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How we can pass the response if ResponseEntity got failed(400 Error)

I am hitting one API using RestTemplate exchange method, Here I am getting responseEntity of ClientResponse Type. If we have any Bad request in first line of code, I'll get 400 and cursor will go to the catch and throwing Error. So remaining code(For setting a response Data) is not executing .Instead of this I want to set the response Data and I want to set status code also and want to execute remain code. How we can do it, Do we need to use Flag variable ??
ResponseEntity<ClientResponse> responseEntity = this.getRestTemplate().exchange(API_URL,
HttpMethod.POST, entity, ClientResponse.class);
response.setResponseEntity(responseEntity);
response.setValue(inputRequest.getValue));
response.setEndTime(LocalDateTime.now());
response.setRequestPayload(gson.toJson(inputRequest));
response.setHttpMethod(HttpMethod.POST);
response.setRequestHeaders(entity.getHeaders().toSingleValueMap());
} catch (Exception e) {
LOG.error("error occurred in service" + e.getMessage());
}
return response;

You can use restTemplate error handler for that. You can parse the error response returned from the rest template like 404 or some other error.
You can use those status code and error response to rest the response as per your need.
For that you need to define a class by implementing ResponseErrorHander.
public class ServiceResponseErrorHandler implements ResponseErrorHandler {
private List<HttpMessageConverter<?>> messageConverters;
#Override
public boolean hasError(ClientHttpResponse response) throws IOException {
return (response.getStatusCode().is4xxClientError() ||
response.getStatusCode().is5xxServerError());
}
#Override
public void handleError(ClientHttpResponse response) throws IOException {
#SuppressWarnings({ "unchecked", "rawtypes" })
HttpMessageConverterExtractor<ServiceErrorResponse> errorMessageExtractor =
new HttpMessageConverterExtractor(ServiceErrorResponse.class, messageConverters);
ServiceErrorResponse errorObject = errorMessageExtractor.extractData(response);
throw new ResponseEntityErrorException(
ResponseEntity.status(response.getRawStatusCode())
.headers(response.getHeaders())
.body(errorObject)
);
}
public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
this.messageConverters = messageConverters;
}
}
And use it in your rest template bean like this.
RestTemplateResponseErrorHandler errorHandler = new
RestTemplateResponseErrorHandler();
//pass the messageConverters to errror handler and let it convert json to object
errorHandler.setMessageConverters(restTemplate.getMessageConverters());
restTemplate.setErrorHandler(errorHandler);

How to get json response in Java in case of 4XX and 5XX error

I was trying out RestTemplate and Retrofit2. Both the libraries throw exception in case api returns 4XX/5XX. The api when hit from postman gives a JSON response body, along with 4XX/5XX.
How can I retrieve this JSON response using RestTemplate or Retrofit2.
Thanks.

Use the HttpClientErrorException, HttpStatusCodeException after try block as below.
try{
restTemplate.exchange("url", HttpMethod.GET, null, String.class);
}
catch (HttpClientErrorException errorException){
logger.info("Status code :: {}, Exception message :: {} , response body ::{}" , e.getStatusCode()
e.getMessage(), e.getResponseBodyAsString());
}
catch (HttpStatusCodeException e){
logger.info("Status code :: {}, Exception message :: {} , response body ::{}" , e.getStatusCode()
e.getMessage(), e.getResponseBodyAsString());
}

For that you have to create RestTemplateError handler and register that class while creating bean for RestTemplate.
#Bean
public RestTemplate getBasicRestTemplate() {
RestTemplate restTemplate = new RestTemplate();
restTemplate.setErrorHandler(new RestTemplateResponseErrorHandler());
return restTemplate;
}
where your handler class has to implements ResponseErrorHandler. You can read the json response that is stored in the body.
#Component
public class RestTemplateResponseErrorHandler implements ResponseErrorHandler {
private static final Logger LOGGER = LoggerFactory.getLogger(RestTemplateResponseErrorHandler.class);
#Override
public boolean hasError(ClientHttpResponse httpResponse) throws IOException {
return httpResponse.getStatusCode().series() == CLIENT_ERROR
|| httpResponse.getStatusCode().series() == SERVER_ERROR;
}
#Override
public void handleError(ClientHttpResponse httpResponse) throws IOException {
if (httpResponse.getStatusCode().series() == SERVER_ERROR) {
LOGGER.error("Handling server error response statusCode:{} ", httpResponse.getStatusCode());
} else if (httpResponse.getStatusCode().series() == CLIENT_ERROR) {
LOGGER.error("Handling Client error response statusCode:{} ", httpResponse.getStatusCode());
String body;
InputStreamReader inputStreamReader = new InputStreamReader(httpResponse.getBody(),
StandardCharsets.UTF_8);
body = new BufferedReader(inputStreamReader).lines().collect(Collectors.joining("\n"));
throw new CustomException(httpResponse.getStatusCode().toString(), httpResponse, body);
}
}
}

I am not able to alter Spring cloud gate way response in Global filter based on response headers from down stream?

