How to add templated selfrel to Spring HATEOAS PagedResourcesAssembler? - spring

Question

I'm currently building an API using spring hateoas. Most of my controllers provide a list method which returns a PagedResources<>. For some reason the selfrel does not contain the {?page,size,sort} template which is found in all examples. Instead I only get the base URI.
So my e.g. my ProjectContoller looks like
#GetMapping
public PagedResources<ProjectResource> list(Pageable pageable, PagedResourcesAssembler<Project> pagedResourcesAssembler){
Page<Project> projects = service.findAll(pageable);
return pagedResourcesAssembler.toResource(projects, assembler);
}
and returns
{"_embedded":{
"projectResourceList":[
{
"begin":1462053600000,
"end":1469829600000,
"name":"Cool Big Project",
"_links":{"self":{"href":"http://localhost/projects/1"}}
}
]
},
"_links":{"self":{"href":"http://localhost/projects"}},
"page":{
"size":20,
"totalElements":1,
"totalPages":1,
"number":0
}
}
I guess I'm missing something trivial but can't find out what :-/

Answer 1

After reading how HAL should behave in Spring Data Rest it seems there could be some bug.
This is the standard Spring Data Rest links output for a tasks collection resource:
"_links": {
"first": {
"href": "http://localhost:8080/tasks?page=0&size=20"
},
"self": {
"href": "http://localhost:8080/tasks"
},
"next": {
"href": "http://localhost:8080/tasks?page=1&size=20"
},
"last": {
"href": "http://localhost:8080/tasks?page=2&size=20"
},
"profile": {
"href": "http://localhost:8080/profile/tasks"
},
"search": {
"href": "http://localhost:8080/tasks/search"
}
No link is being templated in out of the box HAL responses rendered by Spring Data Rest, contrary to what is shown in docs.
If I follow next link, the self link is not correct:
"_links": {
"first": {
"href": "http://localhost:8080/tasks?page=0&size=20"
},
"prev": {
"href": "http://localhost:8080/tasks?page=0&size=20"
},
"self": {
"href": "http://localhost:8080/tasks"
},
"next": {
"href": "http://localhost:8080/tasks?page=2&size=20"
},
"last": {
"href": "http://localhost:8080/tasks?page=2&size=20"
},
"profile": {
"href": "http://localhost:8080/profile/tasks"
},
"search": {
"href": "http://localhost:8080/tasks/search"
}
}
If I override the Controller:
#RequestMapping(method = RequestMethod.GET, path = "/tasks")
public ResponseEntity<Page<Task>> read(Pageable pageRequest, PersistentEntityResourceAssembler assembler) {
Page<Task> pendingTasks = taskService.read(pageRequest);
return new ResponseEntity(pageAssembler.toResource(pendingTasks, (ResourceAssembler) assembler),
HttpStatus.OK);
}
And add a service between the controller and repository that initializes a Pageable instance to default values even if none is specified:
public Page<Task> read(Pageable pageRequest) {
Pageable effectivePageRequest = pageRequest;
if (effectivePageRequest == null) {
effectivePageRequest = new PageRequest(0, 20, DEFAULT_SORT);
}
if (effectivePageRequest.getSort() == null) {
//override Sort
effectivePageRequest = new PageRequest(effectivePageRequest.getPageNumber(),
effectivePageRequest.getPageSize(), DEFAULT_SORT);
}
return taskRepository.findByStatus(Task.Status.PENDING, effectivePageRequest);
}
I can overcome the problem with the self link. But have seen no way of generating the templlated URIs. These are the links for the second page:
"_links": {
"first": {
"href": "http://localhost:8080/tasks?page=0&size=20&sort=created,desc"
},
"prev": {
"href": "http://localhost:8080/tasks?page=0&size=20&sort=created,desc"
},
"self": {
"href": "http://localhost:8080/tasks?page=1&size=20&sort=created,desc"
},
"next": {
"href": "http://localhost:8080/tasks?page=2&size=20&sort=created,desc"
},
"last": {
"href": "http://localhost:8080/tasks?page=2&size=20&sort=created,desc"
}
Hope this helps discarding possibilities, but default behavior shown here suggests that there may be some problem with Spring HATEOAS/Spring Data Rest when generating collection links.
I'm using org.springframework.boot:spring-boot-starter-data-rest:jar:1.4.0.RELEASE, org.springframework.data:spring-data-rest-webmvc:jar:2.5.2.RELEASE, org.springframework.hateoas:spring-hateoas:jar:0.20.0.RELEASE