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