分页综合应用(分页下拉、当前页、上一页、下一页)

先看需求：

本次练习的数据库sql文件以及代码地址：

http://pan.baidu.com/s/1jIdV7r4

使用Bootstrap构建显示层

JSP+Servlet+EL+JSTL+Dao+MySql+JDBC

主页的jsp代码

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>











新闻列表

	

		

			
		
		

		
	

后台Servlet代码：

package com.zhiqi.web;

import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.zhiqi.dao.NewsDao;
import com.zhiqi.model.News;
import com.zhiqi.model.PageBean;
import com.zhiqi.util.DbUtil;
import com.zhiqi.util.PropertiesUtil;
import com.zhiqi.util.StringUtil;

public class NewsServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private DbUtil dbUtil=new DbUtil();
	private NewsDao newsDao=new NewsDao();
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doPost(req, resp);
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		req.setCharacterEncoding("utf-8");
		String action=req.getParameter("action");
		if("list".equals(action)){//新闻列表
			try {
				newsList(req,resp);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}else if("show".equals(action)){//新闻浏览
			try {
				newsList(req,resp);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}

	private void newsList(HttpServletRequest req, HttpServletResponse resp) throws Exception{
		//分页
		String page=req.getParameter("page");
		if(StringUtil.isEmpty(page)){
			page="1";
		}
		Connection conn=null;
		try {
			conn=dbUtil.getConn();
			int pageCount=0;
			int pageSize=Integer.parseInt(PropertiesUtil.getValue("pageSize"));
			int total=newsDao.newsCount(conn);
			PageBean pageBean=new PageBean(Integer.parseInt(page),Integer.parseInt(PropertiesUtil.getValue("pageSize")));
			ArrayList newsList=newsDao.newsList(conn,pageBean);
			
			//分页总数
			int rowCount=total;
			if(rowCount%pageSize==0){
				pageCount=rowCount/pageSize;
			}else{
				pageCount=rowCount/pageSize+1;
			}
			req.setAttribute("pageCount",pageCount);
			
			//判断
			if(Integer.parseInt(page)<1){
				page="1";
			}
			if(Integer.parseInt(page)>pageCount){
				page=pageCount+"";
			}
			req.setAttribute("page",page);
			
			//分页的下拉
			ArrayList pageNumberList=new ArrayList();;
			for(int i=1;i<=pageCount;i++){
				pageNumberList.add(i+"");
			}
			req.setAttribute("pageNumberList", pageNumberList);
			
			req.setAttribute("newsList", newsList);
			req.setAttribute("mainPage", "news/newsView.jsp");
			req.getRequestDispatcher("main.jsp").forward(req, resp);
		} catch (ClassNotFoundException | SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			try {
				dbUtil.closeConn(conn);
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}

封装的PageBean等工具类有助于简化代码

jsp界面代码：

newView.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>

	

		新闻列表
	
	

	  
			

				${news.title }  -
				『』
			
		  	

		  		${fn:substring(news.memo,0,100) }	
		  	
		  	

		  		详情 >>
		  		

		  	
	  
	
	

	    

	    	
首页
	    	
	    		上一页
	    	
	    	
	    		
上一页
	    	
	    	
	    		
下一页
	    	
	    	
	    		下一页
	    	
		    
尾页
		    

		    	
		    		
		    			第${elem }页
		    		
		    	
		    
		    
当前是第 ${page } 页,一共${pageCount }页
		
	

main.jsp通过引入使得代码层次分明

请求new?action=list后

运行如图：

上一页与下一页的判断使用了标签

遍历下拉列表的option选项，selected的某项使用三目运算符在EL表达式内计算（EL表达式支持三目运算）

下拉列表onchange事件触发时

JavaScript来从新请求后台Servlet

	
		第${elem }页
	

使用JSTL的fn标签的substring()来进行字符串长度的截取

	${fn:substring(news.memo,0,100) }