Branch processing by the return value of RestTemplate and the status code of ResponseEntity in Spring Boot

The method of getting the status code changes without setting DefaultResponseErrorHandler The answer was here, but I missed it.

environment

Java : 11 JUnit : 4.12 Spring Boot : 2.1.6

Common sample code regardless of whether it is set or not

SandboxApplication.java

@SpringBootApplication
public class SandboxApplication {

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

    //Roughly bean registration here
    @Bean
    public RestTemplate setRestTemplate(){
        return new RestTemplate();
    }
}

Hoge.java

class Hoge {
    String message;

    public Hoge(@JsonProperty("message") String message) {
        this.message = message;
    }

    public String getMessage() {
        return message;
    }
}

SampleTest.java

@RunWith(SpringRunner.class)
@SpringBootTest
public class SampleTest {

    @Autowired
    RestTemplate restTemplate;
    @Autowired
    ObjectMapper objectMapper;
    @Autowired
    Sample sut;

    @Test
public void test() throws Exception {
        //2xx series: ex) OK
        setUpMockRestServer(HttpStatus.OK);
        assertThat(sut.getHoge().getMessage(), is("It's 200"));

        //4xx series error: ex) NOT_FOUND
        setUpMockRestServer(HttpStatus.NOT_FOUND);
        assertThat(sut.getHoge().getMessage(), is("It's 404"));

        //5xx series error: ex) INTERNAL_SERVER_ERROR
        setUpMockRestServer(HttpStatus.INTERNAL_SERVER_ERROR);
        assertThat(sut.getHoge().getMessage(), is("It's 500"));
    }

    private void setUpMockRestServer(HttpStatus status) throws JsonProcessingException {
        MockRestServiceServer mockServer = MockRestServiceServer.bindTo(restTemplate).ignoreExpectOrder(true).build();
        String response = objectMapper.writeValueAsString(new Hoge(status.value() + "That's right"));
        mockServer.expect(requestTo("https://hoges/1"))
                .andRespond(withStatus(status).body(response).contentType(MediaType.APPLICATION_JSON_UTF8));
    }
}

Do not set DefaultResponseErrorHandler

--In case of client error system (4xx), HttpClientErrorException --In case of server error system (5xx), HttpServerErrorException --In the case of the code you set yourself, ʻUnknownHttpStatusCodeException Each of the above needs to be handled bytry-catch`

Sample.java

@Component
public class Sample {

    RestTemplate restTemplate;

    public Sample(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    public Hoge getHoge() {
        ResponseEntity<Hoge> response;
        try {
            response = restTemplate.getForEntity("https://hoges/1", Hoge.class);
        } catch (HttpClientErrorException | HttpServerErrorException e) {
            //Can be branched by statusCode
            int statusCode = e.getStatusCode().value();
            return new Hoge(statusCode + "That's right");
        }

        return response.getBody();
    }
}

Set DefaultResponseErrorHandler

This can be achieved by inheriting DefaultResponseErrorHandler and setting it to be unnecessary.

SampleResponseErrorHandler.java

@Component
public class SampleResponseErrorHandler extends DefaultResponseErrorHandler {
    @Override
    public void handleError(ClientHttpResponse response) throws IOException {
        //By writing nothing, it does not raise an exception even if a server error and a client error occur.
    }
}

Sample.java

@Component
public class Sample {

    RestTemplate restTemplate;
    SampleResponseErrorHandler sampleResponseErrorHandler;

    public Sample(RestTemplate restTemplate, SampleResponseErrorHandler sampleResponseErrorHandler) {
        this.restTemplate = restTemplate;
        this.sampleResponseErrorHandler = sampleResponseErrorHandler;
    }

    public Hoge getHoge() {
        //Set your own Defined ErrorHandler in RestTemplate
        restTemplate.setErrorHandler(sampleResponseErrorHandler);
        ResponseEntity<Hoge> response = restTemplate.getForEntity("https://hoges/1", Hoge.class);
        //In the sample, it returns as it is, but here you can branch as much as you want with the status code that can be obtained from ResponseEntity
        return response.getBody();
    }
}

Summary

I wanted to get the status code and branch in detail, but I was addicted to not being able to pick it up with an exception.