newsmanager.java

ajax example 经典。。。。。。。。。。。。。。

package com.eamoi.ajax;

import java.io.IOException;
import java.util.*;
import org.jdom.*;
import org.jdom.output.Format;
import org.jdom.output.XMLOutputter;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class NewsManager extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private static final int COUNTAPAGE = 6;
	/**
	 * 服务的总入口
	 */
	public void service (HttpServletRequest request, HttpServletResponse response)throws IOException, ServletException {
		this.getNews(request,response);
	}
	/**
	 * 将所获取的新闻列表输出为客户端可视的XML文档
	 * @param request
	 * @param response
	 * @throws IOException
	 * @throws ServletException
	 */
	private void getNews(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
		int currentPage = 0;
		if(request.getParameter("currentPage")!=null)
			currentPage = Integer.parseInt(request.getParameter("currentPage"));
//		System.out.println("当前页："+String.valueOf(currentPage));
		//获取新闻列表
		NewsService service = new NewsService();
		Collection results = new ArrayList();
		int totalPage = 0;
		try {
			News[] newslist = service.getAllMessage();
			if((newslist!=null)&&(newslist.length!=0)) {
				totalPage = (newslist.length%COUNTAPAGE==0)?(newslist.length/COUNTAPAGE):(newslist.length/COUNTAPAGE+1);
				if(currentPage<=0) currentPage=1;
				if(currentPage>totalPage) currentPage = totalPage;
				for(int i=((currentPage-1)*COUNTAPAGE);i<COUNTAPAGE*currentPage;i++) {
					if(i>=newslist.length) break;
					results.add(newslist[i]);
				}
			}
			//输出为范式良好的XML文档
			response.setContentType("application/xml");
			Document doc = new Document();
			Element root = new Element("list");
			Element e_page = new Element("currentPage").addContent(String.valueOf(currentPage));
			root.addContent(e_page);
			Element e_total = new Element("totalPage").addContent(String.valueOf(totalPage));;
			root.addContent(e_total);
			Element e_newslist = new Element("newslist");
			Iterator iterator = results.iterator();
			for(int i=0;i<results.size();i++) {
				News news = (News)iterator.next();
				Element e_news = new Element("news").setAttribute("id",news.getId());
				e_news.addContent(new Element("title").addContent(news.getTitle()));
				e_news.addContent(new Element("submittime").addContent(news.getSubmittime()));
				e_newslist.addContent(e_news);
			}
			root.addContent(e_newslist);
			doc.addContent(root);
			XMLOutputter outputter = new XMLOutputter(Format.getPrettyFormat().setEncoding("ISO8859-1"));
			outputter.output(doc,response.getWriter());
		}catch(Exception ex) {
			this.handleError(ex);
		}
	}
	/**
	 * 错误处理
	 * @param ex
	 */
	private void handleError(Exception ex) {
		ex.printStackTrace();
		System.out.println(ex.toString());
	}
    /**
     * 处理页面转向
     * @param strForward
     * @param request
     * @param response
     * @throws IOException
     * @throws ServletException
     */
    private void forward(String strForward, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
		RequestDispatcher dispatcher = request.getRequestDispatcher(strForward);
		dispatcher.forward((ServletRequest)request, (ServletResponse)response);
	}
}