Java基础_MyBatis基础

爱被打了一巴掌 2022-05-22 01:54 191阅读 0赞

mybatis是一个数据持久层（orm）框架  
与传统的JDBC比较减少了61%的代码量  
有2个文件1个接口  
configuration.xml 全局配置文件  
mapper.xml 核心配置文件 映射文件写sql语句的  
sqlSession 接口

###### 别名alias ######

在核心配置文件中

如果数据库中列名与mybatis中不一致

<mapper namespace="com.yunhe.dao.StudentDao">
       <select id="selectAll" resultType="stu">
       select id as id,name as name,age as age,sex as sex from student
       </select>

例子：  
configuration.xml 全局配置文件

<?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>
     <properties resource="java.properties"/>
     
    <typeAliases>
     <typeAlias alias="stu" type="com.yunhe.bean.StudentBean"/>
     </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>
     <mappers>
     <mapper resource="stu.xml"/>
     </mappers>
    
     </configuration>

另还需要一个跟全局配置搭配的数据库信息  
java.properties

jdbc.driver=com.mysql.jdbc.Driver
    jdbc.url=jdbc:mysql://localhost:3306/student
    jdbc.username=root
    jdbc.password=1234

stu.xml(mapper映射文件)

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
      <mapper namespace="com.yunhe.dao.StudentDao">
       <select id="selectAll" resultType="stu">
       select id as id,name as name,age as age,sex as sex from student
        </select>
      </mapper>