MyBatis框架連線資料庫的基本使用第四篇
阿新 • • 發佈：2021-01-27
MyBatis框架連線資料庫的基本使用
- 匯入jar包
- 建立並配置核心配置檔案
- 建立並配置對映檔案
- 保證SQL語句中的id和方法名一致
- 保證對映檔案中的namespace和介面的全限定名一致
/**
* MyBatis 最基本的演示
* MyBatis使用步驟
* 匯入jar包
* 建立並配置核心檔案
* 建立並配置對映檔案
* 對映檔案中SQL語句的ID要和介面方法名一致
* 對映檔案中的nameSpace要和介面的全限定名一致
* 建立測試
* 獲取核心配置檔案的輸入流
* 獲取sqlSessionFactory
* 獲取sqlSession
* 獲取介面的動態代理子類
* 介面的動態代理子類呼叫方法
*
*/ 下面是程式碼可以幫助你更好的理解
匯入jar包
mybatis的jar包以及資料庫連線的jar包
建立並配置核心配置檔案
<?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>
< 建立並配置對映檔案
<?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="mapperInterface.SqlMapper">
<!-- User selectUser1(Integer id); -->
<select id="selectUser1" resultType="User">
select id,userName,age,sex
from testuser where
id=#{id}
</select>
<!-- User selectUser2(Integer id); -->
<select id="selectUser2" resultType="User">
select id,userName,age,sex
from testuser where
id=${value}
</select>
<!-- User selectUserByMore1(Integer id,String userName); -->
<select id="selectUserByMore1" resultType="User">
select
id,userName,age,sex from testuser where id=#{0} and
userName=#{1}
</select>
<!-- User selectUserByMore2(Integer id,String userName); -->
<select id="selectUserByMore2" resultType="User">
select
id,userName,age,sex from testuser where id=${param1} and
userName='${param2}'
</select>
<!-- User selectUserByMap(Map<String,Object> map); -->
<select id="selectUserByMap" resultType="User">
select
id,userName,age,sex from testuser where id=${id} and
userName='${userName}'
</select>
<!-- User selectUserByPram(@Param("id")Integer id,@Param("UserName")String
userName); -->
<select id="selectUserByPram" resultType="User">
select
id,userName,age,sex from testuser where id=${id} and
userName='${userName}'
</select>
<!-- User selectUserByList(List list); -->
<select id="selectUserByList" resultType="User">
</select>
<!-- User selectUserByArray(Integer[] id); -->
<select id="selectUserByArray">
</select>
<!-- 自定義對映 -->
<!-- 自定義對映 <id column="id" property="id" />
<id>：設定主鍵的對映關係，column設定欄位名，property設定屬性名
<result column="sex" property="sex" />
<result>：設定非主鍵的對映關係，column設定欄位名，property設定屬性名
<select>語句中的id還是需要和介面中的方法名一致 resultMap需要和<resultMap>中的id保持一致
<resultMap>中的type是查詢返回結果的型別
column是指查詢到的欄位名 property是指查詢到的欄位名對映給JavaBean中的哪個屬性
-->
<resultMap type="User" id="UserDepList">
<id column="id" property="id" />
<result column="userName" property="userName" />
<result column="age" property="age" />
<result column="sex" property="sex" />
<!-- <result column="depId" property="dep.depId" />
<result column="depName" property="dep.depName" /> -->
<!-- 自定義對映中可以使用<association>來定義JavaBean中的JavaBean -->
<association property="dep" javaType="Dep">
<id column="depId" property="depId" />
<result column="depName" property="depName" />
</association>
</resultMap>
<!-- ArrayList<User> selectUserDep(); -->
<select id="selectUserDep" resultMap="UserDepList">
select
id,userName,age,sex,testdep.depId,depName from testUser left join
testdep on
testuser.id=testdep.depId
</select>
<resultMap type="User" id="moreStep">
<id column="id" property="id"/>
<result column="userName" property="userName"/>
<result column="age" property="age"/>
<result column="sex" property="sex"/>
<!--
select:分步查詢的SQL的id，即介面的全限定名.方法名或namespace.SQL的id
column:分步查詢的條件，注意：此條件必須是從資料庫查詢過得
-->
<association property="dep" select="selectDepByDepId" column="depId"></association>
</resultMap>
<!-- User selectUserDepByMoreStep(Integer id); -->
<select id="selectUserDepByMoreStep" resultMap="moreStep">
select id,userName,age,sex,depId from testuser where id=#{id}
</select>
<!-- Dep selectDepByDepId(Integer depId); -->
<select id="selectDepByDepId" resultType="Dep">
select depId,depName from testdep where depId=#{depId}
</select>
<resultMap type="Dep" id="DepUserList">
<id column="depId" property="depId"/>
<result column="depName" property="depName"/>
<collection property="list" ofType="User">
<id column="id" property="id"/>
<result column="userName" property="userName"/>
<result column="age" property="age"/>
<result column="sex" property="sex"/>
</collection>
</resultMap>
<!-- Dep selectDepUser(Integer depId); -->
<select id="selectDepUser" resultMap="DepUserList">
select testdep.depId,depName,id,userName,age,sex from
testdep left join
testuser on testdep.depId=testuser.depId
where
testdep.depId=#{depId}
</select>
<resultMap type="Dep" id="DepUserByMoreStep">
<id column="depId" property="depId"/>
<result column="depName" property="depName"/>
<!-- collection:處理一對多和多對多的關係 -->
<!-- fetchType 是否開啟延遲載入 lazy開啟 eager不開啟 -->
<collection property="list" select="selectUserBydepId" column="depId" fetchType="eager"></collection>
</resultMap>
<!-- Dep selectDepUserByMoreStep(Integer id); -->
<select id="selectDepUserByMoreStep" resultMap="DepUserByMoreStep">
select depId,depName from testdep where depId=#{depId}
</select>
<!-- ArrayList<User> selectUserBydepId(Integer id); -->
<select id="selectUserBydepId" resultType="User">
select id,userName,age,sex from testuser where depId=#{depId}
</select>
</mapper>