[jboss-user] [JBoss Seam] - [newbie] strategy and implementation of nested java.util.Set

[bolke]

Hello,

Before I start out with my question I would like to tell you upfront that I am quite new to Seam/EJB3/JSF, I am certain that parts of my question will be a little offtopic with regards to the forum topic. However I did actually search the net and did not really find a solution: most of the information was outdated (old examples for JSF1) or did not describe something along the lines I wanted to do. So far for the disclaimer ;-)

Software used:

  | JBoss 4.2.1
  | Seam 2.0CR2
  | JSF 1.2
  | 
  | 
  | I am trying to setup an application with generates lists of allowed chemicals for inland vessels. These lists are multilingual, eg a list can be generated in several languages.
  | 
  | The chemical entity looks like this:
  | 
  | 
  |   | @Entity
  |   | public class Chemical implements Serializable {
  |   | 	private static final long serialVersionUID = -81501463360195381L;
  |   | 
  |   | 	private int id;
  |   | 	private int un;
  |   | 	
  |   | 	private int maxFillRate;
  |   | 	private boolean allowPumpRoom;
  |   | 	private TemperatureClass temperatureClass;
  |   | 	private boolean explosionProtection;
  |   | 	private double density;
  |   | 	private String classification;
  |   | 	private int relievePressure;
  |   | 	
  |   | 	private Date updated;
  |   | 	private User updatedby;
  |   | 	
  |   | 	private String classificationCode;
  |   | 	private String packageGroup;
  |   | 	
  |   | 	private int bluelights;
  |   | 
  |   | 	transient private boolean removed;
  |   | 	transient private Vector<String> removedBy = new Vector<String>();
  |   | 	
  |   | 	private Set<ChemicalNote> notes;
  |   | 	private Set<Compatibility> compatibility;
  |   | 	private Set<Danger> dangers;
  |   | 	private Set<Equipment> equipment;
  |   | 	
  |   | 	private SamplingDevice samplingDevice;
  |   | 	
  |   | 	private Set<Translation> translations;
  |   | 
  |   |         // getters and setters
  |   | }
  |   | 
  | 
  | I will focus on the translations part, which is the part I am having trouble with. 
  | 
  | 
  |   | @Entity
  |   | public class Translation implements Serializable {
  |   | 
  |   | 	private static final long serialVersionUID = 3885895866444687204L;
  |   | 
  |   | 	private int id;
  |   | 	
  |   | 	private Chemical chemical;
  |   | 	private String name;
  |   | 	private String language;
  |   | 	
  |   | 	private User updatedby;
  |   | 	private Date updated;
  |   | 
  |   | }
  |   | 
  | 
  | 
  | On the page showing the list of chemicals I would like to show the translation for the name of the chemical. There is a very basic backingbean:
  | 
  | 
  |   | @Name("chemical")
  |   | @Scope(CONVERSATION)
  |   | @Stateful
  |   | public class ChemicalAction implements Serializable, ChemicalInterface {
  |   | 	private static final long serialVersionUID = -5723276978457496053L;
  |   | 
  |   | 	@PersistenceContext
  |   | 	EntityManager em;
  |   | 
  |   | 	@Logger
  |   | 	Log log;
  |   | 	
  |   |     @In
  |   |     FacesContext facesContext;
  |   | 
  |   | 	public java.util.List<Chemical> getChemicals() {
  |   | 		
  |   | 		java.util.List<Chemical> chemicals = 
  |   | 			em.createQuery("select c from Chemical c order by c.un").getResultList();
  |   | 
  |   | 		return chemicals;
  |   | 	}
  |   | 
  |   |         ...
  |   | }
  |   | 
  | 
  | and a little snippet of the xhtml page:
  | 
  | 
  |   | 			<ui:repeat value="#{chemical.chemicals}" var="c">
  |   | 				#{c.id} - #{c.un} - <ui:repeat value="#{c.translations}" var="t">#{t.name}</ui:repeat> <br />
  |   | 			</ui:repeat>
  |   | 
  | 
  | As you can see I try to loop through all the chemicals (which works) and also through all the translations (which does not work - it generates "Property 'name' not found on type org.hibernate.collection.PersistentSet").
  | 
  | Well the question boils down to: How can I select just one item from a java.util.Set based on the current locale? 
  | 
  | Additional questions could be:
  | 
  |   | Does this need a custom component?
  |   | If so, can I add java.util.Set to a tld?
  |   | How to work around this error?
  |   | 
  | 
  | If additional information is needed, I will be happy to provide it. Thanks in advance.

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