hibernate(8)

이번엔 1:N 관계를 살펴보자. 

바로 소스를 보자. 

package com.zest.hibernate.chapter7.onetomanymapping;
 
import java.util.List;
 
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
 
@Entity
public class College {
 
    @Id
    @GeneratedValue
    private int collegeId;
    private String collegeName;
    
    @OneToMany(targetEntity=Student.class, mappedBy="college"
            ,cascade= CascadeType.ALL,fetch=FetchType.EAGER)
    private List<Student> students ;
    
    
    public int getCollegeId() {
        return collegeId;
    }
    public void setCollegeId(int collegeId) {
        this.collegeId = collegeId;
    }
    public String getCollegeName() {
        return collegeName;
    }
    public void setCollegeName(String collegeName) {
        this.collegeName = collegeName;
    }
    public List<Student> getStudents() {
        return students;
    }
    public void setStudents(List<Student> students) {
        this.students = students;
    }
    
    
}
 

 
package com.zest.hibernate.chapter7.onetomanymapping;
 
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
 
@Entity
public class Student {
 
    @Id
    @GeneratedValue
    private int studentId;
    private String studentName;
    
    @ManyToOne
    @JoinColumn(name="college_id")
    private College college;
    
    public int getStudentId() {
        return studentId;
    }
    public void setStudentId(int studentId) {
        this.studentId = studentId;
    }
    public String getStudentName() {
        return studentName;
    }
    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }
    public College getCollege() {
        return college;
    }
    public void setCollege(College college) {
        this.college = college;
    }
    
    
}
 

몇가지 새로운 어노테이션이 등장했다. @OneToMany, @ManyToOne

OneToMany가 선언되있는 클래스는 One을 지칭하고 targetEntity는 many가 된다. 

mappedBy는 One에 속하는 테이블 명을 써주면 된다. 

Student 객체는 ManyToOne을 선언하고 JoinColumn의 컬럼 명을 정의해주면 된다. 

그럼 테스트 ㄱㄱ

 
package com.zest.hibernate.chapter7.onetomanymapping;
 
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.Test;
 
import com.zest.hibernate.chapter5.inheritancemapping.Module;
import com.zest.hibernate.chapter5.inheritancemapping.Project;
import com.zest.hibernate.chapter5.inheritancemapping.Task;
 
public class OneToManyTest {
 
    @Test
    public void oneTest(){
        AnnotationConfiguration config = new AnnotationConfiguration();
        config.addAnnotatedClass(College.class);
        config.addAnnotatedClass(Student.class);
        config.configure("hibernate.cfg.xml");
        
        new SchemaExport(config).create(true, true);
 
        // 아래 두개의 구문은 객체를 트랜잭션을 컨트롤.
        SessionFactory factory = config.buildSessionFactory();
        Session session = factory.getCurrentSession();
 
        session.beginTransaction();
        
        College college1 = new College();
        college1.setCollegeName("Newyork College");
        
        Student s1 = new Student();
        s1.setStudentName("Alex Rod");
        
        Student s2 = new Student();
        s2.setStudentName("Linda Berry");
        
        s1.setCollege(college1);
        s2.setCollege(college1);
        
        session.save(college1);
        session.save(s1);
        session.save(s2);
        //session.save(alexdetail); 이건 안함. 카스케이드 라서 
        session.getTransaction().commit();
        
        
    }
}
 

결과는 다음과 같다. 

 
Hibernate: insert into TESTSCHEMA.College (collegeName, collegeId) values (?, ?)
Hibernate: insert into TESTSCHEMA.Student (college_id, studentName, studentId) values (?, ?, ?)
Hibernate: insert into TESTSCHEMA.Student (college_id, studentName, studentId) values (?, ?, ?)

예상했던 대로 College_ID는 FK로 셋팅이 된다.