mysql映射 mybatis映射数据库

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boyboy 2023-10-17 09:29:47

文章标签 mysql映射 mybatis mysql java User 文章分类 MySQL 数据库

一、MyBatis相关概念回顾

1.对象/关系数据库映射（ORM）

ORM 全称Object Relation Mapping : 表示对象-关系映射的缩写
ORM 完成面向对象的编程语言到关系数据库的映射，它把关系数据库包装成面向对象的模型。采用ORM框架后，应用程序不再直接访问底层数据库，而是以面向对象的方式来操作持久化对象，ORM将把这些对象的操作转换成底层SQL操作。

2.MyBatis简介

MyBatis是一款优秀的基于ORM的半自动的轻量级的持久层框架,它支持定制化SQL以及高级映射。它避免了几乎所有的JDBC代码和手动设置参数以及获取结果集。
MyBatis可以使用简单的XML或者注解来配置和映射原生类型、接口和Java的POJO成数据库中的记录。

3.MyBatis历史

它原是apache的一个开源项目iBatis,于2010年6月由apache迁移到了google，iBatis3.x正式更名为MyBatis,代码于2013年11月迁移到GitHub。
iBatis一词来源于"internet"和"abatis"的组合，是一个基于JAVA的持久层框架。它包括SQL Maps和Data Access Objects(DAO)

4.MyBatis优势

MyBatis是一个半自动的持久层框架，对于开发人员来说，核心的sql还是需要自己进行优化。
sql和java的编码进行了分离，功能边界更清晰，一个专注业务，一个专注数据。
全自动框架生成的sql不易进行优化。当bean字段很多时，无法做到只映射部分字段。

二、MyBatis环境搭建回顾

1.开发步骤

引入myBatis的maven坐标
创建数据库表
创建实体类
编写映射文件xxxMapper.xml
编写核心配置文件sqlMapConfig.xml

2.环境搭建

1.创建一个maven项目

并添加pom.xml文件

<properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.encoding>UTF-8</maven.compiler.encoding>
        <java.version>1.8</java.version>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>

        <dependency>
            <groupId>com.w</groupId>
            <artifactId>mybatis_persistence</artifactId>
            <version>1.0-SNAPSHOT</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

2.创建数据库并添加数据

create table user
(
    id       int                    null,
    username varchar(20) default ''
);
insert into user (id,username) values (1,'zhangsan');
insert into user (id,username) values (2,'lisi');

3.创建实体类

package com.w.pojo;

public class User {
    private Integer id;
    private String name;

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

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

4.编写UserMapper.xml

<mapper namespace="com.w.dao.UserDao">
    <select id="findAll" resultType="com.w.pojo.User">
        select * from user;
    </select>
    <select id="findOne" parameterType="com.w.pojo.User" resultType="com.w.pojo.User">
        select * from user where id =#{id}
    </select>

    <insert id="insertUser" parameterType="com.w.pojo.User">
        insert into user values(#{id},#{name})
    </insert>
    <insert id="updateUser" parameterType="com.w.pojo.User">
        update user set name=#{name} where id=#{id}
    </insert>
    <delete id="deleteUserById" parameterType="com.w.pojo.User">
        delete from user where id=#{id}
    </delete>
</mapper>

5.编写sqlMapConfig.xml

<config>
    <dataSource>
        <properties name="jdbcUrl" value="jdbc:mysql://localhost:3306/test1"></properties>
        <properties name="driver" value="com.mysql.jdbc.Driver"></properties>
        <properties name="name" value="root"></properties>
        <properties name="password" value="123456"></properties>
    </dataSource>
    <mappers>
        <mapper resource="UserMapper.xml"></mapper>
    </mappers>
</config>

6.编写测试类

package com.w;

import com.w.dao.UserDao;
import com.w.pojo.User;
import com.w.session.SessionFactory;
import com.w.session.SessionFactoryBuilder;
import com.w.io.Resource;
import com.w.session.SqlSession;
import org.junit.Test;

