mybatis --入门单表增删改查-curd

1. mybatis 环境搭建

这里使用maven项目构建

  <dependencies><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.11</version><scope>test</scope></dependency><!-- mysql 驱动包 --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.20</version></dependency><!-- mybatis 框架 --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.5</version></dependency>    </dependencies>

2. 实体类映射文件配置（写sql）

实体类

package cn.bitqian.entity;/*** user 类* @author echo lovely* @date 2020/9/9 20:59*/
public class User {private Integer userId;private String userName;private String userPassword;public User() {}public User(Integer userId, String userName, String userPassword) {this.userId = userId;this.userName = userName;this.userPassword = userPassword;}// 省略set/get toString..
}

user-mapper.xml(注意命名空间，标签 id，占位符)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><!-- 实体类 与 sql解耦映射文件 -->
<mapper namespace="userMapper"><!-- sql 语句 和 对应的查询结果类型 --><select id="selectAll" resultType="cn.bitqian.entity.User">select * from users1</select><!-- parameterType 为接收参数的类型 #{实体类属性名} 表示占位符 --><!-- 插入操作 需要user参数 --><insert id="insertUser" parameterType="cn.bitqian.entity.User">insert into users1 values (#{userId}, #{userName}, #{userPassword})</insert><!-- 修改操作 --><update id="updateUser" parameterType="cn.bitqian.entity.User">update users1 set username = #{userName}, userpassword = #{userPassword}where userid = #{userId}</update><!-- 根据id删除某个user --><delete id="deleteUser" parameterType="java.lang.Integer">delete from users1 where userid = #{userId}</delete>
</mapper>

3. mybatis核心配置文件（环境配置）

jdbc 连接配置

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis_study?serverTimezone=GMT
username=root
password=123456

mybatis-config 配置 (注意头文件的引入)

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration><!-- 读取jdbc.properties 配置信息 --><properties resource="jdbc.properties"></properties><environments default="development"><!--部署环境--><environment id="development"><!-- 配置事务管理器 --><transactionManager type="JDBC"></transactionManager><!-- 配置数据源 --><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><!-- 加载映射用户 xml这里有个小问题，cn/bitqian/mapper, 看文件夹有没三层 --><mapper resource="cn.bitqian.mapper/user-mapper.xml"/></mappers>
</configuration>

包名就叫cn.bitqian.mapper, 没有分层

4. 测试

由于初学，模板化的代码我写了四遍… 其中包含了单表curd

package DemoTest;import cn.bitqian.entity.User;
import org.apache.ibatis.io.Resources;
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.IOException;
import java.io.InputStream;
import java.util.List;/*** mybatis 单表增删改查操作* @author echo lovely* @date 2020/9/9 21:36*/
public class TestMybatisCurd {// 查询单表@Testpublic void test1() {SqlSession sqlSession = null;try {// mybatis 读取核心文件流InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");// 通过sql 会话工厂构建器 创建session 工厂SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 拿到sessionsqlSession = sqlSessionFactory.openSession();// 进行查询List<User> userList = sqlSession.selectList("userMapper.selectAll");System.out.println(userList);} catch (IOException e) {e.printStackTrace();} finally {// 释放session资源if (sqlSession != null)sqlSession.close();}}@Testpublic void test2() {SqlSession sqlSession = null;try {// 加载mybatis核心配置文件InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");// 获得session工厂SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 通过session工厂获得sessionsqlSession = sqlSessionFactory.openSession();User user = new User(null, "taylor swift", "gorgeous");// 通过user-mapper 命名空间和id进行相应的sql操作int count = sqlSession.insert("userMapper.insertUser", user);// 进行增删改操作时 要提交事务sqlSession.commit();System.out.println("count = " + count);} catch (IOException e) {e.printStackTrace();} finally {if (sqlSession != null)sqlSession.close();}}// 修改单个用户@Testpublic void test3() {SqlSession sqlSession = null;try {InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);sqlSession = sqlSessionFactory.openSession();User user = new User(1, "rose", "love jack");int count = sqlSession.update("userMapper.updateUser", user);sqlSession.commit();System.out.println(count);} catch (IOException e) {e.printStackTrace();} finally {if (sqlSession != null)sqlSession.close();}}// 删除user@Testpublic void tes4() {SqlSession sqlSession = null;try {InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);sqlSession = sqlSessionFactory.openSession();sqlSession.delete("userMapper.deleteUser", 1);sqlSession.commit();} catch (IOException e) {e.printStackTrace();} finally {if (sqlSession != null)sqlSession.close();}}}