第一个MyBatis程序
# 第一个MyBatis程序💛
# 1、搭建环境
- 数据库 gokudb
- 所需Jar包
<!-- mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.6</version>
</dependency>
<!--junit-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<!--mysql-connector-java-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.22</version>
</dependency>
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# 2、mybatis-config.xml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>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://127.0.0.1:3306/goku?serverTimezone=Asia/Shanghai"/>
<property name="username" value="root"/>
<property name="password" value="795200"/>
</dataSource>
</environment>
</environments>
<!--每一个mapper.xml都需要在MyBatis核心配置文件中注册-->
<mappers>
<mapper resource="com/singerw/mapper/UserMapper.xml"/>
</mappers>
</configuration>
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# 3、编写MyBatisUtils工具类
/**
* @Author: CodeSleep
* @Date: 2021/8/23 21:15
* @Description: //TODO MyBatis工具类
*/
public class MyBatisUtils {
private static SqlSessionFactory sqlSessionFactory;
// 加载资源
static {
try {
// 使用MyBatis获取SqlSessionFactory对象
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* @return
* @Author CodeSleep
* @Date: 2021/8/23 21:13
* @Description: //TODO 创建执行SQL的对象
* sqlSessionFactory中获取SqlSession实例
* SqlSession完全包含了面向数据库执行SQL命令所需的所有方法;
*/
public static SqlSession getSqlSession() {
SqlSession sqlSession = sqlSessionFactory.openSession();
return sqlSession;
}
}
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# 4、编写代码
- 实体类(
User.java
)
@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
private int userid;
private String username;
private String userphone;
private String userpassword;
private int jurisdiction;
private String createtime;
private String logintime;
private int userstatus;
}
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- Dao数据持久层接口(
UserMapper.java
)
public interface UserMapper {
List<User> getUsers(int userid);
}
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- Dao数据持久层(
UserMapper.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">
<mapper namespace="com.singerw.mapper.UserMapper">
<select id="getUsers" resultType="com.singerw.pojo.User">
select * from goku.g_users where userid = #{userid}
</select>
</mapper>
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- 测试类(
UserMapperTest.java
)
public class UserMapperTest {
@Test
public void getUsers() {
SqlSession sqlSession = MyBatisUtils.getSqlSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
List<User> users = userMapper.getUsers(1);
for (User user : users) {
System.out.println(user);
}
sqlSession.close();
}
}
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# 5、注意点
在pom.xml
的build
中配置resources
,来防止我们资源在Maven
项目中的导出失败的问题!
<!--在build中配置resources,来防止我们资源导出失败的问题-->
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
</build>
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可能会遇到的问题:
- 配置文件没有注册
- 绑定接口错误
- 方法名不对
- 返回类型不对
- Maven导出资源问题
编辑 (opens new window)