java_mybatis框架——多表關係查詢
阿新 • • 發佈：2021-10-14
基於Maven框架的整體設計 —— 一多一的關係
思路：匯入mybatis、mysql、Junit4.13依賴；
編寫兩個java實體類；
編寫sqMapConfig.xml mybatis核心配置檔案
編寫dao層介面；
編寫mapper 對映檔案；
編寫測試類。
1.匯入相關依賴
<!--配置依賴-->
<dependencies>
<!--配置mybatis-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>
<!--配合mysql-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<!--配置單元測試-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13</version>
</dependency>
</dependencies>
2.編寫兩個java實體類；
Students
package com.mybatis.pojo;
public class Students {
private Integer sid;
private String sName;
private Integer sCid;
private Cards cards; // 一多一的關係
public Integer getSid() {
return sid;
}
public void setSid(Integer sid) {
this.sid = sid;
}
public String getsName() {
return sName;
}
public void setsName(String sName) {
this.sName = sName;
}
public Integer getsCid() {
return sCid;
}
public void setsCid(Integer sCid) {
this.sCid = sCid;
}
public Cards getCards() {
return cards;
}
public void setCards(Cards cards) {
this.cards = cards;
}
@Override
public String toString() {
return "Students{" +
"sid=" + sid +
", sName='" + sName + '\'' +
", sCid=" + sCid +
", cards=" + cards +
'}';
}
}
Cards
package com.mybatis.pojo;
public class Cards {
private Integer cid;
private String cnum;
public Integer getCid() {
return cid;
}
public void setCid(Integer cid) {
this.cid = cid;
}
public String getCnum() {
return cnum;
}
public void setCnum(String cnum) {
this.cnum = cnum;
}
@Override
public String toString() {
return "Cards{" +
"cid=" + cid +
", cnum='" + cnum + '\'' +
'}';
}
}
3.編寫sqMapConfig.xml mybatis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>
<!--
配置外部檔案properties檔案
-->
<properties resource="jdbc.properties"></properties>
<!--配置實體類相對路徑 別名-->
<typeAliases>
<typeAlias type="com.mybatis.pojo.Students" alias="Stu"></typeAlias>
<typeAlias type="com.mybatis.pojo.Cards" alias="Car"></typeAlias>
</typeAliases>
<!--配置mybatis環境-->
<environments default="mybatis">
<environment id="mybatis">
<transactionManager type="jdbc"></transactionManager>
<dataSource type="pooled">
<property name="driver" value="${jdbc.driver}"></property>
<property name="url" value="${jdbc.url}"></property>
<property name="username" value="${jdbc.username}"></property>
<property name="password" value="${jdbc.password}"></property>
</dataSource>
</environment>
</environments>
<!--
配置mapper.xml對映檔案
resource:相對路徑
-->
<mappers>
<mapper resource="com.mybatis.dao/studentsDao.xml"></mapper>
<mapper resource="com.mybatis.dao/CardsDao.xml"></mapper>
<!--<package name="com.mybatis.dao"></package>-->
</mappers>
</configuration>
4.編寫dao層介面；
package com.mybatis.dao;
import com.mybatis.pojo.Students;
import java.util.List;
public interface StudentsDao {
// 查詢學生資訊以及對應的身份證資訊
public List<Students> findAll();
}
還有一個略了；
5.編寫mapper 對映檔案；
StudentsDao.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">
<!--namespace 值是dao層對應的介面-->
<mapper namespace="com.mybatis.dao.StudentsDao">
<!--
配置實體類欄位與資料庫欄位一致
-->
<resultMap id="stuMap" type="Stu">
<id property="sid" column="sid"></id>
<result property="sName" column="sname"></result>
<result property="sCid" column="scid"></result>
<association property="cards" resultMap="com.mybatis.dao.CardsDao.cardsMap"></association>
</resultMap>
<!--
查詢學生資訊以及對應的身份證資訊
resultMap：實體類與資料庫對映的資料型別
-->
<select id="findAll" resultMap="stuMap">
select s.sname,c.cnum from students s,cards c where s.scid=c.cid;
</select>
</mapper>
CardsDao.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">
<!--namespace 值是dao層對應介面的許可權定名-->
<mapper namespace="com.mybatis.dao.CardsDao">
<!--配置實體類欄位與資料庫一致-->
<resultMap id="cardsMap" type="car">
<!--
property：實體欄位
column：資料庫欄位
-->
<id property="cid" column="cid"></id>
<result property="cnum" column="cnum"></result>
</resultMap>
</mapper>
6.編寫測試類
import com.mybatis.dao.StudentsDao;
import com.mybatis.pojo.Students;
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.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class TestMybatis {
InputStream resource;
SqlSession session;
StudentsDao stuDao;
@Before // 在test方法之前執行
public void init() throws IOException {
// 載入核心配置檔案
resource = Resources.getResourceAsStream("sqMapConfig.xml");
// 建立sqlSessionFactoryBuilder物件
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
// 建立sqlSessionFactory物件
SqlSessionFactory build = builder.build(resource);
// 建立Session物件
session = build.openSession();
// 執行方法
stuDao = session.getMapper(StudentsDao.class);
}
@After // 在test方法之後執行
public void close() throws IOException {
// 關閉資源
session.close();
resource.close();
}
@Test
public void test01(){
List<Students> list = stuDao.findAll();
for (Students students : list) {
System.out.println(students);
}
}
}
ok!!!