安装
Gradle 引用org.mybatis:mybatis:3.5.11
引用MySQL：mysql:mysql-connector-java
配置
在resouces文件夹下先新建org/mybatis文件夹，再新建mybatis-config.xml文件和config.properties文件
mybatis-config.xml如下
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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>
<properties resource="org/mybatis/config.properties"/> // 下面的配置可以使用${xxx}代替硬编码
<settings>
<setting name="mapUnderscoreToCamelCase" value="true"/> // 该属性可以开启自动映射
</settings>
<typeAliases>
<typeAlias type="com.cyh.server.domain.User" alias="User"/> // 类路径，简写
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<mappers>
<package name="com.cyh.server.db.mapper"/> // resources下的路径
</mappers>
</configuration>
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config.properties如下
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| driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis_test?useUnicode=true&characterEncoding=utf8
username=root
password=
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Spring 配置代码
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| @Configuration
public class MyBatisConfiguration {
@Bean
public SqlSessionFactory sqlSessionFactory() throws IOException {
String resource = "org/mybatis/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
return new SqlSessionFactoryBuilder().build(inputStream);
}
}
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创建Mapper
开始创建方法，假设我们在com.cyh.server.db.mapper下创建mapper
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| public interface UserMapper {
User selectUser(Long id);
Long insertUser(User user);
}
@Data
public class User {
Long id;
String name;
String hashedPassword;
}
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则需要在resources文件下，创建同路径的mapper文件：
如下：resources/com/cyh/server/db/mapper/UserMapper.xml
⚠️注意：在创建resources下的文件夹时，和创建包路径不一样，不能简单填写”com.cyh.server.db.mapper”，否则会创建一个名为”com.cyh.server.db.mapper”的文件夹，可以填”com/cyh/server/db/mapper”
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| <?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.cyh.server.db.mapper.UserMapper">
<resultMap id="usermap" type="User"> // 这里type可以简写，因为上述的typeAliases
<id column="id" property="id"/>
<result column="name" property="name"/>
<result column="hashed_password" property="hashedPassword"/>
</resultMap>
<select id="selectUser" resultMap="usermap"> // id和方法名一样，resultMap是结果映射
select * from User where id = #{id}
</select>
<insert id="insertUser" parameterType="User" useGeneratedKeys="true" keyColumn="id" keyProperty="id"> // 使用自增id，参数的类型是实体类
INSERT INTO `user` (`id`, `name`, `hashed_password`) VALUES (#{id}, #{name}, #{hashedPassword})
</insert>
</mapper>
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在Spring使用
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| @Repository
public class UserRepository {
@Autowired
private SqlSessionFactory sessionFactory;
public User findById(Long id) {
try (SqlSession session = sessionFactory.openSession()) {
UserMapper mapper = session.getMapper(UserMapper.class);
return mapper.selectUser(id);
}
}
public Long addUser(User user) {
try (SqlSession session = sessionFactory.openSession()) {
UserMapper mapper = session.getMapper(UserMapper.class);
Long ret = mapper.insertUser(user);
session.commit();
return ret;
}
}
}
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常用代码段
批量插入insertAll
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| <insert id="insertAll" useGeneratedKeys="true" keyColumn="id" keyProperty="id" parameterType="xxx">
INSERT INTO <include refid="TableName"/>
(c1, c2)
values <foreach collection="list" item="item" separator=",">
(#{item.f1}, #{item.f2})
</foreach>
</insert>
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相关问题
if标签字符串判断相等问题
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| <if test="a == '1'.toString()">
AND db_field != '-1'
</if>
<if test='a == "2"'>
AND db_field = '-1'
</if>
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模糊查询
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| name like concat("%", #{name}, "%")
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