My Goal is to receive some token from downstream server response headers by using ServerHttpResponseDecorator without this I am not able to get response headers in GlobalFilter. based on token I am planning to alter downstream response by raising a custom exception and handled in ErrorWebExceptionHandler.
The problem is once I have read the response headers from downstream service even exception also not able to stop the flow I am getting an original response whatever is coming from downstream service but if I raised an exception before headers reading It is working as expected.
GlobalFilter Sample code
#Component
public class CustomFilter implements GlobalFilter, Ordered {
#Override
public int getOrder() {
return -2;
}
#Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
ServerHttpResponse originalResponse = exchange.getResponse();
ServerHttpResponseDecorator decoratedResponse = new ServerHttpResponseDecorator(originalResponse) {
#Override
public HttpHeaders getHeaders() {
String tokenFromHeader = super.getHeaders().getFirst("TOKEN");
String regIdFromHeader = super.getHeaders().getFirst("regId");
if (false) { // if (true) { It is hadled by exception handler as expected
// I have some Buginese logic here
throw new RuntimeException();
}
if (tokenFromHeader != null && regIdFromHeader != null) {
if (true) {
//I have some Buginese logic here
// No use I am getting original response from down streams
throw new RuntimeException();
}
}
return getDelegate().getHeaders();
}
};
return chain.filter(exchange.mutate().response(decoratedResponse).build());
}
}
Exception Handler
public class MyWebExceptionHandler implements ErrorWebExceptionHandler {
#Override
public Mono<Void> handle(ServerWebExchange exchange, Throwable ex) {
byte[] bytes = ( "Some custom text").getBytes(StandardCharsets.UTF_8);
DataBuffer buffer = exchange.getResponse().bufferFactory().wrap(bytes);
exchange.getResponse().getHeaders().add("Content-Type", "application/json;charset=UTF-8");
return exchange.getResponse().writeWith(Flux.just(buffer));
}
}
Expected out put is
Some custom text
But I am getting an original response

Spring Boot custom receive responses with HTTP OPTIONS by throw exceptions

I am new to Spring Boot, and I am trying to test a connection using HTTP OPTIONS.
My design is that I have a Service class that contains the logics for the testing. I also have an API Controller class that implements the method from Service.
My currently understanding is that the controller can be used to respond back different HTTP statuses using exceptions.
This is the method I wrote inside the controller for this purpose:
#PostMapping(path = "/test")
public ResponseEntity<Void> testConnection(#RequestBody URL url) {
try {
ControllerService.testConnection(url);
return ResponseEntity.status(HttpStatus.NO_CONTENT).body(null);
} catch (CredentialsException e) {
return ResponseEntity.status(HttpStatus.FORBIDDEN).body(null);
} catch (URLException | URISyntaxException e) {
return ResponseEntity.status(HttpStatus.NOT_FOUND).body(null);
} catch (UnknownException e) {
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(null);
}
}
The way exceptions are triggered and the method testConnection() are inside the service class:
public static void testConnection(URL url)
throws URISyntaxException, CredentialsException, URLException, UnknownException {
String authHeaderValue = "Basic " + Base64.getEncoder().encodeToString(("user" + ':' + "password").getBytes());
HttpHeaders requestHeaders = new HttpHeaders();
requestHeaders.set("Authorization", authHeaderValue);
RestTemplate rest = new RestTemplate();
final ResponseEntity<Object> optionsResponse = rest.exchange(url.toURI(), HttpMethod.OPTIONS, new HttpEntity<>(requestHeaders), Object.class);
int code = optionsResponse.getStatusCodeValue();
if (code == 403) {
throw new InvalidCredentialsException();
} else if (code == 404) {
throw new InvalidURLException();
} else if (code == 500) {
throw new UnknownErrorException();
} else if (code == 200){
String message = "Test connection successful";
LOGGER.info(message);
}
}
I have created those custom exception classes.
Is this the proper way to trigger the right HTTP response inside the controller method or does Spring Boot has some other design? If so, is my list of exceptions comprehensive enough or do I need to add more to the testConnection() method in the service class?

You can write ExceptionHandler for each of the Exception type, so you don't have to repeat the code or use try/ catch block at all. Just let your testConnection and other methods to throw the exception.
import org.springframework.web.bind.annotation.ExceptionHandler;
#ExceptionHandler(CredentialsException.class)
public void credentialsExceptionHandler(CredentialsException e, HttpServletResponse response) throws IOException {
response.sendError(HttpStatus.FORBIDDEN.value(), e.getMessage());
}
There are different ways to define and use the ExceptionHandler method. But conceptually same.

