Spring RestTemplate and generic types ParameterizedTypeReference collections like List<T>
I worked around this using the following generic method:
public <T> List<T> exchangeAsList(String uri, ParameterizedTypeReference<List<T>> responseType) {
return restTemplate.exchange(uri, HttpMethod.GET, null, responseType).getBody();
}
Then I could call:
List<MyDto> dtoList = this.exchangeAsList("http://my/url", new ParameterizedTypeReference<List<MyDto>>() {});
This did burden my callers with having to specify the ParameterizedTypeReference
when calling, but meant that I did not have to keep a static mapping of types like in vels4j's answer
Using ParameterizedTypeReference
for a List<Domain>
, when Domain is an explicit class, that ParameterizedTypeReference
works well, like this:
@Override
public List<Person> listAll() throws Exception {
ResponseEntity<List<E>> response = restTemplate.exchange("http://example.com/person/", HttpMethod.GET, null,
new ParameterizedTypeReference<List<Person>>() {});
return response.getBody();
}
However, if a method listAll
is used in generic flavor, that list should be parameterized itself. The best way I found for this is:
public abstract class WebServiceImpl<E> implements BaseService<E> {
private Class<E> entityClass;
@SuppressWarnings("unchecked")
public WebServiceImpl() {
this.entityClass = (Class<E>) ((ParameterizedType) getClass().getGenericSuperclass())
.getActualTypeArguments()[0];
}
@Override
public List<E> listAll() throws Exception {
ResponseEntity<List<E>> response = restTemplate.exchange("http://example.com/person/", HttpMethod.GET, null,
new ParameterizedTypeReference<List<E>>() {
@Override
public Type getType() {
Type type = super.getType();
if (type instanceof ParameterizedType) {
Type[] responseWrapperActualTypes = { entityClass };
ParameterizedType responseWrapperType = new ParameterizedTypeImpl(List.class,
responseWrapperActualTypes, null);
return responseWrapperType;
}
return type;
}
});
return response.getBody();
}
}
Couldnt find a solution from Spring, hence I have done it with ParameterizedTypeReference
in HashMap
like
public final static HashMap<Class,ParameterizedTypeReference> paramTypeRefMap = new HashMap() ;
static {
paramTypeRefMap.put(AttributeDefinition.class, new ParameterizedTypeReference<List<AttributeDefinition>>(){} );
paramTypeRefMap.put(AttributeInfo.class, new ParameterizedTypeReference<List<AttributeInfo>>(){} );
}
and used it
ParameterizedTypeReference parameterizedTypeReference = paramTypeRefMap.get(requiredClass);
ResponseEntity<List> exchange = restTemplate.exchange(uri, HttpMethod.POST, entity, parameterizedTypeReference);