spring-hateoas，如何在使用onMethod构建超媒体链接时设置位置持有者值

Question

我正在做一个restful应用程序，我一直试图为一个具有路径变量teacherId的方法构建一个超媒体链接，如下面的代码所示。我使用methodOn为getAllToturialByTeacher方法构建一个链接，例如，http://localhost:8080/springexample/teachers/2/toturials

@RestController
@RequestMapping( value = "/teachers", produces = { MediaType.APPLICATION_JSON_VALUE } )
public class ToturialController {

    ......  

    @RequestMapping( value = "/{teacherId}/toturials",method = RequestMethod.GET )
    public ResponseEntity<Resources<Resource<Toturial>>> getAllToturialByTeacher(int teacherId){

        ......

        resource.add(linkTo(ToturialController.class)
                .slash(linkTo(methodOn(ToturialController.class).getAllToturialByTeacher(teacherId)))               
                .withRel("subjectsByTeacher"));
        ....
        return new ResponseEntity<Resources<Resource<Toturial>>>(resource, HttpStatus.OK);
    }
}

我发现了异常错误

java.lang.IllegalArgumentException: Map has no value for 'teacherId'
    at org.springframework.web.util.UriComponents$MapTemplateVariables.getValue(UriComponents.java:306)
    at org.springframework.web.util.UriComponents.expandUriComponent(UriComponents.java:230)
    at org.springframework.web.util.HierarchicalUriComponents$FullPathComponent.expand(HierarchicalUriComponents.java:685)
    at org.springframework.web.util.HierarchicalUriComponents.expandInternal(HierarchicalUriComponents.java:328)
    at org.springframework.web.util.HierarchicalUriComponents.expandInternal(HierarchicalUriComponents.java:47)
    at org.springframework.web.util.UriComponents.expand(UriComponents.java:152)
    at org.springframework.web.util.UriComponentsBuilder.buildAndExpand(UriComponentsBuilder.java:398)
    at org.springframework.hateoas.mvc.ControllerLinkBuilderFactory.linkTo(ControllerLinkBuilderFactory.java:139)
    at org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo(ControllerLinkBuilder.java:138)

无法设置占位符{teacherId}的值。有人能给我一个解决办法或者最好的方法来解决这个问题吗。

Answer 1

在您的控制器中，teacherId不被注释为@PathVariable。

此外，您的链接创建看起来已损坏-请尝试如下：

resource.add(linkTo(methodOn(ToturialController.class).getAllToturialByTeacher(teacherId)).withRel("subjectsByTeacher"))