spring-projects / spring-projects/spring-hateoas
Returns duplicate links causing JSON deserialization exception
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Description
Vanilla resource User -
public class User implements Serializable {
private static final long serialVersionUID = 262950482349139355L;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@Column(name = "FIRST_NAME", nullable = false, unique = false)
@Convert(converter = NameConverter.class)
private String firstName;
@Column(name = "LAST_NAME", nullable = false, unique = false)
@Convert(converter = NameConverter.class)
private String lastName;
@Column(name = "PHONE_NUM", nullable = false, unique = false)
@Convert(converter = PhoneNumberConverter.class)
private String phoneNum;
@Column(name = "EMAIL", nullable = true, unique = false)
@Convert(converter = OptionalStringConverter.class)
private Optional<String> email;
}
Search result with hostname changed in the URL - 2 _links present
{
"_links" : {
"self" : {
"href" : "http://hostname/users/search/findByLastName?lastName=doe{&page,size,sort}",
"templated" : true
}
},
"_embedded" : {
"users" : [ {
"firstName" : "John",
"lastName" : "Doe",
"phoneNum" : "111-111-1111",
"email" : null,
"_links" : { },
"_embedded" : { },
"_links" : {
"self" : {
"href" : "http://hostname/users/1",
"templated" : false
}
}
} ]
},
"page" : {
"size" : 20,
"totalElements" : 1,
"totalPages" : 1,
"number" : 0
}
}
The duplicate links are not present when the resource is accessed on it's own. However, when a client (a microservice in my case) makes a request using a RestTemplate, the response comes back with 2 _links as shown above.
@Override
public Collection<Long> getUserIdsByFirstName(String firstName) {
String findByFirstNameUri = UriComponentsBuilder.fromUriString(userServiceUrl).path("/users/search/findByFirstName").queryParam("firstName", firstName).toUriString();
// This is where ResponseEntity.body would have the 2 _links, if ResponseEntity<String> were used. I used a custom object to weed that out.
ResponseEntity<UserSearchResult> userSearchResult = restTemplate.exchange(findByFirstNameUri, GET, dummyEntity, UserSearchResult.class);
...
}
I'm using Spring Data JPA, Spring Data Rest, Spring HATEOAS and Spring Cloud. Here's a link to the project on my Github.
Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the linked user-service project, especially the RestTemplate exchange in getUserIdsByFirstName, and reproduce the search response with the shown User resource. Trace Spring HATEOAS serialization or deserialization to determine why duplicate _links appear; done means the response has one valid _links object and can be deserialized without the reported exception.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- java, spring
- Domain
- api, backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100