Unable to marshal Resources - HAL should be used

Invalid content type is used, for Resources endpoint in HAL enabled application.

This requires special code @GetMapping(produces = {MediaType.APPLICATION_JSON_VALUE, "application/hal+json"}) for endpoint method returning Resources.

Logged error:

.w.s.m.s.DefaultHandlerExceptionResolver : Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not marshal [Resources { content: [FooApplication.FooResource(foo=foo)], links: [] }]: null; nested exception is javax.xml.bind.MarshalException
 - with linked exception:
[com.sun.istack.internal.SAXException2: unable to marshal type "com.foo.FooApplication$FooResource" as an element because it is missing an @XmlRootElement annotation]

Sample application:

@SpringBootApplication
public class FooApplication {

	public static void main(String[] args) {
		SpringApplication.run(FooApplication.class, args);
	}

	@RestController("/foos")
	public class FooController {

		@GetMapping
		public Resources<FooResource> foo() {
			List<FooResource> foos = Stream.of(new FooResource("foo")).collect(Collectors.toList());
			return new Resources(foos);
		}
	}

	@Data
	public class FooResource extends ResourceSupport {
		private final String foo;
	}

}

Dependencies:

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-hateoas</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>
	</dependencies>

This is similar to bug: https://github.com/spring-guides/tut-bookmarks/issues/8

Start with the FooController.foo entry point and its @GetMapping in the supplied sample application, then trace how the Resources return value is selected for writing. Reproduce the XML marshalling error with the listed dependencies and verify that the endpoint produces HAL without requiring the special produces declaration.