Introduce an include_type_name constant

I started referring to this parameter name from various places in elastic#37149 so I
think it's a good idea to simplify things by referring to a common constant.

Author: Christoph Büscher

server/src/main/java/org/elasticsearch/rest/BaseRestHandler.java

@@ -58,6 +58,12 @@ public abstract class BaseRestHandler extends AbstractComponent implements RestH
 
     private final LongAdder usageCount = new LongAdder();
 
+    /**
+     * Parameter that controls whether certain REST apis should include type names in their requests or responses.
+     * Note: Support for this parameter will be removed after the transition perido to typeless APIs.
+     */
+    protected static final String INCLUDE_TYPE_NAME_PARAMETER = "include_type_name";
+
     protected BaseRestHandler(Settings settings) {
         // TODO drop settings from ctor
     }

server/src/main/java/org/elasticsearch/rest/action/admin/indices/RestCreateIndexAction.java

@@ -49,7 +49,7 @@ public String getName() {
 
     @Override
     public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
-        final boolean includeTypeName = request.paramAsBoolean("include_type_name", true);
+        final boolean includeTypeName = request.paramAsBoolean(INCLUDE_TYPE_NAME_PARAMETER, true);
         CreateIndexRequest createIndexRequest = new CreateIndexRequest(request.param("index"));
         if (request.hasContent()) {
             Map<String, Object> sourceAsMap = XContentHelper.convertToMap(request.content(), false, request.getXContentType()).v2();

server/src/main/java/org/elasticsearch/rest/action/admin/indices/RestGetMappingAction.java

@@ -20,8 +20,9 @@
 package org.elasticsearch.rest.action.admin.indices;
 
 import com.carrotsearch.hppc.cursors.ObjectCursor;
-import org.apache.logging.log4j.Logger;
+
 import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import org.elasticsearch.action.admin.indices.mapping.get.GetMappingsRequest;
 import org.elasticsearch.action.admin.indices.mapping.get.GetMappingsResponse;
 import org.elasticsearch.action.support.IndicesOptions;
@@ -85,7 +86,7 @@ public RestChannelConsumer prepareRequest(final RestRequest request, final NodeC
             deprecationLogger.deprecated("Type exists requests are deprecated, as types have been deprecated.");
         }
 
-        final boolean includeTypeName = request.paramAsBoolean("include_type_name", true);
+        final boolean includeTypeName = request.paramAsBoolean(INCLUDE_TYPE_NAME_PARAMETER, true);
         final String[] indices = Strings.splitStringByCommaToArray(request.param("index"));
         final String[] types = request.paramAsStringArrayOrEmptyIfAll("type");
         final GetMappingsRequest getMappingsRequest = new GetMappingsRequest();

server/src/main/java/org/elasticsearch/rest/action/admin/indices/RestPutMappingAction.java

@@ -68,7 +68,7 @@ public String getName() {
 
     @Override
     public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
-        final boolean includeTypeName = request.paramAsBoolean("include_type_name", true);
+        final boolean includeTypeName = request.paramAsBoolean(INCLUDE_TYPE_NAME_PARAMETER, true);
         PutMappingRequest putMappingRequest = putMappingRequest(Strings.splitStringByCommaToArray(request.param("index")));
         final String type = request.param("type");
         if (type != null && includeTypeName == false) {