Mybatis学习1：从零开始搭建Mybatis环境

Posted 2021-09-05 Z|Star

Mybatis简介

• MyBatis 是一款优秀的持久层框架
• MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集的过程
• MyBatis 可以使用简单的 XML 或注解来配置和映射原生信息，将接口和 Java 的 实体类 【Plain Old Java Objects,普通的 Java对象】映射成数据库中的记录。
• Mybatis就是帮助程序猿将数据存入数据库中，从数据库中取数据。

MyBatis第一个程序

搭建实验数据库

启动mysql，创建一个新的数据库mybatis，并创建一张新的数据表user

CREATE DATABASE `mybatis`;
USE `mybatis`;
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(20) NOT NULL,
`name` varchar(30) DEFAULT NULL,
`pwd` varchar(30) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
insert into `user`(`id`,`name`,`pwd`) values (1,'zstar','123456'),(2,'张三','abcdef'),(3,'李四','987654');

导入MyBatis相关 jar 包

在pom.xml中添加：

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
    </dependencies>

防止Maven静态资源过滤

后面会遇到Maven静态资源过滤问题，因此在pom.xml文件中添加下面内容，防止该问题：

    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>

编写MyBatis核心配置文件

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>
    <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/mybatis?useSSL=false&amp;useUnicode=true&amp;characterEncoding=utf8"/>
                <property name="username" value="root"/>
                <property name="password" value="password"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/kuang/mapper/Mapper.xml"/>
    </mappers>
</configuration>

注：里面3306后面跟着的数据库名称要改为使用的数据库名称，useSSL必须设为false，账号密码根据自己的实际进行设置。

编写MyBatis工具类

MybatisUtils.java

package com.kuang.utils;

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 java.io.IOException;
import java.io.InputStream;
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    //获取SqlSession连接
    public static SqlSession getSession(){
        return sqlSessionFactory.openSession();
    }
}

创建实体类

User.java

package com.kuang.pojo;

public class User {
    private int id; //id
    private String name; //姓名
    private String pwd; //密码

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }
    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getPwd() {
        return pwd;
    }

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

    public void setName(String name) {
        this.name = name;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\\'' +
                ", pwd='" + pwd + '\\'' +
                '}';
    }
}

编写Mapper接口类

UserMapper.java

package com.kuang.mapper;

import com.kuang.pojo.User;
import java.util.List;
public interface UserMapper {
    List<User> selectUser();
}

编写Mapper.xml配置文件

Mapper.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.kuang.mapper.UserMapper">
    <select id="selectUser" resultType="com.kuang.pojo.User">
        select * from user
    </select>
</mapper>

注：mapper里面使用的是sql语句

测试

效果说明：将之前输入的三条记录查询出来

import com.kuang.pojo.User;
import com.kuang.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class MyTest {
    @Test
    public void selectUser() {
        SqlSession session = MybatisUtils.getSession();

        List<User> users = session.selectList("com.kuang.mapper.UserMapper.selectUser");

        for (User user: users){
            System.out.println(user);
        }
        session.close();
    }
}

项目结构

参考资料

【狂神说Java】Mybatis最新完整教程IDEA版通俗易懂