResultMap">
select *
from tb_brand
where status = #{status}
and company_name like #{companyName}
and brand_name like #{brandName}
</select>
myBatisTest.java
@Test
public void testSelectCondition() throws IOException {
//接收参数
int status = 1;
String companyName = "华为";
String brandName = "华为";
// 处理参数
companyName = "%" + companyName + "%";
brandName = "%" + brandName + "%";
//1. 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
SqlSession sqlSession = sqlSessionFactory.openSession();
//3. 获取Mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
//4. 执行方法
List<brand> brands = brandMapper.selectByCondition(status,companyName,brandName);
System.out.println(brands);
//5. 释放资源
sqlSession.close();
}
标签：status,String,MyBatis2,brand,companyName,改查,public,增删,id 来源： https://blog.csdn.net/qq_45764141/article/details/123594646