Add WebClient Bearer token support

Fixes: gh-5389

web/src/test/groovy/org/springframework/security/web/http/SecurityHeadersTests.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2002-2018 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
+ *
+ *      http://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.http;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.*;
+
+/**
+ * @author Rob Winch
+ * @since 5.1
+ */
+public class SecurityHeadersTests {
+
+	@Test
+	public void bearerTokenWhenNullThenIllegalArgumentException() {
+		String bearerTokenValue = null;
+		assertThatThrownBy(() -> SecurityHeaders.bearerToken(bearerTokenValue))
+				.isInstanceOf(IllegalArgumentException.class);
+	}
+
+	@Test
+	public void bearerTokenWhenEmptyStringThenIllegalArgumentException() {
+		assertThatThrownBy(() -> SecurityHeaders.bearerToken(""))
+				.isInstanceOf(IllegalArgumentException.class);
+	}
+
+}