Fix CSV/RAW output header being application/json rather than plain/text (backport #1779 to 1.3)

legacy/src/main/java/org/opensearch/sql/legacy/plugin/RestSQLQueryAction.java

@@ -167,14 +167,15 @@ private ResponseListener<QueryResponse> createQueryResponseListener(RestChannel
       @Override
       public void onResponse(QueryResponse response) {
         sendResponse(channel, OK,
-            formatter.format(new QueryResult(response.getSchema(), response.getResults())));
+            formatter.format(new QueryResult(response.getSchema(), response.getResults())),
+            formatter.contentType());
       }
 
       @Override
       public void onFailure(Exception e) {
         LOG.error("Error happened during query handling", e);
         logAndPublishMetrics(e);
-        sendResponse(channel, INTERNAL_SERVER_ERROR, formatter.format(e));
+        sendResponse(channel, INTERNAL_SERVER_ERROR, formatter.format(e), formatter.contentType());
       }
     };
   }
@@ -188,8 +189,12 @@ private <T> T doPrivileged(PrivilegedExceptionAction<T> action) {
   }
 
   private void sendResponse(RestChannel channel, RestStatus status, String content) {
-    channel.sendResponse(new BytesRestResponse(
-        status, "application/json; charset=UTF-8", content));
+    sendResponse(channel, status, content, "application/json; charset=UTF-8");
+  }
+
+  private void sendResponse(RestChannel channel, RestStatus status, String content,
+                            String contentType) {
+    channel.sendResponse(new BytesRestResponse(status, contentType, content));
   }
 
   private static void logAndPublishMetrics(Exception e) {

protocol/src/main/java/org/opensearch/sql/protocol/response/format/FlatResponseFormatter.java

@@ -19,6 +19,8 @@
 
 @RequiredArgsConstructor
 public abstract class FlatResponseFormatter implements ResponseFormatter<QueryResult> {
+  public static final String CONTENT_TYPE = "plain/text; charset=UTF-8";
+
   private static String INLINE_SEPARATOR = ",";
   private static final String INTERLINE_SEPARATOR = System.lineSeparator();
   private static final Set<String> SENSITIVE_CHAR = ImmutableSet.of("=", "+", "-", "@");
@@ -30,6 +32,10 @@ public FlatResponseFormatter(String seperator, boolean sanitize) {
     this.sanitize = sanitize;
   }
 
+  public String contentType() {
+    return CONTENT_TYPE;
+  }
+
   @Override
   public String format(QueryResult response) {
     FlatResult result = new FlatResult(response, sanitize);

protocol/src/main/java/org/opensearch/sql/protocol/response/format/JsonResponseFormatter.java

@@ -24,6 +24,8 @@
 @RequiredArgsConstructor
 public abstract class JsonResponseFormatter<R> implements ResponseFormatter<R> {
 
+  public static final String CONTENT_TYPE = "application/json; charset=UTF-8";
+
   /**
    * JSON format styles: pretty format or compact format without indent and space.
    */
@@ -36,6 +38,10 @@ public enum Style {
    */
   private final Style style;
 
+  public String contentType() {
+    return CONTENT_TYPE;
+  }
+
   @Override
   public String format(R response) {
     return jsonify(buildJsonObject(response));

protocol/src/main/java/org/opensearch/sql/protocol/response/format/ResponseFormatter.java

@@ -27,4 +27,11 @@ public interface ResponseFormatter<R> {
    */
   String format(Throwable t);
 
+  /**
+   * The contentType of the formatter.
+   *
+   * @return string with the contentType of the formatter
+   */
+  String contentType();
+
 }