mybatis快速入门

发布时间：2024年01月12日

一.Mybatis入门

1.创建user表，添加数据

create table tb_user(
	id int primary key auto_increment,
	username varchar(20) not null,
	birthday date,
	sex char(1) default '男',
	address varchar(50)
);

insert into tb_user values(null,'孙悟空','1980-10-24','男','花果山水帘洞');
insert into tb_user values(null,'白骨精','1992-11-12','女','白虎岭白虎洞');
insert into tb_user values(null,'猪八戒','1983-05-20','男','福临山云洞');
insert into tb_user values(null,'蜘蛛清','1995-10-21','女','盘丝洞');

2.创建maven工程，导入坐标

<?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.itheima</groupId>
    <artifactId>mybatis_day01</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
    </properties>

    <!--依赖管理-->
    <dependencies>
        <!--mysql依赖-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <!--mybatis依赖-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>

    </dependencies>
</project>

3.编写mybatis核心配置文件

<?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">
<!--根元素-->
<configuration>
    <!--配置数据源（数据库连接）-->
    <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://localhost:3306/hsp_db02?useUnicode=true&amp;characterEncoding=utf-8&amp;useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <!--映射映射相关文件-->
    <mappers>
        <mapper resource="com/itheima/dao/UserMapper.xml"/>
    </mappers>
</configuration>

4.定义与SQL映射文件同名的Mapper接口，并将Mapper和SQL映射文件放置在同一目录下

在这里插入图片描述

package com.itheima.dao;

import com.itheima.pojo.User;

import java.util.List;

//dao层
public interface UserMapper {
    /**
     * 功能：查询所有的用户
     * @return
     */
    public List<User> findAllUser();
}

5.编写SQL映射文件，设置SQL映射文件的namespace属性为Mapper接口全限定名

<?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">
<!--利用namespace属性，绑定当前映射文件和mapper接口映射关联-->
<mapper namespace="com.itheima.dao.UserMapper">
  
</mapper>

6.在Mapper接口中定义方法，方法名就是SQL映射文件中的SQL语句的id,并保持参数类型和返回值

<?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">
<!--利用namespace属性，绑定当前映射文件和mapper接口映射关联-->
<mapper namespace="com.itheima.dao.UserMapper">
    <!--SQL查询文件-->
    <select id="findAllUser" resultType="com.itheima.pojo.User">
        select id,username,birthday,sex,address from tb_user
    </select>
</mapper>

7.编写

1.定义POJO类

package com.itheima.pojo;

import java.util.Date;

public class User {
    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    public User() {
    }

    public User(Integer id, String username, Date birthday, String sex, String address) {
        this.id = id;
        this.username = username;
        this.birthday = birthday;
        this.sex = sex;
        this.address = address;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

2.加载核心配置文件，获取SqlSessionFactory对象

//配置文件路径
String resource = "mybatis-config.xml";
//基于配置文件路径，创建字节输入流
InputStream is = Resources.getResourceAsStream(resource);
//创建SqlSessionFactory工厂类
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

3.获取SqlSession对象

//使用SqlSessionFactory工厂类，创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();

4.通过SqlSession的getMapper方法获取Mapper接口的代理

//利用sqlSession，创建一个代理对象
UserMapper sessionMapper = sqlSession.getMapper(UserMapper.class);

5.调用对应方法完成sql执行

//使用代理对象和方法查询用户数据
List<User> userList = sessionMapper.findAllUser();
//测试用户数据
for (User user:userList){
	System.out.println(user);
}

完整代码如下

package com.itheima.test;

import com.itheima.dao.UserMapper;
import com.itheima.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;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisTest {
    @Test
    public void testFindAllUser() throws IOException {
        //配置文件路径
        String resource = "mybatis-config.xml";
        //基于配置文件路径，创建字节输入流
        InputStream is = Resources.getResourceAsStream(resource);
        //创建SqlSessionFactory工厂类
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

        //使用SqlSessionFactory工厂类，创建SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //利用sqlSession，创建一个代理对象
        UserMapper sessionMapper = sqlSession.getMapper(UserMapper.class);

        //使用代理对象和方法查询用户数据
        List<User> userList = sessionMapper.findAllUser();

        //测试用户数据
        for (User user:userList){
            System.out.println(user);
        }
    }
}

测试的结果如下：

D:\jdk17\bin\java.exe -ea -Didea.test.cyclic.buffer.size=1048576 "-javaagent:D:\IntelliJ IDEA 2021.3.3\lib\idea_rt.jar=49230:D:\IntelliJ IDEA 2021.3.3\bin" -Dfile.encoding=UTF-8 -classpath "D:\IntelliJ IDEA 2021.3.3\lib\idea_rt.jar;D:\IntelliJ IDEA 2021.3.3\plugins\junit\lib\junit5-rt.jar;D:\IntelliJ IDEA 2021.3.3\plugins\junit\lib\junit-rt.jar;E:\Linuxshare\mybatis_day01\target\classes;D:\maven_repository\mysql\mysql-connector-java\5.1.47\mysql-connector-java-5.1.47.jar;D:\maven_repository\org\mybatis\mybatis\3.5.1\mybatis-3.5.1.jar;D:\maven_repository\junit\junit\4.12\junit-4.12.jar;D:\maven_repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar" com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 com.itheima.test.MybatisTest,testFindAllUser
User{id=1, username='孙悟空', birthday=Fri Oct 24 00:00:00 CST 1980, sex='男', address='花果山水帘洞'}
User{id=2, username='白骨精', birthday=Thu Nov 12 00:00:00 CST 1992, sex='女', address='白虎岭白虎洞'}
User{id=3, username='猪八戒', birthday=Fri May 20 00:00:00 CST 1983, sex='男', address='福临山云洞'}
User{id=4, username='蜘蛛清', birthday=Sat Oct 21 00:00:00 CST 1995, sex='女', address='盘丝洞'}

Process finished with exit code 0

文章来源:https://blog.csdn.net/lisus2007/article/details/135554984
本文来自互联网用户投稿，该文观点仅代表作者本人，不代表本站立场。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如若内容造成侵权/违法违规/事实不符，请联系我的编程经验分享网邮箱：chenni525@qq.com进行投诉反馈，一经查实，立即删除！