Add a body to a 404 Not Found Exception

In an REST API generated with JHipster, I want to throw some 404 exceptions. It is normally done with
return new ResponseEntity<>(HttpStatus.NOT_FOUND);
which actualy results in a 404 response to the xhr request. The problem is that in the front side, JHipster parses the response with
angular.fromJson(result)
and such result is empty when the 404 is the actual response, which makes the parse to fail.
If I point to an unmapped URI, lets say /api/user while my controller maps to /api/users (note the plural) the 404 I got from the API has a body in it:
{
"timestamp": "2016-04-25T18:33:19.947+0000",
"status": 404,
"error": "Not Found",
"message": "No message available",
"path": "/api/user/myuser/contact"
}
which is correctly parse in angular.
How can I create a body like this? Is this exception thrown by spring or is tomcat who throws it?
I tried this: Trigger 404 in Spring-MVC controller? but I cant set the parameters of the response.

Basic Idea
First option is to define error objects and return them as 404 Not Found body. Something like following:
Map<String, String> errors = ....;
return ResponseEntity.status(HttpStatus.NOT_FOUND).body(errors);
Instead of returning a typical ResponseEntity, you can throw an Exception that will be resolved to a 404 Not Found. Suppose you have a NotFoundException like:
#ResponseStatus(code = HttpStatus.NOT_FOUND)
public class NotFoundException extends RuntimeException {}
Then if you throw this exception in your controllers, you would see something like:
{
"timestamp":1461621047967,
"status":404,
"error":"Not Found",
"exception":"NotFoundException",
"message":"No message available",
"path":"/greet"
}
If you want to customize the message and other parts of body, you should define a ExceptionHandler for NotFoundException.
Introducing Exception Hierarchies
If you're creating a RESTful API and want to have different Error Codes and Error Messages for different exceptional cases, you can create a hierarchy of exceptions representing those cases and extract message and code from each one.
For example, you can introduce an exception, say, APIException which is super-class of all other exceptions thrown by your controllers. This class defines a code/message pair like:
public class APIException extends RuntimeException {
private final int code;
private final String message;
APIException(int code, String message) {
this.code = code;
this.message = message;
}
public int code() {
return code;
}
public String message() {
return message;
}
}
Each subclass depending on the nature of its exception can provide some sensible values for this pair. For example, we could have an InvalidStateException:
#ResponseStatus(code = HttpStatus.BAD_REQUEST)
public class InvalidStateException extends APIException {
public InvalidStateException() {
super(1, "Application is in invalid state");
}
}
Or that notorious not found ones:
#ResponseStatus(code = HttpStatus.NOT_FOUND)
public class SomethingNotFoundException extends APIException {
public SomethingNotFoundException() {
super(2, "Couldn't find something!");
}
}
Then we should define an ErrorController that catches those exceptions and turn them to meaningful JSON representations. That error controller may look like following:
#RestController
public class APIExceptionHandler extends AbstractErrorController {
private static final String ERROR_PATH = "/error";
private final ErrorAttributes errorAttributes;
#Autowired
public APIExceptionHandler(ErrorAttributes errorAttributes) {
super(errorAttributes);
this.errorAttributes = errorAttributes;
}
#RequestMapping(path = ERROR_PATH)
public ResponseEntity<?> handleError(HttpServletRequest request) {
HttpStatus status = getStatus(request);
Map<String, Object> errors = getErrorAttributes(request, false);
getApiException(request).ifPresent(apiError -> {
errors.put("message" , apiError.message());
errors.put("code", apiError.code());
});
// If you don't want to expose exception!
errors.remove("exception");
return ResponseEntity.status(status).body(errors);
}
#Override
public String getErrorPath() {
return ERROR_PATH;
}
private Optional<APIException> getApiException(HttpServletRequest request) {
RequestAttributes attributes = new ServletRequestAttributes(request);
Throwable throwable = errorAttributes.getError(attributes);
if (throwable instanceof APIException) {
APIException exception = (APIException) throwable;
return Optional.of(exception);
}
return Optional.empty();
}
}
So, if you throw an SomethingNotFoundException, the returned JSON would be like:
{
"timestamp":1461621047967,
"status":404,
"error":"Not Found",
"message":"Couldn't find something!",
"code": 2,
"path":"/greet"
}

I guess you can do this if you want to return some message or test with your error code
#ResponseBody
public ResponseEntity somthing() {
HttpHeaders headers = new HttpHeaders();
headers.add("Content-Type", "application/json; charset=utf-8");
return new ResponseEntity<>(new Gson().toJson("hello this is my message"), headers, HttpStatus.NOT_FOUND);
}

throw new ResponseStatusException(HttpStatus.NOT_FOUND, "message");