Jackson adds backslash in json

Question

I\'m building REST service on Jersey and using Jackson to produce JSON from java classes of my model. Model with absolutely simple values, I think

Answer 1

Looks like you are over complicating your JAX-RS resource class.

To use Jackson as a JSON provider for Jersey 2.x, you don't need to create an ObjectMapper instance like that. There's a better way to achieve it. Keep reading for more details.

Adding Jackson module dependencies

To use Jackson 2.x as your JSON provider you need to add jersey-media-json-jackson module to your pom.xml file:

    org.glassfish.jersey.media
    jersey-media-json-jackson
    2.25.1

Registering the Jackson module

Then register the JacksonFeature in your Application / ResourceConfig subclass:

@ApplicationPath("/api")
public class MyApplication extends Application {

    @Override
    public Set> getClasses() {
        Set> classes = new HashSet>();
        classes.add(JacksonFeature.class);
        return classes;
    }
}

@ApplicationPath("/api")
public class MyApplication extends ResourceConfig {

    public MyApplication() {
        register(JacksonFeature.class);
    }
}

If you don't have an Application / ResourceConfig subclass, you can register the JacksonFeature in your web.xml deployment descriptor. The specific resource, provider and feature fully-qualified class names can be provided in a comma-separated value of jersey.config.server.provider.classnames initialization parameter.

    jersey.config.server.provider.classnames
    org.glassfish.jersey.jackson.JacksonFeature

The MessageBodyWriter provided by Jackson is JacksonJsonProvider. For more details on how to use Jackson as a JSON provider, have a look at this answer. If you need to customize the ObjectMapper, refer to this answer.

Fixing your resource class

By using the approach described above, you resource class can be as simple as:

@Path("/users")
public class MyRestService {

  @GET
  @Produces({MediaType.APPLICATION_JSON + ";charset=UTF-8"})
  public List findUsers() {

    List users = new ArrayList<>();
    users.add(new User("Nick", "admin", "32", 47));

    return Response.ok(users).build();
}

When requesting such endpoint, it will give you the expected JSON as result.