[GitHub] [arrow] liyafan82 commented on a change in pull request #9088: ARROW-11114: [Java] Fix Schema and Field metadata JSON serialization

[GitBox <gi...@apache.org>]

liyafan82 commented on a change in pull request #9088:
URL: https://github.com/apache/arrow/pull/9088#discussion_r551302282



##########
File path: java/vector/src/main/java/org/apache/arrow/vector/types/pojo/Schema.java
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@@ -137,15 +138,35 @@ private Schema(@JsonProperty("fields") Iterable<Field> fields,
         .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
   }
 
+  static List<Map<String, String>> convertMetadata(Map<String, String> metadata) {
+    return (metadata == null) ? null : metadata.entrySet()
+        .stream()
+        .map(Schema::convertEntryToKeyValueMap)
+        .collect(Collectors.toList());
+  }
+
+  private static Map<String, String> convertEntryToKeyValueMap(Map.Entry<String, String> entry) {
+    Map<String, String> map = new HashMap<>(2);
+    map.put("key", entry.getKey());

Review comment:
       maybe we can extract the literals as static final variables?




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