Develop Reference

OkHttpClient authenticator without retrofit

Im trying to refresh an Access token in my application following this solution.
My actual problem is handling the callback and then return the new request in the authenticate method.
I tried using an interface to return a String from my callback method but then I cant assign it to a variable, nor can I return the new request from there since its inside my onResponseListener.
How can I solve this issue?
public Request authenticate(Route route, Response response) throws IOException {
// GetAuthRequest is a void method, and I cant assign a String value on the callback.
getAuthRequest(new AuthResponse() {
#Override
public Request onSuccess(String token) {
return response.request().newBuilder()
.header("Authorization", "Bearer " + token)
.build();
}
});

I was using an Asynchronous call instead of Synchronous. Ended up making a method that returns an String like so:
private String getAuthRequest() {
// Make the request above
try (Response response = httpClient.newCall(request).execute()) {
JSONObject jsonObject = new JSONObject(response.body().string());
return jsonObject.getString("access_token");
} catch (IOException | JSONException e) {
e.printStackTrace();
}
return null;
}

Why handleResponse(URI url, HttpMethod method, ClientHttpResponse response) method of RestTemplate.class is getting called for a 200 Succeess response

I am calling an external API from my code using RestTemplate like below:
try {
responseEntity = restTemplate.exchange(url, HttpMethod.POST, requestEntity,
UploadResonse.class);
} catch (BusinessException ex) {
fetchErrorResponseEntity = ex.getResponseEntity();
if (fetchErrorResponseEntity.getStatusCodeValue() == 404) {
throw new BusinessException(ex.getMessage(), ErrorResponse.NOT_FOUND);
} else if (fetchErrorResponseEntity.getStatusCodeValue() == 500) {
throw new BusinessException(ex.getMessage(),
ErrorResponse.INTERNAL_SERVER_ERROR);
} else if (fetchErrorResponseEntity.getStatusCodeValue() == 400) {
throw new BusinessException(ex.getMessage(), ErrorResponse.INVALID_REQUEST);
}
}
This API call is returning 200 Success but when I debug it, it still goes to handleResponse(URI url, HttpMethod method, ClientHttpResponse response) method of RestTemplate.class
And then it's coming to my RestTemplateErrorHandler.java file
#Override
public boolean hasError(ClientHttpResponse clientHttpResponse)
throws IOException {
return clientHttpResponse.getStatusCode() != HttpStatus.OK;
}
#Override
public void handleError(ClientHttpResponse clientHttpResponse)
throws IOException {
String errMessage = getErrMessage(clientHttpResponse);
HttpStatus status = clientHttpResponse.getStatusCode();
switch (status) {
case BAD_REQUEST: // 400
throw new BusinessException(errMessage,
ErrorResponse.INVALID_REQUEST);
case NOT_FOUND:
throw new BusinessException(errMessage, ErrorResponse.NOT_FOUND);
case SERVICE_UNAVAILABLE: // 503
throw new BusinessException(errMessage, ErrorResponse.TIME_OUT);
case METHOD_NOT_ALLOWED: // 405
case INTERNAL_SERVER_ERROR: // 500
default:
throw new BusinessException(errMessage,
ErrorResponse.INTERNAL_SERVER_ERROR);
}
}
Can someone lease help me to understand if it's the correct behaviour.
I suspect that if the response is 200 Success it should not go to the RestTemlate.class and RestTemplateErrorHandler.class
This behaviour is creating problem when API return 201 Created status, that time it goes to handleError() method and return the default case INTERNAL_SERVER_ERROR
Can someone please help me here

The following code will call the error handler every time the response is not 200 OK, event if it is successful like 201 Created.
#Override
public boolean hasError(ClientHttpResponse clientHttpResponse)
throws IOException {
return clientHttpResponse.getStatusCode() != HttpStatus.OK;
}
Try changing the implementation to the following:
#Override
public boolean hasError(ClientHttpResponse clientHttpResponse)
throws IOException {
return !clientHttpResponse.getStatusCode().is2xxSuccessful();
}
This is better suited for your needs as it will consider all 2xx status as successful requests instead of only 200 OK.

