一个相当好的自定义标签---分页(一)

发现在系统中有好多写得很好的代码,也不知道是哪位前辈留下来的.整理一下...
自定义分页标签库

1:在配置文件中配置

   < taglib >
     < taglib-uri > /WEB-INF/self-html.tld taglib-uri>
    <taglib-location>/WEB-INF/self-html.tld taglib-location>
   taglib>

2:在self-html.tld中page标签的配置

< tag >
         < name > page name>
        <tagclass>com.jbbis.netedu.common.util.taglib.PageTag tagclass>
        <bodycontent>empty bodycontent>
        <info>tag here info>
        <attribute>
        <name>name name>
        <required>true required>
        <rtexprvalue>false rtexprvalue>
         attribute>    
        <attribute>
        <name>pageNum name>
        <required>false required>
        <rtexprvalue>false rtexprvalue>
         attribute>        
        <attribute>
        <name>method name>
        <required>false required>
        <rtexprvalue>false rtexprvalue>
         attribute>    
        <attribute>
        <name>methodValue name>
        <required>false required>
        <rtexprvalue>true rtexprvalue>
         attribute>    
        <attribute>
        <name>form name>
        <required>true required>
        <rtexprvalue>false rtexprvalue>
         attribute>        
        <attribute>
        <name>action name>
        <required>flase required>
        <rtexprvalue>true rtexprvalue>
         attribute>
        <attribute>
        <name>returnLevel name>
        <required>flase required>
        <rtexprvalue>true rtexprvalue>
         attribute>                                    
     tag>

其实从这儿也可以看到在PageTag文件中是一些什么值了...

3:PageTag中的具体操作(精华全部在这儿啦)

/**/ /*
 * Created on 2004-6-25
 *
 */
package  com.jbbis.netedu.common.util.taglib;

import  java.io.IOException;

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

import  com.jbbis.netedu.common.page.NullPage;
import  com.jbbis.netedu.common.page.Page;

/** */ /**
 * @author leo_deng
 *
 */
public   class  PageTag  extends  TagSupport  {
    

    /**//* (non-Javadoc)
     * @see javax.servlet.jsp.tagext.Tag#doStartTag()
     */
    private String name;
    private String pageNum="pageNum";
    private String method="method";
    private String methodValue;
    private String form="mainForm";
    private String action;
    private String returnLevel;
    
    private final int CONST_FIRST=1;
    private final int CONST_NEXT=2;
    private final int CONST_PRIOR=3;
    private final int CONST_LAST=4;
    
    
    
    
    public int doStartTag() throws JspException {
        // TODO Auto-generated method stub
        try{
            JspWriter out = pageContext.getOut() ;
            Page page=(Page)pageContext.getRequest().getAttribute(name);
            if(page==null)
                page=NullPage.instance();
            out.print(getHtml(page.getPageNumber(),page.getPageCount()));
            out.print(getJs(page.getPageNumber(),page.getPageCount()));
            //jspwriter是一个隐含对象，用于向jsp网页输出内容。输出的目标由
            // pagecontext.getout提供
            
            //向jsp网页上下文输出
          }catch(IOException ioException){
            throw new JspException(ioException.getMessage() );
          }//catch
          return(SKIP_BODY);
    }
    /**//*
     * <
     * 
     * 
            
            
            第      页
            
            
            共  1000  页 
        

     *
     *  */
     private  String getJs( int  pageNum, int  totalNum) {
        StringBuffer sb=new StringBuffer();
        sb.append("/n<script language=/"JavaScript/">/n /n</script>");

        return sb.toString();
    }
    private void getGoJs(StringBuffer sb,int pageNum,int totalNum){
        sb.append("function page_go(obj){/n");
        sb.append("var page_number=document.getElementById(/"page_number/");/n");
        sb.append("if( page_number.value != new Number(page_number.value))return alert(/"请输入正确的页数/");/n");
        sb.append("if(page_number.value<1) page_number.value=1;if(page_number.value>");
        sb.append(totalNum);
        sb.append(")page_number.value=");
        sb.append(totalNum);
        sb.append(";/n");
        sb.append("if(page_number.value!="+pageNum+")");
        sb.append("submitForPageNum(obj);/n");
        sb.append("}");
    }
    private StringBuffer printFunction(String function,int pageNumber,int totalNumber,int pageConst){
        StringBuffer sb=new StringBuffer();
        sb.append("/nfunction "+function+"(){");
        sb.append("/nevent.returnValue=false;");
        sb.append(printAction());
        sb.append(printMethod());
        //sb.append("/n"+this.form+".submit();/n}");
        if(totalNumber>1){
            switch(pageConst){
                case CONST_FIRST:
                    if(pageNumber>1){
                        sb.append(printPageNum(String.valueOf(1)));
                        sb.append("/n submitForPageNum("+this.form+");");
                    }
                    break;
                case CONST_LAST:
                    if(pageNumber<totalNumber){
                        sb.append(printPageNum(String.valueOf(totalNumber)));
                        sb.append("/n submitForPageNum("+this.form+");");
                    }
                    break;
                case CONST_PRIOR:
                    if(pageNumber>1){
                        sb.append(printPageNum(String.valueOf(pageNumber-1)));
                        sb.append("/n submitForPageNum("+this.form+");");
                    }
                    break;                        
                case CONST_NEXT:
                    if(pageNumber<totalNumber){
                        sb.append(printPageNum(String.valueOf(pageNumber+1)));
                        sb.append("/n submitForPageNum("+this.form+");");
                    }
                    break;
            }
        }
        
        sb.append("/n}");
        return sb;        
    }
    /**//*
    private StringBuffer printFunction(String function,String pageNum,int pageConst){
        StringBuffer sb=new StringBuffer();
        sb.append("/nfunction "+function+"(){");
        sb.append("/nevent.returnValue=false;");
        sb.append(printAction());
        sb.append(printMethod());
        sb.append(printPageNum(pageNum));
        //sb.append("/n"+this.form+".submit();/n}");

