Hibernate的联合主键

一个项目中，数据库的一个表用了联合主键，以前都是用jdbc来做的，现在要改用hibernate来做，在网上找了些资料，都提到联合主键的问题。大家都不推荐使用联合主键，关键是因为其需要自己手工维护，比较麻烦。数据库已经定好了，由于一些原因没办法更改了，所以只能这样做了。
数据库表：
if exists (select * from dbo.sysobjects where id = object_id('dbo.FRX_TRADE_SEQUENCE') and type = 'U')
drop table [dbo].[FRX_TRADE_SEQUENCE]
GO
CREATE TABLE [dbo].[FRX_TRADE_SEQUENCE](
     [TREASURY_BRANCH_CD]        not null,
     [KEY_DT] [datetime]       not null,
     [SEQ_NUM] [SeqNum]       not null
) on [default]

GO

alter table dbo.FRX_TRADE_SEQUENCE add primary key (TREASURY_BRANCH_CD, KEY_DT)

GO


Model： 共两个，TradeSequence 和 TradeSequenceId。

TradeSequence ：

import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import javax.persistence.Table;

/**
* FrxTradeSequence generated by hbm2java
*/
@Entity
@Table(name = "FRX_TRADE_SEQUENCE")
public class TradeSequence implements java.io.Serializable {

private TradeSequenceId id;
private Integer seqNum;

public TradeSequence() {
}

public TradeSequence(TradeSequenceId id, Integer seqNum) {
this.id = id;
this.seqNum = seqNum;
}

@EmbeddedId
@AttributeOverrides( {
@AttributeOverride(name = "treasuryBranchCd", column = @Column(name = "TREASURY_BRANCH_CD", nullable = false, length = 12)),
@AttributeOverride(name = "keyDt", column = @Column(name = "KEY_DT", nullable = false, length = 23)) })
public TradeSequenceId getId() {
return this.id;
}

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

@Column(name = "SEQ_NUM", nullable = false)
public Integer getSeqNum() {
return this.seqNum;
}

public void setSeqNum(Integer seqNum) {
this.seqNum = seqNum;
}

}

TradeSequenceId ：

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Embeddable;

/**
* FrxTradeSequenceId generated by hbm2java
*/
@Embeddable
public class TradeSequenceId implements java.io.Serializable {

private String treasuryBranchCd;
private Date keyDt;

public TradeSequenceId() {
}

public TradeSequenceId(String treasuryBranchCd, Date keyDt) {
this.treasuryBranchCd = treasuryBranchCd;
this.keyDt = keyDt;
}

@Column(name = "TREASURY_BRANCH_CD", nullable = false, length = 12)
public String getTreasuryBranchCd() {
return this.treasuryBranchCd;
}

public void setTreasuryBranchCd(String treasuryBranchCd) {
this.treasuryBranchCd = treasuryBranchCd;
}

@Column(name = "KEY_DT", nullable = false, length = 23)
public Date getKeyDt() {
return this.keyDt;
}

public void setKeyDt(Date keyDt) {
this.keyDt = keyDt;
}

}


对此表的操作，需求是要根据主键 treasuryBranchCd 和 keyDt 使字段seqNum实现自增。即每次调用时加1.
TradeSequenceId tid = new TradeSequenceId();
tid.setKeyDt(keyDate);
tid.setTreasuryBranchCd(treasuryBranchCd);
TradeSequence ts = new TradeSequence();
ts.setId(tid);

DetachedCriteria criteria = DetachedCriteria.forClass(TradeSequence.class);
criteria.add(Restrictions.idEq(tid));
List list = manager.findByCriteria(criteria);
if(list!=null && list.size()>0)
{
ts = (TradeSequence)(list.get(0));
ts.setSeqNum(ts.getSeqNum()+1);
}
else
{
ts.setSeqNum(new Integer(1));
}
manager.save(ts);

                  System.out.println("返回的SeqNum="+ts.getSeqNum());

在Hibernate3、tomcat6、JDK1.6环境下测试成功。