According to documentation method handleResponse() as it name suggests will handle the given response, perform appropriate logging and invoke the ResponseErrorHandler (if needed) which is interface used by the RestTemplate to determine whether a particular response has an error or not.
RestTemplateErrorHandler class implements implements ResponseErrorHandler.
If the hasError() method returns true then Spring will automatically call the handleError() method. This is the flow.
If you check implementation for handleResponse method, given below, you will see that there is a call to hasError method to check if the response has any errors. Default implementation of hasError method will return true is response code is 4XX or 5XX. If there is no errors, method will proceed execution and handleError method won't be invoked, as I explained above.
protected void handleResponse(URI url, HttpMethod method, ClientHttpResponse response) throws IOException {
ResponseErrorHandler errorHandler = this.getErrorHandler();
boolean hasError = errorHandler.hasError(response);
if (this.logger.isDebugEnabled()) {
try {
this.logger.debug(method.name() + " request for \"" + url + "\" resulted in " + response.getRawStatusCode() + " (" + response.getStatusText() + ")" + (hasError ? "; invoking error handler" : ""));
} catch (IOException var7) {
;
}
}
if (hasError) {
errorHandler.handleError(url, method, response);
}
}
In code you posted hasError will return true for all response codes that are different from 200. That's why handleError is invoked.

How to avoid waiting on main thread when adding headers to requests using retrofit?

I use this to config my retrofit:
RestAdapter restAdapter = new RestAdapter.Builder()
//add headers to requests
.setRequestInterceptor(getAuthenticatedRequestInterceptor())
.setEndpoint(BASE_URL)
.setConverter(new GsonConverter(getGson()))
.build();
and The getAuthenticatedRequestInterceptor() method adds headers to request:
public AccountRequestInterceptor getAuthenticatedRequestInterceptor() {
AccountRequestInterceptor interceptor = new AccountRequestInterceptor();
Map<String, String> headers = new HashMap<>();
String accessToken = null;
try {
accessToken = TokenProvider.getInstance(mContext).getToken();
} catch (InterruptedException e) {
}
headers.put(HeadersContract.HEADER_AUTHONRIZATION, O_AUTH_AUTHENTICATION + accessToken);
interceptor.setHeader(headers);
return interceptor;
}
getToken() method is:
private synchronized string getToken() throws InterruptedException {
if (!isRefreshing()) {
//This is very important to call notify() on the same object that we call wait();
final TokenProvider myInstance = this;
setRefreshing(true);
MyApplication.getRestClient().getAccountService().getRefreshedToken(mLoginData.getRefreshToken())
.subscribe(new Observer<LoginResponse>() {
#Override
public void onCompleted() {
synchronized (myInstance) {
setRefreshing(false);
myInstance.notifyAll();
}
}
#Override
public void onError(Throwable e) {
synchronized (myInstance) {
setRefreshing(false);
myInstance.notifyAll();
}
}
#Override
public void onNext(LoginResponse loginResponse) {
synchronized (myInstance) {
mLoginData = loginResponse;
mAccountProvider.saveLoginData(loginResponse);
myInstance.notifyAll();
}
}
});
}
this.wait();
return mLoginData.getToken();
}
The TokenProvider.getInstance(mContext).getToken() has a wait() on main thread to get the response from an async method and i know that is a bad thing to do but i need this here to wait for the response to take the token from it and then return the token.how can i do this in a separate thread to avoid waiting on the main thread?
Note:
1 - that this is called before any request with retrofit.
2 - I read this and i know i can refresh token after a fail request, but for business reasons i want to avoid having an invalid token.
3 - I call MyApplication.getRestClient().getAccountService().login(loginRequest,callback...‌​) in my Activity and before adding token everything happened in background thread. so I want to use my token and do not block the main thread.
UPDATE: I added the following Interceptor to my new OkHttp:
public class RequestTokenInterceptor implements Interceptor {
#Override
public Response intercept(Interceptor.Chain chain) throws IOException {
Request request = chain.request();
Request newRequest;
try {
Log.d("addHeader", "Before");
String token = TokenProvider.getInstance(mContext).getToken();
if (token != null) {
newRequest = request.newBuilder()
.addHeader("Bearer", token)
.build();
} else {
// I want to cancel the request or raise an exception to catch it in onError method
// of retrofit callback.
}
} catch (InterruptedException e) {
Log.d("addHeader", "Error");
e.printStackTrace();
return chain.proceed(request);
}
Log.d("addHeader", "after");
return chain.proceed(newRequest);
}
}
Now how can i cancel the request or raise an exception to catch it in onError method of retrofit callback, if token is null?

