一个简单的mybatis demo实现

灰太狼 2022-10-13 02:20 239阅读 0赞

## 数据库 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NDYzMTc1_size_16_color_FFFFFF_t_70]

## 项目目录： ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NDYzMTc1_size_16_color_FFFFFF_t_70 1]

## mybatis-conf.xml文件内容： ##

<?xml version="1.0" encoding="UTF8" ?>
    <!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.cj.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&allowPublicKeyRetrieval=true&useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC"/>
                    <property name="username" value="root"/>
                    <property name="password" value="mysql"/>
                </dataSource>
            </environment>
        </environments>
    
        
        <mappers>
            <mapper resource="com/kuang/dao/UseMapper.xml"/>
        </mappers>
    </configuration>

## mybatisUtil.java文件内容： ##

用来获取SqlSession对象，连接了数据库后，要记得关闭

package com.kuang.util;
    
    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.io.Reader;
    
    //获取ssqlSessionFactory对象
    public class MybatisUtils { 
        public   static SqlSessionFactory sqlSessionFactory;
        //private static InputStream inputStream = null;
        //private static SqlSessionFactory sqlSessionFactory;
    
        static { 
            try { 
    //使用Mybatis第一步 获取sqlSessionFactory对象
                String resource = "mybatis-conf.xml";
                Reader resourceAsReader = Resources.getResourceAsReader(resource);
                System.out.println(resource);
    //SqlSessionFactory 出现问题
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsReader);
                System.out.println(resourceAsReader);
            } catch (Exception e) { 
                e.printStackTrace();
    
            }
        }
    
    
    
        public static SqlSession getSqlSession(){ 
            SqlSession  sqlSession= sqlSessionFactory.openSession();
            return sqlSession;
        }
    
    
    }

## UserDao或者UserMaper.java: ##

以后只知道负责写接口就好了，接口的实现放到xml文件里面去写

package com.kuang.dao;
    
    import com.kuang.pojo.User;
    
    import java.util.List;
    
    //Dao==mapper
    public interface UserDao { 
        public List<User> getUser();
    }

## 接口的实现类，UserMapper ##

没有mybaits之前，是通过xxxImpl.java来实现  
id="getUser"表示接口里面的方法  
resultType=“com.kuang.pojo.User” sql执行后返回的类型

<?xml version="1.0" encoding="UTF8" ?>
    <!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="getUser" resultType="com.kuang.pojo.User" >
            select * from mybatis.user
        </select>
    </mapper>

## 测试主类： ##

package com.kuang.dao;
    
    import com.kuang.pojo.User;
    
    import org.apache.ibatis.binding.MapperMethod;
    import org.junit.Test;
    import org.apache.ibatis.session.SqlSession;
    import com.kuang.util.MybatisUtils;
    
    import java.util.List;
    
    public class UserDaoTest { 
        @Test
        public void test(){ 
            //1 获取SqlSession
            SqlSession sqlSession= MybatisUtils.getSqlSession();
            //方式1 getMapper
            UserDao userDao=sqlSession.getMapper(com.kuang.dao.UserDao.class);
            List<User>  userDaos =userDao.getUser();
    
            for (User user:userDaos) { 
                System.out.println(user.getId()+user.getName());
            }
    
            sqlSession.close();
        }
    }

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