hate

HATEOAS with HAL for Java. Create hypermedia APIs by easily serializing your Java models into HAL JSON.
More info in the wiki.

Install with Maven

<dependencies>
  <dependency>
    <groupId>black.door</groupId>
    <artifactId>hate</artifactId>
    <version>v1r4t5</version>
  </dependency>
</dependencies>

Basic usage

Implement the HalResource interface in your model by implementing the location() and representationBuilder() methods. For example:

public class Order implements HalResource{

    private int id;
    private double total;
    private String currency;
    private String status;
    //note: Basket and Customer implement HalResource
    private Basket basket;
    private Customer customer;

    ...

    @Override
    public URI location(){
        return new URI("/orders/" + id);
    }

    @Override
    public HalRepresentationBuilder representationBuilder() {
        return HalRepresentation.builder()
                .addProperty("total", total)
                .addProperty("currency", currency)
                .addProperty("status", status)
                .addLink("basket", basket)
                .addLink("customer", customer)
                .addLink("self", this);
    }
}   

Now to get the HalRepresentation of an Order object, simply do HalRepresentation hal = myOrder.asEmbedded(). You can serialize hal using hal.serialize() or with Jackson (eg. new ObjectMapper().writeValueAsString(hal))

The result would look like this:

{
  "total": 30,
  "currency": "USD",
  "status": "shipped",
  "_links": {
    "basket": {
      "href": "/baskets/97212"
    },
    "self": {
      "href": "/orders/123"
    },
    "customer": {
      "href": "/customers/7809"
    }
  }
}

Paginated Collections

To get a paginated HAL representation of a REST collection, simply use HalRepresentation.paginated(String, String, Stream, long, long).
For example:

Collection<Order> orders;

HalRepresentation hal = HalRepresentation.paginated(
    "orders", // the name of the resource collection
    "/orders", // the path the resource collection can be found at
    orders.stream(), // the resources
    pageNumber,
    pageSize // the number of resources per page
    ).build();

Would give you something like this:

{
  "_links": {
    "next": {
      "href": "/orders?page=2"
    },
    "self": {
      "href": "/orders"
    }
  },
  "_embedded": {
    "orders": [
      {
        "total": 30,
        "currency": "USD",
        "status": "shipped",
        "_links": {
          "basket": {
            "href": "/baskets/97212"
          },
          "self": {
            "href": "/orders/123"
          },
          "customer": {
            "href": "/customers/7809"
          }
        }
      },
      {
        "total": 20,
        "currency": "USD",
        "status": "processing",
        "_links": {
          "basket": {
            "href": "/baskets/97213"
          },
          "self": {
            "href": "/orders/124"
          },
          "customer": {
            "href": "/customers/12369"
          }
        }
      }
    ]
  }
}