映射同一个类关系-继续
这篇文章是这个的延续职位我有DlUser类，该类的每个对象都可以具有DLFaceBook类，DlFaceBook的每个对象都可以具有被映射为myFriends的Friends。
我正在尝试使用包映射，复合主键和静态内部类将同一类的关系映射为多对多关系。我的代码如下：
public class DlUser{ public DlUser(){}
Long Id;
String FirstName;
String LastName;
....
DlFaceBook fbuser;
//// all requred
getters and setters...
}
Facebook用户类如下所示，您可以看到我具有MyFriends类的对象集合：
public class DlFaceBook {private long dlpId;
private String FbId;
private Collection<MyFriends> Friends;
public DlFaceBook(){}
public void setFbId(String FbId)
{
this.FbId = FbId;
}
public void setFriends(Collection<MyFriends> friends)
{
this.Friends = friends;
}
public Collection<MyFriends> getFriends()
{
return this.Friends;
}
public void setdlpId(long id)
{
this.dlpId = id;
}
public long getdlpId()
{
return this.dlpId;
}
public String getFbId()
{
return this.FbId;
}
}
MyFriends类如下所示：
public class MyFriends { private MyFriendsId myFriendId;
private DlFaceBook me;
private DlFaceBook myFriend;
public MyFriendsId getmyFriendId(){
return this.myFriendId;
}
public void setmyFriendId(MyFriendsId fid){
this.myFriendId = fid;
}
public void setme(DlFaceBook me){
this.me = me;
}
public void setmyFriend(DlFaceBook friend){
this.myFriend = friend;
}
public DlFaceBook getme(){
return this.me ;
}
public DlFaceBook getmyFriend(){
return this.myFriend ;
}
public MyFriends(DlFaceBook me, DlFaceBook user){
this.me = me ;
this.myFriend = user;
this.myFriendId = new MyFriendsId(me.getdlpId(),user.getdlpId());
}
public static class MyFriendsId implements Serializable {
private long meId;
private long myFrId;
// getter's and setter's
public MyFriendsId() {}
public MyFriendsId(long meId, long myFriendId) {
this.meId = meId;
this.myFrId = myFriendId;
}
// getter's and setter's
public long getmeId(){
return this.meId;
}
public void setmeId(Integer id){
this.meId = id;
}
public long getmyFrId(){
return this.myFrId;
}
public void setmyFrId(long id){
this.myFrId = id;
}
}
}
现在的映射：
DlUser.hbm.xml如下，它很简单：
<hibernate-mapping> <class name="DlUser" table="Users">
<id name="Id" column="id" >
<generator class="sequence">
<param name="sequence">userseq</param>
</generator>
</id>
<property name="firstName">
<column name="FirstName" />
</property>
<property name="lastName">
<column name="LastName"/>
</property>
<many-to-one
name="FaceBook"
class="DlFaceBook"
cascade="all"
column="dlpId"
unique="true"
/>
</class>
</hibernate-mapping>
DlFacebook.hbm.xml看起来像这样：
<hibernate-mapping> <class name="DlFaceBook" table="dlfacebook">
<id name="dlpId" type="java.lang.Long" column="dlpId">
<generator class="increment" />
</id>
<property name="fbId">
<column name="fbId" />
</property>
<bag name="Friends">
<key column="me_Id" />
<one-to-many class="MyFriends"/>
</bag>
</class>
</hibernate-mapping>
然后MyFriends.hbm.xml看起来像这样：
<hibernate-mapping> <class name="MyFriends">
<composite-id name="myFriendId" class="MyFriends$MyFriendsId">
<key-property name="meId"/>
<key-property name="myFrId"/>
</composite-id>
<many-to-one name="me" class="DlFaceBook" insert="false" update="false"/>
<many-to-one name="myFriend" class="DlFaceBook" insert="false" update="false"/>
</class>
</hibernate-mapping>
当我执行查询时，出现以下错误：
Hibernate: insert into dlfacebook (fbId, dlpId) values (?, ?)Hibernate: insert into Users (FirstName, LastName, email, twitter, birthday, dlpId, id) values (?, ?, ?, ?, ?, ?, ?)
Hibernate: update MyFriends set me_Id=? where meId=? and myFrId=?
Hibernate: update MyFriends set me_Id=? where meId=? and myFrId=?
