Add DelegatingAuthenticationConverter

Closes gh-14644

web/src/main/java/org/springframework/security/web/authentication/DelegatingAuthenticationConverter.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2002-2024 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.web.authentication;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import jakarta.servlet.http.HttpServletRequest;
+
+import org.springframework.security.core.Authentication;
+import org.springframework.util.Assert;
+
+/**
+ * A {@link AuthenticationConverter}, that iterates over multiple
+ * {@link AuthenticationConverter}. The first non-null {@link Authentication} will be used
+ * as a result.
+ *
+ * @author Max Batischev
+ * @since 6.3
+ */
+public final class DelegatingAuthenticationConverter implements AuthenticationConverter {
+
+	private final List<AuthenticationConverter> delegates;
+
+	public DelegatingAuthenticationConverter(List<AuthenticationConverter> delegates) {
+		Assert.notEmpty(delegates, "delegates cannot be null");
+		this.delegates = new ArrayList<>(delegates);
+	}
+
+	public DelegatingAuthenticationConverter(AuthenticationConverter... delegates) {
+		Assert.notEmpty(delegates, "delegates cannot be null");
+		this.delegates = List.of(delegates);
+	}
+
+	@Override
+	public Authentication convert(HttpServletRequest request) {
+		for (AuthenticationConverter delegate : this.delegates) {
+			Authentication authentication = delegate.convert(request);
+			if (authentication != null) {
+				return authentication;
+			}
+		}
+		return null;
+	}
+
+}