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ErrorDecoder.java
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/*
* Copyright 2013 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package feign.codec;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.Date;
import java.util.Map;
import feign.FeignException;
import feign.Response;
import feign.RetryableException;
import static feign.FeignException.errorStatus;
import static feign.Util.RETRY_AFTER;
import static feign.Util.checkNotNull;
import static java.util.Locale.US;
import static java.util.concurrent.TimeUnit.NANOSECONDS;
import static java.util.concurrent.TimeUnit.SECONDS;
/**
* Allows you to massage an exception into a application-specific one. Converting out to a throttle
* exception are examples of this in use.
* <br>
* Ex.
* <br>
* <pre>
* class IllegalArgumentExceptionOn404Decoder extends ErrorDecoder {
*
* @Override
* public Exception decode(String methodKey, Response response) {
* if (response.status() == 404)
* throw new IllegalArgumentException("zone not found");
* return ErrorDecoder.DEFAULT.decode(methodKey, request, response);
* }
*
* }
* </pre>
* <br>
* <b>Error handling</b><br>
* <br>
* Responses where {@link Response#status()} is not in the 2xx range are
* classified as errors, addressed by the {@link ErrorDecoder}. That said,
* certain RPC apis return errors defined in the {@link Response#body()} even on
* a 200 status. For example, in the DynECT api, a job still running condition
* is returned with a 200 status, encoded in json. When scenarios like this
* occur, you should raise an application-specific exception (which may be
* {@link feign.RetryableException retryable}).
*/
public interface ErrorDecoder {
/**
* Implement this method in order to decode an HTTP {@link Response} when
* {@link Response#status()} is not in the 2xx range. Please raise application-specific exceptions where possible.
* If your exception is retryable, wrap or subclass {@link RetryableException}
*
* @param methodKey {@link feign.Feign#configKey} of the java method that invoked the request. ex. {@code IAM#getUser()}
* @param response HTTP response where {@link Response#status() status} is greater than or equal to {@code 300}.
* @return Exception IOException, if there was a network error reading the
* response or an application-specific exception decoded by the
* implementation. If the throwable is retryable, it should be
* wrapped, or a subtype of {@link RetryableException}
*/
public Exception decode(String methodKey, Response response);
public static class Default implements ErrorDecoder {
private final RetryAfterDecoder retryAfterDecoder = new RetryAfterDecoder();
@Override
public Exception decode(String methodKey, Response response) {
FeignException exception = errorStatus(methodKey, response);
Date retryAfter = retryAfterDecoder.apply(firstOrNull(response.headers(), RETRY_AFTER));
if (retryAfter != null)
return new RetryableException(exception.getMessage(), exception, retryAfter);
return exception;
}
private <T> T firstOrNull(Map<String, Collection<T>> map, String key) {
if (map.containsKey(key) && !map.get(key).isEmpty()) {
return map.get(key).iterator().next();
}
return null;
}
}
/**
* Decodes a {@link feign.Util#RETRY_AFTER} header into an absolute date,
* if possible.
* <br>
* See <a
* href="https://tools.ietf.org/html/rfc2616#section-14.37">Retry-After
* format</a>
*/
static class RetryAfterDecoder {
static final DateFormat RFC822_FORMAT = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss 'GMT'", US);
private final DateFormat rfc822Format;
RetryAfterDecoder() {
this(RFC822_FORMAT);
}
protected long currentTimeNanos() {
return System.currentTimeMillis();
}
RetryAfterDecoder(DateFormat rfc822Format) {
this.rfc822Format = checkNotNull(rfc822Format, "rfc822Format");
}
/**
* returns a date that corresponds to the first time a request can be
* retried.
*
* @param retryAfter String in <a
* href="https://tools.ietf.org/html/rfc2616#section-14.37"
* >Retry-After format</a>
*/
public Date apply(String retryAfter) {
if (retryAfter == null)
return null;
if (retryAfter.matches("^[0-9]+$")) {
long currentTimeMillis = NANOSECONDS.toMillis(currentTimeNanos());
long deltaMillis = SECONDS.toMillis(Long.parseLong(retryAfter));
return new Date(currentTimeMillis + deltaMillis);
}
synchronized (rfc822Format) {
try {
return rfc822Format.parse(retryAfter);
} catch (ParseException ignored) {
return null;
}
}
}
}
}