Hibernate双向一对一外键关联

设置一对一双向外键关联关系，通过Husband可以找到Wife，也能通过Wife找到Husband

1、编写Husband类，并在Husband中添加Wife的引用 ；
使用Annotation时，将实体类进行注解，@Entity 、@Id；同时添加注解，设置关联关系为@OneToOne ；

package com.hibernate._0700_one2one_bi_fk;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;

/**双向一对一外间关联，*/
@Entity
public class Husband {
private Integer id;
private String name;
private Wife wife; //去参考wife的id，此时wife必须先id

@Id
@GeneratedValue
public Integer getId() {
return id;
}
public String getName() {
return name;
}
@OneToOne //设置关联关系
@JoinColumn(name="wifeId") //指定数据库中的名字，默认为wife_id
public Wife getWife() {
return wife;
}
public void setId(Integer id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setWife(Wife wife) {
this.wife = wife;
}
}

package com.hibernate._0700_one2one_bi_fk;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;

/**双向一对一外间关联，*/
@Entity
public class Husband {
	private Integer id;
	private String name;
	private Wife wife;	  //去参考wife的id，此时wife必须先id

	@Id
	@GeneratedValue
	public Integer getId() {
		return id;
	}
	public String getName() {
		return name;
	}
	@OneToOne    //设置关联关系
	@JoinColumn(name="wifeId")            //指定数据库中的名字，默认为wife_id
	public Wife getWife() {
		return wife;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public void setName(String name) {
		this.name = name;
	}
	public void setWife(Wife wife) {
		this.wife = wife;
	}	
}

2、编写实体类Wife，并在Wife中引用Husband；

package com.hibernate._0700_one2one_bi_fk;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Wife {
private Integer id;
private String name;
private Husband husband;

/** mappedBy="wife"中的这个wife是Husband中的wife属性，表示Husband起主导作用
如果不加，在数据库中Wife表中会生成husband_id这个冗余字段*/

@OneToOne(mappedBy="wife")
public Husband getHusband() {
return husband;
}
@Id
public Integer getId() {
return id;
}
public String getName() {
return name;
}
public void setHusband(Husband husband) {
this.husband = husband;
}
public void setId(Integer id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}

}

package com.hibernate._0700_one2one_bi_fk;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Wife {
	private Integer id;
	private String name;
	private Husband husband;
	
/** mappedBy="wife"中的这个wife是Husband中的wife属性，表示Husband起主导作用
	如果不加，在数据库中Wife表中会生成husband_id这个冗余字段*/
	
	@OneToOne(mappedBy="wife")   
	public Husband getHusband() {
		return husband;
	}
	@Id
	public Integer getId() {
		return id;
	}
	public String getName() {
		return name;
	}
	public void setHusband(Husband husband) {
		this.husband = husband;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public void setName(String name) {
		this.name = name;
	}	
	
}

使用Annotation时，将实体类进行注解，@Entity 、@Id；

同时也设置设置关联关系为@OneToOne，但是此时要加上属性mappedBy属性，

mappedBy="wife"中的这个wife是Husband中的wife属性，表示Husband起主导作用。
如果不加，在数据库中Wife表中会生成husband_id这个冗余字段；

3、编写测试类，生成数据库表，查看表的关系；

4、在xml文件中，在class标签中设置关联关系。
在Husband.hbm.xml 配置文件中介入

<many-to-one name="wife" column="wifeId" unique="true"></many-to-one>
unique="ture" 约束成一对一关联；

在Wife.hbm.xml 中添加

<one-to-one name="husband" property-ref="wife"></one-to-one>

property-ref指的是与之关联的类Husband中的属性wife。

5、总结：

凡是双向关联，mappedBy必设。