It's a little bit strange issue but let me try to help you. :)
As you know you can refresh token after a failed request with retrofit using response interceptor.
Let's try to use interceptor before request.
public class RequestTokenInterceptor implements Interceptor {
#Override
public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
// Here where we'll try to refresh token.
// with an retrofit call
// After we succeed we'll proceed our request
Response response = chain.proceed(request);
return response;
}
}
And when you're creating your api create a new HttpClient:
OkHttpClient client = new OkHttpClient();
client.interceptors().add(new RequestTokenInterceptor());
And add your http client to your adapter like below:
.setClient(new OkClient(client))
If this works, before every request you'll try to refresh token first and then will proceed your api request. So in ui there'll be no difference with your normal api calls.
Edit:
I'm editing my answer too. If you want to return an error in else case if token null, in else case you can create your custom response:
private Response(Builder builder) {
this.request = builder.request;
this.protocol = builder.protocol;
this.code = builder.code;
this.message = builder.message;
this.handshake = builder.handshake;
this.headers = builder.headers.build();
this.body = builder.body;
this.networkResponse = builder.networkResponse;
this.cacheResponse = builder.cacheResponse;
this.priorResponse = builder.priorResponse;
}
or simply you can return a null response. if you build your custom response and set your code not to 200 such as 401 or 400+ you'll receive that response in Retrofit's callbacks failure method. Than you can do what ever you want.
If you return null you'll get a RuntimeException i think and still you can catch response in your callback's failure method.
After you create your own response in else you can create your custom callback and catch your null response and transform your custom error how ever you want like below:
public abstract class DefaultRequestCallback<T> implements Callback<T> {
public abstract void failure(YourCustomException ex);
public abstract void success(T responseBean);
#Override
public void success(T baseResponseBean, Response response) {
if (response == null) {
// Here we catch null response and transform it to our custom Exception
failure(new YourCustomException());
}
} else {
success(baseResponseBean);
}
}
#Override
public void failure(RetrofitError error) {
// Here's your failure method.
// Also you can transform default retrofit errors to your customerrors
YourCustomException ex = new YourCustomException();
failure(ex);
}
}
This can help you i think.
Edit 2:
You can build a new Response like below. There's a builder pattern in Retrofit's Response class. You can check it from there.
Response response = new Response.Builder().setCode(401).setMessage("Error Message").build();

You could make all long actions in AsyncTask doInBackground method, while in onPre- and onPostExecute you could show/hide some progress bars when user is waiting

Ok, I think if you are calling your getAuthenticatedRequestInterceptor() on the main thread and which in turns call getInstance(),in which i feel you would be creating an object of Type TokenProvider hence when you create this object in the main thread your object.wait() runs on main thread hence to run this on a background thread probably modify your getAuthenticatedRequestInterceptor() method to execute the following lines in a new thread.
try {
accessToken = TokenProvider.getInstance(mContext).getToken();
} catch (InterruptedException e) {
}
headers.put(HeadersContract.HEADER_AUTHONRIZATION, O_AUTH_AUTHENTICATION + accessToken);
interceptor.setHeader(headers);
return interceptor;
but this will have problems for notifying your RestAdapter as the main thread will proceed executing, hence i would suggest
you call getAuthenticatedRequestInterceptor() method first in a new thread and then notify your main thread to build your RestAdapter.This will free your main thread but with the strategy you are employing you will have to wait until you receive the token to make any calls.

How to capture exceptions on a REST client?

