Allow KafkaProperties to build properties with empty bundle name

Update `KafkaProperties` so that properties can still be built when
the bundle name has no text.

Fixes gh-43561

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/kafka/KafkaProperties.java

@@ -43,6 +43,7 @@ import org.springframework.core.io.Resource;
 import org.springframework.kafka.listener.ContainerProperties.AckMode;
 import org.springframework.kafka.security.jaas.KafkaJaasLoginModuleInitializer;
 import org.springframework.util.CollectionUtils;
+import org.springframework.util.StringUtils;
 import org.springframework.util.unit.DataSize;
 
 /**
@@ -1427,13 +1428,11 @@ public class KafkaProperties {
 
 		public Map<String, Object> buildProperties(SslBundles sslBundles) {
 			validate();
-			Properties properties = new Properties();
-			if (getBundle() != null) {
-				properties.in(SslConfigs.SSL_ENGINE_FACTORY_CLASS_CONFIG)
-					.accept(SslBundleSslEngineFactory.class.getName());
-				properties.in(SslBundle.class.getName()).accept(sslBundles.getBundle(getBundle()));
+			String bundleName = getBundle();
+			if (StringUtils.hasText(bundleName)) {
+				return buildPropertiesForSslBundle(sslBundles, bundleName);
 			}
-			else {
+			Properties properties = new Properties();
 			PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
 			map.from(this::getKeyPassword).to(properties.in(SslConfigs.SSL_KEY_PASSWORD_CONFIG));
 			map.from(this::getKeyStoreCertificateChain)
@@ -1444,43 +1443,52 @@ public class KafkaProperties {
 				.to(properties.in(SslConfigs.SSL_KEYSTORE_LOCATION_CONFIG));
 			map.from(this::getKeyStorePassword).to(properties.in(SslConfigs.SSL_KEYSTORE_PASSWORD_CONFIG));
 			map.from(this::getKeyStoreType).to(properties.in(SslConfigs.SSL_KEYSTORE_TYPE_CONFIG));
-				map.from(this::getTrustStoreCertificates)
-					.to(properties.in(SslConfigs.SSL_TRUSTSTORE_CERTIFICATES_CONFIG));
+			map.from(this::getTrustStoreCertificates).to(properties.in(SslConfigs.SSL_TRUSTSTORE_CERTIFICATES_CONFIG));
 			map.from(this::getTrustStoreLocation)
 				.as(this::resourceToPath)
 				.to(properties.in(SslConfigs.SSL_TRUSTSTORE_LOCATION_CONFIG));
 			map.from(this::getTrustStorePassword).to(properties.in(SslConfigs.SSL_TRUSTSTORE_PASSWORD_CONFIG));
 			map.from(this::getTrustStoreType).to(properties.in(SslConfigs.SSL_TRUSTSTORE_TYPE_CONFIG));
 			map.from(this::getProtocol).to(properties.in(SslConfigs.SSL_PROTOCOL_CONFIG));
+			return properties;
 		}
+
+		private Map<String, Object> buildPropertiesForSslBundle(SslBundles sslBundles, String name) {
+			Properties properties = new Properties();
+			properties.in(SslConfigs.SSL_ENGINE_FACTORY_CLASS_CONFIG).accept(SslBundleSslEngineFactory.class.getName());
+			properties.in(SslBundle.class.getName()).accept(sslBundles.getBundle(name));
 			return properties;
 		}
 
 		private void validate() {
-			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleNonNullValuesIn((entries) -> {
+			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleMatchingValuesIn((entries) -> {
 				entries.put("spring.kafka.ssl.key-store-key", getKeyStoreKey());
 				entries.put("spring.kafka.ssl.key-store-location", getKeyStoreLocation());
-			});
-			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleNonNullValuesIn((entries) -> {
+			}, this::hasValue);
+			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleMatchingValuesIn((entries) -> {
 				entries.put("spring.kafka.ssl.trust-store-certificates", getTrustStoreCertificates());
 				entries.put("spring.kafka.ssl.trust-store-location", getTrustStoreLocation());
-			});
-			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleNonNullValuesIn((entries) -> {
+			}, this::hasValue);
+			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleMatchingValuesIn((entries) -> {
 				entries.put("spring.kafka.ssl.bundle", getBundle());
 				entries.put("spring.kafka.ssl.key-store-key", getKeyStoreKey());
-			});
-			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleNonNullValuesIn((entries) -> {
+			}, this::hasValue);
+			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleMatchingValuesIn((entries) -> {
 				entries.put("spring.kafka.ssl.bundle", getBundle());
 				entries.put("spring.kafka.ssl.key-store-location", getKeyStoreLocation());
-			});
-			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleNonNullValuesIn((entries) -> {
+			}, this::hasValue);
+			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleMatchingValuesIn((entries) -> {
 				entries.put("spring.kafka.ssl.bundle", getBundle());
 				entries.put("spring.kafka.ssl.trust-store-certificates", getTrustStoreCertificates());
-			});
-			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleNonNullValuesIn((entries) -> {
+			}, this::hasValue);
+			MutuallyExclusiveConfigurationPropertiesException.throwIfMultipleMatchingValuesIn((entries) -> {
 				entries.put("spring.kafka.ssl.bundle", getBundle());
 				entries.put("spring.kafka.ssl.trust-store-location", getTrustStoreLocation());
-			});
+			}, this::hasValue);
+		}
+
+		private boolean hasValue(Object value) {
+			return (value instanceof String string) ? StringUtils.hasText(string) : value != null;
 		}
 
