Add alwaysMapUrl flag to ServletRegistrationBean

Add an additional constructor to ServletRegistrationBean that indicates
if a URL mapping is always required. If set to false, the registration
will not longer use the default '/*' mapping.

Fixes gh-2596

Author: philwebb

spring-boot/src/main/java/org/springframework/boot/context/embedded/ServletRegistrationBean.java

@@ -31,6 +31,7 @@
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * A {@link ServletContextInitializer} to register {@link Servlet}s in a Servlet 3.0+
@@ -40,7 +41,9 @@
  * <p>
  * The {@link #setServlet(Servlet) servlet} must be specified before calling
  * {@link #onStartup}. URL mapping can be configured used {@link #setUrlMappings} or
- * omitted when mapping to '/*'. The servlet name will be deduced if not specified.
+ * omitted when mapping to '/*' (unless
+ * {@link #ServletRegistrationBean(Servlet, boolean, String...) alwaysMapUrl} is set to
+ * {@code false}). The servlet name will be deduced if not specified.
  *
  * @author Phillip Webb
  * @see ServletContextInitializer
@@ -56,6 +59,8 @@ public class ServletRegistrationBean extends RegistrationBean {
 
 	private Set<String> urlMappings = new LinkedHashSet<String>();
 
+	private boolean alwaysMapUrl = true;
+
 	private int loadOnStartup = -1;
 
 	private MultipartConfigElement multipartConfig;
@@ -73,9 +78,22 @@ public ServletRegistrationBean() {
 	 * @param urlMappings the URLs being mapped
 	 */
 	public ServletRegistrationBean(Servlet servlet, String... urlMappings) {
+		this(servlet, true, urlMappings);
+	}
+
+	/**
+	 * Create a new {@link ServletRegistrationBean} instance with the specified
+	 * {@link Servlet} and URL mappings.
+	 * @param servlet the servlet being mapped
+	 * @param alwaysMapUrl if omitted URL mappings should be replaced with '/*'
+	 * @param urlMappings the URLs being mapped
+	 */
+	public ServletRegistrationBean(Servlet servlet, boolean alwaysMapUrl,
+			String... urlMappings) {
 		Assert.notNull(servlet, "Servlet must not be null");
 		Assert.notNull(urlMappings, "UrlMappings must not be null");
 		this.servlet = servlet;
+		this.alwaysMapUrl = alwaysMapUrl;
 		this.urlMappings.addAll(Arrays.asList(urlMappings));
 	}
 
@@ -164,7 +182,7 @@ public void onStartup(ServletContext servletContext) throws ServletException {
 		Assert.notNull(this.servlet, "Servlet must not be null");
 		String name = getServletName();
 		if (!isEnabled()) {
-			logger.info("Filter " + name + " was not registered (disabled)");
+			logger.info("Servlet " + name + " was not registered (disabled)");
 			return;
 		}
 		logger.info("Mapping servlet: '" + name + "' to " + this.urlMappings);
@@ -186,10 +204,12 @@ protected void configure(ServletRegistration.Dynamic registration) {
 		super.configure(registration);
 		String[] urlMapping = this.urlMappings
 				.toArray(new String[this.urlMappings.size()]);
-		if (urlMapping.length == 0) {
+		if (urlMapping.length == 0 && this.alwaysMapUrl) {
 			urlMapping = DEFAULT_MAPPINGS;
 		}
-		registration.addMapping(urlMapping);
+		if (!ObjectUtils.isEmpty(urlMapping)) {
+			registration.addMapping(urlMapping);
+		}
 		registration.setLoadOnStartup(this.loadOnStartup);
 		if (this.multipartConfig != null) {
 			registration.setMultipartConfig(this.multipartConfig);

spring-boot/src/test/java/org/springframework/boot/context/embedded/ServletRegistrationBeanTests.java

@@ -36,6 +36,7 @@
 import org.mockito.MockitoAnnotations;
 
 import static org.mockito.BDDMockito.given;
+import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyObject;
 import static org.mockito.Matchers.anyString;
 import static org.mockito.Mockito.never;
@@ -196,4 +197,11 @@ public void modifyInitParameters() throws Exception {
 		verify(this.registration).setInitParameters(Collections.singletonMap("a", "c"));
 	}
 
+	@Test
+	public void withoutDefaultMappings() throws Exception {
+		ServletRegistrationBean bean = new ServletRegistrationBean(this.servlet, false);
+		bean.onStartup(this.servletContext);
+		verify(this.registration, never()).addMapping((String[]) any());
+	}
+
 }