Pagination Problem

[vipul John]

Hi

I had 4000+ records. I already worked on a kind of pagination where for every page number, request hits the database. I want to
modify the design .

First i want store 300 records in arraylist from database. i will show 25 records for each page number. so for each page click, request will not hit the database. It fetches records from arraylist. If arraylist get scarce of records then another 300 records should be fetched and then displayed.

Any one having ideas or suggestions, Please share....:)


Thanks
Vipul Kumar

[Bear Bibeault]

Sounds like a simple matter of book-keeping to me. You just need to keep track of what you have on hand and what you have already shown.

Give the code a try and post with specific problems you are having with it.

[vipul John]

Thanks Bear


This is my Action Class code.

public class PaginationAction extends Action {

	public ActionForward execute(ActionMapping mapping,ActionForm form,HttpServletRequest request,HttpServletResponse response)
	{
		List analysisList = new ArrayList();
		List subList = new ArrayList();
		String target = "";
		int low,high;
		int page = 1;
		int recordsPerPage = 29;
		String pageNo = request.getParameter("page");
		try
		{
			if(pageNo!=null && !pageNo.equals(""))
			{
				page = Integer.parseInt(pageNo);
				
			}
				
			PaginationDao dao = new PaginationDao();
			HttpSession session = request.getSession();
			analysisList = (List)session.getAttribute("analysisList");
			if(analysisList==null)
				analysisList = dao.getAnalysisList(0, 300);
			PaginationUtil util = new PaginationUtil(analysisList,recordsPerPage);
			int noOfPagesPerPage = util.computedPageCount();
			System.out.println("page===> "+page+" No of pages: "+noOfPagesPerPage);
			if(util.checkNextIndex(page,analysisList))
			{
				int fromIndex = util.getFirstIndexForPage(page);
				analysisList = dao.getAnalysisList(fromIndex, fromIndex+299);
				
			}
			subList = util.getListForPage(page);
			int totalAnalysisCount = dao.getTotalAnalysisCount();
			int noOfPagesForDB = util.computedPageCount(totalAnalysisCount);
			System.out.println(totalAnalysisCount+" total count "+noOfPagesForDB);
			if(subList.size()>0)
			{ 
				target  = "analysisPage";
				request.setAttribute("subList", subList);
				request.setAttribute("analysisList", analysisList);
				request.setAttribute("noOfPagesPerPage", noOfPagesPerPage);
				request.setAttribute("noOfPagesForDB", noOfPagesForDB);
				request.setAttribute("currentPage", page);
			}else
			{
				target  = "norecords";
			}
		}catch(Exception e)
		{
			e.printStackTrace();
		}
		return mapping.findForward(target);
	}

}

This is PaginationUtil class which supports ....

public class PaginationUtil {

	private List list;
	private int fullListSize;
	private int itemsInPage;
	private int pageCount;
	public PaginationUtil(List fullList,int itemsInPage)
	{
		this.list = fullList;
		this.fullListSize = fullList.size();
		System.out.println(this.fullListSize);
		this.itemsInPage = itemsInPage;
		this.pageCount = computedPageCount();
	}
	
	
	public int computedPageCount()
    {
        int size = this.fullListSize;
        
        int result = computedPageCount(size);
        
        return result;
    }
	
	public int computedPageCount(int totalAnalysisCount)
    {
        int size = totalAnalysisCount;
        
        int div = size / this.itemsInPage;
        int result = (size % this.itemsInPage == 0) ? div : div + 1;

        return result;
    }
	
	
	 public int getFirstIndexForPage(int pageNumber)
	    {
	        int retval = (pageNumber - 1) * this.itemsInPage;
	        return retval >= 0 ? retval : 0;
	    }
	 public int getLastIndexForPage(int pageNumber)
	    {
		 int result = getFirstIndexForPage(pageNumber) + this.itemsInPage - 1;
	        return result;
	    }
	 
	 public boolean checkNextIndex(int pageNumber,List partialList)
	 {
		 int lastIndex = getLastIndexForPage(pageNumber);
		 System.out.println(lastIndex+" last index and partial list "+partialList.size());
		 if(lastIndex>partialList.size())
			 return true;
		 return false;
	 }
	 
	 
	 public List getListForPage(int pageNumber)
	    {
	        

	        int firstIndex = getFirstIndexForPage(pageNumber);
	        int lastIndex = getLastIndexForPage(pageNumber);

                return this.list.subList(firstIndex, lastIndex + 1);
	        
