Mybatis基础教程(二)
第一个mybatis案例
入门案例： 使用mybatis查询指定编号的用户资料。
1.创建users表
-- ----------------------------
-- Table structure for users
-- ----------------------------
DROP TABLE IF EXISTS `users`;
CREATE TABLE `users` (
`uid` int NOT NULL AUTO_INCREMENT,
`username` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NULL DEFAULT NULL,
`password` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NULL DEFAULT NULL,
PRIMARY KEY (`uid`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_bin ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of users
-- ----------------------------
INSERT INTO `users` VALUES (1, 'zhangsan', '123456');
INSERT INTO `users` VALUES (2, 'lisi', '654321');
INSERT INTO `users` VALUES (3, '王老虎', '888888');
2.项目结构图
创建maven项目，项目结构图如下：
pom.xml添加依赖：
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.simoniu</groupId>
<artifactId>firstdemo</artifactId>
<version>1.0-SNAPSHOT</version>
<!--解决Maven默认使用JDK1.5的问题-->
<properties>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<!--添加mybatis的依赖-->
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.9</version>
</dependency>
<!--添加MySQL的依赖-->
<!--MySQL的依赖去哪里找呢？官网找-->
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.21</version>
</dependency>
<!--添加单元测试的依赖Junit-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
3.创建实体类
package com.entity;
public class Users {
private Integer uid; //用户编号，主键
private String username; //用户名
private String password; //密码
public Users() {
}
public Users(Integer uid, String username, String password) {
this.uid = uid;
this.username = username;
this.password = password;
}
public Integer getUid() {
return uid;
}
public void setUid(Integer uid) {
this.uid = uid;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "Users{" +
"uid=" + uid +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
4.创建usersMapper.xml 在resources/com/mapper下创建usersMapper.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.mapper.usersMapper">
<!--根据用户编号查询某个用户资料-->
<select id="getUser" parameterType="int" resultType="Users">
select * from users where uid=#{uid}
</select>
</mapper>
5.创建mybatis-config.xml
<?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>
<!--配置属性-->
<properties>
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url"
value="jdbc:mysql://localhost:3306/test?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false&allowPublicKeyRetrieval=true"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</properties>
<!-- 配置映射类的别名 -->
<typeAliases>
<typeAlias alias="Users" type="com.entity.Users"/>
</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>
<mapper resource="com/mapper/usersMapper.xml"/>
</mappers>
</configuration>
6.单元测试
在test下创建UsersMapperTest单元测试
package com.mapper;
//单元测试
import com.entity.Users;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.InputStream;
public class UsersMapperTest {
@Test
public void testSelectUserByUid(){
String resource = "mybatis-config.xml";
//使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）
InputStream is = UsersMapperTest.class.getClassLoader().getResourceAsStream(resource);
//构建sqlSession的工厂
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
SqlSession session = sessionFactory.openSession();
/**
* 映射sql的标识字符串，
* com.mapper.usersMapper是userMapper.xml文件中mapper标签的namespace属性的值，
* getUser是select标签的id属性值，通过select标签的id属性值就可以找到要执行的SQL
*/
String statement = "com.mapper.usersMapper.getUser";//映射sql的标识字符串
//执行查询返回一个唯一user对象的sql
Users user = session.selectOne(statement,3);
System.out.println(user);
}
}
运行结果：
Users{uid=3, username='王老虎', password='888888'}