From 48528af37a6172fb58b51acf3cbfbba9177a643e Mon Sep 17 00:00:00 2001
From: Andrew Ross <andrross@amazon.com>
Date: Thu, 17 Oct 2024 11:46:42 -0500
Subject: [PATCH] Skip media type parsing for known string values (#16358)

Signed-off-by: Andrew Ross <andrross@amazon.com>
---
 .../core/xcontent/MediaTypeRegistry.java           | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/libs/core/src/main/java/org/opensearch/core/xcontent/MediaTypeRegistry.java b/libs/core/src/main/java/org/opensearch/core/xcontent/MediaTypeRegistry.java
index bbb55204712d1..82cc3951be753 100644
--- a/libs/core/src/main/java/org/opensearch/core/xcontent/MediaTypeRegistry.java
+++ b/libs/core/src/main/java/org/opensearch/core/xcontent/MediaTypeRegistry.java
@@ -57,6 +57,7 @@
 public final class MediaTypeRegistry {
     private static Map<String, MediaType> formatToMediaType = Map.of();
     private static Map<String, MediaType> typeWithSubtypeToMediaType = Map.of();
+    private static Map<String, MediaType> knownStringsToMediaType = Map.of();
 
     // Default mediaType singleton
     private static MediaType DEFAULT_MEDIA_TYPE;
@@ -84,6 +85,8 @@ private static void register(MediaType[] acceptedMediaTypes, Map<String, MediaTy
         // ensures the map is not overwritten:
         Map<String, MediaType> typeMap = new HashMap<>(typeWithSubtypeToMediaType);
         Map<String, MediaType> formatMap = new HashMap<>(formatToMediaType);
+        Map<String, MediaType> knownStringMap = new HashMap<>(knownStringsToMediaType);
+
         for (MediaType mediaType : acceptedMediaTypes) {
             if (formatMap.containsKey(mediaType.format())) {
                 throw new IllegalArgumentException("unable to register mediaType: [" + mediaType.format() + "]. Type already exists.");
@@ -107,13 +110,24 @@ private static void register(MediaType[] acceptedMediaTypes, Map<String, MediaTy
             MediaType mediaType = entry.getValue();
             typeMap.put(typeWithSubtype, mediaType);
             formatMap.putIfAbsent(mediaType.format(), mediaType); // ignore if the additional type mapping already exists
+            knownStringMap.put(mediaType.mediaType(), mediaType);
+            knownStringMap.put(mediaType.mediaTypeWithoutParameters(), mediaType);
         }
 
         formatToMediaType = Map.copyOf(formatMap);
         typeWithSubtypeToMediaType = Map.copyOf(typeMap);
+        knownStringsToMediaType = Map.copyOf(knownStringMap);
     }
 
     public static MediaType fromMediaType(String mediaType) {
+        if (mediaType == null) {
+            return null;
+        }
+        // Skip parsing if the string is an exact match for any known string value
+        final MediaType knownMediaType = knownStringsToMediaType.get(mediaType);
+        if (knownMediaType != null) {
+            return knownMediaType;
+        }
         ParsedMediaType parsedMediaType = parseMediaType(mediaType);
         return parsedMediaType != null ? parsedMediaType.getMediaType() : null;
     }