jpa - Why is a field of my entity class null? -

i have these 2 entities in 1 many relation:

public class category implements serializable {      private static final long serialversionuid = 1l;     @id     @generatedvalue(strategy = generationtype.identity)     @basic(optional = false)     @column(name = "id")     private short id;     @basic(optional = false)     @column(name = "name")     private string name;     @onetomany(cascade = cascadetype.all, mappedby = "categoryid")     private collection<product> productcollection;      ...      @xmltransient     public collection<product> getproductcollection() {         return productcollection;     }      ... 

and

public class product implements serializable {      ...      @joincolumn(name = "category_id", referencedcolumnname = "id")     @manytoone(optional = false)     private category categoryid;      ... 

generated netbeans. problem when method getproductcollection() called controllerservlet collection of product null.

    @override protected void doget(httpservletrequest request, httpservletresponse response)         throws servletexception, ioexception {      string userpath = request.getservletpath();     category selectedcategory;     collection<product> categoryproducts;      // if category page requested     if (userpath.equals("/category")) {         // categoryid request         string categoryid = request.getquerystring();          if (categoryid != null) {              // selected category             selectedcategory = categoryfacade.find(short.parseshort(categoryid));              // place selected category in request scope             request.setattribute("selectedcategory", selectedcategory);              // products selected category             categoryproducts = selectedcategory.getproductcollection();              // place category products in request scope             request.setattribute("categoryproducts", categoryproducts);         } 

notice null value of productcollection when other fields has been yet initialized

edit 1: declared categoryfacade in controllerservlet applying @ejb annotation

public class controllerservlet extends httpservlet {      @ejb     private categoryfacade categoryfacade; 

edit 2: here persistence.xml document

<?xml version="1.0" encoding="utf-8"?> <persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/xmlschema-instance" xsi:schemalocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">     <persistence-unit name="affablebeanpu" transaction-type="jta">         <jta-data-source>jdbc/affablebean</jta-data-source>         <properties/>     </persistence-unit> </persistence> 

edit 3: i'm using tomee 7.0.2

the collection may loaded lazily :) when object initialized, internal collection may null. try adding fetch=fetchtype.eager field @onetomany annotation.