文章目录
XML映射器操作（XxxMapper.xml）
文件目录
1.基本介绍
1.优点
2.常用顶级元素
2.环境配置
1.在原来的父模块下创建一个子模块
2.删除没用的两个文件夹
3.创建基本目录
4.父模块的pom.xml
xml
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<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 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>mybatis</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
<name>Archetype - mybatis</name>
<url>http://maven.apache.org</url>
<modules>
<module>mybatis_quickstart</module>
<module>xml-mapper</module>
</modules>
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.49</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.7</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<!--如果设置scope为test,则只能在test包下使用-->
<scope>test</scope>
</dependency>
</dependencies>
<!--在父模块中的pom.xml文件中配置在build的时候要扫描的文件，解决某些类型文件拷贝到target目录失败的问题-->
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<!--在java文件夹下的多级目录下的xml文件-->
<include>**/*.xml</include>
</includes>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<!--在resources文件夹下的多级目录下的xml文件和properties文件-->
<include>**/*.xml</include>
<include>**/*.properties</include>
</includes>
</resource>
</resources>
</build>
</project> 5.jdbc.properties
properties
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jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8
jdbc.username=root
jdbc.password=root 6.mybatis-config.xml
xml
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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!--引入外部文件jdbc.properties-->
<properties resource="jdbc.properties"/>
<!--配置mybatis自带的日志，settings需要放到最前面-->
<settings>
<setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>
<!--配置类型别名-->
<typeAliases>
<!--方式二：这样配置完了在这个包下的所有类都可以直接使用类名表示-->
<package name="com.sun.entity"/>
</typeAliases>
<environments default="development">
<environment id="development">
<!--配置事务管理器-->
<transactionManager type="JDBC"/>
<!--配置数据源-->
<dataSource type="POOLED">
<!--配置驱动-->
<property name="driver" value="${jdbc.driver}"/>
<!--配置连接url-->
<!--
1.jdbc:mysql：协议
2.127.0.0.1:3306：指定连接mysql的ip+端口
3.mybatis：连接的db
4.useSSL：使用安全连接
5.&：表示&
6.useUnicode=true：使用unicode,防止编码错误
7.characterEncoding=UTF-8：字符集使用utf-8
-->
<property name="url" value="${jdbc.url}"/>
<!--用户名-->
<property name="username" value="${jdbc.username}"/>
<!--密码-->
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>
<mappers>
<!--包的方式引入含有Mapper.xml的类-->
<package name="com.sun.mapper"/>
</mappers>
</configuration> 7.测试使用MonsterMapperTest.java
java
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package com.sun.mapper;
import com.util.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Before;
import org.junit.Test;
/**
* @author 孙显圣
* @version 1.0
*/
public class MonsterMapperTest {
//两个属性
private SqlSession sqlSession; //相当于连接
private MonsterMapper monsterMapper;
//编写方法完成初始化
@Before //标注了Before之后表示了在执行目标测试方法前会执行该方法
public void init() {
//获取到sqlSession
sqlSession = MyBatisUtils.getSqlSession();
//获取到MonsterMapper对象
monsterMapper = sqlSession.getMapper(MonsterMapper.class);
System.out.println(monsterMapper.getClass());
}
@Test
public void test() {
System.out.println("ssss");
}
} 3.parameterType（输入参数类型）
1.基本介绍
2.案例一
1.MonsterMapper.java
java
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package com.sun.mapper;
import com.sun.entity.Monster;
import java.util.List;
/**
* 这个接口用于声明操作monster表的方法
*
* @author 孙显圣
* @version 1.0
*/
public interface MonsterMapper {
//通过id或者名字查询
public List<Monster> findMonsterByNameORId(Monster monster);
} 2.MonsterMapper.xml
xml
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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--指定该xml文件和哪个接口对应-->
<mapper namespace="com.sun.mapper.MonsterMapper">
<!--实现public List<Monster> findMonsterByNameORId(Monster monster);
这里能直接写Monster是因为配置文件里配置了类型别名
-->
<select id="findMonsterByNameORId" parameterType="Monster" resultType="Monster">
SELECT * FROM monster WHERE id = #{id} OR `name` = #{name}
</select>
</mapper> 3.测试
java
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package com.sun.mapper;
import com.sun.entity.Monster;
import com.util.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Before;
import org.junit.Test;
import java.util.List;
/**
* @author 孙显圣
* @version 1.0
*/
public class MonsterMapperTest {
//两个属性
private SqlSession sqlSession; //相当于连接
private MonsterMapper monsterMapper;
//编写方法完成初始化
@Before //标注了Before之后表示了在执行目标测试方法前会执行该方法
public void init() {
//获取到sqlSession
sqlSession = MyBatisUtils.getSqlSession();
//获取到MonsterMapper对象
monsterMapper = sqlSession.getMapper(MonsterMapper.class);
System.out.println(monsterMapper.getClass());
}
@Test
public void test() {
Monster monster = new Monster();
monster.setId(1);
monster.setName("大象精");
List<Monster> monsterList = monsterMapper.findMonsterByNameORId(monster);
for (Monster monster1 : monsterList) {
System.out.println(monster1);
}
//关闭sqlsession
if (sqlSession != null) {
sqlSession.close();
}
}
} 3.案例二（模糊查询）
1.MonsterMapper.java添加方法
java
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public List<Monster> findMonsterByName(String name); 2.MonsterMapper.xml添加实现类
xml
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<!--实现public List<Monster> findMonsterByName(String name);-->
<select id="findMonsterByName" parameterType="String" resultType="Monster">
