Illegal character in wildfly with GZIP Encoding

I have a client that sends a request to a REST webservice using Encoding: gzip. This triggers an exception in Wildfly:

> org.jboss.resteasy.spi.ReaderException: com.fasterxml.jackson.core.JsonParseException: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens

By default, GZIP encoding/decoding is disabled in Wildfly/RESTEasy for security reasons:

> Decompression carries a risk of attack from a bad actor that can package an entity that will expand greatly. Consequently, RESTEasy disables GZIP compression / decompression by default.

Your server receives a zipped stream and tries to parse it as a JSON string.

There are several ways to enable GZIP handling in Wildfly. One is to include the Encoder/Decoder classnames in a META-INF/services/javax.ws.rs.ext.Providers and amend the deployment-structure.xml file.

Or you can add providers to your code (kotlin example below):

import org.jboss.resteasy.plugins.interceptors.GZIPDecodingInterceptor
import org.jboss.resteasy.plugins.interceptors.GZIPEncodingInterceptor
import javax.ws.rs.ext.Provider
@Provider class GZIPDecoder : GZIPDecodingInterceptor()
@Provider class GZIPEncoder : GZIPEncodingInterceptor()

And add RESTEasy core dependency in pom.xml:

<dependency>
  <groupId>org.jboss.resteasy</groupId>
  <artifactId>resteasy-core</artifactId>
  <version>5.0.0.Final</version>
  <scope>provided</scope>
</dependency>

Or you could create your own Interceptors, for example (basic implementation, should only be used in simple cases):

@Provider
public class GZIPDecoder implements ReaderInterceptor {
  @Override
  public Object aroundReadFrom(ReaderInterceptorContext ctx) throws IOException, WebApplicationException {
    if (ctx.getHeaders().getOrDefault("Content-Encoding", emptyList()).contains("gzip")) {
      GZIPInputStream is = new GZIPInputStream(ctx.getInputStream());
      ctx.setInputStream(is);
    }
    return ctx.proceed();
  }
}