Add allowHeader property to WebContentGenerator

The WebContentGenerator now maintains an additional property that
sub-classes can use for an "Allow" header in response to an HTTP
OPTIONS request. This property is pre-initialized once at startup
and does not have to rely on getSupportedMethods in addition to
adding HTTP OPTIONS if not explicitly listed.

Issue: SPR-13130

spring-webmvc/src/test/java/org/springframework/web/servlet/support/WebContentGeneratorTests.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2002-2016 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.web.servlet.support;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Unit tests for {@link WebContentGenerator}.
+ * @author Rossen Stoyanchev
+ */
+public class WebContentGeneratorTests {
+
+
+	@Test
+	public void getAllowHeaderWithConstructorTrue() throws Exception {
+		WebContentGenerator generator = new TestWebContentGenerator(true);
+		assertEquals("GET,HEAD,POST,OPTIONS", generator.getAllowHeader());
+	}
+
+	@Test
+	public void getAllowHeaderWithConstructorFalse() throws Exception {
+		WebContentGenerator generator = new TestWebContentGenerator(false);
+		assertEquals("GET,HEAD,POST,PUT,PATCH,DELETE,OPTIONS", generator.getAllowHeader());
+	}
+
+	@Test
+	public void getAllowHeaderWithSupportedMethodsConstructor() throws Exception {
+		WebContentGenerator generator = new TestWebContentGenerator("POST");
+		assertEquals("POST,OPTIONS", generator.getAllowHeader());
+	}
+
+	@Test
+	public void getAllowHeaderWithSupportedMethodsSetter() throws Exception {
+		WebContentGenerator generator = new TestWebContentGenerator();
+		generator.setSupportedMethods("POST");
+		assertEquals("POST,OPTIONS", generator.getAllowHeader());
+	}
+
+	@Test
+	public void getAllowHeaderWithSupportedMethodsSetterEmpty() throws Exception {
+		WebContentGenerator generator = new TestWebContentGenerator();
+		generator.setSupportedMethods();
+		assertEquals("Effectively \"no restriction\" on supported methods",
+				"GET,HEAD,POST,PUT,PATCH,DELETE,OPTIONS", generator.getAllowHeader());
+	}
+
+
+	private static class TestWebContentGenerator extends WebContentGenerator {
+
+		public TestWebContentGenerator() {
+		}
+
+		public TestWebContentGenerator(boolean restrictDefaultSupportedMethods) {
+			super(restrictDefaultSupportedMethods);
+		}
+
+		public TestWebContentGenerator(String... supportedMethods) {
+			super(supportedMethods);
+		}
+	}
+}