从零开始学Ｍybatis－Mybatyis 的概述

曾经终败给现在 2022-04-15 04:51 318阅读 0赞

### 文章目录 ###

*   *   *  什么是MyBatis？
         *  ORM :对象关系映射
         *  Mybatis 的基本概述
         *  Mybatis 的优势
         *  Mybatis 使用场景
         *  Mybatis 的开发环境的搭建
         *   *  获取Mybatis 的下载
         *  Mybatis 基本使用案例
         *   *  执行结果

[欢迎来到我的个人博客][Link 1]

### 什么是MyBatis？ ###

MyBatis是一个第一类持久性框架，支持自定义SQL，存储过程和高级映射。MyBatis几乎消除了所有JDBC代码和手动设置参数以及检索结果。MyBatis可以使用简单的XML或Annotations来配置和映射基元，Map接口和Java POJO（Plain Old Java Objects）到数据库记录。

### ORM :对象关系映射 ###

Object Relation Mapping

\#\#\#传统JDBC 程序的设计缺陷  
１．大量的配置信息的硬代码  
２．大量的无关业务处理  
３．编码扩展优化极其不便

### Mybatis 的基本概述 ###

*  避免传统的jdbc 硬编码
 *  XML配置或者注解
 *  POJP对像和数据库记录直接映射
 *  完善的文档支持

### Mybatis 的优势 ###

*  简单易学，快速上手，学习成本低
 *  数据库交互信息配置化
 *  动态SQL语句

### Mybatis 使用场景 ###

*  更加关注SQL优化的项目
 *  需求更换平凡的项目

### Mybatis 的开发环境的搭建 ###

#### 获取Mybatis 的下载 ####

*  Mybatis的官方网站 : [http://www.mybatis.org/mybatis-3/zh/index.htm][http_www.mybatis.org_mybatis-3_zh_index.htm]
 *  Mubatis 的下载方式：  
    　　１.github代码库下载：[https://github.com/mybatis/mybatis-3/tree/master/src/site][https_github.com_mybatis_mybatis-3_tree_master_src_site]  
    　　２.Maven 方式引入

### Mybatis 基本使用案例 ###

0．导入所需jar包

<?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.imooc.Mybatis</groupId>
        <artifactId>Mybatis-Demo1</artifactId>
        <version>1.0-SNAPSHOT</version>
        <dependencies>
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.4.3</version>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.44</version>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
            </dependency>
        </dependencies>
    
    </project>

１．创建数据库和表

id INT AUTO_INCREMENT PRIMARY KEY COMMENT '用户编号',
     username VARCHAR(50) COMMENT '用户名',
     userpass VARCHAR(50) COMMENT '用户密码',
    nikename VARCHAR(20) COMMENT '昵称'
    );
    SELECT * FROM users;
    INSERT INTO users VALUES(4,'wh','wh','wh' );

2.创建数据库对应的实体类

package com.imooc.Demo;
    
    public class Users { 
        private int id;
        private String username;
        private String userpass;
        private String nikename;
    
        public int getId() { 
            return id;
        }
    
        public void setId(int id) { 
            this.id = id;
        }
    
        public String getUsername() { 
            return username;
        }
    
        public void setUsername(String username) { 
            this.username = username;
        }
    
        public String getUserpass() { 
            return userpass;
        }
    
        public void setUserpass(String userpass) { 
            this.userpass = userpass;
        }
    
        public String getNikename() { 
            return nikename;
        }
    
        public void setNikename(String nikename) { 
            this.nikename = nikename;
        }
    
        @Override
        public String toString() { 
            return "Users{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", userpass='" + userpass + '\'' +
                    ", nikename='" + nikename + '\'' +
                    '}';
        }
    }

3.创建mybatyis的配置文件mybatis.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/test?&useUnicode=true&characterEncoding=UTF8"/>
                    <property name="username" value="root"/>
                    <property name="password" value="root"/>
                </dataSource>
            </environment>
        </environments>
    
    
        <mappers>
            <mapper resource="mapper/usersMapper.XML"/>
        </mappers>
    </configuration>

4.创建mapper配置文件usersMapper.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.imooc.Demo.Users">
        
        <select id="DemoUsers" resultType="com.imooc.Demo.Users">
            select * from users
        </select>
    </mapper>

5.进行测试

import com.imooc.Demo.Users;
    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;
    import java.util.List;
    
    public class Test { 
        @org.junit.Test
        public void test() throws IOException { 
    // 初始化mybatis 的配置文件
            String resources = "Mybatis_Demo1.XML";
            InputStream resources1 = Resources.getResourceAsStream(resources);
            SqlSessionFactory Factory = new SqlSessionFactoryBuilder().build(resources1);
    // 建立数据库之间的会话
            SqlSession sqlSession = Factory.openSession();
            List<Users> demoUsers = sqlSession.selectList("DemoUsers");
            for (Users users : demoUsers
            ) { 
                System.out.println(users);
            }
    
        }
    }

#### 执行结果 ####

Users{ id=1, username='admin', userpass='admin', nikename='gyc'}
    Users{ id=2, username='gyc', userpass='gyc', nikename='gyc'}
    Users{ id=3, username='zero', userpass='zero', nikename='zero'}
    Users{ id=4, username='wh', userpass='wh', nikename='wh'}

[Link 1]: http://www.zerolg.com/
[http_www.mybatis.org_mybatis-3_zh_index.htm]: http://www.mybatis.org/mybatis-3/zh/index.htm
[https_github.com_mybatis_mybatis-3_tree_master_src_site]: https://github.com/mybatis/mybatis-3/tree/master/src/site