注解高级（原文再续书接上一回）
5.双向关联
A.一对一
1 package com.rong.entity;
2
3 import javax.persistence.Entity;
4 import javax.persistence.FetchType;
5 import javax.persistence.GeneratedValue;
6 import javax.persistence.GenerationType;
7 import javax.persistence.Id;
8 import javax.persistence.OneToOne;
9 import javax.persistence.Table;
10
11 @Entity
12 @Table(name="t_citizen")
13 public class Citizen {
14 @Id
15 @GeneratedValue(strategy=GenerationType.AUTO)
16 private int id;
17 private String name;
18 private int sex;
19 @OneToOne(targetEntity=IDcard.class,fetch=FetchType.LAZY,mappedBy="citizen") // 不维护关联关系(主表)
20 private IDcard iDcard; //由iDcard对象的成员变量citizen来维护
21 public int getId() {
22 return id;
23 }
24 public void setId(int id) {
25 this.id = id;
26 }
27 public String getName() {
28 return name;
29 }
30 public void setName(String name) {
31 this.name = name;
32 }
33 public int getSex() {
34 return sex;
35 }
36 public void setSex(int sex) {
37 this.sex = sex;
38 }
39 public IDcard getiDcard() {
40 return iDcard;
41 }
42 public void setiDcard(IDcard iDcard) {
43 this.iDcard = iDcard;
44 }
45 @Override
46 public String toString() {
47 return "Citizen [id=" + id + ", name=" + name + ", sex=" + sex + ", iDcard=" + iDcard + "]";
48 }
49 }
1 package com.rong.entity;
2
3 import javax.persistence.Entity;
4 import javax.persistence.FetchType;
5 import javax.persistence.GeneratedValue;
6 import javax.persistence.GenerationType;
7 import javax.persistence.Id;
8 import javax.persistence.JoinColumn;
9 import javax.persistence.OneToOne;
10 import javax.persistence.Table;
11
12 @Entity
13 @Table(name="t_idcard")
14 public class IDcard {
15 @Id
16 @GeneratedValue(strategy=GenerationType.AUTO)
17 private int cardid;
18 private String name;
19 private String addr;
20 @OneToOne(targetEntity=Citizen.class,fetch=FetchType.LAZY) // 维护关联关系(从表)
21 @JoinColumn(name="t_id",referencedColumnName="id",unique=true)//生成外键列，参考citizen的id
22 private Citizen citizen;
23 public int getCardid() {
24 return cardid;
25 }
26 public void setCardid(int cardid) {
27 this.cardid = cardid;
28 }
29 public String getName() {
30 return name;
31 }
32 public void setName(String name) {
33 this.name = name;
34 }
35 public String getAddr() {
36 return addr;
37 }
38 public void setAddr(String addr) {
39 this.addr = addr;
40 }
41 public Citizen getCitizen() {
42 return citizen;
43 }
44 public void setCitizen(Citizen citizen) {
45 this.citizen = citizen;
46 }
47 @Override
48 public String toString() {
49 return "IDcard [cardid=" + cardid + ", name=" + name + ", addr=" + addr + ", citizen=" + citizen + "]";
50 }
51 }
1 package com.rong.test;
2
3 import org.hibernate.Session;
4 import org.hibernate.SessionFactory;
5 import org.hibernate.Transaction;
6 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
7 import org.hibernate.cfg.Configuration;
8 import org.hibernate.service.ServiceRegistry;
9 import org.junit.Test;
10
11 import com.rong.entity.Citizen;
12 import com.rong.entity.IDcard;
13
14 public class HibernateTest {
15 @Test
16 public void test1(){
17 Configuration configuration=new Configuration().configure();
18 ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
19 SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
20 Session session = sessionFactory.openSession();
21 Transaction transaction = session.beginTransaction();
22
23 Citizen citizen=new Citizen();
24 citizen.setName("容杰龙");
25 citizen.setSex(0);
26 IDcard iDcard=new IDcard();
27 iDcard.setAddr("广东");
28 iDcard.setCitizen(citizen);
29
30 session.save(citizen);
31 session.save(iDcard);
32 //查找
33 Citizen person = (Citizen) session.get(Citizen.class, 1);
34 System.out.println(person);
35 IDcard card = (IDcard) session.get(IDcard.class, 1);
36 System.out.println(card);
37 transaction.commit();
38 session.close();
39 sessionFactory.close();
40 }
41 }
B.一对多（多的那端维护）
1 package com.rong.entity;
2
3 import java.util.HashSet;
4 import java.util.Set;
5
6 import javax.persistence.CascadeType;
7 import javax.persistence.Entity;
8 import javax.persistence.FetchType;
9 import javax.persistence.GeneratedValue;
10 import javax.persistence.GenerationType;
11 import javax.persistence.Id;
