In the previous blog post in this series, we looked at the basics of JWT. We will move on to building the Spring API that we will use JWT for authentication in this blog post.

These are the blog posts in this series:

  • Part 1 - Discussion of JWT and implementation
  • Part 2 - A Spring User Profiles API
  • Part 3 - Issuing a token from the server
  • Part 4 - Verifying the token sent back by the client
  • Part 5 - Securing the front end

The API

The API we will be using in the example gives access to user profiles. It has the following end points:

  • GET /profiles/{:username}
  • GET /profiles/details/{:username}

The profiles that we use for this example were generated using the Random User Generator and stored in a JSON file, for convenience for this example. In the real world, you never want to store user information in a file. All the code for this example is available on GitHub.

Structure of the User Profile

For this example, I specifically generated 500 random profiles with only a subset of fields - name, email, login and picture. With these fields, a profile has the following structure:

{
  "name": {
    "title": "mr",
    "first": "matt",
    "last": "hahn"
  },
  "email": "[email protected]",
  "login": {
    "username": "greenostrich307",
    "password": "darkange",
    "salt": "V5xi38lN",
    "md5": "cba0d5fb77ae3e0dbe177b9624df5ceb",
    "sha1": "5f22fdcc79affdef604d89b64b7db599ed454c5e",
    "sha256": "23afb0983e874169669f96cd72b69234aef4cf54a86f89a25e14e91941ac95a2"
  },
  "picture": {
    "large": "https://randomuser.me/api/portraits/men/20.jpg",
    "medium": "https://randomuser.me/api/portraits/med/men/20.jpg",
    "thumbnail": "https://randomuser.me/api/portraits/thumb/men/20.jpg"
  }
}

At this point, you can see the password and hash in there. As I explained above, you do not want to do this in a real application. As such, this example focuses on JWT and we are doing this purely for convenience.

The data models

The models for representing the data provided from the random user generator are as follows. We will be using the Lombok 1 @Data annotation to stay away from having to write explicit setters and getters.

Profile

import lombok.Data;

@Data
public class Profile {
    private Name name;
    private String email;
    private Login login;
    private Picture picture;
}

Name

@Data
public class Name {
    private String title;
    private String first;
    private String last;
}

Login

@Data
public class Login {
    String username;
    String password;
    String salt;
    String md5;
    String sha1;
    String sha256;
}

Picture

@Data
public class Picture {
    private URL large;
    private URL medium;
    private URL thumbnail;
}

We will also create two other data models that expose a minimal set of profile information without the credentials.

MinimalProfile

@Data
public class MinimalProfile {
    private final String username;
    private final Name name;
    private final URL thumbnail;

    public MinimalProfile(Profile profile) {
        name = profile.getName();
        username = profile.getLogin().getUsername();
        thumbnail = profile.getPicture().getThumbnail();
    }
}

DetailedProfile

@Data
public class DetailedProfile {

    private final Picture picture;
    private final Name name;
    private final String email;
    private final String username;

    public DetailedProfile(Profile profile) {
        name = profile.getName();
        email = profile.getEmail();
        picture = profile.getPicture();
        username = profile.getLogin().getUsername();
    }
}

The Controllers

The code for the API’s controller is as follows:

@RestController
@RequestMapping(path = "/profile")
public class ProfileController {

    private final ProfileService profileService;

    @SuppressWarnings("unused")
    public ProfileController() {
        this(null);
    }

    @Autowired
    public ProfileController(ProfileService profileService) {
        this.profileService = profileService;
    }

    @RequestMapping(path = "/{username}",
            method = GET,
            produces = APPLICATION_JSON_VALUE)
    public MinimalProfile minimal(@PathVariable String username) {
        return profileService.minimal(username)
                .orElseThrow(() -> new ProfileNotFoundException(username));
    }

    @RequestMapping(path = "/details/{username}",
            method = GET,
            produces = APPLICATION_JSON_VALUE)
    public DetailedProfile details(@PathVariable String username) {
        return profileService.detailed(username)
                .orElseThrow(() -> new ProfileNotFoundException(username));
    }
}

It delegates querying for profiles to the ProfileService and throws exceptions if a Profile is not present. Notice the use of Java’s Optional to throw exceptions.

The ProfileService

@Component
public class ProfileService {
    private final List<Profile> profiles;

    private final Path PROFILES_FILE = Paths.get(this.getClass().getResource("/profiles.json").toURI());

    public ProfileService() throws IOException, URISyntaxException {
        ObjectMapper objectMapper = new ObjectMapper();
        profiles = objectMapper.readValue(PROFILES_FILE.toFile(), new TypeReference<List<Profile>>() {
        });
    }

    protected Optional<Profile> get(String username) {
        return profiles.stream()
                .filter(profile -> profile.getLogin().getUsername().equals(username))
                .findFirst();
    }

    public Optional<MinimalProfile> minimal(String username) {
        return get(username).map(profile -> new MinimalProfile(profile));
    }

    public Optional<DetailedProfile> detailed(String username) {
        return get(username).map(profile -> new DetailedProfile(profile));
    }
}

Exception Handling

We will also need to wire up a ControllerAdvice to handle exceptions appropriately:

@ControllerAdvice
public class GlobalExceptionHandler {
    @ResponseStatus(NOT_FOUND)
    @ExceptionHandler(ProfileNotFoundException.class)
    public void profileNotFound() {
    }
}

With this, you should have a profile service up and running.

Minimal profile

$ curl -s "http://localhost:8080/profile/yellowfrog347" | jq .
{
  "username": "yellowfrog347",
  "name": {
    "title": "ms",
    "first": "sofia",
    "last": "hansen"
  },
  "thumbnail": "https://randomuser.me/api/portraits/thumb/women/71.jpg"
}

Detailed Profile

$ curl -s "http://localhost:8080/profile/details/yellowfrog347" | jq .
{
  "picture": {
    "large": "https://randomuser.me/api/portraits/women/71.jpg",
    "medium": "https://randomuser.me/api/portraits/med/women/71.jpg",
    "thumbnail": "https://randomuser.me/api/portraits/thumb/women/71.jpg"
  },
  "name": {
    "title": "ms",
    "first": "sofia",
    "last": "hansen"
  },
  "email": "[email protected]",
  "username": "yellowfrog347"
}

The code for the application so far can be found here. In the next blog post of the series, we will wire up Spring Security and build a login feature that issues a JWT after successful login.


  1. Project Lombok is a Java library that helps minimize boiler plate code by replacing them with a set of convenient annotations. I tend to use it when I have to build data objects. [return]

If you have questions or comments about this blog post, you can get in touch with me on Twitter @sdqali.

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