i have implemented rest webservices using Jersey, and whenever some exception occur on the server side, the client gets a generic HTTP 500 Internal Server Error, with no more info of the real exception. I found that people usually catch any exception on the server side, then throws a WebApplicationException, but even this way the client keeps getting the generic HTTP 500 Internal Server Error.
This is my webservice:
#PUT
#Produces(MediaType.APPLICATION_XML)
#Consumes(MediaType.APPLICATION_XML)
#Path("/transmitir")
public WrapperTransmissaoRetorno receber(WrapperTransmissao wrapperRecepcao) {
WrapperTransmissaoRetorno retorno = new WrapperTransmissaoRetorno();
retorno.setCodigoMaster(new Random().nextInt());
retorno.setDataRetorno(new Date());
if(true){
throw new WebApplicationException("Este pau eh bem graudo");
}
return retorno;
}
This is the code that calls the client:
try {
WsTransmissaoCliente client = new WsTransmissaoCliente();
WrapperTransmissao wrapperRecepcao = new WrapperTransmissao();
Transferencia transferencia = new Transferencia();
transferencia.setCodigoTabela(23);
transferencia.setCodigoTransferencia(56);
transferencia.setDataRetorno(new Date());
transferencia.setDataTransmissao(new Date(System.currentTimeMillis()+3000000));
transferencia.setNomeTabela("CUPOM");
transferencia.setTipoOperacao(TipoOperacao.UPDATE);
wrapperRecepcao.setTransferencia(transferencia);
Jumento jumento = new Jumento();
jumento.setIdade(24);
jumento.setNome("José");
wrapperRecepcao.setObjeto(jumento);
// Cabrito cabrito = new Cabrito();
// cabrito.setAltura(56);
// cabrito.setPeso(120.0);
// wrapperRecepcao.setObjeto(cabrito);
WrapperTransmissaoRetorno retorno = client.transmitir(wrapperRecepcao);
System.out.println("Retorno do WS: "+retorno);
} catch (Exception e) {
WebApplicationException exx = (WebApplicationException) e;
exx.printStackTrace();
}
How to avoid this and get the real exception? Or at least the message?
UPDATE
Here is the object i am sending as a response:
package br.atualy.integracaocheckout.wrappers;
import java.util.Date;
import javax.xml.bind.annotation.XmlRootElement;
#XmlRootElement
public class WrapperTransmissaoRetorno {
private Date dataRetorno;
private Integer codigoMaster;
public Date getDataRetorno() {
return dataRetorno;
}
public void setDataRetorno(Date dataRetorno) {
this.dataRetorno = dataRetorno;
}
public Integer getCodigoMaster() {
return codigoMaster;
}
public void setCodigoMaster(Integer codigoMaster) {
this.codigoMaster = codigoMaster;
}
#Override
public String toString() {
return "WrapperRecepcaoRetorno{" + "dataRetorno=" + dataRetorno + ", codigoMaster=" + codigoMaster + '}';
}
}
UPDATE 2
And here is the client:
import br.atualy.integracaocheckout.wrappers.WrapperTransmissao;
import br.atualy.integracaocheckout.wrappers.WrapperTransmissaoRetorno;
import javax.ws.rs.ClientErrorException;
import javax.ws.rs.client.Client;
import javax.ws.rs.client.WebTarget;
public class WsTransmissaoCliente {
private final WebTarget webTarget;
private final Client client;
private static final String BASE_URI = "http://localhost:8080/IntegracaoCheckout/webresources";
public WsTransmissaoCliente() {
client = javax.ws.rs.client.ClientBuilder.newClient();
webTarget = client.target(BASE_URI).path("transmissao");
}
// public String receber() throws ClientErrorException {
// WebTarget resource = webTarget;
// resource = resource.path("receber");
// return resource.request(javax.ws.rs.core.MediaType.APPLICATION_XML).get(String.class);
// }
public WrapperTransmissaoRetorno transmitir(WrapperTransmissao requestEntity) throws ClientErrorException {
return webTarget.path("transmitir")
.request(javax.ws.rs.core.MediaType.APPLICATION_XML)
.put(javax.ws.rs.client.Entity.entity(requestEntity, javax.ws.rs.core.MediaType.APPLICATION_XML), WrapperTransmissaoRetorno.class);
}
public void close() {
client.close();
}
}

If using jawax.ws.rs.core.Response object.
SERVER :: In case of exception/failure set it as :
// do stuff
// here e.getMessage() can be custom failure message too
response = Response.serverError().entity(e.getMessage()).build();
// return response object
return response;
CLIENT :: On the client side check following :
if(response != null && reponse.getStatus() == Response.Status.INTERNAL_SERVER_ERROR.getStatusCode()) {
String serverErrorMsg = response.readEntity(String.class);
throw new Exception(serverErrorMsg);
}