12 import javax.persistence.OneToMany;
13 import javax.persistence.Table;
14
15 @Entity
16 @Table(name="t_teacher")
17 public class Teacher {
18 @Id
19 @GeneratedValue(strategy=GenerationType.AUTO)
20 private int tid;
21 private String tname;
22 //一的一端(主表)
23 @OneToMany(targetEntity=Student.class // 指定关联的持久化
24 ,fetch=FetchType.LAZY // 延迟加载
25 ,cascade={CascadeType.REMOVE} // 级联删除(级联到关联的持久化类)
26 ,orphanRemoval=true // 删除孤儿记录
27 ,mappedBy="tea"//关联关系(外键列由从表维护), 写关联的持久化中哪个属性引用了它自己
28 )
29 private Set<Student> stu=new HashSet<Student>();
30 public int getTid() {
31 return tid;
32 }
33 public void setTid(int tid) {
34 this.tid = tid;
35 }
36 public String getTname() {
37 return tname;
38 }
39 public void setTname(String tname) {
40 this.tname = tname;
41 }
42 public Set<Student> getStu() {
43 return stu;
44 }
45 public void setStu(Set<Student> stu) {
46 this.stu = stu;
47 }
48 @Override
49 public String toString() {
50 return "Teacher [tid=" + tid + ", tname=" + tname + ", stu=" + stu + "]";
51 }
52 }
1 package com.rong.entity;
2
3 import javax.persistence.CascadeType;
4 import javax.persistence.Entity;
5 import javax.persistence.FetchType;
6 import javax.persistence.GeneratedValue;
7 import javax.persistence.GenerationType;
8 import javax.persistence.Id;
9 import javax.persistence.JoinColumn;
10 import javax.persistence.ManyToOne;
11 import javax.persistence.Table;
12
13 @Entity
14 @Table(name="t_student")
15 public class Student {
16 @Id
17 @GeneratedValue(strategy=GenerationType.AUTO)
18 private int sid;
19 private String sname;
20 //多的一端 (从表，有外键)
21 @ManyToOne(targetEntity=Teacher.class// 指定关联的持久化类
22 ,fetch=FetchType.LAZY // 延迟加载
23 ,cascade=CascadeType.REMOVE// 级联删除
24 )
25 //生成外键列
26 @JoinColumn(name="t_id",referencedColumnName="tid")
27 private Teacher tea;
28 public int getSid() {
29 return sid;
30 }
31 public void setSid(int sid) {
32 this.sid = sid;
33 }
34 public String getSname() {
35 return sname;
36 }
37 public void setSname(String sname) {
38 this.sname = sname;
39 }
40 public Teacher getTea() {
41 return tea;
42 }
43 public void setTea(Teacher tea) {
44 this.tea = tea;
45 }
46 @Override
47 public String toString() {
48 return "Student [sid=" + sid + ", sname=" + sname + ", tea=" + tea + "]";
49 }
50 }
1 package com.rong.test;
2
3 import java.util.Set;
4
5 import org.hibernate.Session;
6 import org.hibernate.SessionFactory;
7 import org.hibernate.Transaction;
8 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
9 import org.hibernate.cfg.Configuration;
10 import org.hibernate.service.ServiceRegistry;
11 import org.junit.Test;
12
13 import com.rong.entity.Student;
14 import com.rong.entity.Teacher;
15
16 public class HibernateTest {
17 @Test
18 public void test1(){
19 Configuration configuration=new Configuration().configure();
20 ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
21 SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
22 Session session = sessionFactory.openSession();
23 Transaction transaction = session.beginTransaction();
24 /* //t_teacher 这个表是主表
25 Teacher teacher=new Teacher();
26 teacher.setTname("局长");
27 //t_student 是从表（有外键的是从表，需要维护关联关系）
28 Student student1=new Student();
29 student1.setSname("容杰龙");
30 student1.setTea(teacher);
31 Student student2=new Student();
32 student2.setSname("古月哥欠");
33 student2.setTea(teacher);
34 //保存的时候，必须先保存主表，后保存从表
35 session.save(teacher);
36 session.save(student1);
37 session.save(student2);*/
38 //查找
39 Teacher tea=(Teacher) session.get(Teacher.class, 1);
40 System.out.println(tea.getTname());
41 Set<Student> set = tea.getStu();
42 for (Student student : set) {
43 System.out.println(student.getSid()+":"+student.getSname());
44 }
45
46 transaction.commit();
47 session.close();
48 sessionFactory.close();
49 }
50 }
C.多对多
1 package com.rong.entity;
2
3 import java.util.HashSet;
4 import java.util.Set;
5
6 import javax.persistence.Entity;
7 import javax.persistence.FetchType;
8 import javax.persistence.GeneratedValue;
9 import javax.persistence.GenerationType;
10 import javax.persistence.Id;
11 import javax.persistence.ManyToMany;
12 import javax.persistence.Table;
13
14 @Entity
15 @Table(name="t_teacher")
16 public class Teacher {
