JacksonDataFormat dataFormat1 = new JacksonDataFormat(Distance.class);

from("direct:getDistance")
.marshal()// What are you serializing here? Could add dataFormat1 inside marshal also
.setHeader("Content-Type").constant("application/json")
.setHeader("Accept").constant("application/json")
.setHeader(Exchange.HTTP_METHOD).constant("GET")
.removeHeader(Exchange.HTTP_PATH)
.toD("https://www.zipcodeapi.com/rest/qqZmn6H64bx2BdF9UWZKivRu5vQVZtejqIQOVXCkPiRwwPVht3feiPEqxIMY3S5P/distance.json/48335/48336/km")
.unmarshal(dataFormat1)
.process(new Processor() 
{ @Override public void process(Exchange exchange) throws Exception 
{ System.out.println("in the processor"+ exchange.getIn().getBody()); 
Distance employeelist = exchange.getIn().getBody(Distance.class) ; 
System.out.println("distance value"+ employeelist.getDist­ance());