null value after convert set to list

[kormem]

Env.:Spring 2.5 Hibernate 3 icefaces 1.7
I try to convert all the products items to product beans depends param_catelog id.
but I always get null value in converting method.
I use two backing bean 1.productbean 2.productlistbean
Here is part of backing bean
#backing bean-productbean

import dao.hibernate.Product;
.
.

public class ProductBean extends BaseBean {
	//the product id
	private String id ;
	
	//the product name
	private String name;
	
	//the product description
	private String description;
	
	//the product price
	private double price;
	
	//the product width
	private double width;
	
	//the product height
	private double height;
	
	//the category ids associated with the product
	private Set productCategories;
	
	//the category id selected by the user on the page
	private List selectedCategoryIds;
.
.
.
.
.
public Set getCategoryIds() {
		return this.productCategories;
	}
	
	public void setCategoryIds(Set newCategoryIds) {
		this.productCategories = newCategoryIds;
		
		if (this.productCategories != null) {
			this.selectedCategoryIds = ViewUtils.convertToList(this.productCategories);
		}
	}
	
	public List getSelectedCategoryIds() {
		return this.selectedCategoryIds;
	}
	
	public void setSelectedCategoryIds(List newSelectedCategoryIds) {
		this.selectedCategoryIds = newSelectedCategoryIds;
		this.productCategories = ViewUtils.convertToSet(selectedCategoryIds);
	}

#backing bean-productlistbean

public class ProductListBean extends BaseBean {
	
	private static final int DEFAULT_PRODUCTS_PER_PAGE = 6;
	
	
	private List productBeans;
	
	
	private List currentProductBeans;
	
	
	private Map productBeansMap;
	
	
	private String currentCategoryId;
	
	
	private String currentCategoryName;
	

	private int productsPerPage;
	
		private int totalPages;
	
	
	private int pageNo;
	
	
	public ProductListBean() {
		this.productBeans = new ArrayList();
		this.currentProductBeans = new ArrayList();
		this.productBeansMap = new HashMap();
		
		this.logger.debug("ProductListBean is created");
	}
	
	
	protected void init() {
		try {
			List products = this.serviceLocator.getCatalogService().getAllProducts();
			//getCatalogService().getAllProducts();
			log.info("products size = " + products.size());
			for (int i=0; i<products.size(); i++) {
				Product product = (Product)products.get(i);
				
				ProductBean productBean = ProductBuilder.createProductBean(product);
				productBean.setServiceLocator(this.serviceLocator);
				
				this.productBeans.add(productBean);
			}
			
			this.currentProductBeans = this.productBeans;
			
			this.setProductsPerPage();
			
			this.buildProductBeansMap();
		} catch (Exception e) {
			String msg = "Could not initialize ProductListBean";
			log.info("Could not initialize ProductListBean", e);
			throw new FacesException(msg, e);
		}
		
		this.log.info("ProductListBean is initialized"+currentProductBeans);
	}

public String searchByCategoryAction() {
		this.currentCategoryId = FacesUtils.getRequestParameter(RequestParamNames.CATEGORY_ID);
		String pageNoString = FacesUtils.getRequestParameter(RequestParamNames.PAGE_NO);
		
		try {
			this.pageNo = Integer.parseInt(pageNoString);
		} catch (Exception e) {
			this.pageNo = 1;
		}
		
		this.totalPages = 0;
		
		this.currentProductBeans = new ArrayList();
		
		this.logger.debug("searchByCategoryAction is invoked");
		log.info("categoryId = " + this.currentCategoryId);
		log.info("pageNo = " + this.pageNo);
		
		if (this.currentCategoryId == null || this.currentCategoryId.equals("")) {
			//get all products, no pagination
			this.currentProductBeans = this.productBeans;
		
			return NavigationResults.PRODUCT_LIST;
		}
		else {
			//catalog
		
			Map categoryProductBeans = (Map)this.productBeansMap.get(currentCategoryId);
			log.info("categoryProductBeans Map = " + categoryProductBeans);
			if (categoryProductBeans != null) {
				this.totalPages = categoryProductBeans.size();
				log.info("total pages = " + this.totalPages);
				List productBeans = (List)categoryProductBeans.get(new Integer(this.pageNo));
				log.info("List productbeans = " + this.productBeans.size());
				if (productBeans != null) {
					this.currentProductBeans = productBeans;
				}
			}
			
			log.info("currentProductBeans size = " + this.currentProductBeans.size());
			
