How to consume a spring data rest service with java? - spring

Question

I have the following spring boot + data Rest repository:
#RepositoryRestResource(collectionResourceRel = "dto", path = "produtos")
public interface ProdutoRepository extends CrudRepository<Produto, Integer> {
#Query("SELECT p FROM Produto p where descricao LIKE CONCAT(UPPER(:like),'%')")
List<Produto> findByLike(#Param("like") String like);
}
I also have a java client that access this method (this is my example of doing it):
String url = "http://localhost:8080/produtos/search/findByLike?like={like}";
RestTemplate t = new RestTemplate();
ProdutoDto resp = t.getForObject(url, ProdutoDto.class, txtLoc.getText());
ProdutoDto (this one is not totally necessary):
public class ProdutoDto extends HalDto<Produto> {}
HalDto:
public class HalDto<T extends ResourceSupport> extends ResourceSupport {
#JsonProperty("_embedded")
private EmbeddedDto<T> embedded;
public EmbeddedDto<T> getEmbedded() {
return embedded;
}
public void setEmbedded(EmbeddedDto<T> embedded) {
this.embedded = embedded;
}
}
EmbeddedDto:
public class EmbeddedDto<T> {
#JsonProperty("dto")
private List<T> dtoList;
public List<T> getDtoList()
{
return dtoList;
}
public void setDto(List<T> dtoList) {
this.dtoList = dtoList;
}
}
Those classes are necessary (i think) because Spring Data returns data in the HAL (https://en.wikipedia.org/wiki/Hypertext_Application_Language) format.
Note: Produto must extend ResourceSupport.
Caveats: All collectionResourceRel must be named "dto" and it only works for collections (may be adjusted).
Is this the proper way to do this?
I have googled around and found plenty of examples of doing the server side, but almost nothing on building clients.
Thanks.

Answer 1

This is a solution that I have found which seems to work well.
First, setup your RestTemplate so that it expects JSON/HAL and knows what to do with it:
#Bean
public RestTemplate restTemplate() {
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new Jackson2HalModule());
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
MappingJackson2HttpMessageConverter messageConverter =
new MappingJackson2HttpMessageConverter();
messageConverter.setObjectMapper(objectMapper);
messageConverter.setSupportedMediaTypes(Arrays.asList(MediaTypes.HAL_JSON, MediaType.APPLICATION_JSON_UTF8));
return new RestTemplate(Arrays.asList(messageConverter));
}
Then you can use the exchange method of the RestTemplate to specify that you want your result to be ResponseEntity<PagedResources<Producto>>
ResponseEntity<PagedResources<Producto>> resultResponse = restTemplate.exchange(uri, HttpMethod.GET, HttpEntity.EMPTY, new ParameterizedTypeReference<PagedResources<Producto>>(){});
if(resultResponse.getStatusCode() == HttpStatus.OK){
Collection<Producto> results = resultResponse.getBody().getContent();
log.info("{} results obtained", results.size());
}
You can instantiate restTemplate by either calling the restTemplate() method defined above or you can inject (autowire) it.