在Dropwizard yaml中找不到DatabaseConfiguration子类中的property（分层问题）

Question

I want to know. Can i do this or a derivation of it? In my Dropwizard config.yml I wanted to extend databaseConfiguration class so to add another property to the config.yml as below

config.yml

database
  driverClass: org.postgresql.Driver
  user: user1
  password: password
  exampleProperty: property1 (Tried a few other permutations)

Assume theres a DatabaseConfiguration class that has fields with getters and annotations for driverClass, user, password etc

public class AppConfiguration extends Configuration {
  @Valid
  @NotNull
  @JsonProperty
  private DatabaseConfiguration database = new DatabaseConfiguration();

  public DatabaseConfiguration getDatabaseConfiguration() {
    return database;
  }

  @Valid
  @NotNull
  @JsonProperty
  private ExtendedDatabaseConfiguration extDatabase;
  public ExtendedDatabaseConfiguration getExtendedDatabaseConfiguration() {
     return extDatabase;
  }

  public class ExtendedDatabaseConfiguration extends DatabaseConfiguration {
  @Valid
  @NotNull
  @JsonProperty
  private String exampleProperty;
  public String getExampleProperty() { return exampleProperty; };
  }

The main class Server.java passes the ExtendedDatabaseConfiguration to the Hibernate Bundle via the call (formerly passed the DatabaseConfiguration)

    private final CustomHibernateBundle<AppConfiguration> hibernateBundle = new CustomHibernateBundle<AppConfiguration>() {
    @Override
    //Giving the subclass holding the new database property to the CustomHibernateBundle
    public DatabaseConfiguration getDatabaseConfiguration(AppConfiguration configuration) {
        return configuration.getExtendedDatabaseConfiguration();
    }
};
    SimpleModule simpleModule = new SimpleModule();
    simpleModule.addAbstractTypeMapping(DatabaseConfiguration.class, ExtendedDatabaseConfiguration.class);
    bootstrap.getObjectMapperFactory().registerModule(simpleModule);

This is all in order for CustomHibernateBundle to then use this field as it pleases.

Whatever i tried either i got the error jackson.databind.exc.UnrecognizedPropertyException or i get the following

Exception in thread "main" com.yammer.dropwizard.config.ConfigurationException: powaaim.yml has the     following errors:
* extDatabase may not be null (was null)
* exampleProperty may not be null (was null)

Just to note. I have no access to modify DatabaseConfiguration but i can extend it. Wondering whether this can be achieved so that i can define more database configuration properties via this methodology.

Or is there just a simpler way?

Answer 1

You should be able to extend DatabaseConfiguration - I think you just added an extra configuration field that the parser is now expecting (although I'm not sure where the warning about the missing key is coming from). Try the following configuration class:

public class AppConfiguration extends Configuration {
  @Valid
  @NotNull
  @JsonProperty
  private ExtendedDatabaseConfiguration database = new ExtendedDatabaseConfiguration();

  public ExtendedDatabaseConfiguration getDatabaseConfiguration() {
    return database;
  }

  static class ExtendedDatabaseConfiguration extends DatabaseConfiguration {
    @Valid
    @NotNull
    @JsonProperty
    private String exampleProperty;
    public String getExampleProperty() { return exampleProperty; };
  }
}