用hibernate实现分页

Hibernate3 提供了DetachedCriteria，使得我们可以在Web层构造detachedCriteria，然后调用业务层Bean，进行动态条件查询，根 据这一功能，我设计了通用的抽象Bean基类和分页类支持，代码来自于Quake Wang的javaeye-core包的相应类，然后又做了很多修改。

分页支持类：

package org.exam.util;
 
 import java.util.List; 
  
 public class PaginationSupport { 
  
     public final static int PAGESIZE = 30; 
  
     private int pageSize = PAGESIZE; 
  
     private List items; 
  
     private int totalCount; 
  
     private int[] indexes = new int[0]; 
  
     private int startIndex = 0; 
  
     public PaginationSupport(List items, int totalCount) { 
         setPageSize(PAGESIZE); 
                 setTotalCount(totalCount); 
         setItems(items);         
         setStartIndex(0); 
     } 
  
     public PaginationSupport(List items, int totalCount, int startIndex) { 
                 setPageSize(PAGESIZE); 
         setTotalCount(totalCount); 
         setItems(items);         
         setStartIndex(startIndex); 
     } 
  
     public PaginationSupport(List items, int totalCount, int pageSize, int startIndex) { 
                 setPageSize(pageSize); 
         setTotalCount(totalCount); 
         setItems(items); 
         setStartIndex(startIndex); 
     } 
  
     public List getItems() { 
        return items; 
     } 
  
     public void setItems(List items) { 
         this.items = items; 
     } 
  
     public int getPageSize() { 
         return pageSize; 
     } 
  
     public void setPageSize(int pageSize) { 
         this.pageSize = pageSize; 
     } 
  
     public int getTotalCount() { 
         return totalCount; 
     } 
  
     public void setTotalCount(int totalCount) { 
         if (totalCount > 0) { 
             this.totalCount = totalCount; 
             int count = totalCount / pageSize; 
             if (totalCount % pageSize > 0) 
                 count++; 
             indexes = new int[count]; 
             for (int i = 0; i < count; i++) { 
                 indexes[i] = pageSize * i; 
             } 
         } else { 
             this.totalCount = 0; 
         } 
     } 
  
     public int[] getIndexes() { 
         return indexes; 
     } 
  
     public void setIndexes(int[] indexes) { 
         this.indexes = indexes; 
     } 
  
     public int getStartIndex() { 
         return startIndex; 
     } 
  
     public void setStartIndex(int startIndex) { 
         if (totalCount <= 0) 
             this.startIndex = 0; 
         else if (startIndex >= totalCount) 
             this.startIndex = indexes[indexes.length - 1]; 
         else if (startIndex < 0) 
             this.startIndex = 0; 
         else { 
             this.startIndex = indexes[startIndex / pageSize]; 
         } 
     } 
  
     public int getNextIndex() { 
         int nextIndex = getStartIndex() + pageSize; 
         if (nextIndex >= totalCount) 
            return getStartIndex(); 
         else 
             return nextIndex; 
     } 
  
     public int getPreviousIndex() { 
        int previousIndex = getStartIndex() - pageSize; 
         if (previousIndex < 0) 
             return 0; 
         else 
             return previousIndex; 
     } 
  
 } 

service层方法:

package org.exam.service.impl;

import java.util.List;

import org.exam.dao.QuestionDao;
import org.exam.dao.TestQuestionsDao;
import org.exam.model.Question;
import org.exam.model.TestQuestions;
import org.exam.service.QuestionService;
import org.exam.util.PaginationSupport;
import org.hibernate.criterion.DetachedCriteria;
import org.hibernate.criterion.Restrictions;

public class QuestionServiceImpl implements QuestionService{
    private QuestionDao questionDao;
    private TestQuestionsDao testQuestionsDao;
   
    public TestQuestionsDao getTestQuestionsDao() {
        return testQuestionsDao;
    }
    public void setTestQuestionsDao(TestQuestionsDao testQuestionsDao) {
        this.testQuestionsDao = testQuestionsDao;
    }
    public QuestionDao getQuestionDao() {
        return questionDao;
    }
    public void setQuestionDao(QuestionDao questionDao) {
        this.questionDao = questionDao;
    }
    public Integer add(Integer tqid , String title , String hard , String type , Integer score)
    {
        Question q = new Question();
        q.setTq((TestQuestions)testQuestionsDao.findById(tqid).get(0));
        q.setTitle(title);
        q.setHard(hard);
        q.setType(type);
        q.setScore(score);
        questionDao.save(q);
        return q.getId();
    }
    public boolean delete(Integer id)
    {
        questionDao.delete(id);
        return true;
    }
   
