我开始就是为了在Hibernate中使用分页才设计这个分页实现的，因为使用Hibernate时，查询后的结果被自动封装到一个List中了，所以使用起来特别方便，这里我做了一个比较庸俗的实现，就是查询参数只适合字符串类型,不过大部分查询还真的只是对字符串操作。
package treeroot.util;
import net.sf.hibernate.HibernateException;
import treeroot.common.dao.AbstractBaseDao;
/**
* @author treerot
* @version 1.0
* @since 2004-9-30
*/
public class HibernatePage extends AbstractPage implements Pageable
{
private String querySql;
private String countSql;
private String[] parameters;
public HibernatePage(int currentPage,String querySql,String countSql,String[] parameters) throws PageException{
this(currentPage,Pageable.DEFAULT_PAGESIZE,querySql,countSql,parameters);
}
public HibernatePage(int currentPage,int pageSize,String querySql,String countSql,String[] parameters) throws PageException
{
super(currentPage, pageSize);
this.querySql = querySql;
this.countSql = countSql;
this.parameters = parameters;
init();
}
protected void init() throws PageException
{
try{
this.count = AbstractBaseDao.queryCount(countSql);
int fromIndex = (this.getCurrentPage() - 1) * this.getPageSize();
int toIndex = Math.min(this.count, fromIndex + this.getPageSize());
this.result = AbstractBaseDao.find(this.querySql,this.parameters,fromIndex,toIndex);
}
catch (HibernateException e)
{
throw new PageException(e.getMessage());
}
}
}
这个类的设计并不是很合理的，因为查询只能接受字符串参数，但是如果只需要字符串参数就足够了。另外查询语句必须是JDBC风格的参数(?), 而不是Hibernate风格的(:=)，你看过Dao里面的代码就知道为什么了。先看一下如何使用吧(一个Dao中的方法):
public Pageable findByName(String name,int currentPage) throws PageException{
String countSql="select count(*) from MyClass as c where c.name like ?";
String querySql="from MyClass as c where c.name like ?";
String[] parameter=new String[]{name};
return new HibernatePage(currentPage,countSql,querySql,parameter);
}
这个方法应该是比较简洁的，这里给出queryCount和find的实现,我对Hibernate的了解比较肤浅，所以下面的方法如果有什么不当的地方还望指出，谢谢！
public static int queryCount(String hql, String[] args) throws HibernateException
{
if (hql == null) throw new NullPointerException();
Object obj = null;
Transaction trans = null;
Session s = null;
try
{
s = HibernateSessionFactory.currentSession();
trans = s.beginTransaction();
Query q = s.createQuery(hql);
if (args != null)
{
for (int i = 0; i < args.length; i++){
q.setString(i, args[i]);
}
}
obj = q.uniqueResult();
trans.commit();
}
catch (HibernateException e)
{
if (trans != null)
{
try{
trans.rollback();
}
catch (HibernateException ex){//no need to care this Exception }
}
throw e;
}
return ((Integer) obj).intValue();
}
public static List find(String hql, String[] args, int fromIndex, int toIndex) throws HibernateException
{
if (hql == null) throw new NullPointerException();
List l = null;
Transaction trans = null;
Session s = null;
try{
s = HibernateSessionFactory.currentSession();
trans = s.beginTransaction();
Query q = s.createQuery(hql);
if (args != null){
for (int i = 0; i < args.length; i++){
q.setString(i, args[i]);
}
}
if (fromIndex > -1){
if (toIndex > fromIndex){
q.setFirstResult(fromIndex);
q.setMaxResults(toIndex - fromIndex);
}
else{
throw new IndexOutOfBoundsException();
}
}
l = q.list();
trans.commit();
}
catch (HibernateException e){
if (trans != null){
try{
trans.rollback();
}
catch (HibernateException ex){ //no need to care this Exception }
}
throw e;
}
return l;
}
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