hibernate映射关系注解分析总结（2012.06.15）

hibernate映射关系注解配置：
Hibernate实体关系：双向关联，mappedBy必设

注解方式

1、一对一单向

@Entity

public class Husband{

@Id

@GenerateValue

pirvate int id;

private String name;

@OneToOne

@JoinColumn(name="wifeId")

private Wife wife;

}

@Entity

public class Wife{

@Id

@GenerateValue

private int id;

private String name;

}

2.、一对一双向

@Entity

public class Husband{

@Id

@GenerateValue

pirvate int id;

private String name;

@OneToOne

@JoinColumn(name="wifeId")

private Wife wife;

}

@Entity

public class Wife{

@Id

@GenerateValue

private int id;

private String name;

@OneToOne(mappedBy="wife")

private Husband husband;

}

3.、一对多单向

package com.bjsxt.hibernate;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name="t_group")
public class Group {
private int id;
private String name;
private Set<User> users = new HashSet<User>();
@Id
@GeneratedValue
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;
}
@OneToMany
@JoinColumn(name="groupId") //不加出现3张表
public Set<User> getUsers() {
return users;
}
public void setUsers(Set<User> users) {
this.users = users;
}
}

package com.bjsxt.hibernate;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name="t_user")
public class User {
private int id;
private String name;
@Id
@GeneratedValue
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;
}
}

4、多对一单向

package com.bjsxt.hibernate;

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

@Entity
@Table(name="t_group")
public class Group {
private int id;
private String name;
@Id
@GeneratedValue
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;
}
}

package com.bjsxt.hibernate;

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

@Entity
@Table(name="t_user")
public class User {
private int id;
private String name;
private Group group;
@ManyToOne

public Group getGroup() {
return group;
}
public void setGroup(Group group) {
this.group = group;
}
@Id
@GeneratedValue
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;
}
}

5、一对多双向

package com.bjsxt.hibernate;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name="t_group")
public class Group {
private int id;
private String name;
private Set<User> users = new HashSet<User>();
@Id
@GeneratedValue
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;
}
@OneToMany(mappedBy="group")

public Set<User> getUsers() {
return users;
}
public void setUsers(Set<User> users) {
this.users = users;
}
}

package com.bjsxt.hibernate;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name="t_user")
public class User {
private int id;
private String name;
private Group group;
@ManyToOne
public Group getGroup() {
return group;
}
public void setGroup(Group group) {
this.group = group;
}
@Id
@GeneratedValue
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;
}
}

6、多对多单向

@Entity
public class Student {
private int id;
private String name;
@Id
@GeneratedValue
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;
}
}

@Entity
public class Teacher {
private int id;
private String name;
private Set<Student> students = new HashSet<Student>();
@Id
@GeneratedValue
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;
}
@ManyToMany
@JoinTable(name="t_s",
joinColumns={@JoinColumn(name="teacher_id")},
inverseJoinColumns={@JoinColumn(name="student_id")}
) //改变中间表的名字和字段名字
public Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}
}

7、多对多双向

@Entity
public class Student {
private int id;
private String name;
private Set<Teacher> teachers = new HashSet<Teacher>();
@ManyToMany(mappedBy="students")
public Set<Teacher> getTeachers() {
return teachers;
}
public void setTeachers(Set<Teacher> teachers) {
this.teachers = teachers;
}
@Id
@GeneratedValue
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;
}
}

@Entity
public class Teacher {
private int id;
private String name;
private Set<Student> students = new HashSet<Student>();
@Id
@GeneratedValue
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;
}
@ManyToMany
@JoinTable(name="t_s",
joinColumns={@JoinColumn(name="teacher_id")},
inverseJoinColumns={@JoinColumn(name="student_id")}
)
public Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}
}

注解意思介绍
a) @Entity 映射一个实体类
@Table　指定关联的表

b) @Id 映射OID

c) @GeneratedValue 指定OID的生成策略

@GeneratedValue的属性strategy指定生成策略，

IDENTITY（自增长方式，如mysql）

SEQUENCE (序列方式，如oracle)

TABLE （表方式，该方式便于数据库移植，但效率不高，主键的值是从这个表中取得的。）

AUTO （自动方式，该方式会把主键生成交给JPA的实现者来决定，Hibernate会根据底层数据库选择合适的方 式，如果用这种方式，可以不写，默认如此）

例如：@GenericGenerator(name="uuid_s",strategy="uuid")

d) @Version 映射版本号属性

e) @Column 指定属性对应的列的信息

f) @Temporal 指定日期时间的类型(TIMESTAMP,DATE,TIME)

g) 简单属性可以不用注解。默认就是@Basic

h) @Transient 指定属性不需要映射

i) 复杂属性：关联，继承，组件，联合主键，集合