    public List<Question> getByTqid(Integer id)
    {       
        List<Question> tmp = questionDao.findByTqId(id);
         return tmp;
    }
    public List<Question> getAll(int pageSize , int index)
    {
        DetachedCriteria detachedCriteria = getDetachedCriteria();
        PaginationSupport  ps = questionDao.findPageByCriteria(detachedCriteria , pageSize , index);   
        return(ps.getItems());
    }
    private DetachedCriteria getDetachedCriteria(String key)
    {
        DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Question.class);
        detachedCriteria.add(Restrictions.like("title", "%"+key+"%"));
        return detachedCriteria;
    }
    private DetachedCriteria getDetachedCriteria()
    {
        DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Question.class);
        return detachedCriteria;
    }
    public List<Question> getByKey(String key , int pageSize , int index)
    {               
        DetachedCriteria detachedCriteria = getDetachedCriteria(key);
        PaginationSupport  ps = questionDao.findPageByCriteria(detachedCriteria , pageSize , index);   
        return(ps.getItems());
    }
    public int getCount(String key)
    {
        DetachedCriteria detachedCriteria = getDetachedCriteria(key);
        PaginationSupport  ps = questionDao.findPageByCriteria(detachedCriteria);
        return ps.getTotalCount();
    }
   
    public int getIndex(String key)
    {
        DetachedCriteria detachedCriteria = getDetachedCriteria(key);
        PaginationSupport  ps = questionDao.findPageByCriteria(detachedCriteria);
        return ps.getStartIndex();
    }
   
    public int getCount()
    {
        DetachedCriteria detachedCriteria = getDetachedCriteria();
        PaginationSupport  ps = questionDao.findPageByCriteria(detachedCriteria);
        return ps.getTotalCount();
    }
   
    public int getIndex()
    {
        DetachedCriteria detachedCriteria = getDetachedCriteria();
        PaginationSupport  ps = questionDao.findPageByCriteria(detachedCriteria);
        return ps.getStartIndex();
    }
   
    public int getNextIndex(String key , int pageSize , int index)
    {
        DetachedCriteria detachedCriteria = null;
        if(key == null)
        {
            detachedCriteria = getDetachedCriteria();
        }
        else
        {
            detachedCriteria = getDetachedCriteria(key);
        }
        PaginationSupport  ps = questionDao.findPageByCriteria(detachedCriteria , pageSize , index);   
        return ps.getNextIndex();
    }
   
    public int getPreviousIndex(String key , int pageSize , int index)
    {
        DetachedCriteria detachedCriteria = null;
        if(key == null)
        {
            detachedCriteria = getDetachedCriteria();
        }
        else
        {
            detachedCriteria = getDetachedCriteria(key);
        }
        PaginationSupport  ps = questionDao.findPageByCriteria(detachedCriteria , pageSize , index);   
        return ps.getPreviousIndex();
    }
   
    public int getLast(String key , int pageSize)
    {
        DetachedCriteria detachedCriteria = null;
        if(key == null)
        {
            detachedCriteria = getDetachedCriteria();
        }
        else
        {
            detachedCriteria = getDetachedCriteria(key);
        }
        PaginationSupport  ps = questionDao.findPageByCriteria(detachedCriteria);   
        int index = ps.getTotalCount()/pageSize + ps.getTotalCount()%pageSize;
        return (index - 1) * pageSize;
    }
   
   
}

用户在web层构造查询条件detachedCriteria，和可选的startIndex，调用业务bean的相应findByCriteria方法，返回一个PaginationSupport的实例ps。

ps.getItems()得到已分页好的结果集
ps.getIndexes()得到分页索引的数组
ps.getTotalCount()得到总结果数
ps.getStartIndex()当前分页索引
ps.getNextIndex()下一页索引
ps.getPreviousIndex()上一页索引