I am trying to customize Jackson serialization for ISO dates. Per Spring Boot instructions, I created a @Bean of type Jackson2ObjectMapperBuilder:

    @Bean
    public Jackson2ObjectMapperBuilder objectMapperBuilder() {
        Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
        builder.featuresToDisable(
                SerializationFeature.WRITE_DATES_AS_TIMESTAMPS,
                DeserializationFeature.ADJUST_DATES_TO_CONTEXT_TIME_ZONE);
        return builder;
    }

However, I find that these settings are not applied when using @EnableHypermediaSupport. When I remove the annotation, I see the effects of the Jackson serialization settings.

Hi, Google is full of questions around how to create embedded HAL resources of different types inside the main root resource. I looked at the Resources Interface, but that can only be leveraged by same types to model collection of a particular type. I am currently using Spring-Hateoas to create a nested resource hierarchy and creating "_embedded" jsonproperty looks like a hack. Spring Data Rest has support for embedding entities, so it will be really helpful if you could please create a sample for embedding different type of single and collection of resources within a root resource.

Having ResourceSupport.getId() method return Link is too restrictive IMO. It makes my representation unable to have id field and corresponding getId() method with different type. It seems a very common use case to assume in UI that the id field of resource would return actual id of the resource and not a link. Probably ResourceSupport could also be made generic where the id return type is passed by the class extending ResourceSupport.

The Resources type (and any derived types, ie PagedResource) should allow you to name the collection that will eventually be the embedded set. It's auto named now, but the api developer should really have control over this.

Currently the BoundMethodParameter class references a static, default instance of ConversionService. This means that should a user add Converters to their ApplicationContext they will not be picked up and used. This should be changed such that a ConversionService specified in the ApplicationContext will be used, otherwise the default will be.

because of the naming. because of a known bug (that concernes jsonUnwrap) in jackson it is not possible to create an "id" property on model objects that are wrapped into resources. the resourceSupport.getId will shadow the model property getId.

you can successfuly serialize such resources but you can not deserialize them. jackson will simply ignore the "id" property because it is annotated with jsonignore on the resourcesupport class.

the easy workaround is to rename the model property into something other than "id". but thats a bit annoying.

I create this feature request after some discussions and thoughts that happen after the JSON API in a Java Web Application blog post and on the SPR-13570.

JSON API is a specification for how a client should request that resources be fetched or modified, and how a server should respond to those requests. Clients built around JSON API are able to take advantage of its features around efficiently caching responses, sometimes eliminating network requests entirely. Why not use the HAL specification? is also worth to read.

Ultimately, the goal of this feature is to provide support for the client-side Javascript JSON API libraries, like the most advanced one Ember Data.

I am not a Spring HATEOAS expert, but my thoughts about that is that such support may be achieved by adding JSON API format support in addition to HAL, and providing standardized ResourceController/RelationshipController Spring MVC controller interfaces that may the the Spring couterpart of Katharsis ResourceRepository/RelationshipRepository. This last point seems quite important since JSON API is not just a format, and also defines standardized REST endpoints for dealing with CRUD and relationship operation. You can have a look to RESThub RestController for an example of such controller interface.

I have not the knowledge to contribute that support alone, but I will be happy to contribute.

For the following test:

@Test
fun `GET links uses proto headers`() {
     mvc.perform(get("/v1/").header("x-forwarded-proto", "https"))
              .andExpect(status().isOk)
              .andExpect(jsonPath("$._links.activate.href", startsWith("https")))
}

And the following implementation:

private fun buildLinkForUser(currentUser: User) =  
entityLinks.linkToCollectionResource(UserResource::class.java).withRel("activate")

Or alternatively with controller links, e.g.:

fun buildLinkForUser(): Link = linkTo(methodOn(UserController::class.java).activate())
                .withRel("activate")

I get the test passing in Spring Boot 2.0.7 and failing in Spring Boot 2.1.1 - because the link gets http instead of https.

I checked Spring Hateoas in both boot releases and it remains 0.25.0. Obviously, this makes me think this issue doesn't belong here. However, I was hoping you could help me reassign it where it belongs?

As explained in the last comment of #966 , an application using spring-hateoas-1.0.0 does not start if the bean factory is setup in a way that the ParameterNameDiscoverer is null or an alternative implementation.

The reason is that when autowiring of PluginRegistry into the bean _relProvider it finds two candidates and choosing one soley relies on the constructor argument name (same in EntityLinksConfigurationwhere the other instance of PluginRegistry is created.)

