Hibernate（四）

注解高级（原文再续书接上一回）

6.单向关联

即单向配置注解关联信息

　　单向关联的数据库生成的表与双向关联生成的表是相同的，只是在查询的时候不同。双向是双方都可以查询各自的信息，而单向只有加了注解的表可以查询另一方的信息！！！一对多以及多对一是同一概念，只是参考系不一样。一般会由多的一端来维护生成外键，这样效率更高；而作为一的那端也可以作为维护生成外键，但是效率普遍较低，一般不推荐使用。需要用哪种关联，归根到底还是要看实际业务需求。

A.一对一

 主表不需要配置注解信息，而从表需要

package com.rong.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="t_citizen")
public class Citizen {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String name;
    private int sex; 
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getSex() {
        return sex;
    }
    public void setSex(int sex) {
        this.sex = sex;
    }
    @Override
    public String toString() {
        return "Citizen [id=" + id + ", name=" + name + ", sex=" + sex + "]";
    }
}

package com.rong.entity;

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name="t_idcard")
public class IDcard {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int cardid;
    private String name;
    private String addr;
    @OneToOne(targetEntity=Citizen.class,fetch=FetchType.LAZY) // 维护关联关系(从表)
    @JoinColumn(name="t_id",referencedColumnName="id",unique=true)//生成外键列，参考citizen的id
    private Citizen citizen;
    public int getCardid() {
        return cardid;
    }
    public void setCardid(int cardid) {
        this.cardid = cardid;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getAddr() {
        return addr;
    }
    public void setAddr(String addr) {
        this.addr = addr;
    }
    public Citizen getCitizen() {
        return citizen;
    }
    public void setCitizen(Citizen citizen) {
        this.citizen = citizen;
    }
    @Override
    public String toString() {
        return "IDcard [cardid=" + cardid + ", name=" + name + ", addr=" + addr + ", citizen=" + citizen + "]";
    }
}

package com.rong.test;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.junit.Test;

import com.rong.entity.Citizen;
import com.rong.entity.IDcard;

public class HibernateTest {
    @Test
    public void test1(){
        Configuration configuration=new Configuration().configure();
        ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
        SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();

        Citizen citizen=new Citizen();
        citizen.setName("rjl");
        citizen.setSex(0);
        IDcard iDcard=new IDcard();
        iDcard.setName("rjl");
        iDcard.setAddr("中国");
        iDcard.setCitizen(citizen);
        
        session.save(citizen);
        session.save(iDcard);
        //查询
        Citizen findCitizen=(Citizen) session.get(Citizen.class, 1);
        //单向关联中主表查不到另一端的数据信息，只能查找自身信息
        System.out.println(findCitizen.getId()+":"+findCitizen.getName());
        IDcard findIDcard=(IDcard)session.get(IDcard.class, 1);
        //单向关联中从表不仅能查找自身信息，还可以查到另一端的数据信息
        System.out.println(findIDcard.getCardid()+":"+findIDcard.getAddr()+findIDcard.getCitizen());
        transaction.commit();
        session.close();
        sessionFactory.close();
    }
}

B.一对多

package com.rong.entity;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name="t_teacher")
public class Teacher {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int tid;
    private String tname;
    //一的一端
    @OneToMany(targetEntity=Student.class
            ,fetch=FetchType.LAZY
            ,cascade=CascadeType.REMOVE
            ,orphanRemoval=true)
    @JoinColumn(name="t_id",referencedColumnName="tid")
    private Set<Student> stu=new HashSet<Student>();
    public int getTid() {
        return tid;
    }
    public void setTid(int tid) {
        this.tid = tid;
    }
    public String getTname() {
        return tname;
    }
    public void setTname(String tname) {
        this.tname = tname;
    }
    public Set<Student> getStu() {
        return stu;
    }
    public void setStu(Set<Student> stu) {
        this.stu = stu;
    }
    @Override
    public String toString() {
        return "Teacher [tid=" + tid + ", tname=" + tname + ", stu=" + stu + "]";
    }
}

package com.rong.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="t_student")
public class Student {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int sid;
    private String sname;
    public int getSid() {
        return sid;
    }
    public void setSid(int sid) {
        this.sid = sid;
    }
    public String getSname() {
        return sname;
    }
    public void setSname(String sname) {
        this.sname = sname;
    }
    @Override
    public String toString() {
        return "Student [sid=" + sid + ", sname=" + sname + "]";
    }
}

package com.rong.test;

import java.util.Set;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.junit.Test;

import com.rong.entity.Citizen;
import com.rong.entity.IDcard;
import com.rong.entity.Student;
import com.rong.entity.Teacher;

public class HibernateTest {
    @Test
    public void test1(){
        Configuration configuration=new Configuration().configure();
        ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
        SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();

        Teacher teacher=new Teacher();
        teacher.setTname("夏雨");
        Student student1=new Student();
        student1.setSname("曹操");
        Student student2=new Student();
        student2.setSname("刘备");
        Set<Student> set = teacher.getStu();
        set.add(student1);
        set.add(student2);
        session.save(student1);
        session.save(student2);
        session.save(teacher);
        //
        Student stu=(Student) session.get(Student.class, 1);
        System.out.println(stu.getSid()+":"+stu.getSname());
        
