MyBatis的xml实现方式

1、该项目引入的依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.example</groupId><artifactId>demo</artifactId><version>0.0.1-SNAPSHOT</version><name>demo</name><description>Demo project for Spring Boot</description><properties><java.version>1.8</java.version><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding><spring-boot.version>2.7.6</spring-boot.version></properties><dependencies><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.24</version><scope>provided</scope></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>com.oopsguy.kaptcha</groupId><artifactId>kaptcha-spring-boot-starter</artifactId><version>1.0.0-beta-2</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>2.3.1</version></dependency><dependency><groupId>com.mysql</groupId><artifactId>mysql-connector-j</artifactId><scope>runtime</scope></dependency><dependency><groupId>tk.mybatis</groupId><artifactId>mapper</artifactId><version>4.0.0</version></dependency><dependency><groupId>com.mysql</groupId><artifactId>mysql-connector-j</artifactId><scope>runtime</scope></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-dependencies</artifactId><version>${spring-boot.version}</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><version>3.8.1</version><configuration><source>1.8</source><target>1.8</target><encoding>UTF-8</encoding></configuration></plugin><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId><version>${spring-boot.version}</version><configuration><mainClass>com.example.demo.DemoApplication</mainClass><skip>true</skip></configuration><executions><execution><id>repackage</id><goals><goal>repackage</goal></goals></execution></executions></plugin></plugins></build>
</project>

2、引入配置文件

（1）yml的

spring:datasource:url: jdbc:mysql://127.0.0.1:3306/mybatis_test?characterEncoding=utf8&useSSL=falseusername: 你的数据库名称password: 你的数据库密码driver-class-name: com.mysql.cj.jdbc.Driver
mybatis:configuration: # 配置打印 MyBatis⽇志log-impl: org.apache.ibatis.logging.stdout.StdOutImplmapper-locations: classpath:mapper/**Mapper.xml

（2）properties的

#驱动类名称
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#数据库连接的url
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/mybatis_test?
characterEncoding=utf8&useSSL=false
#连接数据库的⽤⼾名
spring.datasource.username=root
#连接数据库的密码
spring.datasource.password=root
# 配置 mybatis xml 的⽂件路径，在 resources/mapper 创建所有表的 xml ⽂件
mybatis.mapper-locations=classpath:mapper/**Mapper.xml

3、我们设置的xml的固定格式

<?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">
<mapper namespace="com.bite.mybatis.mapper.UserInfoXmlMapper"></mapper>   

4、查找操作（只有查询需要写 resultType="com.example.demo.UserInfo"）

（1）各个文件存放的位置

（2）接口代码

package com.example.demo;import org.apache.ibatis.annotations.Mapper;import java.util.List;@Mapper
public interface UserInfoXmlMapper {List<UserInfo> queryUserList();
}

（3）XML代码（一定要注意地址映射要正确）

<?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">
<mapper namespace="com.example.demo.UserInfoXmlMapper"><select id="queryUserList" resultType="com.example.demo.UserInfo">select * from userinfo</select>
</mapper>

（4）测试部分代码（@SpringBootTest记得这个注解一定要加）

package com.example.demo;import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import static org.junit.jupiter.api.Assertions.*;
@SpringBootTest
class UserInfoXmlMapperTest {
@Autowired
private UserInfoXmlMapper userInfoXmlMapper;@Testvoid queryUserList() {userInfoXmlMapper.queryUserList();}
}

5、插入操作

（1）接口部分代码

Integer insert(UserInfo userInfo);

（2）XML代码

<?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">
<mapper namespace="com.example.demo.UserInfoXmlMapper"><select id="queryUserList" resultType="com.example.demo.UserInfo">select * from userinfo</select><insert id="insert">insert intouserinfo(username,password,age,gender,phone)values(#{username},#{password},#{age},#{gender},#{phone})</insert>
</mapper>

（3）测试部分代码

  @Testvoid insert() {UserInfo userInfo=new UserInfo();userInfo.setUsername("wanwu");userInfo.setAge(17);userInfo.setPassword("147258369");userInfo.setGender(1);userInfoXmlMapper.insert(userInfo);}

6、删除操作

（1）接口部分代码

Integer delete(Integer id);

（2）XML部分代码

 <delete id="delete">delete from userinfo where id=#{id}</delete>

（3）测试部分代码

 @Testvoid delete() {userInfoXmlMapper.delete(14);}

7、改操作

（1）接口部分代码

 Integer update(String password,Integer id);

（2）XML部分代码（idea创建的项目）

<update id="update">update userinfo setpassword=#{password}where id=#{id}</update>

（2）XML部分代码（阿里云创建的项目）

<update id="update">update userinfo setpassword=#{param1}where id=#{param2}</update>

（3）测试部分代码

 @Testvoid update() {userInfoXmlMapper.update("999999",15);}

8、mybatis赋值失败原因

（1）起别名

 <select id="queryUserList" resultType="com.example.demo.UserInfo">select delete_flag as deleteFlag from userinfo</select>

（2）通过resultmap方式（要记得把对象写全，id username等都映射上）

<resultMap id="base" type="com.example.demo.UserInfo"><result column="delete_flag" property="deleteFlag"></result>
</resultMap>
<select id="queryUserList" resultMap="base">select * from userinfo
</select>

（3）配置yml文件（驼峰命名）

mybatis:configuration:map-underscore-to-camel-case: true

9、返回自增主键

其他不变，和普通插入操作一样，就是在xml地方增加了一些设置

（1）xml地方代码

<insert id="insert" useGeneratedKeys="true" keyProperty="id">insert intouserinfo(username,password,age,gender,phone)values(#{username},#{password},#{age},#{gender},#{phone})
</insert>