			//set current category name
			this.currentCategoryName = FacesUtils.getApplicationBean().getCategoryName(this.currentCategoryId);
			log.info("currentCategoryName = " + this.currentCategoryName);
			
			return NavigationResults.CATALOG;
		}
	}
private void buildProductBeansMap() {
		log.info("buildProductBeansMap is invoked");
		
		this.productBeansMap = new HashMap();
		
		Map categoryProductsMap = new HashMap();
		
		for (int i=0; i<this.productBeans.size(); i++) {
			ProductBean product = (ProductBean)this.productBeans.get(i);
			log.info("product_buildMap"+product.getId());
			Set categoryIds = product.getCategoryIds();
			log.info("product_categoryIds"+categoryIds);
			Iterator ite = categoryIds.iterator();
			while (ite.hasNext()) {
				String categoryId = (String)ite.next();
				
				if (! categoryProductsMap.containsKey(categoryId)) {
					//new category
					List list = new ArrayList();
					list.add(product);
					categoryProductsMap.put(categoryId, list);
				}
				else {
					List list = (List) categoryProductsMap.get(categoryId);
					list.add(product);
				}
			}
		}
		
		Iterator ite = categoryProductsMap.keySet().iterator();
		
		while (ite.hasNext()) {
			Object category = ite.next();
			
			List productBeans = (List)categoryProductsMap.get(category);
			this.productBeansMap.put(category, this.pagination(productBeans));

****log result****

2009-06-23 11:37:50,173: buildProductBeansMap is invoked
2009-06-23 11:37:50,173: product_buildMapL001
2009-06-23 11:37:50,173: product_categoryIds[]
2009-06-23 11:37:50,173: product_buildMapL002
2009-06-23 11:37:50,173: product_categoryIds[]
2009-06-23 11:37:50,173: product_buildMapL003
2009-06-23 11:37:50,173: product_categoryIds[]
2009-06-23 11:37:50,173: product_buildMapL004
2009-06-23 11:37:50,173: product_categoryIds[]
2009-06-23 11:37:50,173: product_buildMapL005
2009-06-23 11:37:50,173: product_categoryIds[]
2009-06-23 11:37:50,173: product_buildMapL006
2009-06-23 11:37:50,173: product_categoryIds[]
2009-06-23 11:37:50,173: product_buildMapL007
2009-06-23 11:37:50,173: product_categoryIds[]
2009-06-23 11:37:50,173: product_buildMapL008
2009-06-23 11:37:50,173: product_categoryIds[]
2009-06-23 11:37:50,173: ProductListBean is initialized[id=L001 name=Product1, id=L002 name=Product2, id=L003 name=Product3, id=L004 name=Product4, id=L005 name=Product5, id=L006 name=Product6, id=L007 name=Product7, id=L008 name=Product8]
2009-06-23 11:37:50,173: service locator is set
2009-06-23 11:37:50,173: categoryId = 1
2009-06-23 11:37:50,173: pageNo = 1
2009-06-23 11:37:50,173: categoryProductBeans Map = null
2009-06-23 11:37:50,173: currentProductBeans size = 0
2009-06-23 11:37:50,173: currentCategoryName = null

as you known, buildProductBeansMap array has null value. also categoryProductBeans Map = null

so looked the production bean and call ViewUtil pacage
***ViewUtil****

import java.util.Set;
import java.util.HashSet;
import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;


public class ViewUtils {
	/**
	 * Convert a list to a set.
	 * 
	 * @param orig the list to be converted
	 * @return the set converted from the list
	 */
	public static Set convertToSet(List orig) {
		Set result = new HashSet();
		
		if (orig != null) {
			Iterator ite = orig.iterator();
			
			while (ite.hasNext()) {
				result.add(ite.next());
			}
		}
		
		return result;
	}
	
	/**
	 * Convert a set to a list.
	 * @param orig the set to be converted
	 * @return the list converted from the set
	 */
	public static List convertToList(Set orig) {
		List result = new ArrayList();
		
		if (orig != null) {
			Iterator ite = orig.iterator();
			
			while (ite.hasNext()) {
				result.add(ite.next());
			}
		}
		
		return result;
	}
}

would you help me how to fix this problem