Mybatis一對多的關係
阿新 • • 發佈：2018-11-16
前言：本專案是使用idea進行開發，資料庫使用的是Mysql。
province(一）----------city(多)
1.搭建maven專案,引入mybatis需要的依賴
預設沒有java、resources、test等資料夾，習慣性建立這幾個資料夾，建立資料夾的時候注意標記資料夾的用途（不然編譯器無法識別，無法編譯程式碼）
pom.xml(注意要將實體包下面的xml檔案設定可編譯)
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns: 2.專案模組圖：
3.在resources目錄下新建mybatis的核心配置檔案mybatis-config.xml
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>
<!--給com.zs.entity包取別名-->
<typeAliases>
<package name="com.zs.entity"/>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<!--配置獲取資料庫連線例項的資料來源 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url"
value="jdbc:mysql://localhost:3306/zs?characterEncoding=utf-8" />
<property name="username" value="root" />
<property name="password" value="1234" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/zs/entity/City.xml"></mapper>
<mapper resource="com/zs/entity/Province.xml"></mapper>
</mappers>
</configuration>
4.建立與資料庫對應的實體包，包下建立類與對應的xml檔案（這裡沒有使用介面呼叫方法，是使用xml檔案呼叫方法）
Province.java
package com.zs.entity;
import java.util.List;
/**
* @author 小思
* @PackageName:com.zs.entity
* @ClassName: Province
* @Description:對應資料庫Province表的實體類
* @date 2018/10/31 16:32
*/
public class Province {
private Integer pid;
private String pname;
private List<city> cities;
public Province() {
}
public Province(Integer pid) {
this.pid = pid;
}
public Province(String pname) {
this.pname = pname;
}
public Province(Integer pid, String pname) {
this.pid = pid;
this.pname = pname;
}
public Province(Integer pid, String pname, List<city> cities) {
this.pid = pid;
this.pname = pname;
this.cities = cities;
}
public Integer getPid() {
return pid;
}
public void setPid(Integer pid) {
this.pid = pid;
}
public String getPname() {
return pname;
}
public void setPname(String pname) {
this.pname = pname;
}
public List<city> getCities() {
return cities;
}
public void setCities(List<city> cities) {
this.cities = cities;
}
}
city.java
package com.zs.entity;
/**
* @author 小思
* @PackageName:com.zs.entity
* @ClassName: city
* @Description:對應資料庫City表的實體類
* @date 2018/10/31 16:33
*/
public class city {
private Integer cid;//城市的Id
private String cname;//城市的名稱
private Province province;//城市所對應的省份
public Integer getCid() {
return cid;
}
public void setCid(Integer cid) {
this.cid = cid;
}
public String getCname() {
return cname;
}
public void setCname(String cname) {
this.cname = cname;
}
public Province getProvince() {
return province;
}
public void setProvince(Province province) {
this.province = province;
}
public city() {
}
public city(Integer cid) {
this.cid = cid;
}
public city(String cname) {
this.cname = cname;
}
public city(Integer cid, String cname) {
this.cid = cid;
this.cname = cname;
}
public city(Integer cid, String cname, Province province) {
this.cid = cid;
this.cname = cname;
this.province = province;
}
}
Province.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">
<mapper namespace="com.zs.dao.ProvinceDao">
<!--通過對映檔案的配置資訊，通過載入ProvinceDao介面找尋對應的方法-->
<select id="getAllProvince" resultType="Province">
select * from province
</select>
<!--根據省份的Id查詢城市-->
<select id="findCityById" resultType="city" parameterType="int">
select * from city where pid=#{pid}
</select>
</mapper>
5.在test資料夾下新建com.zs.test資料夾，並且新建單元測試類TestOneToMany.java
package com.zs.test;
import com.zs.dao.ProvinceDao;
import com.zs.entity.city;
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.util.List;
/**
* @author 小思
* @PackageName:com.zs.test
* @ClassName: TestOneToMany
* @Description:
* @date 2018/10/31 16:42
*/
@SuppressWarnings("unused")
public class TestOneToMany {
SqlSessionFactory sessionFactory;
SqlSession session;
@Before
public void before() {
//從mybatis-config.xml mybatis的核心配置檔案中獲取SqlSessionFactory
sessionFactory = new SqlSessionFactoryBuilder().build(getClass().getClassLoader().getResourceAsStream("mybatis-config.xml"));
//通過工廠獲取SqlSession
session = sessionFactory.openSession();
}
@Test
public void testProvince() {
// 對映器是一個你建立來繫結你對映的語句的介面，呼叫合理描述引數和返回值的介面來獲取相應的方法
ProvinceDao pd = session.getMapper(ProvinceDao.class);
// //查詢所有的省份
// List<Province> list = pd.getAllProvince();
// for (Province p : list) {
// System.out.println(p.getPname());
// }
//根據省份的Id查詢城市
List<city> c=pd.findCityById(1);
for (city city : c) {
System.out.println(city.getCname());
}
}
@After
public void after() {
//提交session和關閉session(釋放無用資源)
session.commit();
session.close();
}
}
6.測試時，取消註釋，執行測試類即可
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