SELECT * FROM monster WHERE `name` LIKE '%${name}%'
</select> 3.测试
java
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@Test
public void MonsterMapper() {
List<Monster> monsterList = monsterMapper.findMonsterByName("孙");
for (Monster monster : monsterList) {
System.out.println(monster);
}
} 4.传入HashMap
1.基本介绍
2.案例一（参数为map）
1.MonsterMapper.java添加方法
java
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//传入map
public List<Monster> findMonsterByIdAndName_ParamMap(Map<String, Object> map); 2.MonsterMapper.xml
xml
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<!--这里如果想要获取到id和name则需要这个Map里面有这两个key-->
<select id="findMonsterByIdAndName_ParamMap" parameterType="Map" resultType="Monster">
SELECT * FROM monster WHERE id = #{id} OR `name` = #{name}
</select> 3.测试
java
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@Test
public void findMonsterByIdAndName_ParamMap() {
Map map = new HashMap<String, Object>();
map.put("id", 1);
map.put("name", "大象精");
List<Monster> monsters = monsterMapper.findMonsterByIdAndName_ParamMap(map);
for (Monster monster : monsters) {
System.out.println(monster);
}
} 3.案例二（返回值为map）
1.MonsterMapper.java添加方法
java
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//以map作为返回参数
public List<Map<String, Object>> findMonsterByIdAndName_ParamMap_returnMap(Map<String, Object> map); 2.MonsterMapper.xml
xml
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<!--返回值是List，每一个元素都是一个map，而一个map代表了一条记录，key代表列，value代表值-->
<select id="findMonsterByIdAndName_ParamMap_returnMap" parameterType="Map" resultType="Map">
SELECT * FROM monster WHERE id = #{id} OR `name` = #{name}
</select> 3.测试
java
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@Test
public void findMonsterByIdAndName_ParamMap_returnMap() {
Map map = new HashMap<String, Object>();
map.put("id", 6);
map.put("name", "大象精");
List<Map<String, Object>> mapList = monsterMapper.findMonsterByIdAndName_ParamMap_returnMap(map);
//取出所有map
for (Map<String, Object> stringObjectMap : mapList) {
for (Map.Entry<String, Object> entry : stringObjectMap.entrySet()) {
System.out.println(entry.getKey() + " " + entry.getValue());
}
}
} 5.ResultMap
1.基本介绍
2.案例
1.创建数据表
sql
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CREATE TABLE `user` (
user_id INT NOT NULL auto_increment,
user_email VARCHAR(255) DEFAULT '',
user_name VARCHAR(255) DEFAULT'',
PRIMARY KEY (user_id)
) 2.创建映射类User.java
java
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package com.sun.entity;
/**
* @author 孙显圣
* @version 1.0
*/
public class User {
private Integer user_id;
//下面两个字段与数据表的字段不对应
private String username;
private String useremail;
public User() {
}
public User(Integer user_id, String username, String useremail) {
this.user_id = user_id;
this.username = username;
this.useremail = useremail;
}
public Integer getUser_id() {
return user_id;
}
public void setUser_id(Integer user_id) {
this.user_id = user_id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getUseremail() {
return useremail;
}
public void setUseremail(String useremail) {
this.useremail = useremail;
}
@Override
public String toString() {
return "User{" +
"user_id=" + user_id +
", username='" + username + '\'' +
", useremail='" + useremail + '\'' +
'}';
}
} 3.UserMapper.java
java
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UserMapper.xmlpackage com.sun.mapper;
import com.sun.entity.User;
import java.util.List;
/**
* @author 孙显圣
* @version 1.0
*/
public interface UserMapper {
//查询所有UserMapper.xmlser
public List<User> findAllUser();
} 4.UserMapper.xml
xml
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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--指定该xml文件和哪个接口对应-->
<mapper namespace="com.sun.mapper.UserMapper">
<select id="findAllUser" resultType="User">
SELECT * FROM user
</select>
</mapper> 5.测试（数据未填充！）
java
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package com.sun.mapper;
import com.sun.entity.User;
import com.util.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Before;
import org.junit.Test;
import java.util.List;
/**
* @author 孙显圣
* @version 1.0
*/
public class UserMapperTest {
//两个属性
private SqlSession sqlSession; //相当于连接
private UserMapper userMapper;
//编写方法完成初始化
@Before //标注了Before之后表示了在执行目标测试方法前会执行该方法
public void init() {
//获取到sqlSession
sqlSession = MyBatisUtils.getSqlSession();
//获取到MonsterMapper对象
userMapper = sqlSession.getMapper(UserMapper.class);
System.out.println(userMapper.getClass());
}
@Test
public void findAllUser() {
List<User> allUser = userMapper.findAllUser();
System.out.println(allUser);
}
} 6.使用resultMap替换resultType解决，修改UserMapper.xml
xml
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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--指定该xml文件和哪个接口对应-->
<mapper namespace="com.sun.mapper.UserMapper">
<!--使用resultMap替换resultType，来进行映射类的属性与表之间的映射-->
<resultMap id="findAllUserResultType" type="User">
<result column="user_email" property="useremail"/>
<result column="user_name" property="username"/>
</resultMap>
<select id="findAllUser" resultMap="findAllUserResultType">
SELECT * FROM user
</select>
</mapper> 7.结果
3.注意事项与细节
如果没有使用resultMap，但是表的列名与映射类的属性不匹配，则返回的结果不会填充，则该位置会是对象属性的默认值
解决列名与属性名不同也可以使用别名，简单来说就是查询出来结果的时候使用as ，将结果所在的列名设置成跟属性一致的名字，但是不推荐
MyBatis-Plus可以直接使用@TableField注解或者@TableName注解来解决
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