hibernate一对多

末蓝、 2022-08-17 15:28 133阅读 0赞

今天把ssh中hibernate一对多双向实现了下,贴出来分享下,有不足的,请兄弟们指正.

最主要的两个model  person(1端) score(多端),一个人可能有多个分数.

package com.fk.model;

import java.util.HashSet;  
import java.util.Set;

public class Person \{

private int id;

private String name;

private String phone;

private String address;

private Set<Score> scores = new HashSet<Score>();

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;  
 \}

public String getPhone() \{  
  return phone;  
 \}

public void setPhone(String phone) \{  
  this.phone = phone;  
 \}

public String getAddress() \{  
  return address;  
 \}

public void setAddress(String address) \{  
  this.address = address;  
 \}

public Set<Score> getScores() \{  
  return scores;  
 \}

public void setScores(Set<Score> scores) \{  
  this.scores = scores;  
 \}

package com.fk.model;

public class Score \{

private int id;

private String scorename;

private int scorevalue;

private Person person;

public int getId() \{  
  return id;  
 \}

public void setId(int id) \{  
  this.id = id;  
 \}

public String getScorename() \{  
  return scorename;  
 \}

public void setScorename(String scorename) \{  
  this.scorename = scorename;  
 \}

public int getScorevalue() \{  
  return scorevalue;  
 \}

public void setScorevalue(int scorevalue) \{  
  this.scorevalue = scorevalue;  
 \}

public Person getPerson() \{  
  return person;  
 \}

public void setPerson(Person person) \{  
  this.person = person;  
 \}

两个实体类,关键是 在person中要设置\`set集合,集合的类型是Set<Score>,在Score中要设置Person.

首先来讲,为啥要设置双向关联阿,其实单项也ok,不过单项关联,在存储的时候,会发出多条update语句,单项的话,就没有必要在score中设置person了,单项存储的话,流程是这样,先存储score,再创建person对象,然后把set集合设置上.这样会发update语句,更新score表中的外键字段.

维护关系等与在一的一端维护,要存1个person,100条score,发1个insert person,100条insertscore,外加100条update,

如果就发100条insert score 1条person多好,这样就必须用到双向关联了.

person.hbm.xml

<hibernate-mapping>  
 <class name="com.fk.model.Person" table="t\_person">  
  <id name="id" column="id" type="int">  
   <generator class="increment" />  
  </id>  
  <property name="name" />  
  <property name="phone"  />  
  <property name="address" />  
  <set name="scores" inverse="true">  
   <key column="person\_id"></key>  
   <one-to-many class="com.fk.model.Score"></one-to-many>  
  </set>  
 </class>  
</hibernate-mapping>

这个注意inverse,说明这个维护关系转到score来搞,不要person搞了,不要发update了

<hibernate-mapping>  
 <class name="com.fk.model.Score" table="t\_score">  
  <id name="id" column="id" type="int">  
   <generator class="increment" />  
  </id>  
  <property name="scorename" column="scorename" type="string" />  
  <property name="scorevalue" column="scorevalue" type="int" />  
  <many-to-one name="person" column="person\_id"></many-to-one>  
 </class>  
</hibernate-mapping>

添加了多对一的标签了,name属性填Score中person属性,column中填person\_id,外键.

保存时候,先存person,不需要知道person的set集合了,再存score,在存score时,把person设置上,就可以了.