Rest Infrastructure

Bennu provides an out-of-the-box configuration of JAX RS 2. It creates an Application class, mapped to /api, meaning that all Resource classes will be mapped as follows: /api/.

To all Resources extending JsonAwareResource a mechanism for translating objects into json is also provided. Three families of methods are provided:

• viewers: turn objects into json
• creators: turn json into a new object of a given type
• updaters: apply the changes given in json format to a given object instance

These methods rely on a registry system of type translators. The registry is based on annotations: **JsonCreator**, **JsonUpdater**, **JsonViewer**, or simply **JsonAdapter** that extends the other three.

As an example, this is the adapter for the Group type:

@DefaultJsonAdapter(Group.class)
public class GroupJsonAdapter implements JsonAdapter<Group> {
    @Override
    public Group create(JsonElement json, JsonBuilder ctx) {
        return Group.parse(json.getAsJsonObject().get("expression").getAsString());
    }
    @Override
    public Group update(JsonElement json, Group obj, JsonBuilder ctx) {
        return Group.parse(json.getAsJsonObject().get("expression").getAsString());
    }
    @Override
    public JsonElement view(Group group, JsonBuilder ctx) {
        JsonObject object = new JsonObject();
        object.addProperty("expression", group.expression());
        object.addProperty("name", group.getPresentationName());
        object.addProperty("accessible", group.isMember(Authenticate.getUser()));
        return object;
    }
}

With this defined, in a JsonAwareResource one could simply return:

return view(Group.managers()); 

And the endpoint in question with return the json format of the Group.

The methods in the JsonAwareResource can be parameterized to use custom JsonAdapters.

Parameter Converters

Bennu provides multiple Parameter Converters for commonly used types, which are not supported by JAX RS out of the box:

• DomainObject subclasses
• Gson’s JsonElement subclasses