Mybatis系列--01-什么是Mybatis?

什么是Mybatis?

简介

中文文档
MyBatis是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的JDBC代码以及设置参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

maven包导入

<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.10</version>
</dependency>

实践

0. 数据库中数据插入

create table `user` (
`id` int(20) not null ,
`name` varchar(30) default null,
`pwd` varchar(30) default  null
)engine=innodb default charset=utf8;

insert into `user`(`id`,`name`,`pwd`) values
(1,'狂神','123456'),
(2,'张三','111'),
(3,'李四','222');

1. pom.xml依赖 主要是三个包：mysql,mybatis,junit

<?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">
    <parent>
        <artifactId>Mybatis-Study</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>Mybatis-Study01</artifactId>

    <!--父工程-->
    <dependencies>
        <!--  junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>
        <!--  mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.9</version>
        </dependency>
        <!--  mysql driver-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.20</version>
        </dependency>

    </dependencies>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

</project>

2. mybatis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">
<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/test?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF8" />
                <property name="username" value="root" />
                <property name="password" value="xxxx" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/UserMapper.xml"></mapper>
    </mappers>
</configuration>

3. 业务代码
   User类

package com.kuang.pojo;

/**
 * 功能描述
 *
 * @since 2022-07-11
 */
public class User {
    private int id;
    private String name;
    private String pwd;

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

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

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

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

util工具类

package com.kuang.util;

import java.io.IOException;
import java.io.InputStream;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

/**
 * 功能描述
 *
 * @since 2022-07-11
 */
public class MyBatisUtils {
    private static SqlSessionFactory sqlSessionFactory;

    static {
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;

        try {
            // get SqlSessionFactory
            inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

Mapper层,需放在resource目录下的mapper文件夹下

<?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.dao.UserDao">
    <select id="getUserList" resultType="com.kuang.pojo.User">
        select *
        from user
    </select>
</mapper>

4. 测试类

package com.kuang.dao;

import java.util.Iterator;
import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import com.kuang.pojo.User;
import com.kuang.util.MyBatisUtils;

/**
 * 功能描述
 *
 * @since 2022-07-11
 */
public class UserDaoTest {
    @Test
    public void test1() {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getUserList();
        Iterator<User> iterator = userList.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }

    }
}

5. 结果

User{id=1, name='狂神', pwd='123456'}
User{id=2, name='张三', pwd='111'}
User{id=3, name='李四', pwd='222'}