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package com.bjsxt.oa.web;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;

import com.bjsxt.oa.SystemContext;

public class PagerFilter implements Filter {

	public void destroy() {
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		
		HttpServletRequest httpRequest = (HttpServletRequest)request;
		SystemContext.setOffset(getOffset(httpRequest));
		SystemContext.setPagesize(getPagesize(httpRequest));
		
		try{
			chain.doFilter(request, response);
		}finally{
			//清空ThreadLocal中的值
			SystemContext.removeOffset();
			SystemContext.removePagesize();
		}
		
	}
	
	protected int getOffset(HttpServletRequest request){
		int offset = 0;
		try {
			offset = Integer.parseInt(request.getParameter("pager.offset"));
		} catch (NumberFormatException ignore) {
		}
		return offset;
	}
	
	protected int getPagesize(HttpServletRequest request){
		return 10;
	}

	public void init(FilterConfig arg0) throws ServletException {
	}

}

package com.bjsxt.oa;

public class SystemContext {
	private static ThreadLocal offset = new ThreadLocal();
	private static ThreadLocal pagesize = new ThreadLocal();
	
	public static int getOffset(){
		Integer os = (Integer)offset.get();
		if(os == null){
			return 0;
		}
		return os;
	}
	
	public static void setOffset(int offsetvalue){
		offset.set(offsetvalue);
	}
	
	public static void removeOffset(){
		offset.remove();
	}
	
	public static int getPagesize(){
		Integer ps = (Integer)pagesize.get();
		if(ps == null){
			return Integer.MAX_VALUE;
		}
		return ps;
	}
	
	public static void setPagesize(int pagesizevalue){
		pagesize.set(pagesizevalue);
	}
	
	public static void removePagesize(){
		pagesize.remove();
	}
	
}

package com.bjsxt.oa.manager.impl;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Query;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;

import com.bjsxt.oa.PagerModel;
import com.bjsxt.oa.SystemContext;
import com.bjsxt.oa.manager.SystemException;

public class AbstractManager extends HibernateDaoSupport {
	
	public PagerModel searchPaginated(String hql){
		return searchPaginated(hql,null,SystemContext.getOffset(),SystemContext.getPagesize());
	}
	
	public PagerModel searchPaginated(String hql,Object param){
		return searchPaginated(hql,new Object[]{param},SystemContext.getOffset(),SystemContext.getPagesize());
	}
	
	public PagerModel searchPaginated(String hql,Object[] params){
		return searchPaginated(hql,params,SystemContext.getOffset(),SystemContext.getPagesize());
	}
	
	public PagerModel searchPaginated(String hql,int offset,int pagesize){
		return searchPaginated(hql,null,offset,pagesize);
	}
	 
	public PagerModel searchPaginated(String hql,Object obj,int offset,int pagesize){
		return searchPaginated(hql,new Object[]{obj},offset,pagesize);
	}
	
	/**
	 * 根据HQL语句进行分页查询
	 * @param hql HQL语句
	 * @param params HQL语句带的多个参数值
	 * @param offset 从第几条记录开始查询
	 * @param pagesize 每页显示多少行
	 * @return
	 */
	public PagerModel searchPaginated(String hql,Object[] params,int offset,int pagesize){
		
		//获取记录总数
		String countHql = getCountQuery(hql);
		Query query = getSession().createQuery(countHql);
		if(params != null && params.length > 0){
			for(int i=0; i<params.length; i++){
				query.setParameter(i, params[i]);
			}
		}
		int total = ((Long)query.uniqueResult()).intValue();
		
		//获取当前页的结果集
		query = getSession().createQuery(hql);
		if(params != null && params.length > 0){
			for(int i=0; i<params.length; i++){
				query.setParameter(i, params[i]);
			}
		}
		
		query.setFirstResult(offset);
		query.setMaxResults(pagesize);
		List datas = query.list();
		
		PagerModel pm = new PagerModel();
		pm.setTotal(total);
		pm.setDatas(datas);
		return pm;
	}
	
	/**
	 * 根据HQL语句，获得查找总记录数的HQL语句
	 * 如：
	 * select ... from Orgnization o where o.parent is null
	 * 经过转换，可以得到：
	 * select count(*) from Orgnization o where o.parent is null
	 * @param hql
	 * @return
	 */
	private String getCountQuery(String hql){
		int index = hql.indexOf("from");
		if(index != -1){
			return "select count(*) " + hql.substring(index);
		}
		
		throw new SystemException("无效的HQL查询语句！");
	}
}

package com.bjsxt.oa;

import java.util.List;

public class PagerModel {
	
	/**
	 * 总记录数
	 */
	private int total;
	
	/**
	 * 当前页结果集
	 */
	private List datas;

	public List getDatas() {
		return datas;
	}

	public void setDatas(List datas) {
		this.datas = datas;
	}

	public int getTotal() {
		return total;
	}

	public void setTotal(int total) {
		this.total = total;
	}
}