Sorry if this is considered spamming the list ....
Speaking of storing stuff in session scope. I've developed what I think is a handy class which I think it useful for
when I want to store something like a search in a session variable.
For instance if I want to page through it ( using displaytags.org (10 out of 10)) or simply if I don't want to fetch
from the database time and time again.
By default the data expires on an hourly basis. And if a different combination of parameters is sent it expires
the cached stuff.
Here is the class
snip= package ie.jestate.struts.client;
import java.util.Date;
/**
* @author Bryan Hunt
*/
//TODO:Perhaps I should be generating a MD5 or something but I can't see a good reason to use any more CPU
public class HashGenerator {
private StringBuffer buffer;
/**
*
*/
public HashGenerator() {
super();
buffer = new StringBuffer(50);
// TODO Auto-generated constructor stub
}
/**
* @param urbanAreas
*/
public void add(Integer[] array,String fieldname) {
for (int i = 0; i < array.length; i++) {
Integer integer = array[i];
buffer.append(integer);
}
buffer.append(fieldname);
buffer.append("-");
} /**
* @param priceRangeStart
*/
public void add(Integer integer,String fieldname) {
// TODO Auto-generated method stub
buffer.append(integer);
buffer.append(fieldname);
buffer.append("-");
}/**
* @return
*/
public String getHash() {
//I append the hour onto the end of the string so that a hash will
//only be good for a max of one hour.
Date date = new Date();
return buffer.toString()+ "-" + new Integer(date.getHours());
}
}
=snip
And here is example usage. snip= /* * Created on 24-Jun-2004 */ package ie.jestate.struts.client;
import ie.jestate.struts.BaseAction;
import java.util.Set;
import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession;
import org.apache.struts.action.ActionForm; import org.apache.struts.action.ActionForward; import org.apache.struts.action.ActionMapping; import org.apache.struts.action.DynaActionForm;
/**
* @author Bryan Hunt
*
*/
public class ForSaleSearchAction extends BaseAction {/* (non-Javadoc)
* @see org.apache.struts.action.Action#execute(org.apache.struts.action.ActionMapping, org.apache.struts.action.ActionForm, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
*/
public ActionForward execute(
ActionMapping actionMapping,
ActionForm actionForm,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
//TODO: Database based initialization of the countries collection
DynaActionForm dynaform = (DynaActionForm) actionForm;
HttpSession session = request.getSession();
String forSalePropertiesSearchCheckSum = (String) session.getAttribute(Constants.FOR_SALE_CHECK_SUM);
String newForSalePropertiesSearchCheckSum = null;
Integer[] urbanAreas = (Integer[]) dynaform.get("urbanAreas");
Integer priceRangeStart = (Integer) dynaform.get("priceRangeStart");
Integer priceRangeEnd = (Integer) dynaform.get("priceRangeEnd");
Integer[] propertyTypes = (Integer[]) dynaform.get("propertyTypes");
HashGenerator hashGenerator = new HashGenerator();
hashGenerator.add(urbanAreas,"urbanAreas");
hashGenerator.add(priceRangeStart,"priceRangeStart");
hashGenerator.add(priceRangeEnd,"priceRangeEnd");
hashGenerator.add(propertyTypes,"propertyTypes");
newForSalePropertiesSearchCheckSum = hashGenerator.getHash();
if(forSalePropertiesSearchCheckSum != null && forSalePropertiesSearchCheckSum.equals(newForSalePropertiesSearchCheckSum)) {
System.out.println("Checksums match");
}
if (forSalePropertiesSearchCheckSum == null
|| !forSalePropertiesSearchCheckSum.equals(newForSalePropertiesSearchCheckSum)){
Set forSaleProperties =
findForSaleProperties(
urbanAreas,
priceRangeStart,
priceRangeEnd,
propertyTypes);
session.setAttribute(Constants.FOR_SALE_PROPERTIES_SEARCH_RESULT, forSaleProperties);
session.setAttribute(
Constants.FOR_SALE_CHECK_SUM,
newForSalePropertiesSearchCheckSum);
// TODO:Add logging functionality
System.out.println("Returning fresh search results");
} else
/*
if (
session.getAttribute("forSalePropertiesSearchCheckSum").equals(
forSalePropertiesSearchCheckSum))
*/
{
//This means that it is the same search, just called again.
//TODO:Add logging functionality
System.out.println("Returning cached search results");
}
//TODO: Decent logging is needed here
System.out.println(forSalePropertiesSearchCheckSum);
System.out.println(newForSalePropertiesSearchCheckSum);
System.out.println(" ---------------------------------------" );
return actionMapping.findForward("success");
}
}
=snip
Christina Siena wrote:
I recently developed an application with a complex UI. One of the pages required querying the database based on user selection and re-displaying the page with the retrieved data and any previous existing user selections. Four different fields can trigger a db query resulting in page re-display and validations can also result in page re-display. Each time the page is re-displayed, the "state" of the page must be "remembered" from the last time it was displayed. (still with me so far?) Most of the data re
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