com.fasterxml.jackson.databind.exc.MismatchedInputException: Unexpected token

Question

I am trying to POST a user group:

public UserGroup createUserGroup(UserGroup userGroup) {
    ResponseEntity<UserGroup> userGroupResponseEntity = oauthRestTemplate
            .postForEntity(GROUPS_ENDPOINT, userGroup, UserGroup.class);
    return userGroupResponseEntity.getBody();
}

Since I am using @RepositoryRestResource I had to configure the object mapper:

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new Jackson2HalModule());
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);

MappingJackson2HttpMessageConverter messageConverter = new MappingJackson2HttpMessageConverter();
messageConverter.setObjectMapper(objectMapper);
messageConverter.setSupportedMediaTypes(Collections.singletonList(MediaTypes.HAL_JSON));

this.oauthRestTemplate.setMessageConverters(Collections.singletonList(messageConverter));

However, running the POST from above will throw me

Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Unexpected token (START_OBJECT), expected VALUE_STRING: Expected array or string.
 at [Source: (org.apache.catalina.connector.CoyoteInputStream); line: 1, column: 87] (through reference chain: mahlzeit.api.hibernate.model.UserGroup["voteUntil"])
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63) ~[jackson-databind-2.9.4.jar:2.9.4]
    at com.fasterxml.jackson.databind.DeserializationContext.wrongTokenException(DeserializationContext.java:1507) ~[jackson-databind-2.9.4.jar:2.9.4]
    at com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer.deserialize(LocalDateTimeDeserializer.java:138) ~[jackson-datatype-jsr310-2.9.2.jar:2.9.2]
    at com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer.deserialize(LocalDateTimeDeserializer.java:39) ~[jackson-datatype-jsr310-2.9.2.jar:2.9.2]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:127) ~[jackson-databind-2.9.4.jar:2.9.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:369) ~[jackson-databind-2.9.4.jar:2.9.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159) ~[jackson-databind-2.9.4.jar:2.9.4]
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001) ~[jackson-databind-2.9.4.jar:2.9.4]
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3072) ~[jackson-databind-2.9.4.jar:2.9.4]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:235) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
    ... 93 common frames omitted

2018-04-02 15:12:52.788 DEBUG 1811 --- [nio-8081-exec-3] o.s.s.w.header.writers.HstsHeaderWriter  : Not injecting HSTS header since it did not match the requestMatcher org.springframework.security.web.header.writers.HstsHeaderWriter$SecureRequestMatcher@24f17053
2018-04-02 15:12:52.789 DEBUG 1811 --- [nio-8081-exec-3] o.s.s.w.a.ExceptionTranslationFilter     : Chain processed normally
2018-04-02 15:12:52.789 DEBUG 1811 --- [           main] o.s.s.oauth2.client.OAuth2RestTemplate   : POST request for "http://localhost:8081/groups" resulted in 400 (null); invoking error handler
2018-04-02 15:12:52.789 DEBUG 1811 --- [nio-8081-exec-3] s.s.w.c.SecurityContextPersistenceFilter : SecurityContextHolder now cleared, as request processing completed
org.springframework.web.client.HttpClientErrorException: 400 null
    at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:94)
    at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:79)
    at org.springframework.security.oauth2.client.http.OAuth2ErrorHandler.handleError(OAuth2ErrorHandler.java:172)
    at org.springframework.web.client.ResponseErrorHandler.handleError(ResponseErrorHandler.java:63)
    at org.springframework.web.client.RestTemplate.handleResponse(RestTemplate.java:777)
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:730)
    at org.springframework.security.oauth2.client.OAuth2RestTemplate.doExecute(OAuth2RestTemplate.java:128)
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:686)
    at org.springframework.web.client.RestTemplate.postForEntity(RestTemplate.java:468)

and I just don't get why!

Answer 1

For anybody who runs into this - and this is why Spring can get so immense frustrating sometimes if you are not careful or remember a million things that you configured beforehand.

So in case you're like me and used application-test.properties in order to configure certain things, let's say something like this:

# Used to enable ISO format for time data
spring.jackson.serialization.WRITE_DATES_AS_TIMESTAMPS = false

but have already forgotten about that, then you might want to bear in mind that this property gets ignored as soon as you set, like me, your custom ObjectMapper in order to consume the hal+json output from Spring Data REST endpoints. And because of that you might want to set:

objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
objectMapper.registerModule(new JavaTimeModule());