实战分页功能及分析1-功能介绍

这是web开发中一个很常用的功能，下面给出一个示例代码，大家先分析一下有哪些不足，随后会给出我的简单分析。

 

一.简介：

首先从数据库中查询指定数目的记录，例如：业务规定每个页面显示10条记录，则点击“第一页”时，查询第1-10条记录，然后将数据保存到一个DTO中，通常这个DTO保存在request中；同时生成页面对象，设置该对象的属性的值，例如下一页=2，总记录数=(需要查询)，总页数=(总记录数/每页显示的记录数)等等，并将该对象保存到request中。

 

然后，转发到jsp页面，从request中取出业务数据，显示之；取出页面对象数据，之所以需要该对象是因为：页面对象是作为jsp和业务层之间传递参数数据的载体。

 

二.各文件功能简介：

1.PageInfo对象中保存的是页面的一些数据，比如：当前页号，总记录数，总页数等，该对象一般保存在request中，在各层之间传递。

2.PaginationTag是个jsp的标签类，继承了SimpleTagSupport，它有两个属性

  (1.)action: 提供jsp页面来指定处理类的路径

  (2.)pageinfo: 当前页面对象。

3.paginationTag.tld

jsp标签文件，指定了PageInfo标签的属性的规则。

 

4.test.jsp

示例jsp。显示当前页面的信息。

 

 

 三.源文件：

1.PageInfo.java

 

public class PageInfo implements Serializable {
	private int currPageNo = 1; //当前页码
	private int rowCountsEPage = AgentConstants.RS_SIZE_PER_PAGE_DEFALUT; //每页行数
	
	public static int totalRowCounts = -1; //总行数
	public static int totalPageCounts = -1; //总页数
		
	int start = 0;
	private boolean previous;//前一页是否能用
	private boolean next;//后一页是否能用
	private boolean pagination = true;//是否分页
	
	
	public int getCurrPageNo() {
		return currPageNo;
	}
	public int getRowCountsEPage() {
		return rowCountsEPage;
	}
	public static int getTotalRowCounts() {
		return totalRowCounts;
	}
	public static int getTotalPageCounts() {
		return totalPageCounts;
	}
	public int getStart() {
		if (this.start<0) {
            return 0;
        }else {
        	return (currPageNo - 1) * rowCountsEPage;
        }
    }	
	public boolean getPrevious() {
		return previous;
	}
	public boolean getNext() {
		return next;
	}
	public boolean getPagination() {
		return pagination;
	}
	
	

	public void setCurrPageNo(int currPageNo) {
		this.currPageNo = currPageNo;
	}
	public void setRowCountsEPage(int rowCountsEPage) {
		if (rowCountsEPage == 0) {//0-->不分页
			pagination = false;
			totalPageCounts = 1;
			currPageNo = 1;
			previous = false;
			next = false;
		}
		this.rowCountsEPage = rowCountsEPage;
	}
	
	public void setTotalRowCounts(int totalRowCounts) {
		this.totalRowCounts = totalRowCounts;
		
		if (pagination) {
			totalPageCounts = (totalRowCounts % rowCountsEPage == 0) ? (totalRowCounts / rowCountsEPage)
					: (totalRowCounts / rowCountsEPage + 1);
			previous = currPageNo == 1 ? false : true;
			next = currPageNo == totalPageCounts ? false : true;
		}
	}
	
	public void setTotalPageCounts(int totalPageCounts) {
		this.totalPageCounts = totalPageCounts;
	}
	
	public void setPrevious(boolean previous) {
		this.previous = previous;
	}
	public void setNext(boolean next) {
		this.next = next;
	}
	public void setPagination(boolean pagination) {
		this.pagination = pagination;
	}
	
	public String toString() {
		return ToStringBuilder.reflectionToString(this);
	}
}

 

2.PaginationTag.java

 

import java.io.*;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.SimpleTagSupport;

import org.apache.log4j.Logger;

/**
 * 分页标签类
 * @author Administrator
 *
 */
public class PaginationTag extends SimpleTagSupport{
	protected final Logger logger = Logger.getLogger("PaginationTag.class");
	
    private PageInfo pageinfo = null;
    private String action = null;
        
        
    public PageInfo getPageinfo() {
        return pageinfo;
    }
    public void setPageinfo(PageInfo pageinfo) {
        this.pageinfo = pageinfo;
    }    
    
    public String getAction() {
        return action;
    }   
    public void setAction(String action) {
        this.action = action;
    }   
    

    /**
     * 处理分页显示
     */
    public void doTag() throws JspException, IOException {
        JspWriter out = getJspContext().getOut();
        
        int totalpage = getPageinfo().getTotalPageCounts();
        int totalcount = getPageinfo().getTotalRowCounts();
        int pageNo = getPageinfo().getCurrPageNo();
        int nextPageNo = pageNo + 1;
        int prePageNo = pageNo - 1;
        logger.error("** totalpage = " + totalpage);
        logger.error("** totalcount = " + totalcount);
        logger.error("** pageNo = " + pageNo);
        logger.error("** nextPageNo = " + nextPageNo);
        logger.error("** prePageNo = " + prePageNo);
        

        out.println("<table width=\"400\" align=\"center\"  cellPadding=\"0\" cellSpacing=\"0\"> ");
        out.print("<tr >");
        out.println("<td width=47%>共" + totalcount + "条，第" + pageNo + "/" + totalpage + "页</td>");
                
        out.println("<td width=53% align='left'> ");
        if (pageNo > 1) {
            out.println("&<a href=\"#\" onclick=\"submitForm()\" >" );
        }
        out.print("首页");
        out.println("</a> ");
        
        
        if (pageNo > 1) {
            out.println("&<a href=\"#\" onclick=\"submitForm()\" >");
        }
        out.print("上页");
        out.println("</a> ");
        
        
        if (pageNo < totalpage) {
            out.println("&<a href=\"#\" onclick=\"submitForm()\">");
        }
        out.print("下页");
        out.println("</a> ");
        
        
        if (pageNo < totalpage) {
            out.println("<a href=\"#\" onclick=\"submitForm()\">");
        }
        
        out.print("末页");
        out.println("</a> ");
        out.println("</td> </tr> </table>");
      }
}

 

3.paginationTag.tld

 

<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated by Taglib Descriptor Wizard -->
<taglib version="2.0" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd">

  <tlib-version>1.0</tlib-version>
  <short-name>paginationTag</short-name>
  
  <tag>
    <name>page</name>
    <tag-class>cn.lottery.agentmanage.common.pagination.PaginationTag</tag-class>
    <body-content>empty</body-content>
    <attribute>
      <name>pageinfo</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
      <name>action</name>
      <required>false</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
        
  </tag>
</taglib>

 

4. test.jsp

 

PageInfo pageinfo = (PageInfo)request.getAttribute("pageinfo");



<%if(pageinfo != null){%>
  <pagination:page pageinfo="<%=pageinfo%>" action="userBaseInfoQuery.do" />
<%}%>