Is there a rule to define a sequential list of links using HATEOAS?
It is easy to add self, next and previous links to a HATEOAS-based response. Below is a sample response:
{
links : [{
rel : "next",
href : "http://localhost:8080/persons?page=1&size=20"
}],
content : [{
id: "",
name: "",
lastname: "",
age: 0
}],
pageMetadata : {
size : 20,
totalElements : 30,
totalPages : 2,
number : 0
}
};
So, pagination with next and previous links is not difficult but I couldn't figure out how it is possible to access for example 10th page directly, for example using a select element (let's assume there are more than 10 pages). Should I add all the links to the response as, for example, page1, page2, page3, etc? Of course I know the format of the request so I could just create the appropriate query but that seems kind of wrong because the whole point seems to be not relying on the actual link of the service. I am not an expert on this issue and I couldn't find an answer in this site or from Google. Thanks in advance.
The common solution is to use URI templates. Specifically, section 3.2.8 regarding Form-Style Query Expansion.
Assuming both page and size are optional, you would construct your link URI template as localhost:8080/persons{?page,size}.
URI templates do not define which values are acceptable; there's no mechanism for restricting page or size to numeric values. As such, you should include this template in addition to your existing next/prev links. I'm not exactly sure which link relation best describes such a resource, but "collection" doesn't seem too far off.
In order to use URI templates, you'll need a library in whichever languages will be producing/consuming the template. A quick search produced a list of libraries in various languages which you may find helpful.
Lastly, depending on your hypermedia format you may need to specify a templated URI as such. For example, HAL+JSON uses a boolean templated property.
{
"_links": {
"collection": {
"href": "/persons{?page,size}",
"templated": true
}
}
}