Question

For pagination purposes, our UI guy is specifying the items ranges in the Http header as follows:

Range: items=0-15

In subsequent requests the ranges from the web can be either

Range: items=16-31
Range: items=32-45

…etc…etc

In my controller SearchRequestController.java, I am trying to extract these ranges so that I can send it over to the Solr server to return the values in the requested chucks by setting the start and the offset.

What I am doing is as follows(In SearchRequestController.java):

@RequestMapping("/billsSearch")
@ResponseBody
public SearchResult searchBills(HttpServletRequest request,@RequestBody SearchRequest searchRequest){
    String rangeRequest = request.getHeader("Range");
    //(1)Parse the rangeRequest using some mechanism
    //(2)Set the start using the first value of the range
    //(3) Add the second value to the start to get the offset
    searchRequest.setStart(startValue);
    searchRequest.setOffset(offsetValue);
    return searchHelper(request,searchRequest);
}

There are a couple of questions that I have:
Is this the best way to request data in a chunked fashion from the server?

How do I extract the ranges from the request header?

I am assuming the request.getHeader("Range") will return “items=16-31“.

Is regular expression the best way to grab 16 and 31 from this string?

If I decide to use regular expression, wouldn’t the expression break if I change the range header to be billItems=16-31?

I am a regex n00b, so it is quite possible I am thinking of this in a wrong way.

Are there alternatives to regex to parse range information like this from the http headers within SpringMVC?

Answer 1

Is this the best way to request data in a chunked fashion from the server?

Another approach is to use request parameters:

/billsSearch?from=15&to=31

BTW you can use @RequestHeader annotation:

public SearchResult searchBills(
        @RequestBody SearchRequest searchRequest,
        @RequestHeader("Range") String range) {
    //...
}

How do I extract the ranges from the request header? […] Is regular expression the best way to grab 16 and 31 from this string?

I would cut the trailing "items=" string, split on - character and parse two resulting numbers:

String[] ranges = range.substring("items=".length()).split("-");
int from = Integer.valueOf(ranges[0]);
int to = Integer.valueOf(ranges[1]);