Validating Null Values of a JSON Message in Camel

Issue

• The example given for using JSonPath in http://camel.apache.org/jsonpath.html does not work as expected. For example, the following syntax does not filter the books according to their prices:

<jsonpath>$.store.book[?(@.price < 10)]</jsonpath>

• I want to validate if the value of an element in a JSON message is null. Please provide the syntax that can be used in a Camel route for validating null elements.