How to write a custom converter for <p:pickList>

Question

How can I write a custom converter when working with PrimeFaces components that use a list of POJO? My particular problem is with <p:pickList>

<p:pickList converter="????" value="#{bean.projects}" var="project" 
                             itemLabel="#{project.name}" itemValue="#{project}">

Without a converter I get java.lang.ClassCastException because JSF sets the submitted values with unconverted java.lang.String submitted values.

Answer 1

After research on how to write custom converter, here is the solution.
1. create a Java Class that implement javax.faces.convert.Converter;

public class ProjectConverter implements Converter{

   @EJB
   DocumentSBean sBean;

   public ProjectConverter(){
   }

   public Object getAsObject(FacesContext context, UIComponent component, String value){
     return sBean.getProjectById(value);
     //If u look below, I convert the object into a unique string, which is its id.
     //Therefore, I just need to write a method that query the object back from the 
     //database if given a id. getProjectById, is a method inside my Session Bean that
     //does what I just described
   }

   public String getAsString(FacesContext context, UIComponent component, Object value)     
   {
     return ((Project) value).getId().toString(); //--> convert to a unique string.
   }
}

2. Register your custom converter in faces-config.xml

<converter>
    <converter-id>projectConverter</converter-id>
    <converter-class>org.xdrawing.converter.ProjectConverter</converter-class>
</converter>

3. So now inside Primefaces component, u just do converter="projectConverter". Note that projectConverter is the <convert-id> I just created. So to solve my problem above, I do this:

<p:pickList converter="projectConverter" value="#{bean.projects}" var="project" 
                            itemLabel="#{project.name}" itemValue="#{project}">