How to parse jsonObject and JsonArray for the same field in REST Response

Question

I have calling a api using RestTemplate, let's suppose /getCompany

Usually response is as below:-

"Organization":{
  "name": "My Company",
  "department": {
     "id": "1",
     "employee": [{
       "id": "84",
       "name": "abc"
      },
      {
       "id": "85",
       "name": "xyz"
      }]
 }
}

So I am parsing this as below:-

ResponseEntity<Organization> company= new RestTemplate().exchange(new URI(companyUrl),HttpMethod.GET,request, Organization.class);
Organization comp= company.getBody();
Department dept= comp.getDepartment();
Employee[] emp = dept.getEmployees()

But sometimes in the response I am also getting the below json string:

"Organization":{
  "name": "My Company",
  "department": {
     "id": "1",
     "employee": {
       "id": "84",
       "name": "abc"
      }     
   }
}

Now I am getting the below Exception:-

Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of Employee[] out of START_OBJECT token

So Is there any way to handle Both situation ?

Update:-

As per comment added the below code:-

@Bean
public ObjectMapper getObjectMapper() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY);
    return objectMapper;
}

@Bean
public MappingJackson2HttpMessageConverter mappingJacksonHttpMessageConverter(ObjectMapper objectMapper) {
    MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
    converter.setObjectMapper(objectMapper);
    return converter;
}

But still getting the same exception.

Thanks,

Answer 1

The registered objectMapper must be used with ACCEPT_SINGLE_VALUE_AS_ARRAY parameter.

Maybe the easiest way to achive this is to register a properly initialized ObjectMapper and MappingJacksonHttpMessageConverter in a class annotated with @Configuration :

@Bean
public ObjectMapper getObjectMapper() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.enable(ACCEPT_SINGLE_VALUE_AS_ARRAY);
    return objectMapper;
}

@Bean
public MappingJacksonHttpMessageConverter mappingJacksonHttpMessageConverter(ObjectMapper objectMapper) {
    MappingJacksonHttpMessageConverter converter = new MappingJacksonHttpMessageConverter();
    converter.setObjectMapper(objectMapper);
    return converter;
}

Another way is to set the converter directly to the restTemplate object:

public ObjectMapper objectMapper() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.enable(ACCEPT_SINGLE_VALUE_AS_ARRAY);
    return objectMapper;
}


public MappingJackson2HttpMessageConverter httpConverter(ObjectMapper objectMapper) {
    return new MappingJackson2HttpMessageConverter(objectMapper);
}

public void restTemplate() {
    RestTemplate restTemplate = new RestTemplate();
    restTemplate.setMessageConverters(Arrays.asList(httpConverter(objectMapper())));
    restTemplate.exchange(...);
}

Answer 2

JSON is a javascript object notation. JSON is the same syntax as the javascript. In JSON, array values must be of type string, array, number, object boolean or null.