Spring Boot (HATEOAS) ControllerLinkBuilder.linkTo(...) 查询参数丢失/未创建 [英] Spring Boot (HATEOAS) ControllerLinkBuilder.linkTo(...) query parameter missing/not created

问题描述

我正在使用 Spring Boot (1.4) 开发 REST API，并且还使用 PagedResourcesAssembler 来创建带有分页的 JSON 响应，这很有魅力.来自 Spring 的家伙们做得很好！但是，我在提供 URL 查询参数(如果提供)时遇到了问题.我知道 PagedResourcesAssembler 无法自己找出 URL 查询参数，所以我想为它提供一个链接，使用 ControllerLinkBuilder.linkTo(controller, parameters) 方法:

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));
}

如您所见，我为链接明确提供了一个参数，但相应的响应中没有 URL 查询:

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"
        }
    }

我也尝试调试它，他正在调用:

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)直到此时他仍然拥有我的 text=foobar，同时作为 QueryUriTemplateVariable但随后在

expandInternal:341, HierarchicalUriComponents (org.springframework.web.util)他不会进入他会/可以将我的 text=foobar 放入他的结果地图的 for 循环

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

非常感谢任何帮助.

最好的问候，彼得

更新

为了完成这项工作，我必须做两件事.首先，更改方法签名并添加带有相应参数的@RequestParam，我希望将其作为分页链接中的参数，然后使用 ControllerLinkBuilder 中的 methodOn:>

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();

非常感谢你们的帮助，干杯.

Thank you both very much for your help, cheers.

附言有没有办法在没有 methodOn 的情况下完成这项工作?

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

推荐答案

根据@RequestMapping 生成链接.您传递的参数仅用于替换指定 URL 中的变量.它们不是添加的查询参数.你需要自己做.

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.

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