        //
        Teacher tea=(Teacher) session.get(Teacher.class, 1);
        System.out.println(tea.getTname()+tea.getStu());
        transaction.commit();
        session.close();
        sessionFactory.close();
    }
}

C.多对一

package com.rong.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="t_teacher")
public class Teacher {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int tid;
    private String tname;
    
    public int getTid() {
        return tid;
    }
    public void setTid(int tid) {
        this.tid = tid;
    }
    public String getTname() {
        return tname;
    }
    public void setTname(String tname) {
        this.tname = tname;
    }
    @Override
    public String toString() {
        return "Teacher [tid=" + tid + ", tname=" + tname + "]";
    }
}

package com.rong.entity;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name="t_student")
public class Student {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int sid;
    private String sname;
    //多的一端
    @ManyToOne(targetEntity=Teacher.class
                ,fetch=FetchType.LAZY
                ,cascade=CascadeType.REMOVE
                )
    @JoinColumn(name="t_id",referencedColumnName="tid")
    private Teacher teach;
    public int getSid() {
        return sid;
    }
    public void setSid(int sid) {
        this.sid = sid;
    }
    public String getSname() {
        return sname;
    }
    public void setSname(String sname) {
        this.sname = sname;
    }
    public Teacher getTeach() {
        return teach;
    }
    public void setTeach(Teacher teach) {
        this.teach = teach;
    }
    @Override
    public String toString() {
        return "Student [sid=" + sid + ", sname=" + sname + ", teach=" + teach + "]";
    }
}

package com.rong.test;

import java.util.Set;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.junit.Test;

import com.rong.entity.Student;
import com.rong.entity.Teacher;

public class HibernateTest {
    @Test
    public void test1(){
        Configuration configuration=new Configuration().configure();
        ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
        SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();

        Teacher teacher=new Teacher();
        teacher.setTname("夏雨");
        Student student1=new Student();
        student1.setSname("曹操");
        student1.setTeach(teacher);
        Student student2=new Student();
        student2.setSname("刘备");
        student2.setTeach(teacher);
        session.save(teacher);
        session.save(student1);
        session.save(student2);
        //
        Student stu=(Student) session.get(Student.class, 2);
        System.out.println(stu.getSname()+":"+stu.getTeach().getTname());
        
        //
        Teacher tea=(Teacher) session.get(Teacher.class, 1);
        System.out.println(tea.getTid()+tea.getTname());
        transaction.commit();
        session.close();
        sessionFactory.close();
    }
}

D.多对多

package com.rong.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="t_teacher")
public class Teacher {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int tid;
    private String tname;
    
    public int getTid() {
        return tid;
    }
    public void setTid(int tid) {
        this.tid = tid;
    }
    public String getTname() {
        return tname;
    }
    public void setTname(String tname) {
        this.tname = tname;
    }
    @Override
    public String toString() {
        return "Teacher [tid=" + tid + ", tname=" + tname + "]";
    }
}

package com.rong.entity;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

@Entity
@Table(name="t_student")
public class Student {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int sid;
    private String sname;
    @ManyToMany(targetEntity=Teacher.class
            ,fetch=FetchType.LAZY
            ,cascade=CascadeType.REMOVE)
    // 生成中间表
    @JoinTable(name="tea_stu"
                ,joinColumns=@JoinColumn(name="s_id",referencedColumnName="sid")
                ,inverseJoinColumns=@JoinColumn(name="t_id",referencedColumnName="tid")
                )
    private Set<Teacher> teacherSet=new HashSet<Teacher>();
    public int getSid() {
        return sid;
    }
    public void setSid(int sid) {
        this.sid = sid;
    }
    public String getSname() {
        return sname;
    }
    public void setSname(String sname) {
        this.sname = sname;
    }
    public Set<Teacher> getTeacherSet() {
        return teacherSet;
    }
    public void setTeacherSet(Set<Teacher> teacherSet) {
        this.teacherSet = teacherSet;
    }
    @Override
    public String toString() {
        return "Student [sid=" + sid + ", sname=" + sname + ", teacherSet=" + teacherSet + "]";
    }
}

package com.rong.test;

import java.util.Set;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.junit.Test;

import com.rong.entity.Student;
import com.rong.entity.Teacher;

public class HibernateTest {
    @Test
    public void test1(){
        Configuration configuration=new Configuration().configure();
        ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
        SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();

        Teacher teacher1=new Teacher();
        teacher1.setTname("夏雨");
        Teacher teacher2=new Teacher();
        teacher2.setTname("陈雅静");
        Student student1=new Student();
        student1.setSname("曹操");
        student1.getTeacherSet().add(teacher1);
        student1.getTeacherSet().add(teacher2);
        Student student2=new Student();
        student2.setSname("刘备");
        student2.getTeacherSet().add(teacher1);
        student2.getTeacherSet().add(teacher2);
        session.save(teacher1);
        session.save(teacher2);
        session.save(student1);
        session.save(student2);
        //////////////////////////
        Student stu=(Student) session.get(Student.class, 2);
        Set<Teacher> teacherSet = stu.getTeacherSet();
        for (Teacher teacher : teacherSet) {
            System.out.println(teacher.getTid()+":"+teacher.getTname());
        }
        //////////////////////////
        Teacher tea=(Teacher) session.get(Teacher.class, 2);
        System.out.println(tea.getTid()+tea.getTname());
        transaction.commit();
        session.close();
        sessionFactory.close();
    }
}