mybatis學習筆記(eclipse)

概述

mybatis針對dao層的良好管理框架，傳統的對于JDBC的操作繁瑣冗余，mybatis通過映射配置文件的方式良好的管理JDBC驅動，還支持注解配置

JDBC驅動

import java.sql.DriverManager.*;
import org.junit.*;

class Test{
    @Test
    public void test1(){
        //1.加載驅動程序
        Class.forName("com.mysql.jdbc.Driver");
        //2. 獲得數據庫連接
        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        //3.操作數據庫，實現增刪改查
        Statement stmt = conn.createStatement();
        ResultSet rs = stmt.executeQuery("SELECT user_name, age FROM imooc_goddess");
        //如果有數據，rs.next()返回true
        while(rs.next()){
            System.out.println(rs.getString("user_name")+" 年齡："+rs.getInt("age"));
        }
    }
}

mybatis的一個簡單構建

文件配置(Maven管理項目)

dao

src/main/java/dao/IUserDao.java

package org.mybati.dao;

import java.util.List;

//import org.apache.ibatis.annotations.Select;
import org.mybati.domain.User;

public interface IUserDao {
	/**
	 * 	查詢所有
	 * 
	 * @return
	 */
	List<User> findAll();
}

domain

src/main/java/domain/User.java

JavaBean(User)	MySql field
String username	username
String address	address
id	id

xml 的Configurations(必須)

src/main/resources/SqlConfiguration.xml

<configuration>
	<!-- url可以代替resource : file:///c/.../jdbcConfig.properties -->
	<properties resource="jdbcConfig.properties"></properties>

	<settings>
		<!-- 開啟動態加載 -->
		<setting name="lazyLoadingEnabled" value="true" />
	</settings>

	<!-- 指定 resultType="user" resultType="usEr"均可以 -->
	<typeAliases>
		<!-- <typeAlias type="org.mybati.domain.User" alias="user"/> -->
		<!-- 自動尋找package name 下面的javabean 類，自動起別名 -->
        <package name="org.mybati.domain" />
	</typeAliases>

	<!--default="MySQL"選中mysql環境-->
	<environments default="mysql">
		<environment id="mysql">
			<!-- 驅動管理 -->
			<transactionManager type="JDBC"></transactionManager>
			<!-- UNPOOLED：非連接池 -->
			<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>
		<!-- 映射配置文件，對于IUserDao 接口的代理實現
		<mapper class="org.mybati.dao.IUserDao"/> 
		<mapper resource="org/mybati/dao/IUserDao.xml"/> 
		-->
		<!-- 自動尋找目錄下的配置文件 -->
		<package name="org.mybati.dao" />
	</mappers>
</configuration>

xml 的mapper 映射配置(非注解配置)

src/main/resources/dao/IUserDao.xml(此文件路徑為上一步指定)

    <!--
		mapper:
		詳細位置在SqlConfiguration.mappers.mapper或者
		SqlConfiguration.mappers.package.name中已經限定好
	-->
<mapper namespace="全限定類名">
	<!--sql語句-->
    <!--id="接口中的相關的方法名"-->
    <!--resultType="查詢到的數據庫包裝成Bean(User)"-->
    <select id="findAll" resultType="Bean">
    	select * from user
    </select>
</mapper>

測試類

src/test/java/test/myBatis.java

讀取配置文件

@Before

InputStream is = Resources.getResourceAsStream(“SqlConfiguration.xml”);

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

SqlSession session = sqlSessionFactory.openSession(false);

獲取代理對象

IUserDao userDao = session.getMapper(IUserDao.class);

@After

session.commit();//提交事務

is.close();

session.close();

@Test

代理對象操作數據庫(實際實際上時Mapper映射實現的)

List users = userDao.findAll();

mybatis的crud(mapper)

大綱

?

