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ErrorDecoder.java
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/**
* Copyright 2012-2020 The Feign Authors
*
* 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 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.SECONDS;
import feign.FeignException;
import feign.Response;
import feign.RetryableException;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.Date;
import java.util.Map;
/**
* Allows you to massage an exception into a application-specific one. Converting out to a throttle
* exception are examples of this in use.
*
* <p/>
* Ex:
*
* <pre>
* class IllegalArgumentExceptionOn404Decoder implements ErrorDecoder {
*
* @Override
* public Exception decode(String methodKey, Response response) {
* if (response.status() == 400)
* throw new IllegalArgumentException("bad zone name");
* return new ErrorDecoder.Default().decode(methodKey, response);
* }
*
* }
* </pre>
*
* <p/>
* <b>Error handling</b>
*
* <p/>
* 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}).
*
* <p/>
* <b>Not Found Semantics</b>
* <p/>
* It is commonly the case that 404 (Not Found) status has semantic value in HTTP apis. While the
* default behavior is to raise exeception, users can alternatively enable 404 processing via
* {@link feign.Feign.Builder#decode404()}.
*/
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(
response.status(),
exception.getMessage(),
response.request().httpMethod(),
exception,
retryAfter,
response.request());
}
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);
}
RetryAfterDecoder(DateFormat rfc822Format) {
this.rfc822Format = checkNotNull(rfc822Format, "rfc822Format");
}
protected long currentTimeMillis() {
return System.currentTimeMillis();
}
/**
* 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]+\\.?0*$")) {
retryAfter = retryAfter.replaceAll("\\.0*$", "");
long deltaMillis = SECONDS.toMillis(Long.parseLong(retryAfter));
return new Date(currentTimeMillis() + deltaMillis);
}
synchronized (rfc822Format) {
try {
return rfc822Format.parse(retryAfter);
} catch (ParseException ignored) {
return null;
}
}
}
}
}