Handling Java Optional in JXPath object hierachy?

Question

I have an object graph and one of the accessor methods returns a java Optional and as a result my XPath expression stops from that point onwards.

The xpath is data/someData[1]/optionalObject/field

How can I get JXPath to return the actual object rather than the Optional or does JXPath pre date java Optionals and so it will never work?

Answer 1

If anyone is interested I solved the issue with Optional objects by creating a custom NodePointerFactory instance. I could not find any documentation on doing this, but I hope the below helps anyone who comes across this problem as well.

Steps are as follows.

1. Register the instance with the call

   JXPathContextReferenceImpl.addNodePointerFactory(new OptionalHandlerPointerFactory());

2. The implementation

   private static class OptionalHandlerPointerFactory implements NodePointerFactory {

   @Override
   public int getOrder() {
       //Insert before the bean pointer factory
       return BeanPointerFactory.BEAN_POINTER_FACTORY_ORDER - 1;
   }
   
   @Override
   public NodePointer createNodePointer(QName name, Object bean, Locale locale) {
       if(bean != null && bean instanceof Optional) {
           if(!((Optional)bean).isPresent()) {
               return new NullPointer(name, locale);           
           }
   
           final Object beanObject = ((Optional)bean).get();
           final Class beanClass  = beanObject.getClass();
   
           JXPathBeanInfo bi = JXPathIntrospector.getBeanInfo(beanClass);
           return new BeanPointer(name, beanObject, bi, locale);               
       }
   
       return null;
   }       
   
   @Override
   public NodePointer createNodePointer(NodePointer parent, QName name, Object bean) {
       if(bean != null && bean instanceof Optional ) {
           if(!((Optional)bean).isPresent()) {
               return new NullPointer(parent, name);                   
           }
   
           final Object beanObject = ((Optional)bean).get();
           final Class beanClass  = beanObject.getClass();
   
           final JXPathBeanInfo bi = JXPathIntrospector.getBeanInfo(beanClass);
           return new BeanPointer(parent, name, beanObject, bi);                   
       }
   
       return null;
   }       
   

   }