MyBatis入门配置及增删改查

一、MyBatis简介

1、什么是MyBatis？

MyBatis 是支持普通 SQL 查询,存储过程和高级映射的优秀持久层框架。

2、MyBatis的优点

1. 与JDBC相比，减少了50%以上的代码量。

2. MyBatis是最简单的持久化框架，小巧并且简单易学。

3. MyBatis灵活，不会对应用程序或者数据库的现有设计强加任何影响，SQL写在XML里，从程序代码中彻底分离，降低耦合度，便于统一管理和优化，可重用。

4. 提供XML标签，支持编写动态SQL语句（XML中使用if, else）。

5. 提供映射标签，支持对象与数据库的ORM字段关系映射（在XML中配置映射关系，也可以使用注解）。

3、MyBatis框架的缺点

1. SQL语句的编写工作量较大，尤其是字段多、关联表多时，更是如此，对开发人员编写SQL语句的功底有一定要求。

2. SQL语句依赖于数据库，导致数据库移植性差，不能随意更换数据库。

4、MyBatis框架适用场合：

MyBatis专注于SQL本身，是一个足够灵活的DAO层解决方案。

对性能的要求很高，或者需求变化较多的项目，如互联网项目，MyBatis将是不错的选择。

二、代码操作

整个项目的类图，记得导入相关的jar包

1、首先建好表 然后写成实体类

DROP TABLE IF EXISTS `users`;
CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(32) NOT NULL COMMENT '用户名称',
  `birthday` date DEFAULT NULL COMMENT '生日',
  `sex` char(1) NOT NULL COMMENT '性别',
  `address` varchar(256) DEFAULT NULL COMMENT '地址',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=utf8;


INSERT INTO `users` VALUES ('1', '猪八戒', '2021-04-29', '男', '中国');
INSERT INTO `users` VALUES ('3', '猪猪侠', '2021-04-20', '女', '西国');
INSERT INTO `users` VALUES ('8', '沙悟净', null, '妖', null);
INSERT INTO `users` VALUES ('10', '沙悟净', null, '妖', null);
INSERT INTO `users` VALUES ('12', '沙悟净', '2001-08-03', '妖', '西北');
INSERT INTO `users` VALUES ('13', '李村', '2002-02-02', '男', '黄土坡');
SET FOREIGN_KEY_CHECKS=1;

2、配置adbc.properties

jdbc.url = jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8
jdbc.username = root
jdbc.password = 123456
jdbc.driver = com.mysql.jdbc.Driver

3、新建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>
    <!--引入jdbc的配置文件-->
    <properties resource="jdbc.properties"/>
    <settings>
        <!--  开启驼峰映射：数据库：user_name   ===> java:userName  -->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <typeAliases>
        <package name="zxy.entity"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!--配置sql映射文件-->

    <mappers>
        <package name="zxy.mapper"/>
    </mappers>

</configuration>

4、配置增删改查的mapper接口

5、配置数据映射

<?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">
        <!--namespace：命名空间 用于唯一一个sql标识-->
<mapper namespace="zxy.mapper.UserMapper">
    <!--sql映射 id：sql对应映射的唯一标识-->
    <select id="selectUser" resultType="user"  >
        select * from users where username like '__戒'
    </select>

    <insert id="insertUser" parameterType="zxy.entity.User">
      insert into users VALUE (#{
   id},#{
   username},#{
   birthday},#{
   sex},#{
   address})
    </insert>

    <insert id="insert" parameterType="zxy.entity.User"
            useGeneratedKeys="true" keyProperty="id">
      insert into users(username,birthday,sex,address) VALUE (#{
   username},#{
   birthday},#{
   sex},#{
   address})
    </insert>

    <update id="updateUser" parameterType="zxy.entity.User">
        update users set username=#{
   username},#{
   birthday},sex=#{
   sex},#{
   address where id=#{
   id}
    </update>

    <delete id="deleteUser" parameterType="int">
        delete from users where id=#{
   id}
    </delete>

    <insert id="insertCopy" parameterType="users" >
<selectKey keyProperty="id" order="BEFORE" resultType="String">
        select uuid();
</selectKey>
      insert into users_copy(id,username,birthday,sex,address) VALUE (#{
   id},#{
   username},#{
   birthday},#{
   sex},#{
   address})
    </insert>

    <select id="findByid" resultType="user">
        select
        id,username,sex,birthday,address from ${
   tbName}
        where
        id=#{
   id}
        and
        username=#{
   userName}
    </select>
</mapper>

6、测试写好的增删改查

public class text1 {
   
    SqlSessionFactory sqlSessionFactory;

    @Before
    public void init() {
   
        try {
   
            InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        } catch (IOException e) {
   
            e.printStackTrace();
        }
    }

    @Test
    public void update(){
   
        SqlSession session = sqlSessionFactory.openSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        //mapper.updateUser(new User(88,"猪八戒","女","2000-8-22","东岸"));
        session.commit();
        session.close();
    }
    @Test
    public void delect(){
   
        SqlSession session = sqlSessionFactory.openSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        mapper.deleteUser(2);
        session.commit();
        session.close();
    }

    @Test
    public void insert(){
   
        SqlSession session = sqlSessionFactory.openSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        //mapper.insertUser(new User(12,"沙悟净","妖","2001-8-3","西北"));
        session.commit();
        session.close();
    }

    @Test
    public void select(){
   
        SqlSession session = sqlSessionFactory.openSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        User ss = mapper.selectUser("");
        System.out.println(ss);
        session.commit();
        session.close();
    }
    @Test
    public void inserts(){
   
        SqlSession session = sqlSessionFactory.openSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        User user =new User();
        user.setUsername("李村");
        user.setBirthday("2002-2-2");
        user.setSex("男");
        user.setAddress("黄土坡");
       int rest= mapper.insert(user);
        System.out.println("rest==="+rest);
        System.out.println("getid==="+user.getId());
        session.commit();
        session.close();
    }

    @Test
    public void insertCopy(){
   
        SqlSession session = sqlSessionFactory.openSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        Usre_Copy user  =new Usre_Copy();
        user.setUsername("老王");
        user.setBirthday("2002-2-2");
        user.setSex("女");
        user.setAddress("黄土高坡");
        int rest = mapper.insertCopy(user);
        System.out.println("rest==="+rest);
        System.out.println("getid==="+user.getId());
        session.commit();
        session.close();
    }

    @Test
    public void findByid(){
   
        SqlSession session = sqlSessionFactory.openSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        User byid = mapper.findByid(1, "猪八戒", "users");
        System.out.println("user"+byid);

    }

    @Test
    public void testorder(){
   
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
   
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
   
            e.printStackTrace();
        }
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        OrderMapper mapper = session.getMapper(OrderMapper.class);
        Order orderUserByid = mapper.findOrderUserByid(100);
        System.out.println("结果=="+orderUserByid);
    }
}

转载：https://blog.csdn.net/weixin_52841956/article/details/116504428