前言
公司要求没办法，前端也要了解一下后端知识，这里记录一下自己的学习
学习教程：黑马mybatis教程全套视频教程，2天Mybatis框架从入门到精通
文档：
https://mybatis.net.cn/index.html
MyBatis
快速入门：查询user表中所有数据
- 创建user表，添加数据
- 创建模块，导入坐标
- 编写mybatis核心配置文件 ---->替换连接信息，解决硬编码问题
- 编写sql映射文件—> 统一管理sql语句，解决硬编码问题
- 编码
- 定义POJO类，对应数据库的表
- 加载核心配置文件，获取SqlSessionFactory对象
- 获取SQLSession对象，执行sql语句
- 释放资源
创建模块
创建模块
File - > New -> Module
导入坐标
pom.xml
<dependencies><!--mybatis依赖--><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.9</version></dependency><!--mysql驱动依赖--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.31</version></dependency><!-- junit 单元测试 --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.13.2</version><scope>test</scope></dependency><!-- slf4j 日志 --><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-api</artifactId><version>1.7.30</version></dependency><!-- logback 日志 --><dependency><groupId>ch.qos.logback</groupId><artifactId>logback-classic</artifactId><version>1.2.3</version></dependency><dependency><groupId>ch.qos.logback</groupId><artifactId>logback-core</artifactId><version>1.2.3</version></dependency></dependencies>
src/main/resources/logback.xml
<?xml version="1.0" encoding="UTF-8"?>
<configuration><!-- console表示当前日志信息是可以输出到控制台的--><appender name="Console" class="ch.qos.logback.core.ConsoleAppender"><encoder><pattern>【%level】 %cyan(【%thread】) %boldGreen(%logger{15}) - %msg %n</pattern></encoder></appender><logger name="com.Carter_x" level="DEBUG" additivity="false"><appender-ref ref="Console"/></logger>
</configuration>
核心配置文件
src/main/resources/mybatis-config.xml
<?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><environments default="development"><environment id="development"><transactionManager type="JDBC"/><dataSource type="POOLED"><!-- 数据库连接信息--><property name="driver" value="com.mysql.cj.jdbc.Driver"/><property name="url" value="jdbc:mysql://localhost:3306/test"/><property name="username" value="root"/><property name="password" value="123456"/></dataSource></environment></environments><mappers><mapper resource="org/mybatis/example/BlogMapper.xml"/></mappers>
</configuration>
sql映射文件
src/main/resources/UserMapper.xml，表示是来操作user表的sql映射文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><!--
namespace: 命名空间
resultType:返回值的类型，一般是实体类
id:唯一标识
-->
<mapper namespace="test"><select id="selectAllUser" resultType="com.example.pojo.User">select * from user;</select>
</mapper>
在src/main/java下创建对于的实体类
package com.example.pojo;public class User {
}
修改mybatis-config.xml文件，指定刚才创建的sql映射文件
<mappers><!-- 加载sql映射文件--><mapper resource="userMapper.xml"/>
</mappers>
编码
修改之前创建的User类，类的属性要与对应表里的字段对应
package com.example.pojo;public class User {private Integer id;private String name;private Integer age;private String email;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}@Overridepublic String toString() {return "User{" +"id=" + id +", name='" + name + '\'' +", age=" + age +", email='" + email + '\'' +'}';}}
编写测试类
编写一个测试类，用于测试代码
package org.example;import java.io.IOException;
import java.io.InputStream;
import java.util.List;import com.example.pojo.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;public class Main {public static void main(String[] args) throws IOException {// 1、加载mybatis的核心配置文件，获取SqlSessionFactory对象，下面的是从官网复制的String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 2、获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();// 3、执行sql语句，查询所有数据// 指定要执行的sql语句，这里传入对应的标识，对应UserMapper.xml文件中<select id="selectAllUser" resultType="User">List<User> userList = sqlSession.selectList("test.selectAllUser");System.out.println(userList);System.out.println("数据总条数：" + userList.size());// 4、关闭资源sqlSession.close();}
}
执行结果
