利用hibernate的DetachedCriteria进行分页

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 com.javaeye.common.util;  
  
import java.util.List;  
  
public class PaginationSupport {  
  
    public final static int PAGESIZE = 30;  //定义一页显示多少行记录
  
    private int pageSize = PAGESIZE;  
  
    private List items;                              //查询的结果集
  
    private int totalCount;                       //一共有多少条适合的记录

  
    private int[] indexes = new int[0];     //查出总记录数后，记录每一页开始的记录号

  
    private int startIndex = 0;                 //当前为第几页

  /*------------------------------三个构造函数*/
    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;  
    }  
  //设置总的记录数，总页数(count)  ,每一页的开始记录号

    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;  
    }  
  //设置起始页的位置
    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];  
        }  
    }  
  //下一页
    public int getNextIndex() {  
        int nextIndex = getStartIndex() + pageSize;  
        if (nextIndex >= totalCount)  
            return getStartIndex();  
        else  
            return nextIndex;  
    }  
  //上一页
    public int getPreviousIndex() {  
        int previousIndex = getStartIndex() - pageSize;  
        if (previousIndex < 0)  
            return 0;  
        else  
            return previousIndex;  
    }  
  
} 

抽象业务类(我们的类要继承这个抽象类， 以便使用里面的类进行分类)

package com.javaeye.common.business;  
  
import java.io.Serializable;  
import java.util.List;  
  
import org.hibernate.Criteria;  
import org.hibernate.HibernateException;  
import org.hibernate.Session;  
import org.hibernate.criterion.DetachedCriteria;  
import org.hibernate.criterion.Projections;  
import org.springframework.orm.hibernate3.HibernateCallback;  
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;  
  
import com.javaeye.common.util.PaginationSupport;  
  
public abstract class AbstractManager extends HibernateDaoSupport {  
  
    private boolean cacheQueries = false;  
  
    private String queryCacheRegion;  
  
    public void setCacheQueries(boolean cacheQueries) {  
        this.cacheQueries = cacheQueries;  
    }  
  
    public void setQueryCacheRegion(String queryCacheRegion) {  
        this.queryCacheRegion = queryCacheRegion;  
    }  
   //保存

    public void save(final Object entity) {  
        getHibernateTemplate().save(entity);  
    }  
  
    public void persist(final Object entity) {  
        getHibernateTemplate().save(entity);  
    }  
  //更新
    public void update(final Object entity) {  
        getHibernateTemplate().update(entity);  
    }  
  //删除
    public void delete(final Object entity) {  
        getHibernateTemplate().delete(entity);  
    }  
   //加载

    public Object load(final Class entity, final Serializable id) {  
        return getHibernateTemplate().load(entity, id);  
    }  
  
    public Object get(final Class entity, final Serializable id) {  
        return getHibernateTemplate().get(entity, id);  
    }  
   //查询全部

    public List findAll(final Class entity) {  
        return getHibernateTemplate().find("from " + entity.getName());  
    }  
   //通过名字查询

    public List findByNamedQuery(final String namedQuery) {  
        return getHibernateTemplate().findByNamedQuery(namedQuery);  
    }  
  //通过参数动态查询
    public List findByNamedQuery(final String query, final Object parameter) {  
        return getHibernateTemplate().findByNamedQuery(query, parameter);  
    }  
  
    public List findByNamedQuery(final String query, final Object[] parameters) {  
        return getHibernateTemplate().findByNamedQuery(query, parameters);  
    }  
   

    public List find(final String query) {  
        return getHibernateTemplate().find(query);  
    }  
  
    public List find(final String query, final Object parameter) {  
        return getHibernateTemplate().find(query, parameter);  
    }  
  //以下是分页查询
    public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria) { 

             //通过detachedCriteri，一页显示记录数,   当前是第几页查询(0)

        return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE, 0);  
    }  
  
    public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria, final int startIndex) {  
           //用户指定当前为第几页

           return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE, startIndex);  
    }  
  
    public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria, final int pageSize,  
            final int startIndex) { 

           //用户同时指定  每页显示的记录数，和  当前页为第几页

        return (PaginationSupport) getHibernateTemplate().execute(new HibernateCallback() {  
            public Object doInHibernate(Session session) throws HibernateException {  
                Criteria criteria = detachedCriteria.getExecutableCriteria(session);  
                int totalCount = ((Integer) criteria.setProjection(Projections.rowCount()).uniqueResult()).intValue();  
                criteria.setProjection(null);  
                List items = criteria.setFirstResult(startIndex).setMaxResults(pageSize).list();  
                PaginationSupport ps = new PaginationSupport(items, totalCount, pageSize, startIndex);  
                return ps;  
            }  
        }, true);  
    }  
  
    public List findAllByCriteria(final DetachedCriteria detachedCriteria) {  
        return (List) getHibernateTemplate().execute(new HibernateCallback() {  
            public Object doInHibernate(Session session) throws HibernateException {  
                Criteria criteria = detachedCriteria.getExecutableCriteria(session);  
                return criteria.list();  
            }  
        }, true);  
    }  
  
    public int getCountByCriteria(final DetachedCriteria detachedCriteria) {  
        Integer count = (Integer) getHibernateTemplate().execute(new HibernateCallback() {  
            public Object doInHibernate(Session session) throws HibernateException {  
                Criteria criteria = detachedCriteria.getExecutableCriteria(session);  
                return criteria.setProjection(Projections.rowCount()).uniqueResult();  
            }  
        }, true);  
        return count.intValue();  
    }  
} 

 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