review
Hibernate annotation development and other level annotations
Hibernate annotation development of attribute-level annotations
1. One-to-one single foreign key association
Students04
@Entity
public class Students04 implements Serializable {
@Id //设置为主键
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int sid;
@OneToOne(cascade = CascadeType.ALL)//指定被控类, 默认是全级联
@JoinColumn(name = "pid", unique = true)//name指定被控类(IdCard类)的主键, unique说明该键是唯一的
private IdCard card;
private String gender; //性别
private Date birthday; //出生日期
private String major; //专业 ... 构造方法和settergetter方法自行补充 ...}IdCard
@Entity
public class IdCard {
@Id
@GeneratedValue(generator = "pid")
@GenericGenerator(name = "pid", strategy = "assigned")
@Column(length = 18)
private String pid; //身份证号码
private String sname; //学生姓名 ... 构造方法和settergetter方法自行补充 ...}Configuration file
<mapping class="com.idea.hibernate.oto_fk.Students04"/>
<mapping class="com.idea.hibernate.oto_fk.IdCard"/>Test (Before saving the main table object, you should save the foreign key object)
@Test
public void addStudents04(){
Configuration configuration = new Configuration().configure();
SessionFactory sessionFactory = createSessionFactory(configuration);
Session session = sessionFactory.getCurrentSession();
Transaction tx = session.beginTransaction();
IdCard card = new IdCard("1234567890123456", "王五");
Students04 students04 = new Students04(card, "男", new Date(), "Java开发");
session.save(card);
session.save(students04);
tx.commit();
}
/**
* 建表策略
*/
private SessionFactory createSessionFactory(Configuration configuration){
//创建服务注册对象
StandardServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
//生成SssionFactory
SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
//返回配置对象
return sessionFactory;
}
ps: The annotations in the same entity class should either be written on the attributes, or written on the getXxx method, and cannot be mixed.
2. One-to-one bidirectional foreign key association
Features: I am in you, you in me
The writing of the master party is the same as the one-to-one one-way association, the difference lies in the accused party (IdCard)
For two-way association, the mappedBy attribute must be set and handed over to the master to control.
IdCard02
@Entity
public class IdCard02 {
@Id
@GeneratedValue(generator = "pid")
@GenericGenerator(name = "pid", strategy = "assigned")
@Column(length = 18)
private String pid; //身份证号码
private String sname; //学生姓名
@OneToOne(mappedBy = "card") //指定主控方(Students05)中的属性
private Students05 students05; ... 构造方法和settergetter方法自行补充 ...}The other parts are the same.
3. One-to-one bidirectional foreign key union primary key
① Create the primary key class StudentsPK
② Annotation @Embeddable on the primary key class
@Embeddable
public class StudentsPK implements Serializable {
private static final long serialVersionUID = 6632444697825110476L;
@Column(length = 18)
private String id; //ID number
@Column(length = 8)
private String sid; //Student ID...}
③ Introduce the attribute of the primary key class in the entity class, and use the annotation @EmbeddedId on the attribute
Move to the attribute-level annotations of Hibernate annotation development in detail
4. One-to-many single foreign key association
One party holds a collection of many parties, such as a class with multiple students (one-to-many)
Students07
@Entity
public class Students07 implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int sid;
private String sname;
private String gender;
private String major;
private Date birthday; ...}ClassRoom01
@Entity
public class ClassRoom01 {
@Id
@GeneratedValue(generator = "cid")
@GenericGenerator(name = "cid", strategy = "assigned")
@Column(length = 4)
private String cid;
private String cname;
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY) //多的一方使用急加载, 一的一方使用懒加载
@JoinColumn(name = "CID")
private Set<Students07> stus; //一的一方持有多的一方的集合 ...}
5. One-to-many two-way foreign key association
The configuration of the class class and the one-way is the same, except that the class class reference is added to the student class
Students08
@Entity
public class Students08 implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int sid;
private String sname;
private String gender;
private String major;
private Date birthday;
@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER) //多的一方需要设为急加载
@JoinColumn(name = "CID")
private ClassRoom02 classRoom02; //多的一方持有一的一方的引用 ...}6. Many-to-many single foreign key association
① The corresponding relationship between students and teachers is a many-to-many relationship
② Student table holds the collection of teacher table
③ Create an intermediate table
Students09
@Entity
public class Students09 implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int sid;
private String sname;
private String gender;
private String major;
private Date birthday;
@ManyToMany
@JoinTable(
name = "teachers_students", //中间表的名称
joinColumns = {@JoinColumn(name = "SID")}, //中间表外键关联字段的名称
inverseJoinColumns = {@JoinColumn(name = "TID")} //中间表外键关联字段的名称
)
private Set<Teachers> teachers; //学生持有教师的集合 ...}Teachers
@Entity
public class Teachers {
@Id
@GeneratedValue(generator = "tid")
@GenericGenerator(name = "tid", strategy = "assigned")
@Column(length = 4)
private String tid; //教师的编号
private String tname; //教师的姓名 ...}
7. Many-to-many two-way foreign key association
Both parties hold each other's collection, involving the master and the accused, and need to transfer control to the master
@Entity
public class Teachers01 {
@Id
@GeneratedValue(generator = "tid")
@GenericGenerator(name = "tid", strategy = "assigned")
@Column(length = 4)
private String tid; //教师的编号
private String tname; //教师的姓名
@ManyToMany(mappedBy = "teachers") //将主控权给学生方, teachers是学生类中的属性
private Set<Students10> stus; ...}The student class is the same as the test