NullPointedException when using Spring RestTemplate in Java

Question

I'm using the latest Springframework, and having issues trying to GET an int from my server. All code was writen in Java.

When I interact with the server throught browser everything is OK. And when interacting with the server through the client I'm getting a NullPointerException.

Keep in mind I am a beginner software student.

Server Code (I tried both, works fine when using browser):

public class RestController {

    private GameSession gameSession = new GameSession();

    @RequestMapping(value = "registerPlayer")
    public int registerPlayer(@RequestParam("name") String name, @RequestParam("mode") boolean mode) {
        return gameSession.registerPlayer(name, mode);
    }

    @RequestMapping(value = "registerPlayer/{name}/{mode}")
    public int registerPlayer(@PathVariable String name, @PathVariable boolean mode) {
        return gameSession.registerPlayer(name, mode);
    }

}

Client Code (again tried both, with the same result):

@Component
public class GameSessionClient implements ISeaBattleGame{

    @Autowired
    private RestOperations restOperations;
    private String url;

    @Override
    public int registerPlayer(String name, boolean singlePlayerMode) {
        url = "http://localhost:8080/" + "registerPlayer?name=" + name + "&mode=" + (singlePlayerMode ? 1 : 0);
        return restOperations.getForObject(url, int.class);
    }

    @Override
    public int registerPlayer(String name, boolean singlePlayerMode) {
        url = "http://localhost:8080/" + "registerPlayer/" + name + "/" + (singlePlayerMode ? 1 : 0);
        return restOperations.getForObject(url, int.class);
    }
}

RestConfig Code:

@Configuration
public class RestConfig {

    @Bean
    public RestOperations createRestTemplate(final ClientHttpRequestFactory clientHttpRequestFactory){
        return new RestTemplate(clientHttpRequestFactory);
    }

    @Bean
    public ClientHttpRequestFactory clientHttpRequestFactory(@Value("${connect.timeout}") final int connectTimeout, @Value("${read.timeout}") final int readTimeout){
        HttpComponentsClientHttpRequestFactory httpComponentsClientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory();
        httpComponentsClientHttpRequestFactory.setReadTimeout(readTimeout);
        httpComponentsClientHttpRequestFactory.setConnectTimeout(connectTimeout);
        return httpComponentsClientHttpRequestFactory;
    }
}

App Code:

@SpringBootApplication
public class App implements CommandLineRunner {

    private static final Logger logger = LoggerFactory.getLogger(Application.class);

    @Autowired
    private GameSessionClient gameSessionClient;

    public static void main(String[] args){
        SpringApplication.run(Application.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        int playerNr = gameSessionClient.registerPlayer("test", true);
        logger.info("Response: {}", playerNr);
    }
}

The return restOperations.getForObject(url, int.class); results in a java.lang.NullPointerException

url: http://localhost:8080/registerPlayer/test/1 or http://localhost:8080/registerPlayer?name=test&mode=1 both result in 1 when using my browser

Any help would be much appreciated, as I'm getting pretty confused from this.

Please do keep in mind that this is a very common error message that has lots of information on how to solve already. — EJoshuaS - Stand with Ukraine, Mar 28 '18 at 14:29
Please also see: [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — EJoshuaS - Stand with Ukraine, Mar 28 '18 at 14:29
Renaming it to `restOperations` did not work. Although I changed: `private RestOperations restOperations;` to `private RestOperations restOperations = new RestConfig().createRestTemplate(new RestConfig().clientHttpRequestFactory(10000,10000)); ` Which is a work around, still trying to figure out why it's not AutoWiring — Kevin de Wit, Mar 28 '18 at 16:13

Jeryl Cook · Answer 1 · 2018-03-29T18:42:44.177

0

Update you code to below..will remove the NullPointer Exception your getting:

@Bean
    public RestOperations restOperations(final ClientHttpRequestFactory clientHttpRequestFactory){
        return new RestTemplate(clientHttpRequestFactory);
    }

and do this , instead of "Application.class":

public static void main(String[] args){
    SpringApplication.run(App.class, args);
}

edited Mar 29 '18 at 18:42

answered Mar 28 '18 at 16:42

Jeryl Cook

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1

As explained above, renaming it is still giving me a `NullPointerException` – Kevin de Wit Mar 28 '18 at 20:30
updated my answer..you have Application.class, and not App.class(to match the name of the class) – Jeryl Cook Mar 29 '18 at 18:43

NullPointedException when using Spring RestTemplate in Java

1 Answers1