Generally it's better to declare your method as returning a Response object instead of a user-defined type, and set the data as the entity. Then if you want to indicate that an exception has happened, you can just pass that exception as the entity of the Response you are returning.
e.g.
#GET
#Path("/foo")
public Response getFoo() {
try {
// do stuff
return Response.ok(someData).build();
} catch (Exception e) {
return Response.serverError().entity(e).build();
}
}
You'll notice that this way you don't ever end up actually throwing an exception out of your method, but rather return an explicit 500 response with an exception as the entity. This way you can still throw exceptions out of your code, but they'll be handled nicely.
EDIT
I'm not sure what your client wrapper code is doing, but you can pass the expected response data type into your call with the normal REST client:
Client client = ClientBuilder.newClient();
WebTarget target = client.target("http://foo.com/foo");
String response = target.request().get(String.class);
or you can also pull it out of the Response using the readEntity() method:
Client client = ClientBuilder.newClient();
WebTarget target = client.target("http://foo.com/foo");
Response response = target.request().get();
String entity = response.readEntity(String.class);
It sounds like what you need to do is check the return code, and then parse the entity as a either a WrapperTransmissaoRetorno or a WebApplicationException depending on what code was returned:
Response response = client.transmitir(wrapperRecepcao);
if (response.getStatus() == Response.Status.OK.getStatusCode()) { // 200
WrapperTransmissaoRetorno retorno = response.readEntity(WrapperTransmissaoRetorno.class);
// do stuff
} else if (response.getStatus() == Response.Status.INTERNAL_SERVER_ERROR.getStatusCode()) { // 500
WebApplicationException e = response.readEntity(WebApplicationException.class);
// do stuff
} // etc for other response codes

Use response object in webapplication excemption. It should work.
From java docs:
WebApplicationException(String message)
Construct a new instance with a blank message and default HTTP status code of 500.
Its a blank message. I haven't tried it myself. I guess this is the problem.
https://jersey.java.net/apidocs/2.6/jersey/javax/ws/rs/WebApplicationException.html

Even after all the suggestions i could not manage to throw the exception to the client.
So what i did was to put a String property inside my returning class, so when an exception occurs on the server side, this String will contain the exception message and i can get it on the client.

Handling custom error response in JAX-RS 2.0 client library

I am starting to use the new client API library in JAX-RS and really loving it so far. I have found one thing I cannot figure out however. The API I am using has a custom error message format that looks like this for example:
{
"code": 400,
"message": "This is a message which describes why there was a code 400."
}
It returns 400 as the status code but also includes a descriptive error message to tell you what you did wrong.
However the JAX-RS 2.0 client is re-mapping the 400 status into something generic and I lose the good error message. It correctly maps it to a BadRequestException, but with a generic "HTTP 400 Bad Request" message.
javax.ws.rs.BadRequestException: HTTP 400 Bad Request
at org.glassfish.jersey.client.JerseyInvocation.convertToException(JerseyInvocation.java:908)
at org.glassfish.jersey.client.JerseyInvocation.translate(JerseyInvocation.java:770)
at org.glassfish.jersey.client.JerseyInvocation.access$500(JerseyInvocation.java:90)
at org.glassfish.jersey.client.JerseyInvocation$2.call(JerseyInvocation.java:671)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:228)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:424)
at org.glassfish.jersey.client.JerseyInvocation.invoke(JerseyInvocation.java:667)
at org.glassfish.jersey.client.JerseyInvocation$Builder.method(JerseyInvocation.java:396)
at org.glassfish.jersey.client.JerseyInvocation$Builder.get(JerseyInvocation.java:296)
Is there some sort of interceptor or custom error handler that can be injected so that I get access to the real error message. I've been looking through documentation but can't see any way of doing it.
I am using Jersey right now, but I tried this using CXF and got the same result. Here is what the code looks like.
Client client = ClientBuilder.newClient().register(JacksonFeature.class).register(GzipInterceptor.class);
WebTarget target = client.target("https://somesite.com").path("/api/test");
Invocation.Builder builder = target.request()
.header("some_header", value)
.accept(MediaType.APPLICATION_JSON_TYPE)
.acceptEncoding("gzip");
MyEntity entity = builder.get(MyEntity.class);
UPDATE:
I implemented the solution listed in the comment below. It is slightly different since the classes have changed a bit in the JAX-RS 2.0 client API. I still think it is wrong that the default behavior is to give a generic error message and discard the real one. I understand why it wouldn't parse my error object, but the un-parsed version should have been returned. I end up having the replicate exception mapping that the library already does.
Thanks for the help.
Here is my filter class:
#Provider
public class ErrorResponseFilter implements ClientResponseFilter {
private static ObjectMapper _MAPPER = new ObjectMapper();
#Override
public void filter(ClientRequestContext requestContext, ClientResponseContext responseContext) throws IOException {
// for non-200 response, deal with the custom error messages
if (responseContext.getStatus() != Response.Status.OK.getStatusCode()) {
if (responseContext.hasEntity()) {
// get the "real" error message
ErrorResponse error = _MAPPER.readValue(responseContext.getEntityStream(), ErrorResponse.class);
String message = error.getMessage();
Response.Status status = Response.Status.fromStatusCode(responseContext.getStatus());
WebApplicationException webAppException;
switch (status) {
case BAD_REQUEST:
webAppException = new BadRequestException(message);
break;
case UNAUTHORIZED:
webAppException = new NotAuthorizedException(message);
break;
case FORBIDDEN:
webAppException = new ForbiddenException(message);
break;
case NOT_FOUND:
webAppException = new NotFoundException(message);
break;
case METHOD_NOT_ALLOWED:
webAppException = new NotAllowedException(message);
break;
case NOT_ACCEPTABLE:
webAppException = new NotAcceptableException(message);
break;
case UNSUPPORTED_MEDIA_TYPE:
webAppException = new NotSupportedException(message);
break;
case INTERNAL_SERVER_ERROR:
webAppException = new InternalServerErrorException(message);
break;
case SERVICE_UNAVAILABLE:
webAppException = new ServiceUnavailableException(message);
break;
default:
webAppException = new WebApplicationException(message);
}
throw webAppException;
}
}
}
}

