How to use the config string and DAO in a resource in Dropwizard

Question

I want to use a String from my config.yml and inject some DAO with guice in a resource. Consider the following code example

@Path("/upload")
@Produces(MediaType.APPLICATION_JSON)
public class UploadResource {

  private static String UPLOAD_PATH;

  public UploadResource(String uploadPath) {
    this.UPLOAD_PATH = uploadPath;
  }
}

I have added a the config.yml parameter in my constructor and used the following command to add the string in the application class

final UploadResource uploadResource = new UploadResource(
configuration.getUploadFileLocation());
environment.jersey().register(uploadResource);

Usually I would inject some Dao as follows

@Produces(MediaType.APPLICATION_JSON)
public class UploadResource {

  private final SomeDao someDao;

  @Inject
  public UploadResource(SomeDao someDao) {
    this.someDao = someDao;
  }
}

but since my constructor has already an string entry. how would I handle this elegantly with Dropwizard? simple extending the arguments seems to be unclean.

Answer 1

So if you are using Dropwizard with Guice and would like to use some string in from the config.yml you need to do the following

to the resource you

@Path("/upload")
@Produces(MediaType.APPLICATION_JSON)
public class UploadResource {

  private final FileDao fileDao;
  private final String uploadPath;

  @Inject
  public UploadResource(FileDao fileDao, @Named("{someName}") String uploadPath) {
    this.fileDao = fileDao;
    this.uploadPath = uploadPath;
  }

}

and in the application class you need to bind a constant as follows

@Override
  public void run(
      final BackendConfiguration configuration,
      final Environment environment) {
    Injector injector =
        Guice.createInjector(
            new AbstractModule() {
              @Override
              protected void configure() {

                bindConstant().annotatedWith(Names.named("{someName}"))
                    .to(configuration.getUploadFileLocation());
              }
            });

Make sure you implemented the method getUploadFileLocation as discribed by lutz from this post here