Add support for configuring LDAP's referral property

See gh-44850

Signed-off-by: Andras, Dobrosi <dobrosi@gmail.com>

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ldap/LdapAutoConfiguration.java

@@ -17,12 +17,14 @@
 package org.springframework.boot.autoconfigure.ldap;
 
 import java.util.Collections;
+import java.util.Optional;
 
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.ldap.LdapProperties.Referral;
 import org.springframework.boot.autoconfigure.ldap.LdapProperties.Template;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.context.properties.PropertyMapper;
@@ -67,6 +69,7 @@ public class LdapAutoConfiguration {
 		propertyMapper.from(connectionDetails.getUsername()).to(source::setUserDn);
 		propertyMapper.from(connectionDetails.getPassword()).to(source::setPassword);
 		propertyMapper.from(properties.getAnonymousReadOnly()).to(source::setAnonymousReadOnly);
+		Optional.ofNullable(properties.getReferral()).map(Referral::getMode).ifPresent(source::setReferral);
 		propertyMapper.from(connectionDetails.getBase()).to(source::setBase);
 		propertyMapper.from(connectionDetails.getUrls()).to(source::setUrls);
 		propertyMapper.from(properties.getBaseEnvironment())

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ldap/LdapProperties.java

@@ -21,6 +21,7 @@ import java.util.Map;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.core.env.Environment;
+import org.springframework.ldap.ReferralException;
 import org.springframework.ldap.core.LdapTemplate;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -62,6 +63,11 @@ public class LdapProperties {
 	 */
 	private Boolean anonymousReadOnly;
 
+	/**
+	 * Set the method to handle referrals.
+	 */
+	private Referral referral;
+
 	/**
 	 * LDAP specification settings.
 	 */
@@ -109,6 +115,14 @@ public class LdapProperties {
 		this.anonymousReadOnly = anonymousReadOnly;
 	}
 
+	public Referral getReferral() {
+		return this.referral;
+	}
+
+	public void setReferral(Referral referral) {
+		this.referral = referral;
+	}
+
 	public Map<String, String> getBaseEnvironment() {
 		return this.baseEnvironment;
 	}
@@ -182,4 +196,36 @@ public class LdapProperties {
 
 	}
 
+	/**
+	 * Enum to define how referrals encountered by the service provider are to be processed.
+	 */
+	public enum Referral {
+
+		/**
+		 * follow referrals automatically
+		 */
+		FOLLOW("follow"),
+
+		/**
+		 * ignore referrals
+		 */
+		IGNORE("ignore"),
+
+		/**
+		 * throw a {@link ReferralException} for each referral
+		 */
+		THROW("throw");
+
+		private final String mode;
+
+		Referral(String mode) {
+			this.mode = mode;
+		}
+
+		public String getMode() {
+			return this.mode;
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/ldap/LdapAutoConfigurationTests.java

@@ -38,6 +38,7 @@ import org.springframework.ldap.support.LdapUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.mock;
+import static org.springframework.test.util.ReflectionTestUtils.getField;
 
 /**
  * Tests for {@link LdapAutoConfiguration}.
@@ -88,6 +89,14 @@ class LdapAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void contextSourceWithReferral() {
+		this.contextRunner.withPropertyValues("spring.ldap.referral:ignore").run((context) -> {
+			LdapContextSource contextSource = context.getBean(LdapContextSource.class);
+			assertThat(getField(contextSource, "referral")).isEqualTo("ignore");
+		});
+	}
+
 	@Test
 	void contextSourceWithExtraCustomization() {
 		this.contextRunner