 		private String resourceToPath(Resource resource) {

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/client/ClientsConfiguredCondition.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,7 +36,6 @@ import org.springframework.core.type.AnnotatedTypeMetadata;
  * @author Madhura Bhave
  * @since 2.1.0
  */
-
 public class ClientsConfiguredCondition extends SpringBootCondition {
 
 	private static final Bindable<Map<String, OAuth2ClientProperties.Registration>> STRING_REGISTRATION_MAP = Bindable

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/kafka/KafkaPropertiesTests.java

@@ -87,6 +87,20 @@ class KafkaPropertiesTests {
 				"-----BEGINchain");
 	}
 
+	@Test
+	void sslPemConfigurationWithEmptyBundle() {
+		KafkaProperties properties = new KafkaProperties();
+		properties.getSsl().setKeyStoreKey("-----BEGINkey");
+		properties.getSsl().setTrustStoreCertificates("-----BEGINtrust");
+		properties.getSsl().setKeyStoreCertificateChain("-----BEGINchain");
+		properties.getSsl().setBundle("");
+		Map<String, Object> consumerProperties = properties.buildConsumerProperties();
+		assertThat(consumerProperties).containsEntry(SslConfigs.SSL_KEYSTORE_KEY_CONFIG, "-----BEGINkey");
+		assertThat(consumerProperties).containsEntry(SslConfigs.SSL_TRUSTSTORE_CERTIFICATES_CONFIG, "-----BEGINtrust");
+		assertThat(consumerProperties).containsEntry(SslConfigs.SSL_KEYSTORE_CERTIFICATE_CHAIN_CONFIG,
+				"-----BEGINchain");
+	}
+
 	@Test
 	void sslBundleConfiguration() {
 		KafkaProperties properties = new KafkaProperties();

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/MutuallyExclusiveConfigurationPropertiesException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,8 +20,10 @@ import java.util.Collection;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.function.Consumer;
+import java.util.function.Predicate;
 import java.util.stream.Collectors;
 
 import org.springframework.util.Assert;
@@ -96,11 +98,23 @@ public class MutuallyExclusiveConfigurationPropertiesException extends RuntimeEx
 	 * @param entries a consumer used to populate the entries to check
 	 */
 	public static void throwIfMultipleNonNullValuesIn(Consumer<Map<String, Object>> entries) {
-		Map<String, Object> map = new LinkedHashMap<>();
+		throwIfMultipleMatchingValuesIn(entries, Objects::nonNull);
+	}
+
+	/**
+	 * Throw a new {@link MutuallyExclusiveConfigurationPropertiesException} if multiple
+	 * values are defined in a set of entries that match the given predicate.
+	 * @param <V> the value type
+	 * @param entries a consumer used to populate the entries to check
+	 * @param predicate the predicate used to check for matching values
+	 * @since 3.3.7
+	 */
+	public static <V> void throwIfMultipleMatchingValuesIn(Consumer<Map<String, V>> entries, Predicate<V> predicate) {
+		Map<String, V> map = new LinkedHashMap<>();
 		entries.accept(map);
 		Set<String> configuredNames = map.entrySet()
 			.stream()
-			.filter((entry) -> entry.getValue() != null)
+			.filter((entry) -> predicate.test(entry.getValue()))
 			.map(Map.Entry::getKey)
 			.collect(Collectors.toCollection(LinkedHashSet::new));
 		if (configuredNames.size() > 1) {