How to use java generics with restTemplate

Question

I have an execute method that I've created where I pass in my restTemplate instance along with the class obj. However, I'm getting some warnings about unchecked types. I can't seem to figure out how to do this with generics. Here's what I have so far:

public class RepositoryUtils {
 private static final Logger LOGGER = LoggerFactory.getLogger(RepositoryUtils.class);
 public static ResponseEntity execute(String url, RestTemplate restTemplate, Class generic) {
 LOGGER.info("GET: {}", url);
 ResponseEntity response = null;
 try {
 response = restTemplate.exchange(url, HttpMethod.GET, RequestHelper.getGzipHttpEntity(), generic);
 } catch (Exception e) {
 LOGGER.error("RestTemplate: {} - {}", url, e.getMessage());
 }
 return response;
 }
}

And here is how I make a call to my static execute:

ResponseEntity<Channels> response = RepositoryUtils.execute(channelUrlFinal, restTemplate, Channels.class);

• jhyot: Please let us know the exact error and the location. My guess is you need to change the method signature to public static ResponseEntity execute(String url, RestTemplate restTemplate, Class<?> generic) {
• DanielD: @jhyot I'm not getting an error but two warnings instead. When I'm calling my execute method I get an unchecked assignment warning since I'm expecting a ResponseEntity<Channels> even though my method only returns ResponseEntity

Answer 1

Here is what you could try as signature of your method:

public static <T> ResponseEntity<T> execute(String url, RestTemplate restTemplate, 
 Class<T> generic) {