应用Hibernate3的DetachedCriteria实现分页查询

http://www.iteye.com/topic/14657

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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.iteye.common.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();elsereturn nextIndex;}public int getPreviousIndex() {int previousIndex = getStartIndex() - pageSize;if (previousIndex < 0)return 0;elsereturn previousIndex;}}

抽象业务类

/** * Created on 2005-7-12 */package com.iteye.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.iteye.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;}public void save(final Object entity) {getHibernateTemplate().save(entity);}public void persist(final Object entity) {getHibernateTemplate().save(entity);}public void update(final Object entity) {getHibernateTemplate().update(entity);}public void delete(final Object entity) {getHibernateTemplate().delete(entity);}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);}public List findAll(final Class entity) {return getHibernateTemplate().find("from " + entity.getName());}public List findByNamedQuery(final String namedQuery) {return getHibernateTemplate().findByNamedQuery(namedQuery);}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);}public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria) {return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE, 0);}public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria, final int startIndex) {return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE, startIndex);}public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria, final int pageSize,final int startIndex) {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