17 @Id
18 @GeneratedValue(strategy=GenerationType.AUTO)
19 private int tid;
20 private String tname;
21 //多的一端
22 @ManyToMany(targetEntity=Student.class
23 ,fetch=FetchType.LAZY
24 ,mappedBy="tea"// 老师这边不维护关联关系 (不用生成中间表)
25 )
26 private Set<Student> stu=new HashSet<Student>();
27 public int getTid() {
28 return tid;
29 }
30 public void setTid(int tid) {
31 this.tid = tid;
32 }
33 public String getTname() {
34 return tname;
35 }
36 public void setTname(String tname) {
37 this.tname = tname;
38 }
39 public Set<Student> getStu() {
40 return stu;
41 }
42 public void setStu(Set<Student> stu) {
43 this.stu = stu;
44 }
45 @Override
46 public String toString() {
47 return "Teacher [tid=" + tid + ", tname=" + tname + ", stu=" + stu + "]";
48 }
49 }
1 package com.rong.entity;
2
3 import java.util.HashSet;
4 import java.util.Set;
5
6 import javax.persistence.Entity;
7 import javax.persistence.FetchType;
8 import javax.persistence.GeneratedValue;
9 import javax.persistence.GenerationType;
10 import javax.persistence.Id;
11 import javax.persistence.JoinColumn;
12 import javax.persistence.JoinTable;
13 import javax.persistence.ManyToMany;
14 import javax.persistence.Table;
15
16 @Entity
17 @Table(name="t_student")
18 public class Student {
19 @Id
20 @GeneratedValue(strategy=GenerationType.AUTO)
21 private int sid;
22 private String sname;
23 //多的一端
24 @ManyToMany(targetEntity=Teacher.class,fetch=FetchType.LAZY)
25 //生成中间表
26 @JoinTable(name="tea_stu" // 中间表的表名
27 // @ManyToMany注解中没有加mappedBy表的主键列
28 ,joinColumns={@JoinColumn(name="sid",referencedColumnName="sid")}
29 // @ManyToMany注解中加了mappedBy属性的表的主键列
30 ,inverseJoinColumns={@JoinColumn(name="tid",referencedColumnName="tid")})
31 private Set<Teacher> tea=new HashSet<Teacher>();
32 public int getSid() {
33 return sid;
34 }
35 public void setSid(int sid) {
36 this.sid = sid;
37 }
38 public String getSname() {
39 return sname;
40 }
41 public void setSname(String sname) {
42 this.sname = sname;
43 }
44 public Set<Teacher> getTea() {
45 return tea;
46 }
47 public void setTea(Set<Teacher> tea) {
48 this.tea = tea;
49 }
50 @Override
51 public String toString() {
52 return "Student [sid=" + sid + ", sname=" + sname + ", tea=" + tea + "]";
53 }
54 }
1 package com.rong.test;
2
3 import java.util.Set;
4
5 import org.hibernate.Session;
6 import org.hibernate.SessionFactory;
7 import org.hibernate.Transaction;
8 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
9 import org.hibernate.cfg.Configuration;
10 import org.hibernate.service.ServiceRegistry;
11 import org.junit.Test;
12
13 import com.rong.entity.Student;
14 import com.rong.entity.Teacher;
15
16 public class HibernateTest {
17 @Test
18 public void test1(){
19 Configuration configuration=new Configuration().configure();
20 ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
21 SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
22 Session session = sessionFactory.openSession();
23 Transaction transaction = session.beginTransaction();
24 /* //t_teacher 这个表是主表
25 Teacher teacher1=new Teacher();
26 teacher1.setTname("陈局长");
27 Teacher teacher2=new Teacher();
28 teacher2.setTname("容部长");
29 //t_student 是从表（有外键的是从表，需要维护关联关系）
30 Student student1=new Student();
31 student1.setSname("容杰龙");
32 student1.getTea().add(teacher1);
33 student1.getTea().add(teacher2);
34 Student student2=new Student();
35 student2.setSname("古月哥欠");
36 student2.getTea().add(teacher1);
37 student2.getTea().add(teacher2);
38 //保存的时候，必须先保存主表，后保存从表
39 session.save(teacher1);
40 session.save(teacher2);
41 session.save(student1);
42 session.save(student2);
43 */
44 //查找
45 Teacher tea=(Teacher) session.get(Teacher.class, 1);
46 System.out.println(tea.getTname());
47 Set<Student> set = tea.getStu();
48 for (Student student : set) {
49 System.out.println(student.getSid()+":"+student.getSname());
50 }
51 Student student=(Student) session.get(Student.class, 1);
52 System.out.println(student.getSname());
53 Set<Teacher> set2 = student.getTea();
54 for (Teacher teacher : set2) {
55 System.out.println(teacher.getTid()+":"+teacher.getTname());
56 }
57 transaction.commit();
58 session.close();
59 sessionFactory.close();
60 }
61 }