Oct 2, 2010 1:21:18 PM org.hibernate.jdbc.BatchingBatcher doExecuteBatch
SEVERE: Exception executing batch:
org.hibernate.StaleStateException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1
at org.hibernate.jdbc.Expectations$BasicExpectation.checkBatched(Expectations.java:85)
at org.hibernate.jdbc.Expectations$BasicExpectation.verifyOutcome(Expectations.java:70)
at org.hibernate.jdbc.BatchingBatcher.checkRowCounts(BatchingBatcher.java:90)
at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:70)
at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:268)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:263)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:183)
at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1206)
at Test.main(Test.java:54)
Oct 2, 2010 1:21:18 PM org.hibernate.event.def.AbstractFlushingEventListener performExecutions
SEVERE: Could not synchronize database state with session
org.hibernate.StaleStateException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1
at org.hibernate.jdbc.Expectations$BasicExpectation.checkBatched(Expectations.java:85)
at org.hibernate.jdbc.Expectations$BasicExpectation.verifyOutcome(Expectations.java:70)
at org.hibernate.jdbc.BatchingBatcher.checkRowCounts(BatchingBatcher.java:90)
at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:70)
at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:268)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:263)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:183)
at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1206)
at Test.main(Test.java:54)
Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1
我看到当我们尝试更新不存在的行时会发生此错误，但是如何使此代码起作用？
回答：
只是Facebook和MyFriends
Notice添加便捷方法和MutableLong（后来，我告诉你为什么使用MutableLong）
public class Facebook { private MutableLong id = new MutableLong();
public Long getId() { return id.longValue(); }
public void setId(Long id) { this.id.setValue(id); }
public MutableLong getIdAsMutableLong() {
return id;
}
private Collection<MyFriends> myFriends = new ArrayList<MyFriends>();
public Collection<MyFriends> getMyFriends() { return myFriends; }
public void setMyFriends(Collection<MyFriends> myFriends) { this.myFriends = myFriends; }
/**
* add convenience method
*/
public void addFriend(Facebook myFriendFacebook) {
myFriends.add(new MyFriends(this, myFriendFacebook));
}
}
public class MyFriends { private MyFriendsId myFriendId;
public MyFriendsId getmyFriendId(){ return this.myFriendId; }
public void setmyFriendId(MyFriendsId myFriendId){ this.myFriendId = myFriendId; }
private Facebook me;
public Facebook getme() { return this.me; }
public void setme(Facebook me){ this.me = me; }
private Facebook myFriend;
public Facebook getmyFriend() { return this.myFriend; }
public void setmyFriend(Facebook friend) { this.myFriend = friend; }
public MyFriends() {}
public MyFriends(Facebook meFacebook, Facebook myFriendFacebook){
this.me = meFacebook ;
this.myFriend = myFriendFacebook;
this.myFriendId = new MyFriendsId(meFacebook.getIdAsMutableLong(), myFriendFacebook.getIdAsMutableLong());
}
public static class MyFriendsId implements Serializable {
private MutableLong meId = new MutableLong();
public Long getMeId() { return this.meId.longValue(); }
public void setMeId(Long id) { this.meId.setValue(id); }
private MutableLong myFriendId = new MutableLong();
public Long getMyFriendId(){ return this.myFriendId.longValue(); }
public void setMyFriendId(Long id) { this.myFriendId.setValue(id); }
public MyFriendsId() {}
public MyFriendsId(MutableLong meId, MutableLong myFriendId) {
this.meId = meId;
this.myFriendId = myFriendId;
}
@Override
public boolean equals(Object o) {
if (!(o instanceof MyFriendsId))
return false;
MyFriendsId other = (MyFriendsId) o;
return new EqualsBuilder()
.append(getMeId(), other.getMeId())
.append(getMyFriendId(), getMyFriendId())
.isEquals();
}
@Override
public int hashCode() {
return new HashCodeBuilder()
.append(getMeId())
.append(getMyFriendId())
.hashCode();
}
}
}
<hibernate-mapping package="br.com._3845772.model.domain"> <class name="User">
<id name="id">
<generator class="native"/>
</id>
<many-to-one cascade="all" class="Facebook" name="facebook"/>
</class>
<class name="Facebook">
<id name="id">
<generator class="native"/>
</id>
<bag cascade="all" name="myFriends">
<key column="ME_FACEBOOK_ID" update="false"/>
<one-to-many class="MyFriends"/>
</bag>
</class>
<class name="MyFriends">
<composite-id class="MyFriends$MyFriendsId" name="myFriendId">
<key-property column="ME_FACEBOOK_ID" name="meId"/>
<key-property column="MY_FRIEND_FACEBOOK_ID" name="myFriendId"/>
</composite-id>
<many-to-one class="Facebook" column="ME_FACEBOOK_ID" insert="false" name="me" update="false"/>
<many-to-one class="Facebook" column="MY_FRIEND_FACEBOOK_ID" insert="false" name="myFriend" update="false"/>
</class>
</hibernate-mapping>
还有这个样本
Facebook meFacebook = new Facebook();Facebook myFriendFacebook = new Facebook();
meFacebook.addFriend(myFriendFacebook);
Session session = sessionFactory.openSession();
session.beginTransaction();
session.save(myFriendFacebook);
session.save(meFacebook);
session.getTransaction().commit();
session.close();
这给了我
Hibernate: insert into Facebook values ( )Hibernate: insert into Facebook values ( )
Hibernate: select myfriends_.ME_FACEBOOK_ID, myfriends_.MY_FRIEND_FACEBOOK_ID from MyFriends myfriends_ where myfriends_.ME_FACEBOOK_ID=? and myfriends_.MY_FRIEND_FACEBOOK_ID=?
Hibernate: insert into MyFriends (ME_FACEBOOK_ID, MY_FRIEND_FACEBOOK_ID) values (?, ?)
几个注意事项
- Hibernate 自动生成复合主键。 设置其值，然后再保存
- 您的数据库 （如果您不知道数据库支持哪种生成器策略，请使用 策略）
- 每个实体
现在为什么用MutableLong（用Long属性 ）而不是Long呢？
Number及其子类（Long为Number）。因此，如果要让Facebook.id（由数据库配置）与其对应的MyFriend $MyFriendId.meId。当数据库设置Facebook.id时，MyFriend $MyFriendId.meId将自动获得其最新值。但是，如果您使用MutableLong，就会发生这种情况。
以上是 映射同一个类关系-继续 的全部内容， 来源链接： utcz.com/qa/401691.html