	    }
}

My Dao class:

public class PaginationDao {

	public List getAnalysisList(int low,int high)
	{
		List analysisList = new ArrayList();
		Connection con = null;
		Statement stmt = null;
		ResultSet rs = null;
		try
		{
			Class.forName("oracle.jdbc.driver.OracleDriver");
			con = DriverManager.getConnection("jdbc:oracle:thin:@192.168.200.17:1521:testdb","acebpo","acebpo");
			stmt = con.createStatement();
			String query = "SELECT ROWNUM, ac_sno FROM (SELECT ROWNUM xx, ac_sno FROM m_ace_analysisinfo) WHERE xx between "+low+" and "+high+"";
			System.out.println("query===> "+query);
			rs = stmt.executeQuery(query);
			System.out.println();
			analysisList = rsToArrayList(rs);
			System.out.println("analysisList.size()==> "+analysisList.size());
			return analysisList;
		}catch(ClassNotFoundException e)
		{
			e.printStackTrace();
		}
		catch(SQLException e)
		{
			e.printStackTrace();
		}
		return analysisList;
	}	
		
		
		public static ArrayList rsToArrayList(ResultSet resultSet)
		  {
		    ArrayList arrayList = new ArrayList();
		    if (resultSet!=null)
		    {
		      try
		      {
		        ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
		        
		        while(resultSet.next())
		        {
		        
		          Hashtable hashtable = new Hashtable();
		          for (int i=1;i<=resultSetMetaData.getColumnCount();i++)
		          {
		           
		            if (resultSet.getObject(i)==null)
		              hashtable.put(resultSetMetaData.getColumnName(i),"");
		            else
		              hashtable.put(resultSetMetaData.getColumnName(i),resultSet.getObject(i));              
		          }
		          
		          arrayList.add(hashtable);
		          
		        }
		      }
		      catch(SQLException sqle)
		      {
		       
		        sqle.printStackTrace();
		      }
		    }
		    return arrayList;
		  }
	public int getTotalAnalysisCount()
	{
		Connection con = null;
		Statement stmt = null;
		ResultSet rs = null;
		try
		{
			Class.forName("oracle.jdbc.driver.OracleDriver");
			con = DriverManager.getConnection("jdbc:oracle:thin:@192.168.200.17:1521:testdb","acebpo","acebpo");
			stmt = con.createStatement();
			rs = stmt.executeQuery("select count(*) from M_ACE_ANALYSISINFO");
			while(rs.next())
			{
				return rs.getInt(1);
			}
		}catch(Exception e)
		{
			e.printStackTrace();
		}
		return 0;
	}
}

In Dao code there is duplicate code. I mean class loading and getting connection. After completing the whole thing then i will modify them. Please check the logic...

I am getting ArrayIndexOutOfBoundsException.

java.lang.IndexOutOfBoundsException: toIndex = 319
	at java.util.SubList.<init>(Unknown Source)
	at java.util.RandomAccessSubList.<init>(Unknown Source)
	at java.util.AbstractList.subList(Unknown Source)
	at com.pagination.PaginationUtil.getListForPage(PaginationUtil.java:74)
	at com.pagination.actions.PaginationAction.execute(PaginationAction.java:54)
	at org.apache.struts.chain.commands.servlet.ExecuteAction.execute(ExecuteAction.java:58)
	at org.apache.struts.chain.commands.AbstractExecuteAction.execute(AbstractExecuteAction.java:67)
	at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
	at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
	at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305)
	at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
	at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
	at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
	at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

my JSP page

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1" import="java.util.List,java.util.ArrayList"%>
<%@taglib uri="http://struts.apache.org/tags-logic" prefix="logic"%>  
  <%@taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Pagination</title>
</head>
<body>
<%
List list = (List)request.getAttribute("analysisList");
System.out.println("list in jsp-===:> "+list);
session.setAttribute("analysisList",list);
%>
<table>
<tr><td>Name</td></tr>
<logic:iterate name="subList" id="analysis" scope="request" indexId="i">
<tr><td><bean:write name="analysis" property="AC_SNO"/></td></tr>


</logic:iterate>
</table>


<%--For displaying Previous link except for the 1st page --%>
<%
int currentPage = Integer.parseInt(request.getAttribute("currentPage").toString());
System.out.println(currentPage);
if(currentPage!=1)
{%>
	<a href="analysis.do?page=${currentPage - 1}">Previous</a>
<%}
%>

	
 	
    
    
    
    <%
int noOfPagesPerPage = Integer.parseInt(request.getAttribute("noOfPagesPerPage").toString());
    System.out.println(noOfPagesPerPage);
if(currentPage<noOfPagesPerPage)
{%>
	<a href="analysis.do?page=${currentPage + 1}">Next</a>
<%}
%>
 
</body>
</html>

I used scriptlets in my jsp code. Please ignore it. Anyway i will change the code. I am more concentrating on the pagination . If pagination get succeed then i will change the scriptlet code.

For the first time list is iterating fine. after first 300 records pagination , i will fetch next 300 records from database. fetched records iam storing them in arraylist from index 0 to 299. I am calculating fromIndex and toIndex (i.e. sublist for pagination) based on pageNumber. based on page number fromIndex and toIndex values are some 290 to 318. But in the arraylist index is from 0 to 300.

This clearly states that my design is missing something. Please correct this and share your ideas to generalize it.

Thanks,
Vipul Kumar.