mybatis查询数据库

妖狐艹你老母 2021-07-26 18:39 435阅读 0赞

加载**sqlMapConfig.xml——>****创建SqlSessionFactory——>****创建SqlSession——>****SqlSEssion帮忙生成一个实现类（给接口）——>调用****findUserById得到查询返回的pojo对象**

## **MybatisMapperTest** ##

package com.itheima.mybatis.junit;
    
    import static org.junit.Assert.*;
    import java.io.InputStream;
    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 org.junit.Test;
    import com.itheima.mybatis.mapper.UserMapper;
    import com.itheima.mybatis.pojo.User;
    
    public class MybatisMapperTest {
    	@Test
    	public void testMapper() throws Exception {
    		//加载核心配置文件
    		String resource = "sqlMapConfig.xml";
    		InputStream in = Resources.getResourceAsStream(resource);
    		//创建SqlSessionFactory
    		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
    		//创建SqlSession
    		SqlSession sqlSession = sqlSessionFactory.openSession();
    		//SqlSEssion帮我生成一个实现类  （给接口）
    		UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    		User user = userMapper.findUserById(10);
    		System.out.println(user);
    	}
    }

## **sqlMapConfig.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>
    	<properties resource="jdbc.properties"/>
    	
    	<typeAliases>
    
    		<package name="com.itheima.mybatis.pojo"/>
    	</typeAliases>
    	
    	<environments default="development">
    		<environment id="development">
    			
    			<transactionManager type="JDBC" />
    			
    			<dataSource type="POOLED">
    				<property name="driver" value="${jdbc.driver}" />
    				<property name="url"
    					value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8" />
    				<property name="username" value="root" />
    				<property name="password" value="nideshengri" />
    			</dataSource>
    		</environment>
    	</environments>
    	
    	<mappers>
    
    
    
    
    		<package name="com.itheima.mybatis.mapper"/>
    	</mappers>
    </configuration>

## **UserMapper** ##

package com.itheima.mybatis.mapper;
    import com.itheima.mybatis.pojo.User;
    public interface UserMapper {
    	//遵循四个原则
    	//接口 方法名  == User.xml 中 id 名
    	//返回值类型  与  Mapper.xml文件中返回值类型要一致
    	//方法的入参类型 与Mapper.xml中入参的类型要一致
    	//命名空间 绑定此接口
    	public User findUserById(Integer id);
    }

## **UserMapper.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.itheima.mybatis.mapper.UserMapper">
    	
    	<select id="findUserById" parameterType="Integer" resultType="User">
    		select * from user where id = #{v}
    	</select>
    	
    	
    	<select id="findUserByUsername" parameterType="String" resultType="com.itheima.mybatis.pojo.User">
    		select * from user where username like "%"#{haha}"%"
    	</select>
    	
    	
    	<insert id="insertUser" parameterType="com.itheima.mybatis.pojo.User">
    		<selectKey keyProperty="id" resultType="Integer" order="AFTER">
    			select LAST_INSERT_ID()
    		</selectKey>
    		insert into user (username,birthday,address,sex) 
    		values (#{username},#{birthday},#{address},#{sex})
    	</insert>
    	
    	
    	<update id="updateUserById" parameterType="com.itheima.mybatis.pojo.User">
    		update user 
    		set username = #{username},sex = #{sex},birthday = #{birthday},address = #{address}
    		where id = #{id}
    	</update>
    	
    	
    	<delete id="deleteUserById" parameterType="Integer">
    		delete from user 
    		where id = #{vvvvv}
    	</delete>
    </mapper>