Rosetta

Overview

Rosetta is a Java library that leverages Jackson to take the pain out of mapping objects to/from the DB, designed to integrate seamlessly with jDBI. Jackson is extremely fast, endlessly configurable, and already used by many Java webapps.

Rosetta isn't an ORM. It doesn't silently read and write to your database, validate input, or manage connections. It does two things:

Binds Java objects to SQL query parameters
Maps SQL result sets to Java objects

Usage

To use with jDBI on Maven-based projects, add the following dependency:

<dependency>
  <groupId>com.hubspot.rosetta</groupId>
  <artifactId>RosettaJdbi</artifactId>
  <version>3.7</version>
</dependency>

Binding

You can bind JDBI arguments in your DAO using @BindWithRosetta.

public interface MyDAO {
  @SqlUpdate("UPDATE my_table "
            +"SET some_field=:some_field, another_field=:another_field "
            +"WHERE id=:id")
  void update(@BindWithRosetta MyRow obj);
}

@BindWithRosetta behaves like jDBI's @BindBean, but it converts the object to a tree using Jackson which lets you use all the Jackson annotations you know and love to customize the representation. It's also generally more robust - it supports the not-quite-standard naming conventions, fluent setters, nested objects (with dot-notation), getters without fields, etc.

Mapping

To register Rosetta globally for mapping you can add it to your DBI like so:

dbi.registerMapper(new RosettaMapperFactory());

Or to test it out on a single DAO you would do:

@RegisterMapperFactory(RosettaMapperFactory.class)
public interface MyDAO { /* ... */ }

Configuration

Assuming your Java field names are camel-case and your SQL column names are lowercase with underscores (a pretty common scenario) you can make this work with Rosetta by annotating the Java objects with @RosettaNaming(LowerCaseWithUnderscoresStrategy.class) which will change Jackson's naming strategy to lower case with underscores but only for Rosetta binding/mapping (other Jackson operations throughout your application are unaffected).

Or to make this change globally for Rosetta, you could make a Jackson Module that sets the default naming strategy to lowercase with underscores, something like this:

public class LowerCaseWithUnderscoresModule extends SimpleModule {

  @Override
  public void setupModule(SetupContext context) {
    context.setNamingStrategy(new LowerCaseWithUnderscoresStrategy());
  }
}

You can then register it with Rosetta programmatically during your app's startup with something like:

Rosetta.addModule(new LowerCaseWithUnderscoresModule());

Or even better your module could extend com.hubspot.rosetta.databind.AutoDiscoveredModule, you can create a file located at src/main/resources/META-INF/services/com.hubspot.rosetta.databind.AutoDiscoveredModule

Rosetta also supports injecting from the default Module: src/main/resources/META-INF/services/com.fasterxml.jackson.databind.Module