ResponseEntity<MyDTO> is Returning Missing/Incomplete JSON - spring

Question

I'm seeing an issue with JSON cut-off/missing/incomplete when getting a response back from my service in Spring Boot.
Example:
ResponseEntity<MyDTO> responseEntity = myService.getMyDTO();
return responseEntity;
public class MyService {
public ResponseEntity<MyDTO> getMyDTO() {
return restTemplate.exchange(requestUrl, HttpMethod.GET, new HttpEntity<>(httpHeaders), MyDTO.class)
}
}
When debugging and inspecting the body of ResponseEntity, which is MyDTO instance, it contains
all the expected fields.
public class MyDTO {
private Information information;
private Address address;
}
public class Information {
private String firstName;
private String lastName;
}
public class Address {
private String streetName;
}
Debugging:
MyDTO
body
information
firstName > "John"
lastName > "Doe"
address > null
Expected JSON:
{
"information": {
"firstName": "John",
"lastName": "Doe"
},
"address: null
}
Actual JSON:
{
"information": {
"firstName": "Jo
Yes, the ending brackets are even missing from the response JSON.
Note: address is null because the response from upstream service returns a 400 and we map that response to our DTO (MyDTO). Initially, I thought this was the problem until debugging confirmed that the mapping was done correctly.
Here's what's really strange. If I take that ResponseEntity's body and put it in another ResponseEntity, than it returns fine and works. The service even returns faster, which is weird too.
ResponseEntity responseEntity = myService.getMyDTO();
return new ResponseEntity(responseEntity.getBody(), responseEntity.getStatusCode());
Anyone knows what's going on? Is it a networking, Spring Boot, or my code issue? Why would returning a new ResponseEntity fix the issue?

Answer 1

Found the issue. The upstream service contains a 'Content-Length' header, which is too small and causing the missing/incomplete JSON on client-side.

Answer 2

This is happening because you are calling the restTemplate.exchange() method; if you use the getForObject() method (in case of post call postForObject()) instead it will work.
This method will first create the MyDTO class object and then you need to add that object in the ResponseEntity object to return it.
Example:
MyDTO myDtoObject = restTemplate.getForObject(requestUrl, MyDTO.class);
return new ResponseEntity<>(myDtoObject, HttpStatus.OK);