Improve property defaults

See gh-41851

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/pulsar/PulsarProperties.java

@@ -311,17 +311,15 @@ public class PulsarProperties {
 
 			/**
 			 * Default tenant to use when producing or consuming messages against a
-			 * non-fully-qualified topic URL. When not specified Pulsar uses a default
-			 * tenant of 'public'.
+			 * non-fully-qualified topic URL.
 			 */
-			private String tenant;
+			private String tenant = "public";
 
 			/**
 			 * Default namespace to use when producing or consuming messages against a
-			 * non-fully-qualified topic URL. When not specified Pulsar uses a default
-			 * namespace of 'default'.
+			 * non-fully-qualified topic URL.
 			 */
-			private String namespace;
+			private String namespace = "default";
 
 			public String getTenant() {
 				return this.tenant;

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/pulsar/PulsarPropertiesTests.java

@@ -30,6 +30,7 @@ import org.apache.pulsar.client.api.SubscriptionInitialPosition;
 import org.apache.pulsar.client.api.SubscriptionMode;
 import org.apache.pulsar.client.api.SubscriptionType;
 import org.apache.pulsar.common.schema.SchemaType;
+import org.assertj.core.extractor.Extractors;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
@@ -40,6 +41,7 @@ import org.springframework.boot.autoconfigure.pulsar.PulsarProperties.Failover.B
 import org.springframework.boot.context.properties.bind.BindException;
 import org.springframework.boot.context.properties.bind.Binder;
 import org.springframework.boot.context.properties.source.MapConfigurationPropertySource;
+import org.springframework.pulsar.core.PulsarTopicBuilder;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
@@ -247,9 +249,12 @@ class PulsarPropertiesTests {
 
 		@Test
 		void bindWhenValuesNotSpecified() {
+			PulsarTopicBuilder defaultTopicBuilder = new PulsarTopicBuilder();
 			assertThat(new PulsarProperties().getDefaults().getTopic()).satisfies((defaults) -> {
-				assertThat(defaults.getTenant()).isNull();
-				assertThat(defaults.getNamespace()).isNull();
+				assertThat(defaults.getTenant())
+					.isEqualTo(Extractors.byName("defaultTenant").apply(defaultTopicBuilder));
+				assertThat(defaults.getNamespace())
+					.isEqualTo(Extractors.byName("defaultNamespace").apply(defaultTopicBuilder));
 			});
 		}