This could be easily resolved by using @Qualifier annotations and named beans.

Would be nice to have an easy way of return URL templates directly. For instance, suppose we have a method like

@RequestMapping
public HttpEntity<ListResource> list(
        @RequestParam(value = "query", required = false) String query,
        @RequestParam(value = "page", defaultValue = "1") Integer page,
        @RequestParam(value = "limit", defaultValue = "10") Integer limit) {
    // ...
}

I can reference an specific invocation with linkTo(methodOn(Controller.class).list("foo", 1, 20) but I think there is no easy way to reference a generic call without specifing the method parameters. Invoking with null results in a exception.

I would like to get something like

{
    rel: "list"
    href: "http://localhost:8080/myresource{?query,page,limit}"
}

Is that possible? Regards

Hi,

On the startup of our application Spring instantiates certain processors like HttpEntityMethodProcessor and RequestResponseBodyMethodProcessor. These will be created with a reference to a list of HttpMessageConverters.

The list instance is set in the abstract class AbstractMessageConverterMethodArgumentResolver#messageConverters. But because some of the processors get created before HypermediaSupportBeanDefinitionRegistrar#registerBeanDefinitions is called it occurs that the replacing of the HttpMessageConverters will not have the proper effect.

I.e. HypermediaSupportBeanDefinitionRegistrar#registerBeanDefinitions does :

public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
    ....
    if (JACKSON2_PRESENT) {
        ...
        BeanDefinitionBuilder builder = rootBeanDefinition(Jackson2ModuleRegisteringBeanPostProcessor.class);
        ....
    }
    ....
}

Jackson2ModuleRegisteringBeanPostProcessor#postProcessAfterInitialization does

public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    ....
    if (bean instanceof RequestMappingHandlerAdapter) {
        RequestMappingHandlerAdapter adapter = (RequestMappingHandlerAdapter) bean;
        adapter.setMessageConverters(potentiallyRegisterModule(adapter.getMessageConverters()));
    }
    ....
}

Jackson2ModuleRegisteringBeanPostProcessor#potentiallyRegisterModule does

private List<HttpMessageConverter<?>> potentiallyRegisterModule(List<HttpMessageConverter<?>> converters) {
    ....
    List<HttpMessageConverter<?>> result = new ArrayList<HttpMessageConverter<?>>(converters.size());
    result.add(halConverter);
    result.addAll(converters);
    return result;
}

The problem seems to be here in potentiallyRegisterModule, it returns a new List of HttpMessageConverts while there are still objects looking at the original list.

I tested this with : Spring 3.2.5 Spring Hateoas 0.9.0.BUILD-SNAPSHOT

Many thx in advance for any input on this.

M.

Hi, since Spring 5.1 "Controller parameter annotations get detected on interfaces as well: Allowing for complete mapping contracts in controller interfaces." I am trying to use the linkTo function on a class that implements an interface that has annotations on it for Path variables.

Unfortunately, currently, this does not resolve the actual value of the path variable and instead uses a template. Copying the annotation down to the implementing class is currently a workaround but not pretty or DRY. Is this a bug that is known?

I think #1081 documents this a little however never seems to have been looked at. I am now using spring boot 3.

Thanks

Hello. I would like to know if you have plans for supporting HAL/XML in the future. Since I have seen some other people asking this same question in the past, but they did not receive a proper answer, I am reasking this question in case this has been forgotten.

Best regards. 👍

Source: How do you make Spring Hateoas return HAL/XML?

Hi Spring Hateoas team !

I think I found a bug (I initially created an issue on spring-boot project, by I was told by mhalbritter this is most likely to be an issue for hateoas.

I'm working with Spring-boot 3.0.0, that (through spring dependecy-management) pulls spring-hateoas 2.0.0 in my project. I work in a native context (builder paketobuildpacks/builder:tiny, 'BP_NATIVE_IMAGE': 'true' in my gradle bootBuildImage task)

In a very simple context, when compiling with spring boot native, I can't perform a patch 'for example) update of my entity reffering a child entity with its url identifier.

