Designing a rest url - filter with multiple params over entities (not last entity) - api

Question

Let's say I have the following entities in my libraries app - Library Room, shelf, Book.
Where Room has N shelves, and shelves have N Books.
Now the following url brings me a list of books whose
library is 3, room no. is 5 and shelf no. is 43.
.../library/3/room/5/shelf/43/books
Assuming shelf 43 is unique per room only
(There is shelf 43 also in other rooms)
and Rooms are not unique (There's a few room no. 5 ) in the library.
Here is my questions:
I want to filter with more fields on the entities, here is what i want to do
(representation not in rest):
.../library/id=3&type=3/room/decade=21&topic=horror/shelf/location=east&/books
This is not rest.
How do I represent it in rest?
Notes:
I don't want to do this way
.../books&param1=X&param2=X&param3=X&param4=X
because not all params are related to books.

Answer 1

Couple of things that you need to look into while designing your apis.
1) are type, decade, topic etc required fields? if so, I will probably make them a part of the path itself, such as:
../libraries/{libraryId}/type/{typeId}/rooms/{roomId}/decades/{decadeId}/topics/{topicName}/shelves/{shelfId}/locations/{shelfLocation}/books
Here I am assuming that each library can have rooms which have unique room ids per library, each room can have shelves which has unique ids/locations per room (and so on and so forth). Yes, the url is pretty long, but that's kind of expected
2) if these fields are not required, you could use a different approach which is a bit less verbose but a bit more confusing for client developers who have never used such approach here. Here's a straight up example Restful Java with JAX-RS by Bill Burke
#Path("{first}-{last}")
#GET
#Produces("application/xml")
public StreamingOutput getCustomer(#PathParam("first") String firstName,
#PathParam("last") String lastName) {
...
}
Here, we have the URI path parameters {first} and {last}. If our HTTP request is
GET /customers/bill-burke, bill will be injected into the firstName parameter and
burke will be injected into the lastName parameter.
If we follow this somewhat academic approach (I have not seen this implemented on many platforms. Most platforms normally go with approach # 1, a more verbose but clear approach), your URL would look somewhat like this:
../libraries/{libraryId}-{typeId}/rooms/{roomId}-{decadeId}-{topicName}/shelves/{shelfId}-{shelfLocation}/books
This way, if the client developer doesn't pass in the non-required fields, you can handle it at the business logic level and assign these variables a default value, for example:
../libraries/3-/rooms/2-1-horror/shelves/1-/books
With this url, libraryId = 3, typeId = null (thus can be defaulted to it's default value) and so on and so forth. Remember that if libraryId is required field, then you might want to actually make it a part of the pathparam itself
Hope this helps!