title: getAsString() jsf customed converter fails to convert object
body: <p>I created a custom converter for jsf. The getAsObject() works perfect but the getAsString() is returning an exception. I am not really sure where the problem is, and I have tried converting the object to string in different ways, but it keeps on returning exception.</p>
  
  <p>This my converters code:</p>
  
  <pre><code>    @Named
  public class ProductConverter implements Converter{
  
      @EJB
      private ProductEJB productEjb;
  
      @Override
      public Object getAsObject(FacesContext context, UIComponent component, String value) {
          if(value== null )
          {
              throw new ConverterException("There was an error at getAsObject()");
          }
  
          int id = Integer.parseInt(value);
          return productEjb.findProductById(id);
      }
  
      @Override    
      public String getAsString(FacesContext context, UIComponent component, Object value) {        
  
          if (value == null || value.equals("")) 
          {
              return "";            
          }
          else
          {
              Integer id = ((Product)value).getProduct_id();
              return String.valueOf(id);
          }
  
      }
  
  }
  </code></pre>
  
  <p>This is the Product class (Getters/Setters/equals()/hash() excluded for simplicity):</p>
  
  <pre><code>@Entity
  @NamedQueries({
      @NamedQuery(name="findAllProducts", query = "SELECT p from Product p")
  
  })
  public class Product implements Serializable
  {
      private static final long serialVersionUID = 1L;
  
      @Id @GeneratedValue(strategy= GenerationType.AUTO)
      private int product_id;
      private String name;
      private String description;
      protected byte[] imageFile;
      private Float price;
      @Temporal(TemporalType.TIMESTAMP)
      private Date dateAdded;        
      @ManyToOne
      private Category category_fk;
      @ManyToOne
      private SaleDetails saleDetails_fk;
  </code></pre>
  
  <p>This is stack I'm getting:</p>
  
  <pre><code>java.lang.NumberFormatException: For input string: ""
      at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
      at java.lang.Integer.parseInt(Integer.java:504)
      at java.lang.Integer.parseInt(Integer.java:527)
      at com.lv.Controllers.Converters.ProductConverter.getAsObject(ProductConverter.java:30)
      at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getConvertedValue(HtmlBasicInputRenderer.java:171)
      at javax.faces.component.UIViewParameter.getConvertedValue(UIViewParameter.java:394)
      at javax.faces.component.UIInput.validate(UIInput.java:960)
      at javax.faces.component.UIInput.executeValidate(UIInput.java:1233)
      at javax.faces.component.UIInput.processValidators(UIInput.java:698)
      at javax.faces.component.UIViewParameter.processValidators(UIViewParameter.java:273)
      at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
      at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
      at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1172)
      at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76)
      at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
      at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
      at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
      at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
      at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
      at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
      at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
      at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
      at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
      at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
      at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
      at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
      at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
      at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
      at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
      at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
      at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
      at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
      at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
      at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
      at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
      at java.lang.Thread.run(Thread.java:722)
  </code></pre>
  
  <p>This is the jsf where I am using the converter:</p>
  
  <pre><code>&lt;f:metadata&gt;
      &lt;f:viewParam name="product" value="#{productDelete.product}" converter="#{productConverter}"/&gt;
  &lt;/f:metadata&gt;
  </code></pre>