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
