[FLINK-5705] [WebMonitor] WebMonitor request/response use UTF-8 expli…

…citly

This closes apache#3257

flink-runtime-web/src/main/java/org/apache/flink/runtime/webmonitor/HttpRequestHandler.java

@@ -107,8 +107,8 @@ public void channelRead0(ChannelHandlerContext ctx, HttpObject msg) {
  else if (currentRequest.getMethod() == HttpMethod.POST) {
  // POST comes in multiple objects. First the request, then the contents
  // keep the request and path for the remaining objects of the POST request
- currentRequestPath = new QueryStringDecoder(currentRequest.getUri()).path();
- currentDecoder = new HttpPostRequestDecoder(DATA_FACTORY, currentRequest);
+ currentRequestPath = new QueryStringDecoder(currentRequest.getUri(), ENCODING).path();
+ currentDecoder = new HttpPostRequestDecoder(DATA_FACTORY, currentRequest, ENCODING);
  }
  else {
  throw new IOException("Unsupported HTTP method: " + currentRequest.getMethod().name());

flink-runtime-web/src/main/java/org/apache/flink/runtime/webmonitor/RuntimeMonitorHandler.java

@@ -30,17 +30,18 @@
 import io.netty.handler.codec.http.router.KeepAliveWrite;
 import io.netty.handler.codec.http.router.Routed;
 
-import java.net.URLDecoder;
 import org.apache.flink.runtime.instance.ActorGateway;
 import org.apache.flink.runtime.webmonitor.handlers.RequestHandler;
 import org.apache.flink.util.ExceptionUtils;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+
 import scala.concurrent.Future;
 import scala.concurrent.duration.FiniteDuration;
 
 import java.net.InetSocketAddress;
+import java.net.URLDecoder;
 import java.nio.charset.Charset;
 import java.util.HashMap;
 import java.util.Map;
@@ -116,6 +117,8 @@ protected void respondAsLeader(ChannelHandlerContext ctx, Routed routed, ActorGa
  }
 
  response.headers().set(HttpHeaders.Names.ACCESS_CONTROL_ALLOW_ORIGIN, "*");
+ // Content-Encoding:utf-8
+ response.headers().set(HttpHeaders.Names.CONTENT_ENCODING, ENCODING.name());
 
  KeepAliveWrite.flush(ctx, routed.request(), response);
  }