应用Hibernate3的DetachedCriteria实现分页查询

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：

java 代码

package com.javaeye.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();

else

return nextIndex;

}

public int getPreviousIndex() {

int previousIndex = getStartIndex() - pageSize;

if (previousIndex < 0)

return 0;

else

return previousIndex;

}

}

render_code();

抽象业务类

java 代码

/**

* Created on 2005-7-12

*/

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;

}

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();

}

}

render_code();

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

文章来源:http://www.javaeye.com/topic/14657