How to ensure application/hal+json is the first supported media type - spring-hateoas

Question

I have created a Hateoas enabled Rest service using spring-boot-starter-data-rest, works well.
I then created a client of that rest service in another spring boot module: this is a dependency that can be included in other projects that want to use the rest service. It uses a restTemplate under the hood.
It took a bit of mucking around with HttpMessageConverters and TypeConstrainedMappingJackson2HttpMessageConverter to get it to work but it does.
I tried using this dependency in my main application but it failed to populate the links in ResponseEntity< Resource< Myclass> >, leading to null pointer exceptions.
I couldn't track down the problem so I created a basic Spring Boot application 2.1.5.RELEASE and got the client working, then traced back the problem to this configuration in my main application which unfortunately is need for another problem:
spring:
main:
web-application-type: none
If this configuration is present it seems that hal+json isn't the first accepted media type
org.springframework.core.log.CompositeLog.debug(CompositeLog.java:147) : Accept=[application/json, application/hal+json, application/octet-stream, application/*+json]
When the configuration is removed I see
org.springframework.core.log.CompositeLog.debug(CompositeLog.java:147) : Accept=[application/hal+json, application/json, application/octet-stream, application/*+json]
and I can see this logged which fixes the issue I assume ( it isn't logged when the error happens)
- #ConditionalOnProperty (spring.hateoas.use-hal-as-default-json-media-type) matched (OnPropertyCondition)
I have tried adding this configuration to force the issue but it doesn't work
spring:
hateoas:
use-hal-as-default-json-media-type: true
This is my code in the rest client to configure the message converters:
#Configuration
public class MessageConverterConfiguration {
#Bean public TypeConstrainedMappingJackson2HttpMessageConverter myhalJacksonHttpMessageConverter(){
return new TypeConstrainedMappingJackson2HttpMessageConverter( ResourceSupport.class );
}
/**
* Add {#link TypeConstrainedMappingJackson2HttpMessageConverter} to the list of {#link HttpMessageConverter}s
* configured in the {#link RestTemplate} in first position ( this position is critical ).
* #param halJacksonHttpMessageConverter automagically configured by spring-boot-starter-hateoas
* #return List of {#link HttpMessageConverter}s
*/
#Bean( name = "hal-jackson" ) public List< HttpMessageConverter<?> > mymessageConverters( TypeConstrainedMappingJackson2HttpMessageConverter halJacksonHttpMessageConverter ) {
final List<HttpMessageConverter<?>> all = new ArrayList<>( );
all.add( halJacksonHttpMessageConverter );
all.add( jacksonConverterWithOctetStreamSupport( ) );
all.addAll( new RestTemplate().getMessageConverters() );
return all;
}
/**
* This allows converting octet stream responses into {#link LastApplicationRun} ,
* when we create a last run by posting with {#link RestTemplate#postForObject(URI , Object, Class)}
* : without it we get a
* <pre>org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter
* found for response type [class com.sparknz.ced.spark.sampling.rest.tobesampled.client.domain.LastApplicationRun]
* and content type [application/octet-stream]</pre>.
* <p></p>
* I could find no better solution: it is not needed when we make a get call, don't understand why we get an octet stream response.
* It may only now be useful for tests.
*/
private MappingJackson2HttpMessageConverter jacksonConverterWithOctetStreamSupport( ) {
final MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
converter.setSupportedMediaTypes(
asList(new MediaType[]{
MediaType.valueOf( "application/hal+json" ) ,
MediaType.APPLICATION_JSON,
MediaType.APPLICATION_OCTET_STREAM }));
return converter;
}
}
What is 'web-application-type: none' doing and how can I get HypermediaHttpMessageConverterConfiguration to run?

Answer 1

I found that adding this to my configuration class did the trick:
#Import( RepositoryRestMvcConfiguration.class )
RepositoryRestMvcConfiguration seems to be responsible for making hal+json the highest priority by adding RepositoryRestMvcConfiguration.ResourceSupportHttpMessageConverter at position 0 in the list of HttpMessageConverters.