使用Hibernate3实现分页功能

参考资料:

http://blog.csdn.net/zhjb1025/archive/2006/04/19/668631.aspx

http://www.cnblogs.com/HuaiHuai/archive/2005/08/09/211062.html

整理的代码如下：

Page.java接口

package org.domain.scrm4u.helper;

import java.util.List;

public interface Page {

boolean isFirstPage();

boolean isLastPage();

boolean hasNextPage();

boolean hasPreviousPage();

int getLastPageNumber();

List<?> getThisPageElements();

int getTotalNumberOfElements();

int getThisPageFirstElementNumber();

int getThisPageLastElementNumber();

int getNextPageNumber();

int getPreviousPageNumber();

int getPageSize();

int getPageNumber();

}

ListPage.java实现：

package org.domain.scrm4u.helper.impl;

import java.util.List;

import org.domain.scrm4u.helper.Page;

public class ListPage implements Page {

private List<?> elements;

private int pageSize;

private int pageNumber;

public ListPage(List<?> elements, int pageNumber, int pageSize) {

this.elements = elements;

this.pageSize = pageSize;

this.pageNumber = pageNumber;

if (Integer.MAX_VALUE == this.pageNumber) this.pageNumber = (getTotalNumberOfElements() / this.pageSize);

}

public boolean isFirstPage() {

return getPageNumber() == 0;

}

public boolean isLastPage() {

return getPageNumber() >= getLastPageNumber();

}

public boolean hasNextPage() {

return ((getPageNumber() + 1) * getPageSize()) < (getTotalNumberOfElements() + 1);

}

public boolean hasPreviousPage() {

return getPageNumber() > 0;

}

public int getLastPageNumber() {

double totalResults = new Integer(getTotalNumberOfElements()).doubleValue();

return new Double(Math.floor(totalResults / getPageSize())).intValue();

}

public List<?> getThisPageElements() {

final int start = getPageNumber() * getPageSize();

return elements.subList(

Math.min(start, getTotalNumberOfElements() + 1),

Math.min(start + getPageSize(), getTotalNumberOfElements() + 1)

);

}

public int getTotalNumberOfElements() {

return elements.size() - 1;

}

public int getThisPageFirstElementNumber() {

return getPageNumber() * getPageSize() + 1;

}

public int getThisPageLastElementNumber() {

int fullPage = getThisPageFirstElementNumber() + getPageSize() - 1;

return getTotalNumberOfElements() < fullPage ? getTotalNumberOfElements() : fullPage;

}

public int getNextPageNumber() {

return getPageNumber() + 1;

}

public int getPreviousPageNumber() {

return getPageNumber() - 1;

}

public int getPageSize() {

return pageSize;

}

public int getPageNumber() {

return pageNumber;

}

}

HibernatePage.java实现：

package org.domain.scrm4u.helper.impl;

import java.util.List;

import org.domain.scrm4u.helper.Page;

import org.hibernate.HibernateException;

import org.hibernate.Query;

import org.hibernate.ScrollMode;

import org.hibernate.ScrollableResults;

public class HibernatePage implements Page {

protected List<?> elements;

protected int pageSize;

protected int pageNumber;

protected int totalElements = 0;

private ScrollableResults scrollableResults;

private HibernatePage(int pageNumber, int pageSize) {

this.pageNumber = pageNumber;

this.pageSize = pageSize;

}

public boolean isFirstPage() {

return getPageNumber() == 0;

}

public boolean isLastPage() {

return getPageNumber() >= getLastPageNumber();

}

public boolean hasNextPage() {

return elements.size() > getPageSize();

}

public boolean hasPreviousPage() {

return getPageNumber() > 0;

}

public int getLastPageNumber() {

double totalResults = new Integer(getTotalNumberOfElements()).doubleValue();

return new Double(Math.floor(totalResults / getPageSize())).intValue();

}

public List<?> getThisPageElements() {

return hasNextPage() ? elements.subList(0, getPageSize()) : elements;

}

public int getTotalNumberOfElements() {

return totalElements;

}

public int getThisPageFirstElementNumber() {

return getPageNumber() * getPageSize() + 1;

}

public int getThisPageLastElementNumber() {

int fullPage = getThisPageFirstElementNumber() + getPageSize() - 1;

return getTotalNumberOfElements() < fullPage ? getTotalNumberOfElements() : fullPage;

}

public int getNextPageNumber() {

return getPageNumber() + 1;

}

public int getPreviousPageNumber() {

return getPageNumber() - 1;

}

public int getPageSize() {

return pageSize;

}

public int getPageNumber() {

return pageNumber;

}

public static HibernatePage getScrollPage(Query query, int pageNumber, int pageSize, ScrollMode scrollMode) {

HibernatePage sp = new HibernatePage(pageNumber, pageSize);

try {

sp.scrollableResults = query.scroll(scrollMode);

if(scrollMode == ScrollMode.SCROLL_SENSITIVE){

sp.scrollableResults.last();

sp.totalElements = sp.scrollableResults.getRowNumber();

} else {

sp.totalElements = sp.calculateTotalElementsByList(query);

}

sp.determineElements(query);

} catch (HibernateException e) {

e.printStackTrace();

}

return sp;

}

private void determineElements(Query query) throws HibernateException {

if (Integer.MAX_VALUE == this.pageNumber) this.pageNumber = (getTotalNumberOfElements() / this.pageSize);

elements = query.setFirstResult(this.pageNumber * this.pageSize).setMaxResults(this.pageSize + 1).list();

}

private int calculateTotalElementsByList(Query query) throws HibernateException {

return query.list().size();

}

}

简单分析一下：

ListPage实现需要把查询的结果集全部取出来。

我们着重还是分析一下HibernatePage的实现。

测试代码如下：

import java.io.IOException;

import java.sql.SQLException;

import java.util.List;

import org.hibernate.Query;

import org.hibernate.ScrollMode;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.AnnotationConfiguration;

import org.hibernate.cfg.Configuration;

import org.domain.scrm4u.helper.Page;

import org.domain.scrm4u.helper.impl.HibernatePage;

import org.domain.scrm4u.entity.TPsn;

public class BusinessService {

public static void main(String[] args) throws IOException, SQLException {

Configuration config = new AnnotationConfiguration().configure();

SessionFactory sessionFactory = config.buildSessionFactory();

Session session = sessionFactory.openSession();

String Hql = "from TPsn";

Query query = session.createQuery(Hql);

Page page = HibernatePage.getScrollPage(query, 0, 10, ScrollMode.SCROLL_SENSITIVE);

List<?> list = page.getThisPageElements();

for (int i = 0; i < list.size(); i++) {

TPsn psn = (TPsn)list.get(i);

System.out.println(psn.getPsnNo() + "/t" + psn.getPsnPnm() + "/t" + psn.getPsnBrthDt());

}

session.close();

sessionFactory.close();

}

}

测试中发现：

使用ScrollMode.SCROLL_SENSITIVE比ScrollMode.FORWARD_ONLY在性能上要快很多。具体选择要看使用的JDBC驱动是否支撑了，支持scroll的话就可以使用ScrollableResults类来处理结果集了。

当然，我们还可以配合缓存技术让翻页更有效率。

关于缓存请参看http://blog.csdn.net/kunshan_shenbin/archive/2008/09/03/2874992.aspx。