When I perform a PATH request with a body like this one:

{
  "shouldBeChecked": true,
  "name": "Amical6",
  "parent": null,
  "authority": "https://myurl/api/authorities/e52cdfb6-6f3c-4552-8ea4-e1357b5d052c"
}

I get the following errors :

in the web navigator (running the client app):

{"cause":{"cause":null,"message":"Cannot construct instance of `org.[xxx].Authority` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('https://myurl/api/authorities/e52cdfb6-6f3c-4552-8ea4-e1357b5d052c')\n at [Source: UNKNOWN; byte offset: #UNKNOWN] (through reference chain: org.[xxx].MyObject[\"authority\"])"},"message":"Could not read payload"}

And, in my application logs :

Failed to evaluate Jackson deserialization for type [[simple type, class org.springframework.data.rest.webmvc.PersistentEntityResource]]: java.lang.NullPointerException

While, in the meantime, when run my project in a non native context (for example in my favourite IDE), I've got no problem at all.

Please find below:

• the Stack overflow discussion (https://stackoverflow.com/questions/74573299/how-to-deserialize-json-object-referring-related-data-using-hal-links-with-jacks?noredirect=1)
• A reproducer project (how-to reproduce is described in the readme) (https://github.com/mathieupedreropro/spring-hal-jackson-graalvm).
• the inital issue I submitted to spring boot project (https://github.com/spring-projects/spring-boot/issues/33468)

Thanks a lot !

Hello,

I have a ResourceProcessor that's adding links to a resource:

linkTo(methodOn(MyController.class) .findMyElements(file.getId(), null, null)) .withRel("filterFiles"))

The controller looks like this:

@RequestMapping(method = { POST, GET }, value = "/myFiles/{fileId}/filterFiles") public List<FileDto> findFilterFiles( @PathVariable("fileId") final Long fileId, @RequestParam(name = "fileType") final Long fileType, @RequestBody(required = false) final FileFilterDto filter)

In Spring 2.6.4, it used to work. Now, I've tried upgrading to 2.7.4 and it does not work anymore. I've tracked the issue down and it seems like the required request param must not be null anymore.

I'm getting a null pointer exception with text like this: Illegal character in query at index 93: http://localhost:8080/files/10013/filterFiles?fileType={fileType} with the index pointing to '=' of fileType={fileType} .

Is it a bug? If yes - how can I fix it? Passing a constant number fixes the null-pointer exception:

linkTo(methodOn(MyController.class) .findMyElements(file.getId(), 1L, null)) .withRel("filterFiles"))

but it leads to incorrect code.

I want to add links to some related entities and collection, without all data in one response.

Simple example of data Model

Order Order->AddressFrom Order->PackageItems

Which is the wright HAETOAS way to generate links or how to name entities in response. First problem, how to link address, double in entity name and links part or with another name?

{
   "_embedded":{
      "orders":[
         {
            "id":"e312e342-c5f2-4a1b-8e59-8b36c7d906f3",
            "addressLinkFrom":{
               "href":"http://localhost:8080/api/v1/addresses/21228740-fabb-4eb1-8a3f-855f49efb075"
            },
            "_links":{
               "self":{
                  "href":"http://localhost:8080/api/v1/orders/edf77543-594f-4cf4-903d-80eefe4baa7d"
               },
               "addressFrom":{
                  "href":"http://localhost:8080/api/v1/addresses/60a096ef-29e1-4fef-a26a-e6e909a1f1ad"
               }
            }
         }
      ]
   }
}

or

{
   "_embedded":{
      "orders":[
         {
            "id":"e312e342-c5f2-4a1b-8e59-8b36c7d906f3",
            "addressFrom":{
               "href":"http://localhost:8080/api/v1/addresses/21228740-fabb-4eb1-8a3f-855f49efb075"
            },
            "_links":{
               "self":{
                  "href":"http://localhost:8080/api/v1/orders/edf77543-594f-4cf4-903d-80eefe4baa7d"
               },
               "addressFrom":{
                  "href":"http://localhost:8080/api/v1/addresses/60a096ef-29e1-4fef-a26a-e6e909a1f1ad"
               }
            }
         }
      ]
   }
}

Second how to link collection to specific and not all entities of a endpoint. (Or name to packageItems)

{
   "_embedded":{
      "orders":[
         {
            "id":"e312e342-c5f2-4a1b-8e59-8b36c7d906f3",
            "packageItemIds":[
               {
                  "href":"http://localhost:8080/api/v1/packageitems/d79b3c7a-f3ae-4aff-9bd9-cc4fcbea7d24"
               },
               {
                  "href":"http://localhost:8080/api/v1/packageitems/21ca96e4-5198-4865-8738-23063e18df52"
               }
            ],
            "_links":{
               "self":{
                  "href":"http://localhost:8080/api/v1/orders/edf77543-594f-4cf4-903d-80eefe4baa7d"
               }
            }
         }
      ]
   }
}

or

            "packageItemIds":[
               {
                 "self:"{

                  "href":"http://localhost:8080/api/v1/packageitems/d79b3c7a-f3ae-4aff-9bd9-cc4fcbea7d24"
               }
}]

Third how is the right format for (update, post), which I have to parse, like the address, where I'm sending the ID or like the packageItems, where I sending the link.

