11.4-CRUD以及核心配置的理解

Mybatis 学习

• 环境:
  1.创建Maven项目,倒入Mybatis,mysql,juntis依赖
  
• mybatis项目:
  1.阅读文档配置mybatis-config.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="db.properties"/>
    <typeAliases>
        <package name="com.study.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/study/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

    2.创建CRUD操作的XML文件和CRUD方法接口,UserMapper.xml,UserMapper
    3.UserMapper.xml与接口方法类UserMapper要同名

<?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.study.mapper.UserMapper">
    <select id="selectUser" resultType="user">
        select * from test;
    </select>
    <insert id="insert" parameterType="user">
        insert into test values(#{id},#{age},#{name},#{username},#{password});
    </insert>
    <update id="update" parameterType="user">
        update test set age=#{age},name = #{name}, username = #{username}, password = #{password} where id = #{id};
    </update>
    <delete id="delete" parameterType="user">
        delete from test where id = #{id}
    </delete>
</mapper>

    4.在utils包下创建一个工具类MybatisUtils进行工厂化操作

        package com.study.utils;

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.InputStream;

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try{
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        }catch (Exception e){
            e.printStackTrace();
        }finally {

        }
    }

    public static SqlSession getSession(){
        return sqlSessionFactory.openSession();
    }
}

    5.在写实际代码时,一定要记住关闭资源
    6.在写增删改需要加上事务,commit