Hibernate应用One2Many
Hibernate应用One2Many
size=x-large] 1、一对多或多对一（Group&Person 单向）[/size]
一个团队对应多名成员或多名成员对应一个团队，从单向来操作（主要看Annotation注解@）：
package com.sean.model.one2many;
import java.util.Set;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
/**
* 一对多：团队对象
*
* @author Sean 2013-2-26
*
*/
@Entity
@Table(name = "p_group")
public class Group {
private int id;
private String name;
private Set<Person> pset;
@OneToMany
public Set<Person> getPset() {
return pset;
}
public void setPset(Set<Person> pset) {
this.pset = pset;
}
@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;
}
}
注意：@Table(name = "p_group")这里配置了与数据库不同的表名，原因是Hibernate在建立SQL语句时会将我们的Group类名，误解为Group By SQL语句，所以如果这里不这样配置一下就会报错。
package com.sean.model.one2many;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
/**
* 一对多：成员对象
*
* @author Sean 2013-2-26
*
*/
@Entity
public class Person {
private int id;
private String name;
private Group group;
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;
}
}
从这里可以看出一对多或多对一，只需要对为一的那边设置@OneToMany，可想而知，双向的操作就是对为多的那边设置@ManyToOne就可以了，请看下面。
2、一对多或多对一（Group&Person 双向）
一个团队对应多名成员或多名成员对应一个团队，从双向来操作（主要看Annotation注解@）：
Group类：
package com.sean.model.one2many;
import java.util.Set;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
/**
* 一对多：团队对象
*
* @author Sean 2013-2-26
*
*/
@Entity
@Table(name = "p_group")
public class Group {
private int id;
private String name;
private Set<Person> pset;
@OneToMany
public Set<Person> getPset() {
return pset;
}
public void setPset(Set<Person> pset) {
this.pset = pset;
}
@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;
}
}
Person类：
package com.sean.model.one2many;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
/**
* 一对多：成员对象
*
* @author Sean 2013-2-26
*
*/
@Entity
public class Person {
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;
}
}