I believe you want to do something like this:
Response response = builder.get( Response.class );
if ( response.getStatusCode() != Response.Status.OK.getStatusCode() ) {
System.out.println( response.getStatusType() );
return null;
}
return response.readEntity( MyEntity.class );
Another thing you can try (since I don't know where this API puts stuff -- i.e. in the header or entity or what) is:
Response response = builder.get( Response.class );
if ( response.getStatusCode() != Response.Status.OK.getStatusCode() ) {
// if they put the custom error stuff in the entity
System.out.println( response.readEntity( String.class ) );
return null;
}
return response.readEntity( MyEntity.class );
If you would like to generally map REST response codes to Java exception you can add a client filter to do that:
class ClientResponseLoggingFilter implements ClientResponseFilter {
#Override
public void filter(final ClientRequestContext reqCtx,
final ClientResponseContext resCtx) throws IOException {
if ( resCtx.getStatus() == Response.Status.BAD_REQUEST.getStatusCode() ) {
throw new MyClientException( resCtx.getStatusInfo() );
}
...
In the above filter you can create specific exceptions for each code or create one generic exception type that wraps the Response code and entity.

There are other ways to getting a custom error message to the Jersey client besides writing a custom filter. (although the filter is an excellent solution)
1) Pass error message in an HTTP header field.
The detail error message could be in the JSON response and in an additional header field, such as "x-error-message".
The Server adds the HTTP error header.
ResponseBuilder rb = Response.status(respCode.getCode()).entity(resp);
if (!StringUtils.isEmpty(errMsg)){
rb.header("x-error-message", errMsg);
}
return rb.build();
The Client catches the exception, NotFoundException in my case, and reads the response header.
try {
Integer accountId = 2222;
Client client = ClientBuilder.newClient();
WebTarget webTarget = client.target("http://localhost:8080/rest-jersey/rest");
webTarget = webTarget.path("/accounts/"+ accountId);
Invocation.Builder ib = webTarget.request(MediaType.APPLICATION_JSON);
Account resp = ib.get(new GenericType<Account>() {
});
} catch (NotFoundException e) {
String errorMsg = e.getResponse().getHeaderString("x-error-message");
// do whatever ...
return;
}
2) Another solution is to catch the exception and read the response content.
try {
// same as above ...
} catch (NotFoundException e) {
String respString = e.getResponse().readEntity(String.class);
// you can convert to JSON or search for error message in String ...
return;
}