                
                sb.append("/n submitForPageNum("+this.form+");/n}");

        
        sb.append("/n}");
        
        return sb;
    }
    */
    private String printAction(){
        if(this.action!=null)
            return ("/n"+this.form+".action=/""+action+"/";");
        else
            return "";
    }
    private String printMethod(){
        if(this.methodValue!=null)
            return ("/n"+this.form+"."+this.method+".value=/""+this.methodValue+"/";");
        else
            return "";
    }    
    private String printPageNum(String num){
        return "/n"+this.form+"."+this.pageNum+".value=/""+num+"/";";
    }
    private String getHtml(int pageNum,int totalNum){
        StringBuffer sb=new StringBuffer();
        sb.append("/n "page/" href=/"javascript:void(0)/" οnclick=/"page_first()/" > "public/icon/first.gif/" alt=/"首页/" align=/"absmiddle/" border=/"0/" />");
        sb.append("/n "page/" href='javascript:void(0)' οnclick='page_prior()' > "public/icon/previous.gif/" alt=/"上页/" align=/"absmiddle/" border=/"0/" />");
        sb.append("/n第 "page_number/" class=/"page_number/" name=/"pageNum/" value=/"");
        sb.append(String.valueOf(pageNum));
        sb.append("/"><button class='page_go' onclick='page_go(this.form);'> button>页    ");
        //sb.append("" ");
        sb.append("/n "page/" href=/"javascript:void(0)/" οnclick=/"page_next()/"> "public/icon/next_page.gif/" alt=/"下页/" align=/"absmiddle/" border=/"0/"/>");
        sb.append("/n "page/" href=/"javascript:void(0)/" οnclick=/"page_last()/"> "public/icon/last.gif/" alt=/"末页/" align=/"absmiddle/" border=/"0/"/>");
        sb.append("/n共  "page_sum/">");
        sb.append(String.valueOf(totalNum));
        sb.append(" 页");
        return sb.toString();
    }

    /** *//**
     * @return Returns the pageNum.
     */
    public String getPageNum() {
        return pageNum;
    }
... ....(other getter and setter method ^_^)    
}

4:在JSP布面中导入:

<% @ taglib uri="/WEB-INF/self-html.tld" prefix="netedu"  %>

5:在JSP页面中引用:

< form  name ="newsForm"  method ="post"  action ="<%=request.getContextPath() %>/portal/newsAction.page " id="newsForm">

    < div  class ="listbox_page" >
     < netedu:page  name ="page"  form ="newsForm"   />
    div>

  form>

6:page文件

/**//*
 * Created on 2004-6-8
 */
package com.jbbis.netedu.common.page;

import java.util.Collection;


/** *//**
 * 分页表示 Bean
 * 用于前台显示分页数据
 * @author qqs
 */
public interface Page {

  /** *//**
   * whether or not is the last page of list data
   * 是否为最后一页
   * @return
   */
  public boolean isLast();

  /** *//**
   * 是否为第一页
   * @return
   */
  public boolean isFirst();

  /** *//**
   * List of page data
   * @return Page data
   */
  public Collection getData();
  
  /** *//**
   * List of page data
   * @return Page data
   */
  public void setData(Collection data);

  /** *//**
   * 当前页数
   * @return Page Number
   */
  public int getPageNumber();

  /** *//**
   * Next page number
   * if current page  is the first page then
   *   return 0;
   * else
   *   return pageNumber+1;
   * 下一页的页数
   * 
   * @return next page number
   */
  public int getNextPageNumber();

  /** *//**
   * 前一页的页数
   * if previous pge lest than last the first page then
   *   return 0
   * esle
   *   return PageNumber - 1
   * @return previous page number
   */
  public int getPrevPageNumber();

  /** *//**
   * Current page size
   * 当前页的记录数
   * @return Current page size
   */
  public int getSize();

  /** *//**
   * Page size
   * 定义的每页的页数
   * @return
   */
  public int getPageSize();
  /** *//**
   * Total pages count
   * 总页数
   * @return Total pages count
   */
  public int getPageCount();

  /** *//**
   * 当前页中第一条记录在数据库中的顺序
   * get index of the first data of the page
   * @return index of the first data of the page
   */
  public int getStartIndex();

  /** *//**
   * get index of the last data of the page
   * 当页的最后一条记录在数据库中的顺序
   * @return index of the first data of the page
   */
  public int getEndIndex();

  /** *//**
   * 总的记录数
   * @return
   */
  public int getTotalSize();

  /** *//**
   * 是否为空页
   * @return
   */
  public boolean isNull();
}

7:其它
7.1
可以注意到在标签的定义文件中用到了名为page_go的css层来美化界面,可能是出于满足不同用户对界面的不同要求所以在此没有对此css定义,你可以在JSP布面中重写此css.这儿有个可以参考一下. 下载
7.2
根据标签的定义可以看到,此page应该放到form中.
7.3
根据在标签库中的

Page page = (Page)pageContext.getRequest().getAttribute(name);

语句,可见page应该在request.setAttribute("pageattribute",page);中定义.

7.4
如何通过对DB的操作得到了page ?通过DB操作可以获得一系统的data(应该注意到了在page文件夹中有个data属性,高人就是高人^_^),当然在得到这些data之前,先可能得进行一系统逻辑处理,比如说当前页码(pagenum),页长(pagesize)等等.通过这些数据就可以得到一个page实例了! ~ ~ : )

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