         {
            "id":"e312e342-c5f2-4a1b-8e59-8b36c7d906f3",
"addressFrom":{
"id":"12345"
}

            "packageItems":[
               {
                  "href":"http://localhost:8080/api/v1/packageitems/d79b3c7a-f3ae-4aff-9bd9-cc4fcbea7d24"
               },
               {
                  "href":"http://localhost:8080/api/v1/packageitems/21ca96e4-5198-4865-8738-23063e18df52"
               }
            ],
            "_links":{
               "self":{
                  "href":"http://localhost:8080/api/v1/orders/edf77543-594f-4cf4-903d-80eefe4baa7d"
               }
            }
         }
 

For your information, as frontend Client I'm using lagoshny / ngx-hateoas-client, when someone has their extra information beside the HAETOAS standard, how is the best way, please tell me.

Thanks for your help.

We have a REST service which is implement with SpringBoot and HATEOAS. The following method exists within the WebService

@Override
public ResponseEntity<?> getCar(String carId) {
        Car car = carService.findById(carId).orElseThrow(() -> {
                throw new ResponseStatusException(HttpStatus.NOT_FOUND, "Car not found!");
        });
               
       // toDTO & HATEOAS Links
       CarItem carItem = carModelAssembler.toModel(car);
         
       HalModelBuilder builder = HalModelBuilder.halModelOf(carItem);
       builder.embed(garageModelAssembler.toModel(car.getGarage()), LinkRelation.of("garage"));
            
       return ResponseEntity.ok(builder.build());
}
 

The response looks like this (abbreviated):

{
   "id":"xyu",
   "garageId":"096a07ea-3970-4968-9cd9-4756ae6a9cb1",
   "_embedded": {
       "garage":{
         "id":"abc",
         "location":"XY",
         "_links":{
            "self":{
               "href":"https://localhost:8443/api/v1/garages/096a07ea-3970-4968-9cd9-4756ae6a9cb1"
            },
        }
     }
  },
  "_links": {
    "self": {
      "href":"https://localhost:8443/api/v1/cars/d589852f-0b3f-4025-86cb-2fa3b35a1339"
    }
  }
}

We would also like to output the embedded objects in our paged responses. We came up with the following as a solution:

@Component
public class CarModelAssembler implements RepresentationModelAssembler<Car, RepresentationModel<CarItem>> {
        private GarageModelAssembler garageModelAssembler;
        private CarMapper carMapper;
 
        public BuildingModelAssembler(CarMapper carMapper, GarageModelAssembler garageModelAssembler) {
                this.carMapper = carMapper;
                this.garageModelAssembler = garageModelAssembler;
        }
 
        @Override
        public RepresentationModel<CarItem> toModel(Car car) {
                return toModel(car, true);
        }
       
        public RepresentationModel<CarItem> toModel(Car car, boolean embedded) {
                CarItem carItem = locationMapper.CarToCarItem(car);
                HalModelBuilder builder = HalModelBuilder.halModelOf(carItem);
               
                // add Links
                builder.link(linkTo(methodOn(CarController.class).getBuilding(carItem.getId())).withSelfRel());
                builder.link(linkTo(methodOn(GarageController.class).getGarage(carItem.getGarage.getId())).withRel("garage"));
               
                if(embedded) {
                        builder.embed(garageModelAssembler.toModel(car.getGarage(), false));
                }
               
                return builder.<CarItem>build();
        }
}

The call in the controller is then as follows: CollectionModel carItems = pagedResourcesAssembler.toModel(pCars, carModelAssembler);

The whole thing works in principle, but I don't like the fact that: a. - I have to pack another RepresentationModel (RepresentationModel) around my CarItem (extends RepresentationModel). b. - I still have to install the embedded switch in the assembler so that there are no infinite nestings c. - I have to inject the required assemblers for the embedded objects everywhere, which means that sooner or later I have to work with @Lazy

Unfortunately, I cannot use the HalRepresentationModel directly because it is private

I'm hoping someone here has a better idea.