Consume Spring Data REST HATEOAS HAL with RestTemplate

When you get Spring Data REST HATEOAS HAL in a web browser,

you will get the following result:

{
  "_links" : {
    "self" : {
      "href" : "http://localhost:18080/api/customers?page=0&size=100{&sort}",
      "templated" : true
    },
    "search" : {
      "href" : "http://localhost:18080/api/customers/search"
    }
  },
  "_embedded" : {
    "customers" : [ {
      "firstName" : "Jack",
      "lastName" : "Bauer",
      "_links" : {
        "self" : {
          "href" : "http://localhost:18080/api/customers/1"
        }
      }
    }, {
      "firstName" : "Chloe",
      "lastName" : "O'Brian",
      "_links" : {
        "self" : {
          "href" : "http://localhost:18080/api/customers/2"
        }
      }
    }, {
      "firstName" : "Kim",
      "lastName" : "Bauer",
      "_links" : {
        "self" : {
          "href" : "http://localhost:18080/api/customers/3"
        }
      }
    }, {
      "firstName" : "David",
      "lastName" : "Palmer",
      "_links" : {
        "self" : {
          "href" : "http://localhost:18080/api/customers/4"
        }
      }
    }, {
      "firstName" : "Michelle",
      "lastName" : "Dessler",
      "_links" : {
        "self" : {
          "href" : "http://localhost:18080/api/customers/5"
        }
      }
    } ]
  },
  "page" : {
    "size" : 100,
    "totalElements" : 5,
    "totalPages" : 1,
    "number" : 0
  }
}

but when you get it with RestTemplate,

you will get the following result:

{
  "links" : [ {
    "rel" : "self",
    "href" : "http://localhost:18080/api/customers?page=0&size=100{&sort}"
  }, {
    "rel" : "search",
    "href" : "http://localhost:18080/api/customers/search"
  }, {
    "rel" : "customer",
    "href" : "http://localhost:18080/api/customers/1"
  }, {
    "rel" : "customer",
    "href" : "http://localhost:18080/api/customers/2"
  }, {
    "rel" : "customer",
    "href" : "http://localhost:18080/api/customers/3"
  }, {
    "rel" : "customer",
    "href" : "http://localhost:18080/api/customers/4"
  }, {
    "rel" : "customer",
    "href" : "http://localhost:18080/api/customers/5"
  } ],
  "content" : [ ],
  "page" : {
    "size" : 100,
    "totalElements" : 5,
    "totalPages" : 1,
    "number" : 0
  }
}

Surprisingly the "content" is empty.

This is due to Accept header.

A web browser uses the following Accept header:

Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8

but RestTemplate uses the following Accept header:

Accept: text/plain, application/json, application/*+json, */*

So the content type in a web browser will be as follows:

Content-Type:application/hal+json;charset=UTF-8

but the content type in RestTemplate will be as follows:

Content-Type: application/x-spring-data-compact+json;charset=UTF-8

You can consume it correctly with RestTemplate as follows:

@Test
public void test() {
RestTemplate restTemplate = restTemplate();

String url = "http://localhost:{port}/api/customers?page={page}&size={size}";

ResponseEntity<PagedResources<Customer>> responseEntity = restTemplate.exchange(
url, HttpMethod.GET, null,
new ParameterizedTypeReference<PagedResources<Customer>>() {},
port, 0, 100);
PagedResources<Customer> resources = responseEntity.getBody();
List<Customer> customers = new ArrayList(resources.getContent());
System.out.println(customers);
System.out.println(customers.get(0).getClass());
}

private RestTemplate restTemplate() {
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
mapper.registerModule(new Jackson2HalModule());

MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
converter.setSupportedMediaTypes(MediaType.parseMediaTypes("application/hal+json"));
converter.setObjectMapper(mapper);
return new RestTemplate(Arrays.asList(converter));
}

Reference:
http://stackoverflow.com/questions/23239052/why-does-resttemplate-not-bind-response-representation-to-pagedresources