servlet: extract ServletServerStream.serializeHeaders()

Author: panchenko

servlet/src/main/java/io/grpc/servlet/ServletServerStream.java

@@ -45,6 +45,7 @@
 import java.util.Map;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
+import java.util.function.BiConsumer;
 import java.util.function.Supplier;
 import java.util.logging.Logger;
 import javax.annotation.Nullable;
@@ -123,9 +124,13 @@ private void writeHeadersToServletResponse(Metadata metadata) {
     resp.setStatus(HttpServletResponse.SC_OK);
     resp.setContentType(CONTENT_TYPE_GRPC);
 
+    serializeHeaders(metadata, resp::addHeader);
+  }
+
+  private static void serializeHeaders(Metadata metadata, BiConsumer<String, String> consumer) {
     byte[][] serializedHeaders = TransportFrameUtil.toHttp2Headers(metadata);
     for (int i = 0; i < serializedHeaders.length; i += 2) {
-      resp.addHeader(
+      consumer.accept(
           new String(serializedHeaders[i], StandardCharsets.US_ASCII),
           new String(serializedHeaders[i + 1], StandardCharsets.US_ASCII));
     }
@@ -278,13 +283,8 @@ public void writeTrailers(Metadata trailers, boolean headersSent, Status status)
       if (!headersSent) {
         writeHeadersToServletResponse(trailers);
       } else {
-        byte[][] serializedHeaders = TransportFrameUtil.toHttp2Headers(trailers);
-        for (int i = 0; i < serializedHeaders.length; i += 2) {
-          String key = new String(serializedHeaders[i], StandardCharsets.US_ASCII);
-          String newValue = new String(serializedHeaders[i + 1], StandardCharsets.US_ASCII);
-          trailerSupplier.get().computeIfPresent(key, (k, v) -> v + "," + newValue);
-          trailerSupplier.get().putIfAbsent(key, newValue);
-        }
+        serializeHeaders(trailers, (key, value) ->
+            trailerSupplier.get().merge(key, value, TrailerSupplier::joinValues));
       }
 
       writer.complete();
@@ -322,6 +322,10 @@ private static final class TrailerSupplier implements Supplier<Map<String, Strin
     public Map<String, String> get() {
       return trailers;
     }
+
+    static String joinValues(String oldValue, String newValue) {
+      return oldValue + "," + newValue;
+    }
   }
 
   static String toHexString(byte[] bytes, int length) {