来自 RESTful API 的分页响应有效负载

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As someone who has written several libraries for consuming REST services, let me give you the client perspective on why I think wrapping the result in metadata is the way to go:

Without the total count, how can the client know that it has not yet received everything there is and should continue paging through the result set? In a UI that didn't perform look ahead to the next page, in the worst case this might be represented as a Next/More link that didn't actually fetch any more data.
Including metadata in the response allows the client to track less state. Now I don't have to match up my REST request with the response, as the response contains the metadata necessary to reconstruct the request state (in this case the cursor into the dataset).
If the state is part of the response, I can perform multiple requests into the same dataset simultaneously, and I can handle the requests in any order they happen to arrive in which is not necessarily the order I made the requests in.

And a suggestion: Like the Twitter API, you should replace the page_number with a straight index/cursor. The reason is, the API allows the client to set the page size per-request. Is the returned page_number the number of pages the client has requested so far, or the number of the page given the last used page_size (almost certainly the later, but why not avoid such ambiguity altogether)?

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最佳答案

ReSTful APIs are consumed primarily by other systems, which is why I put paging data in the response headers. However, some API consumers may not have direct access to the response headers, or may be building a UX over your API, so providing a way to retrieve (on demand) the metadata in the JSON response is a plus.

I believe your implementation should include machine-readable metadata as a default, and human-readable metadata when requested. The human-readable metadata could be returned with every request if you like or, preferably, on-demand via a query parameter, such as include=metadata or include_metadata=true.

In your particular scenario, I would include the URI for each product with the record. This makes it easy for the API consumer to create links to the individual products. I would also set some reasonable expectations as per the limits of my paging requests. Implementing and documenting default settings for page size is an acceptable practice. For example, GitHub's API sets the default page size to 30 records with a maximum of 100, plus sets a rate limit on the number of times you can query the API. If your API has a default page size, then the query string can just specify the page index.

In the human-readable scenario, when navigating to /products?page=5&per_page=20&include=metadata, the response could be:

{
"_metadata":
{
"page": 5,
"per_page": 20,
"page_count": 20,
"total_count": 521,
"Links": [
{"self": "/products?page=5&per_page=20"},
{"first": "/products?page=0&per_page=20"},
{"previous": "/products?page=4&per_page=20"},
{"next": "/products?page=6&per_page=20"},
{"last": "/products?page=26&per_page=20"},
]
},
"records": [
{
"id": 1,
"name": "Widget #1",
"uri": "/products/1"
},
{
"id": 2,
"name": "Widget #2",
"uri": "/products/2"
},
{
"id": 3,
"name": "Widget #3",
"uri": "/products/3"
}
]
}

For machine-readable metadata, I would add Link headers to the response:

Link: </products?page=5&perPage=20>;rel=self,</products?page=0&perPage=20>;rel=first,</products?page=4&perPage=20>;rel=previous,</products?page=6&perPage=20>;rel=next,</products?page=26&perPage=20>;rel=last

(the Link header value should be urlencoded)

...and possibly a custom total-count response header, if you so choose:

total-count: 521

The other paging data revealed in the human-centric metadata might be superfluous for machine-centric metadata, as the link headers let me know which page I am on and the number per page, and I can quickly retrieve the number of records in the array. Therefore, I would probably only create a header for the total count. You can always change your mind later and add more metadata.

As an aside, you may notice I removed /index from your URI. A generally accepted convention is to have your ReST endpoint expose collections. Having /index at the end muddies that up slightly.

These are just a few things I like to have when consuming/creating an API. Hope that helps!

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I would recommend adding headers for the same. Moving metadata to headers helps in getting rid of envelops like result , data or records and response body only contains the data we need. You can use Link header if you generate pagination links too.

    HTTP/1.1 200
Pagination-Count: 100
Pagination-Page: 5
Pagination-Limit: 20
Content-Type: application/json


[
{
"id": 10,
"name": "shirt",
"color": "red",
"price": "$23"
},
{
"id": 11,
"name": "shirt",
"color": "blue",
"price": "$25"
}
]

For details refer to:

https://github.com/adnan-kamili/rest-api-response-format

For swagger file:

https://github.com/adnan-kamili/swagger-response-template

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generally, I make by simple way, whatever, I create a restAPI endpoint for example "localhost/api/method/:lastIdObtained/:countDateToReturn" with theses parameters, you can do it a simple request. in the service, eg. .net

jsonData function(lastIdObtained,countDatetoReturn){
'... write your code as you wish..'
and into select query make a filter
select top countDatetoreturn tt.id,tt.desc
from tbANyThing tt
where id > lastIdObtained
order by id
}

In Ionic, when I scroll from bottom to top, I pass the zero value, when I get the answer, I set the value of the last id obtained, and when I slide from top to bottom, I pass the last registration id I got

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just add in your backend API new property's into response body. from example .net core:

[Authorize]
[HttpGet]
public async Task<IActionResult> GetUsers([FromQuery]UserParams userParams)
{
var users = await _repo.GetUsers(userParams);
var usersToReturn = _mapper.Map<IEnumerable<UserForListDto>>(users);




// create new object and add into it total count param etc
var UsersListResult = new
{
usersToReturn,
currentPage = users.CurrentPage,
pageSize = users.PageSize,
totalCount = users.TotalCount,
totalPages = users.TotalPages
};


return Ok(UsersListResult);
}

In body response it look like this

{
"usersToReturn": [
{
"userId": 1,
"username": "nancycaldwell@conjurica.com",
"firstName": "Joann",
"lastName": "Wilson",
"city": "Armstrong",
"phoneNumber": "+1 (893) 515-2172"
},
{
"userId": 2,
"username": "zelmasheppard@conjurica.com",
"firstName": "Booth",
"lastName": "Drake",
"city": "Franks",
"phoneNumber": "+1 (800) 493-2168"
}
],
// metadata to pars in client side
"currentPage": 1,
"pageSize": 2,
"totalCount": 87,
"totalPages": 44

}

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This is an interessting question and may be perceived with different arguments. As per the general standard meta related data should be communicated in the response headers e.g. MIME type and HTTP codes. However, the tendency I seem to have observed is that information related to counts and pagination typically are communicated at the top of the response body. Just to provide an example of this The New York Times REST API communicate the count at the top of the response body (https://developer.nytimes.com/apis).

The question for me is wheter or not to comply with the general norms or adopt and do a response message construction that "fits the purpose" so to speak. You can argue for both and providers do this differently, so I believe it comes down to what makes sense in your particular context.

As a general recommendation ALL meta data should be communicated in the headers. For the same reason I have upvoted the suggested answer from @adnan kamili.

However, it is not "wrong" to included some sort of meta related information such as counts or pagination in the body.