How to consume protobuf parameters using Spring REST?

Question

I'm trying to pass a protobuf parameter to a REST endpoint but I get

org.springframework.web.client.HttpServerErrorException: 500 null

each time I try. What I have now is something like this:

@RestController
public class TestTaskEndpoint {

    @PostMapping(value = "/testTask", consumes = "application/x-protobuf", produces = "application/x-protobuf")
    TestTaskComplete processTestTask(TestTask testTask) {
        // TestTask is a generated protobuf class
        return generateResult(testTask);
    }
}


@Configuration
public class AppConfiguration {

    @Bean
    ProtobufHttpMessageConverter protobufHttpMessageConverter() {
        return new ProtobufHttpMessageConverter();
    }

}

@SpringBootApplication
public class JavaConnectorApplication {

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

and my test looks like this:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
@WebAppConfiguration
public class JavaConnectorApplicationTest {


    @Configuration
    public static class RestClientConfiguration {

        @Bean
        RestTemplate restTemplate(ProtobufHttpMessageConverter hmc) {
            return new RestTemplate(Arrays.asList(hmc));
        }

        @Bean
        ProtobufHttpMessageConverter protobufHttpMessageConverter() {
            return new ProtobufHttpMessageConverter();
        }
    }

    @Autowired
    private RestTemplate restTemplate;

    private int port = 8081;

    @Test
    public void contextLoaded() {

        TestTask testTask = generateTestTask();

        final String url = "http://127.0.0.1:" + port + "/testTask/";
        ResponseEntity<TestTaskComplete> customer = restTemplate.postForEntity(url, testTask, TestTaskComplete.class);

        // ...

    }
}

I'm sure that it is something with the parameters because if I create a variant which does not take a protobuf parameter but returns one it just works fine. I tried debugging the controller code but the execution does not reach the method so the problem is probably somewhere else. How do I correctly parametrize this REST method?

Answer 1

This is my first stack overflow answer but I was a lot to frustred from searching for working examples with protobuf over http and spring.

the answer https://stackoverflow.com/a/44592469/15705964 from Jorge is nearly correct. Like the comments mention: "This won't work in itself. You need to add a converter somewhere at least."

Do it like this:

@Configuration
public class WebConfig implements WebMvcConfigurer {

    @Autowired
    ProtobufHttpMessageConverter protobufHttpMessageConverter;

    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        converters.add(protobufHttpMessageConverter);
    }

}

The ProtobufHttpMessageConverter will do his job automatically and add the object to your controller methode

@RestController
public class ProtobufController {

    @PostMapping(consumes = "application/x-protobuf", produces = "application/x-protobuf")
    public ResponseEntity<TestMessage.Response> handlePost(@RequestBody TestMessage.Request protobuf) {

    TestMessage.Response response = TestMessage.Response.newBuilder().setQuery("This is a protobuf server Response")
            .build();

    return ResponseEntity.ok(response);
}

Working example with send and reseive with rest take a look: https://github.com/Chriz42/spring-boot_protobuf_example