code: public void putContext(Class<?> key, Object contextObject) {
  		if (key == null) {
  			throw new NullPointerException("key is null");
  		}
  		if (context == null) {
  			context = new HashMap<Class<?>, Object>();
  		}
  		context.put(key, contextObject);
  	}
docs: Associates a context object with this ELContext. The ELContext maintains a collection of
  context objects relevant to the evaluation of an expression. These context objects are used
  by ELResolvers. This method is used to add a context object to that collection. By
  convention, the contextObject will be of the type specified by the key. However, this is not
  required and the key is used strictly as a unique identifier.
  
  @param key
  The key used by an {@link ELResolver} to identify this context object.
  @param contextObject
  The context object to add to the collection.
  @throws NullPointerException
  if key is null or contextObject is null.