MINOR: Displaying default entity name in MetadataShell (apache#12053)

When debugging some bugs related to configs, I find we are unable to show default broker/topic entity name since the resourceName="". Changed it to similar to how we trait default client quotas.

Reviewers: Luke Chen <[email protected]>

Author: dengziming

shell/src/main/java/org/apache/kafka/shell/MetadataNodeManager.java

@@ -215,7 +215,7 @@ void handleMessage(ApiMessage message) {
     }
 
     private void handleCommitImpl(MetadataRecordType type, ApiMessage message)
-            throws Exception {
+        throws Exception {
         switch (type) {
             case REGISTER_BROKER_RECORD: {
                 DirectoryNode brokersNode = data.root.mkdirs("brokers");
@@ -268,7 +268,7 @@ private void handleCommitImpl(MetadataRecordType type, ApiMessage message)
                             "Can't handle ConfigResource.Type " + record.resourceType());
                 }
                 DirectoryNode configDirectory = data.root.mkdirs("configs").
-                    mkdirs(typeString).mkdirs(record.resourceName());
+                    mkdirs(typeString).mkdirs(record.resourceName().isEmpty() ? "<default>" : record.resourceName());
                 if (record.value() == null) {
                     configDirectory.rmrf(record.name());
                 } else {

shell/src/test/java/org/apache/kafka/shell/MetadataNodeManagerTest.java

@@ -138,26 +138,32 @@ public void testPartitionRecord() {
 
     @Test
     public void testValidConfigRecord() {
-        checkValidConfigRecord(ConfigResource.Type.BROKER.id(), "broker");
-        checkValidConfigRecord(ConfigResource.Type.TOPIC.id(), "topic");
+        checkValidConfigRecord(ConfigResource.Type.BROKER.id(), "broker", "0", "0");
+        checkValidConfigRecord(ConfigResource.Type.TOPIC.id(), "topic", "0", "0");
     }
 
-    private void checkValidConfigRecord(byte resourceType, String typeString) {
+    @Test
+    public void testDefaultBrokerRecord() {
+        checkValidConfigRecord(ConfigResource.Type.BROKER.id(), "broker", "", "<default>");
+        // Default topic resources are not allowed, so we don't test it.
+    }
+
+    private void checkValidConfigRecord(byte resourceType, String typeString, String resourceName, String resourceNameKey) {
         ConfigRecord configRecord = new ConfigRecord()
             .setResourceType(resourceType)
-            .setResourceName("0")
+            .setResourceName(resourceName)
             .setName("name")
             .setValue("kraft");
 
         metadataNodeManager.handleMessage(configRecord);
         assertEquals("kraft",
-            metadataNodeManager.getData().root().directory("configs", typeString, "0").file("name").contents());
+            metadataNodeManager.getData().root().directory("configs", typeString, resourceNameKey).file("name").contents());
 
         // null value indicates delete
         configRecord.setValue(null);
         metadataNodeManager.handleMessage(configRecord);
         assertFalse(
-            metadataNodeManager.getData().root().directory("configs", typeString, "0").children().containsKey("name"));
+            metadataNodeManager.getData().root().directory("configs", typeString, resourceNameKey).children().containsKey("name"));
     }
 
     @Test