插入

<insert id="function" parameterType="user">
	insert into user(username,addess) values(#{username},#{address})
</insert>

function:

function(paramater),parameter即是要插入的參數

parameterType:

與function中的parameter保持一致，此處user ,User, uSer, usEr, useR均無區別，究其原因是

中指定的別名(同)

#{username}

JNDI 語法

#{username} =>?#{getUsername} =>#{user.getUsername}

更新

<update id="updateUser" parameterType="user">
		update user
		set
		username=#{username},address=#{address},sex=#{sex},birthday=#{birthday}
		where id=#{id}
</update>

刪除

<delete id="deleteUser" parameterType="Integer">
		delete from user where
		id>#{id}
</delete>

#{id}

parameterType=“Integer”

接受一個Integer

模糊查找

<select id="findByName" resultType="user">
		select * from user where
		username like #{name};
</select>

#{name}

可以接受模糊輸入 ：%馬%，查詢username中所有帶馬的信息

動態SQL語句

<select id="findInIds" resultType="user" parameterType="query">
	<include refid="defaultSelect"></include>
	<where>
		<if test="ids!=null and ids.size()>0">
			<foreach collection="ids" open="and id in (" close=")" item="itemId" separator=",">
				#{itemId}
			</foreach>
			</if>
	</where>
</select>

多表連接查詢

table:

user account

JavaBean

User Account

方法一

AccountUser extend Account

<select>之后，封裝到AccountUser 即可:resultType=“accountUser”

<select id="findAllWithUser" resultType="accountUser">
   	select a.*, u.username,
   	u.address from user u, account a where u.id= a.uid
</select>

方法二

內部類(一對一)

	<resultMap type="accountCounterPart" id="accountUserMap">
		<!-- 從表屬性 -->
		<id property="id" column="aid" />
		<result property="uid" column="uid" />
		<result property="money" column="money" />
		<!-- 內部類外鍵屬性 user:要關聯的表，uid:本表的外鍵 -->
		<!-- 主表 -->
		<association property="user" column="uid">
			<id property="id" column="id" />
			<result property="username" column="username" />
			<result property="address" column="address" />
			<result property="sex" column="sex" />
			<result property="birthday" column="birthday" />
		</association>
	</resultMap>

	<select id="findAll" resultMap="accountUserMap">
		select
		u.*, a.id as aid, a.uid, a.money
		from
		account as a, user as u
		where
		a.uid = u.id
	</select>

內部類(一對多)

	<resultMap type="userCounterPart" id="userAccountMap">
		<!-- 主鍵 -->
		<id property="id" column="id" />
		<result property="username" column="username" />
		<result property="address" column="address" />
		<result property="sex" column="sex" />
		<result property="birthday" column="birthday" />
		<!-- ofType:accounts 中的類型 -->
		<collection property="accounts" ofType="account">
			<id property="id" column="aid" />
			<result property="uid" column="uid" />
			<result property="money" column="money" />
		</collection>
	</resultMap>
	<select id="UserToAccount" resultMap="userAccountMap">
		SELECT
		u.*, a.id AS
		aid,a.uid,a.money
		FROM
		ACCOUNT a RIGHT OUTER JOIN USER u
		ON
		u.id = a.uid
	</select>

[resultMap是什么？](#### resultMap)

延遲加載

[延遲加載配置](# xml 的Configurations(必須))(ctrl + 鼠標左鍵)

	<resultMap type="userAccount" id="loadingMap">
		<id property="id" column="id" />
		<result property="username" column="username" />
		<result property="address" column="address" />
		<result property="sex" column="sex" />
		<result property="birthday" column="birthday" />
		<!-- 需要延遲加載的屬性user(accounts) -->
		<!-- 通過什么去加載:user(id) -->
		<!-- 加載的sql語句 -->
		<association property="accounts" column="id"
			select="org.mybati.dao.IUserDao.lazyLoading">
		</association>
	</resultMap>

	<select id="lazyLoading" parameterType="INT"
		resultType="account">
		select *
		from account where uid = #{id}
	</select>

	<select id="findAll" resultMap="loadingMap">
		select * from user
	</select>

resultMap

JavaBean(User)	SQLField(User)
username	_username
address	_address
id	_id

如圖，JavaBean中的變量與SQL中的field不匹配，則從數據庫中查詢到的數據不能夠直接簡單的封裝到User中，這個時候則需要Map映射

<resultMap>
	<id property="Bean屬性名" column="Sql字段名">主鍵</id>
    <result property="Bean屬性名" column="Sql字段名">其他</result>
    <result property="username" column="_username">其他</result>
</resultMap>

緩存

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