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

public class TestDemo {
    /**
     * getMapper方式查询delete
     */
    @Test
    public void testDelete() throws Exception{
        SessionFactoryBuilder sessionFactoryBuilder = new SessionFactoryBuilder();
        SessionFactory build = sessionFactoryBuilder.build(Resource.getResourceAsStream("sqlMapConfig.xml"));
        SqlSession sqlSession = build.openSesssion();
        User inputUser  = new User();
        inputUser.setId(5);
        //inputUser.setName("tom5");
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        userDao.deleteUserById(inputUser);
    }
    /**
     * getMapper方式查询update
     */
    @Test
    public void testUpdate() throws Exception{
        SessionFactoryBuilder sessionFactoryBuilder = new SessionFactoryBuilder();
        SessionFactory build = sessionFactoryBuilder.build(Resource.getResourceAsStream("sqlMapConfig.xml"));
        SqlSession sqlSession = build.openSesssion();
        User inputUser  = new User();
        inputUser.setId(5);
        inputUser.setName("tom5");
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        userDao.updateUser(inputUser);
    }
    /**
     * getMapper方式查询insert
     */
    @Test
    public void testInsertUserByMapper() throws Exception{
        SessionFactoryBuilder sessionFactoryBuilder = new SessionFactoryBuilder();
        SessionFactory build = sessionFactoryBuilder.build(Resource.getResourceAsStream("sqlMapConfig.xml"));
        SqlSession sqlSession = build.openSesssion();
        User inputUser  = new User();
        inputUser.setId(5);
        inputUser.setName("tom");
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        userDao.insertUser(inputUser);
    }
    /**
     * getMapper方式查询select
     */
    @Test
    public void testSelectListBygetMapper() throws Exception{
        SessionFactoryBuilder sessionFactoryBuilder = new SessionFactoryBuilder();
        SessionFactory build = sessionFactoryBuilder.build(Resource.getResourceAsStream("sqlMapConfig.xml"));
        SqlSession sqlSession = build.openSesssion();
        User inputUser  = new User();
        inputUser.setId(1);
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> users = userDao.findAll();
        for (User user : users) {
            System.out.println(user);
        }

    }
    /**
     * getMapper方式查询selectOne
     */
    @Test
    public void testSelectOneBygetMapper() throws Exception{
        SessionFactoryBuilder sessionFactoryBuilder = new SessionFactoryBuilder();
        SessionFactory build = sessionFactoryBuilder.build(Resource.getResourceAsStream("sqlMapConfig.xml"));
        SqlSession sqlSession = build.openSesssion();
        User inputUser  = new User();
        inputUser.setId(1);
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        User user = userDao.findOne(inputUser);
        System.out.println(user);
    }

    /**
     * select方法
     */
    @Test
    public void testSelectById() throws Exception{
        SessionFactoryBuilder sessionFactoryBuilder = new SessionFactoryBuilder();
        SessionFactory build = sessionFactoryBuilder.build(Resource.getResourceAsStream("sqlMapConfig.xml"));
        SqlSession sqlSession = build.openSesssion();
        User inputUser  = new User();
        inputUser.setId(1);
        User user = sqlSession.selectOne("com.w.dao.UserDao.findOne", inputUser);
        System.out.println(user);

    }
    /**
     * 测试获取SessionFactoryBuilder
     */
    @Test
    public void testSessionFactoryBuilder() throws Exception{
        SessionFactoryBuilder sessionFactoryBuilder = new SessionFactoryBuilder();
        SessionFactory build = sessionFactoryBuilder.build(Resource.getResourceAsStream("sqlMapConfig.xml"));
        SqlSession sqlSession = build.openSesssion();
        List<User> users = sqlSession.selectList("com.w.dao.UserDao.findAll");
        for (User user : users) {
            System.out.println(user);
        }

    }

    /**
     * 测试获取输入流对象是否成功
     */
    @Test
    public void testGetResource(){
        InputStream resource = Resource.getResourceAsStream("sqlMapConfig.xml");
        System.out.println(resource);
    }

    /**
     * 第一个测试类。。。
     */
    @Test
    public void test1(){
        System.out.println("测试一下。。。");
    }

}

执行查询所有，即完成mybatis基本查询了。

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