Thursday, May 23, 2013

Support for paging in the RHQ REST-api (updated)

I have just pushed some changes to RHQ master that implement paging for (most) of the REST-endpoints that return collections of data.



If you remember, I was asking the other day if there is a "standard" way to do this. Basically there are two
"big options":
  1. Put paging info in the Http-Header
  2. Put paging info in the body of the message


While I think paging information are meta data that should not "pollute" the body, I understand the arguments from the JavaScript side that says that they don't easily have access to the http headers
within AJAX requests. So what I have now done is to implement both:
  1. Paging in the http header: this is the standard way that you get if you just request the "normal" media types of application/xml or application/json (output from running RestAssured):

    [update]
    My colleague Libor pointed out that the links do not match with format from RFC 5988 Web Linking, which is now fixed.
    [/update]

    Request method: GET
    Request path: http://localhost:7080/rest/resource
    Query params: page=1
    ps=2
    category=service
    Headers: Content-Type=*/*
    Accept=application/json
    HTTP/1.1 200 OK
    Server=Apache-Coyote/1.1
    Pragma=No-cache
    Cache-Control=no-cache
    Expires=Thu, 01 Jan 1970 01:00:00 CET
    Link=<http://localhost:7080/rest/resource?ps=2&category=service&page=2>; rel="next"
    Link=<http://localhost:7080/rest/resource?ps=2&category=service&page=0>; rel="prev"
    Link=<http://localhost:7080/rest/resource?ps=2&category=service&page=152>; rel="last"
    Link=<http://localhost:7080/rest/resource?page=1&ps=2&category=service>; rel="current"
    Content-Encoding=gzip
    X-collection-size=305
    Content-Type=application/json
    Transfer-Encoding=chunked
    Date=Thu, 23 May 2013 07:57:38 GMT

    [
    {
    "resourceName": "/",
    "resourceId": 10041,
    "typeName": "File System",
    "typeId": 10013,
    …..
  2. Paging as part of the body - there the "real collection" is wrapped inside an object that also contains paging meta data as well as the paging links. To request this representation, a media type of application/vnd.rhq.wrapped+json needs to be used (and this is only available with JSON at the moment):

    Request method: GET
    Request path: http://localhost:7080/rest/resource
    Query params: page=1
    ps=2
    category=service
    Headers: Content-Type=*/*
    Accept=application/vnd.rhq.wrapped+json
    Cookies:
    Body:
    HTTP/1.1 200 OK
    Server=Apache-Coyote/1.1
    Pragma=No-cache
    Cache-Control=no-cache
    Expires=Thu, 01 Jan 1970 01:00:00 CET
    Content-Encoding=gzip
    Content-Type=application/vnd.rhq.wrapped+json
    Transfer-Encoding=chunked
    Date=Thu, 23 May 2013 07:57:40 GMT

    {
    "data": [
    {
    "resourceName": "/",
    "resourceId": 10041,
    "typeName": "File System",
    "typeId": 10013,

    ],
    "pageSize": 2,
    "currentPage": 1,
    "lastPage": 152,
    "totalSize": 305,
    "links": [
    {
    "next": {
    "href": "http://localhost:7080/rest/resource?ps=2&category=service&page=2"
    }
    },

    }

Please try this if you can. We want to get that into a "finished" state (as for the whole REST-Api) for RHQ 4.8

2 comments:

Mike Thompson said...

Nice! The best of both worlds. Server side developers can use the more standard header method and client side ajax requests can consume the inline method.

Hendy Irawan said...

Very good resolution indeed!