数据库查询分页问题

private int currentPage;//当前页数
                          private int countRecord;//总记录条数
                          private int countPage;//总页数
                          private int sizePage;//每页记录条数

java.lang.NullPointerException
建议DEBUG下。

Debug 一下，顺便使用简单的测试代码出现NULLPOINTEXCEPTION的地方在哪儿？
建议使用System.out.println("")

本人刚学没多久怎么Debug 调试？

每一个jsp文件都会在应用服务器中编译成相对应的java文件, 你把java文件找出来
然后粘贴出来, 告诉我们发生异常的代码段, 这样就很容易解决问题!

这是编译完的check_jsp.java   只有第一页数据当点击下一页或末页无法继续查询package org.apache.jsp.chap05.usepage;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.sql.*;
import page.*;public final class check_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent {  private static java.util.Vector _jspx_dependants;  public java.util.List getDependants() {
    return _jspx_dependants;
  }  public void _jspService(HttpServletRequest request, HttpServletResponse response)
        throws java.io.IOException, ServletException {    JspFactory _jspxFactory = null;
    PageContext pageContext = null;
    HttpSession session = null;
    ServletContext application = null;
    ServletConfig config = null;
    JspWriter out = null;
    Object page = this;
    JspWriter _jspx_out = null;
    PageContext _jspx_page_context = null;
    try {
      _jspxFactory = JspFactory.getDefaultFactory();
      response.setContentType("text/html;charset=GB2312");
      pageContext = _jspxFactory.getPageContext(this, request, response,
       null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;      out.write("\r\n");
      out.write("\r\n");
      out.write("  \r\n");
      out.write("<a href=\"login.jsp\">返回首页</a>！</h1>\r\n");
      page.pagebean pagebean = null;
      synchronized (session) {
        pagebean = (page.pagebean) _jspx_page_context.getAttribute("pagebean", PageContext.SESSION_SCOPE);
        if (pagebean == null){
          pagebean = new page.pagebean();
          _jspx_page_context.setAttribute("pagebean", pagebean, PageContext.SESSION_SCOPE);
        }
      }
      out.write('\r');
      out.write('\n');
      page.conndb databean = null;
      synchronized (session) {
        databean = (page.conndb) _jspx_page_context.getAttribute("databean", PageContext.SESSION_SCOPE);
        if (databean == null){
          databean = new page.conndb();
          _jspx_page_context.setAttribute("databean", databean, PageContext.SESSION_SCOPE);
        }
      }
      out.write("\r\n");
      out.write("<HTML>\r\n");
      out.write("<title>用户数据</title>\r\n");
      out.write("<BODY>\r\n");


   String s[];
   request.setCharacterEncoding("gb2312");//改变传递时的编码来处理汉字乱码
   String name=request.getParameter("textfield");
   s = name.split(" ");      out.write('\r');
      out.write('\n');         ResultSet rs;
boolean flag = false ;

   String sql="SELECT * FROM da_jnwjb WHERE tmh LIKE '%"+s[0]+"%'  ";
    for(int j=1;j<s.length;j++){
   sql+=" OR tmh LIKE '%"+s[j]+"%'";
   }//拼接SQL语句实现查询S中每一个元素
         rs=databean.executeQuery(sql);         //执行sql语句，使用了javabean conndb中的executeQuery
if(rs.next()){
// 如果有内容，则此处执行，表示查询出来
flag = true ;
}

         String pages=request.getParameter("dipage");  //读取当前的页数
         rs.last();
         int countRecord=rs.getRow();  //得到记录的条数
         int countPageRecord=5;        //设置每页记录条数
         if(pages==null||(pages.trim()).length()==0)   //如果当前页数不存在，也就是初次进入页面
          {
       pagebean.setAll(countRecord,countPageRecord); //参数初始化，使用javabean pagebean中的setall，当前页数设为1
   }
           else
           {
               try
               {
                   pagebean.setCurrentPage(Integer.parseInt(pages));
                   }
               catch(Exception e)
                {
                   out.println("参数不正确！");
                   }
            }
         //当前记录号
         int currentRecord=(pagebean.getCurrentPage()-1)*pagebean.getSizePage();
         if(currentRecord==0)
{
             rs.beforeFirst();
}
         else{
           rs.absolute(currentRecord);
   }
         //显示当前页数据
out.print("<Table Border>");
         out.print("<TR>");
         out.print("<TH width=100>"+"分类号");
         out.print("<TH width=100>"+"全宗号");
         out.print("<TH width=100>"+"页号");
         out.print("<TH width=150>"+"文件题名");
         out.print("<TH width=200>"+"sort1");
         out.print("</TR>");

int i=0;
         while(rs.next())
         {

             out.print("<TR>");
             out.print("<TD >"+rs.getString("flh")+"</TD>");
             out.print("<TD >"+rs.getString("qzh")+"</TD>");
             out.print("<TD >"+rs.getString("yh")+"</TD>");
             out.print("<TD >"+rs.getString("tmh")+"</TD>");
             out.print("<TD >"+rs.getString("sort1")+"</TD>");
             out.print("</TR>") ;
i=i+1;
     if(i>=pagebean.getSizePage()) {
                                break; //当前页显示完，则退出循环
                                                   }}
             out.print("<TR><td colspan=8 align=center>");
             out.print("共"+pagebean.getCountRecord()+"条记录,共"+pagebean.getCountPage()+"页，当前第"+pagebean.getCurrentPage()+"页，每页"+pagebean.getSizePage()+"条记录，");
             if(pagebean.getCurrentPage()==1)//当前是首页
                     ;
             else//当前不是首页
             {
                  out.print("<a href=check.jsp?dipage=1>首页</a>，");
                  out.print("<a href=check.jsp?dipage="+(pagebean.getCurrentPage()-1)+">上一页</a>,");
                  }
             if(pagebean.getCurrentPage()==pagebean.getCountPage())//当前是末页
                    ;
             else//当前不是末页
            {
                  out.print("<a href=check.jsp?dipage="+(pagebean.getCurrentPage()+1)+">下一页</a>,");
                  out.print("<a href=check.jsp?dipage="+pagebean.getCountPage()+">末页</a>");
                  }             out.print("</td></tr>");
             out.print("</Table>");
             databean.freeRs(rs);  //释放rs

      out.write("\r\n");
      out.write("\t\t\t "); if(!flag){ // 登陆成功，应该跳转到success.jsp
      out.write('\r');
      out.write('\n');
      out.write(' ');
      if (true) {
        _jspx_page_context.forward("failure.jsp");
        return;
      }
      out.write('\r');
      out.write('\n'); }      out.write("\r\n");
      out.write("\r\n");
      out.write("</BODY>\r\n");
      out.write("</HTML>\r\n");
    } catch (Throwable t) {
      if (!(t instanceof SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          out.clearBuffer();
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
      }
    } finally {
      if (_jspxFactory != null) _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}

这其实不是一个问题,在ssh中用很简单的方法就能实现,以上写的都不是好的实现

学学ssh这些框架技术吧,因为他们是主流

调试易

数据库查询分页问题

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