Clean basePath if necessary

This commit makes sure that ServletEndpointRegistrar does not add a
duplicate `/` if the basePath is suffixed with it already

Close gh-13964

Author: snicoll

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/web/ServletEndpointRegistrar.java

@@ -27,6 +27,7 @@
 
 import org.springframework.boot.web.servlet.ServletContextInitializer;
 import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
 
 /**
  * {@link ServletContextInitializer} to register {@link ExposableServletEndpoint servlet
@@ -47,10 +48,17 @@ public class ServletEndpointRegistrar implements ServletContextInitializer {
 	public ServletEndpointRegistrar(String basePath,
 			Collection<ExposableServletEndpoint> servletEndpoints) {
 		Assert.notNull(servletEndpoints, "ServletEndpoints must not be null");
-		this.basePath = (basePath != null) ? basePath : "";
+		this.basePath = cleanBasePath(basePath);
 		this.servletEndpoints = servletEndpoints;
 	}
 
+	private static String cleanBasePath(String basePath) {
+		if (StringUtils.hasText(basePath) && basePath.endsWith("/")) {
+			return basePath.substring(0, basePath.length() - 1);
+		}
+		return (basePath != null) ? basePath : "";
+	}
+
 	@Override
 	public void onStartup(ServletContext servletContext) throws ServletException {
 		this.servletEndpoints

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/web/ServletEndpointRegistrarTests.java

@@ -16,7 +16,6 @@
 
 package org.springframework.boot.actuate.endpoint.web;
 
-import java.io.IOException;
 import java.util.Collections;
 
 import javax.servlet.GenericServlet;
@@ -47,6 +46,7 @@
  * Tests for {@link ServletEndpointRegistrar}.
  *
  * @author Phillip Webb
+ * @author Stephane Nicoll
  */
 public class ServletEndpointRegistrarTests {
 
@@ -77,29 +77,38 @@ public void createWhenServletEndpointsIsNullShouldThrowException() {
 	}
 
 	@Test
-	public void onStartupShouldRegisterServlets() throws Exception {
-		ExposableServletEndpoint endpoint = mockEndpoint(
-				new EndpointServlet(TestServlet.class));
-		ServletEndpointRegistrar registrar = new ServletEndpointRegistrar(null,
-				Collections.singleton(endpoint));
-		registrar.onStartup(this.servletContext);
-		verify(this.servletContext).addServlet(eq("test-actuator-endpoint"),
-				this.servlet.capture());
-		assertThat(this.servlet.getValue()).isInstanceOf(TestServlet.class);
-		verify(this.dynamic).addMapping("/test/*");
+	public void onStartupShouldRegisterServlets() throws ServletException {
+		assertBasePath(null, "/test/*");
+	}
+
+	@Test
+	public void onStartupWhenHasBasePathShouldIncludeBasePath() throws ServletException {
+		assertBasePath("/actuator", "/actuator/test/*");
+	}
+
+	@Test
+	public void onStartupWhenHasEmptyBasePathShouldPrefixWithSlash()
+			throws ServletException {
+		assertBasePath("", "/test/*");
 	}
 
 	@Test
-	public void onStartupWhenHasBasePathShouldIncludeBasePath() throws Exception {
+	public void onStartupWhenHasRootBasePathShouldNotAddDuplicateSlash()
+			throws ServletException {
+		assertBasePath("/", "/test/*");
+	}
+
+	private void assertBasePath(String basePath, String expectedMapping)
+			throws ServletException {
 		ExposableServletEndpoint endpoint = mockEndpoint(
 				new EndpointServlet(TestServlet.class));
-		ServletEndpointRegistrar registrar = new ServletEndpointRegistrar("/actuator",
+		ServletEndpointRegistrar registrar = new ServletEndpointRegistrar(basePath,
 				Collections.singleton(endpoint));
 		registrar.onStartup(this.servletContext);
 		verify(this.servletContext).addServlet(eq("test-actuator-endpoint"),
 				this.servlet.capture());
 		assertThat(this.servlet.getValue()).isInstanceOf(TestServlet.class);
-		verify(this.dynamic).addMapping("/actuator/test/*");
+		verify(this.dynamic).addMapping(expectedMapping);
 	}
 
 	@Test
@@ -124,8 +133,7 @@ private ExposableServletEndpoint mockEndpoint(EndpointServlet endpointServlet) {
 	public static class TestServlet extends GenericServlet {
 
 		@Override
-		public void service(ServletRequest req, ServletResponse res)
-				throws ServletException, IOException {
+		public void service(ServletRequest req, ServletResponse res) {
 		}
 
 	}