Spring Boot (HATEOAS) ControllerLinkBuilder.linkTo(…) query parameter missing/not created

问题

I'm working on a REST API with Spring Boot (1.4) and also using the PagedResourcesAssembler to create JSON responses with pagination, which works like a charm. The guys from Spring did a great job! However I'm having issues providing the URL query parameters (if provided). I understand that the PagedResourcesAssembler can't figure out URL query parameter on its own, so I wanted to provide a Link for it, using the ControllerLinkBuilder.linkTo(controller, parameters) method:

@RequestMapping(produces = MediaType.APPLICATION_JSON_VALUE)
public HttpEntity<PagedResources<Document>> find(final DocumentSearch searchForm, final Pageable pageable, final PagedResourcesAssembler assembler) {

    final Page<Document> documents = documentService.find(searchForm, pageable);

    // this map is just for this example ..
    final Map<String, Object> parameters = new HashMap<>();
    parameters.put("text", "foobar");

    final Link link = ControllerLinkBuilder.linkTo(DocumentController.class, parameters).withSelfRel();

    return ResponseEntity.ok(assembler.toResource(documents, link));
}

as you can see I distinctly provided a parameter for the link, but the corresponding response has no URL query in it:

    {
    "_links": {
        "first": {
            "href": "http://localhost:8080/documents?page=0&size=20"
        },
        "self": {
            "href": "http://localhost:8080/documents"
        },
        "next": {
            "href": "http://localhost:8080/documents?page=1&size=20"
        },
        "last": {
            "href": "http://localhost:8080/documents?page=2&size=20"
        }
    }

I also tried to debug into it, he's calling:

linkTo:123, ControllerLinkBuilder (org.springframework.hateoas.mvc)
expand:152, UriComponents (org.springframework.web.util)
expandInternal:47, HierarchicalUriComponents (org.springframework.web.util)
expandInternal:330, HierarchicalUriComponents (org.springframework.web.util)

expandInternal:340, HierarchicalUriComponents (org.springframework.web.util) until this point he still has my text=foobar, meanwhile as QueryUriTemplateVariable but then at

expandInternal:341, HierarchicalUriComponents (org.springframework.web.util) he isn't going into the for-loop where he would/could put my text=foobar into his result map

any help is very much appreciated.

Best Regards, Peter

UPDATE

In order to make this work, I had to do two things. First, change the method signature and add @RequestParam with the corresponding parameter I'd like to have as parameter in pagination link and second, use the methodOn from ControllerLinkBuilder:

public HttpEntity<PagedResources<Document>> find(@RequestParam(value = "text", required = false) final String text, final Pageable pageable, final PagedResourcesAssembler assembler) {

final Link link = ControllerLinkBuilder.linkTo(
            ControllerLinkBuilder.methodOn(
                    DocumentController.class).find(text, pageable, assembler)).withSelfRel();

Thank you both very much for your help, cheers.

P.s. is there any way to make this work without methodOn?

回答1:

Links are generated according to the @RequestMapping. The parameters you pass are only to replace variables in the specified URL. They are not query parameters that are added. You need to do that yourself.

来源：https://stackoverflow.com/questions/39266366/spring-boot-hateoas-controllerlinkbuilder-linkto-query-parameter-missing

标签

java

spring-mvc

spring-boot

spring-hateoas

spring-web