Spring Boot Application: No converter found for return value of type - rest

Question

I am writing a simple REST API according to this Spring-Boot tutorial. On my local dev machines (Ubuntu 15.04 and Windows 8.1) everything works like a charm.
I have an old 32-bit Ubuntu 12.04 LTS server lying around on which I wanted to deploy my REST service.
The starting log is ok, but as soon as I send a GET request to the /user/{id} endpoint, I get the following error:
java.lang.IllegalArgumentException: No converter found for return value of type: class ch.gmazlami.gifty.models.user.User
And then down the stacktrace:
java.lang.IllegalArgumentException: No converter found for return value of type: class java.util.LinkedHashMap
The entire stacktrace is posted here.
I looked into some answers referring this error, but those don't seem to apply to my problem, since I'm using Spring-Boot, no xml configs whatsoever.
The affected controller is:
#RequestMapping(value = "/user/{id}", method = RequestMethod.GET)
public ResponseEntity<User> getUser(#PathVariable Long id){
try{
return new ResponseEntity<User>(userService.getUserById(id), HttpStatus.OK);
}catch(NoSuchUserException e){
return new ResponseEntity<>(HttpStatus.NOT_FOUND);
}
}
Any help would be greatly appreciated. It is very weird since the exact same things work on other machines perfectly.

Answer 1

This happened to me, on one resource only (one method) and I did not understand why. All methods within classes in the same package, with the same annotations, same call to ResponseEntity.ok(...) etc. just worked.
But not this one.
It turns out I had forgottent to generate the getters on my POJO class !
As soon as I had added them it worked.
Hopefully it can save somebody some time eventually...

Answer 2

you should make some changes to your pom.xml and mvc-dispatcher-servlet.xml files:
Add the following dependecies to your pom.xml :
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.4.3</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.4.3</version>
</dependency>
and update your mvc-dispatcher-servlet.xml:
<mvc:annotation-driven>
<mvc:message-converters>
<bean class="org.springframework.http.converter.StringHttpMessageConverter"/>
<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/>
</mvc:message-converters>
</mvc:annotation-driven>

Answer 3

This happens when you forget the "build" call:
return ResponseEntity.status(HttpStatus.BAD_REQUEST);
should be:
return ResponseEntity.status(HttpStatus.BAD_REQUEST).build();

Answer 4

I meet with this problem, because I omitted Getters and Setters method.

Answer 5

To add to the rest of the answers: the methods must be public.
My IDE flagged that the methods could be "package only", prompting me to remove the "public" portion of the declaration (which I foolishly did).
I added public to my methods and solved the problem.

Answer 6

I was using IntelliJ Idea and its auto-generated getters and setters. Since I had a boolean field called success, the getter was named isSucccess(). I renamed it getSuccess() and the error went away.