Mybatis【第一个 Mybatis 程序】网站首页 技术教程

<dependencies>
    <!--   mysql8 驱动,与本地mysql版本需要一致   -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.30</version>
        </dependency>
    <!--  mybatis  -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
    <!--  junit,测试工具   -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

1.2、防止资源导出失败

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

2、在resources下编写 Mybatis核心配置文件

命名为mybatis-config.xml，作用是连接数据库

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//OTD Config 3.0//EN"
        "http://mybatis.org/schema/mybatis-3-config.dtd">
<!-- 核心配置文件 -->
<configuration>
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                    <!--防止乱码 中文出现?-->
                    <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                    <property name="username" value="root"/>
                    <property name="password" value="******"/>
                </dataSource>
            </environment>
        </environments>
</configuration>

二、搭建结构

1、编写mybatis工具类（utils）

作用是获取SqlSession对象，相当于JDBC中的 Statement对象

package com.study.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 {
            //1.获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";//maven项目下路径这么写
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //SqlSessionFactory 顾名思义，我们可以通过工厂创建SqlSession对象
    //SqlSession 完全包含了面向数据库执行 SQL 命令所需的所有方法
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

2、编写实体类（pojo）

实现所有 get和set 方法并重写 toString方法

package com.study.pojo;

public class User {
    //全部按着数据库来,名字一一对应
    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 + ''' +
                '}';
    }
}

3、Mybatis 的实现（dao层）

以添加用户为例

3.1、编写接口（UserMapper.java）

接口的实现在映射文件(UserMapper.xml)中实现

public interface UserMapper {
    int addUser(User user);
}

3.2、通过映射绑定并实现接口（UserMapper.xml）

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//OTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.study.dao.UserMapper">
    <insert id="addUser" parameterType="com.study.pojo.User">
        insert into mybatis.user (id,name,pwd)
        values (#{id},#{name},#{pwd});
    </insert>
</mapper>

三、测试

1、搭建数据库

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;

2、编写测试类

注意：增删改需要提交事务 , 查询语句不需要

Mybatis 操作数据库和 JDBC 比较相似但 Mybatis更加简单便捷！

@Test
    public void updateUser(){
        //1.获取数据库操作对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //2.获取接口
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //3.执行SQL语句
        User user = new User(1,"燕双鹰","123456");
        mapper.addUser(user);

        //4.提交事务
        sqlSession.commit();

        //5.关闭资源
        sqlSession.close();
    }