加载mybatis依赖
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| <dependency>
<!--
数据库操作
https://github.com/mybatis/spring-boot-starter
https://mybatis.org/spring-boot-starter/mybatis-spring-boot-autoconfigure/zh/index.html
-->
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.1.4</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
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通过注解的方式
在配置文件配置数据库连接application.yml
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| server:
port: 8000
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
username: root
password: 123456
url: jdbc:mysql://127.0.0.1:3306/mall?characterEncoding=utf8&useSSL=false
mybatis:
configuration:
map-underscore-to-camel-case: true
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定义CityMapper
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| import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
@Mapper
public interface CityMapper {
@Select("SELECT * FROM CITY WHERE state = #{state}")
City findByState(@Param("state") String state);
}
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当数据库表特别多的时候,我们写一个interface的时候都需要加上@Mapper注解，这时候我们只需要在入口加上
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| import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
@MapperScan(basePackages = "com.github.example.mapper")
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class,args);
}
}
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定义City实体
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| import lombok.Data;
@Data
public class City {
private Integer id;
}
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写测试用例
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| import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@SpringBootTest
public class CityMapperTest {
@Autowired
private CityMapper cityMapper;
public void testFindByState() {
City byState = cityMapper.findByState("1");
System.out.println(byState.getId());
}
}
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Xml方式使用
在配置文件配置数据库连接application.yml
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| server:
port: 8000
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
username: root
password: 123456
url: jdbc:mysql://127.0.0.1:3306/example?characterEncoding=utf8&useSSL=false
mybatis:
configuration:
map-underscore-to-camel-case: true
mapper-locations: classpath:mapper/*.xml
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首先定义city.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">
<mapper namespace="com.github.example.mapper.CityMapper">
<select id="queryByState" resultType="com.github.example.model.City">
SELECT * FROM CITY WHERE state = #{state}
</select>
</mapper>
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namespace：复制完整的包名并包含class
queryByState：class中的queryByState方法
resultType：返回结果映射的实体
定义CityMapper和City
通过注解方式已定义，只需要在CityMapper添加queryByState方法
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| import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
@Mapper
public interface CityMapper {
@Select("SELECT * FROM CITY WHERE state = #{state}")
City findByState(@Param("state") String state);
City queryByState(String state);
}
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写测试用例
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| import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@SpringBootTest
public class CityMapperTest {
@Autowired
private CityMapper cityMapper;
public void testqueryByState() {
City byState = cityMapper.queryByState("1");
System.out.println(byState.getId());
}
}
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