The class WebApplicationException was designed for that but for some reason it ignores and overwrites what you specify as parameter for the message.
For that reason I created my own extension WebAppException that honors the parameters. It is a single class and it doesn't require any response filter or a mapper.
I prefer exceptions than creating a Response as it can be thrown from anywhere while processing.
Simple usage:
throw new WebAppException(Status.BAD_REQUEST, "Field 'name' is missing.");
The class:
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.Status;
import javax.ws.rs.core.Response.Status.Family;
import javax.ws.rs.core.Response.StatusType;
public class WebAppException extends WebApplicationException {
private static final long serialVersionUID = -9079411854450419091L;
public static class MyStatus implements StatusType {
final int statusCode;
final String reasonPhrase;
public MyStatus(int statusCode, String reasonPhrase) {
this.statusCode = statusCode;
this.reasonPhrase = reasonPhrase;
}
#Override
public int getStatusCode() {
return statusCode;
}
#Override
public Family getFamily() {
return Family.familyOf(statusCode);
}
#Override
public String getReasonPhrase() {
return reasonPhrase;
}
}
public WebAppException() {
}
public WebAppException(int status) {
super(status);
}
public WebAppException(Response response) {
super(response);
}
public WebAppException(Status status) {
super(status);
}
public WebAppException(String message, Response response) {
super(message, response);
}
public WebAppException(int status, String message) {
super(message, Response.status(new MyStatus(status, message)). build());
}
public WebAppException(Status status, String message) {
this(status.getStatusCode(), message);
}
public WebAppException(String message) {
this(500, message);
}
}

A much more concise solution for anyone stumbling on this:
Calling .get(Class<T> responseType) or any of the other methods that take the result type as an argument Invocation.Builder will return a value of the desired type instead of a Response. As a side effect, these methods will check if the received status code is in the 2xx range and throw an appropriate WebApplicationException otherwise.
From the documentation:
Throws: WebApplicationException in case the response status code of
the response returned by the server is not successful and the
specified response type is not Response.
This allows to catch the WebApplicationException, retrieve the actual Response, process the contained entity as exception details (ApiExceptionInfo) and throw an appropriate exception (ApiException).
public <Result> Result get(String path, Class<Result> resultType) {
return perform("GET", path, null, resultType);
}
public <Result> Result post(String path, Object content, Class<Result> resultType) {
return perform("POST", path, content, resultType);
}
private <Result> Result perform(String method, String path, Object content, Class<Result> resultType) {
try {
Entity<Object> entity = null == content ? null : Entity.entity(content, MediaType.APPLICATION_JSON);
return client.target(uri).path(path).request(MediaType.APPLICATION_JSON).method(method, entity, resultType);
} catch (WebApplicationException webApplicationException) {
Response response = webApplicationException.getResponse();
if (response.getMediaType().equals(MediaType.APPLICATION_JSON_TYPE)) {
throw new ApiException(response.readEntity(ApiExceptionInfo.class), webApplicationException);
} else {
throw webApplicationException;
}
}
}
ApiExceptionInfo is custom data type in my application:
import lombok.Data;
#Data
public class ApiExceptionInfo {
private int code;
private String message;
}
ApiException is custom exception type in my application:
import lombok.Getter;
public class ApiException extends RuntimeException {
#Getter
private final ApiExceptionInfo info;
public ApiException(ApiExceptionInfo info, Exception cause) {
super(info.toString(), cause);
this.info = info;
}
}

[At least with Resteasy] there is one big disadvantage with the solution offered by #Chuck M and based on ClientResponseFilter.
When you use it based on ClientResponseFilter, your BadRequestException, NotAuthorizedException, ... exceptions are wrapped by javax.ws.rs.ProcessingException.
Clients of your proxy must not be forced to catch this javax.ws.rs.ResponseProcessingException exception.
Without filter, we get an original rest exception. If we catch and handle by default, it does not give us much:
catch (WebApplicationException e) {
//does not return response body:
e.toString();
// returns null:
e.getCause();
}
The problem can be solved on another level, when you extract a description from the error. WebApplicationException exception, which is a parent for all rest exceptions, contains javax.ws.rs.core.Response. Just write a helper method, that in case the exception is of WebApplicationException type, it will also check the response body. Here is a code in Scala, but the idea should be clear. The methord returns a clear description of the rest exception:
private def descriptiveWebException2String(t: WebApplicationException): String = {
if (t.getResponse.hasEntity)
s"${t.toString}. Response: ${t.getResponse.readEntity(classOf[String])}"
else t.toString
}
Now we move a responsibility to show exact error, on the client. Just use a shared exception handler to minimize effort for clients.

The following works for me
Response.status(Response.Status.BAD_REQUEST).entity(e.getMessage()).build();