Add servlet path to /error if it is customized

In addition I added some convenience methods to ServerProperties
(servletMapping() and servletPrefix()) for manipulating the
servlet path as provided by the user (e.g. normalizing it into
a valid Servlet mapping path for the DispatcherServlet).

Fixes gh-939, see also gh-936

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/DispatcherServletAutoConfigurationTests.java

@@ -98,7 +98,7 @@ public class DispatcherServletAutoConfigurationTests {
 		assertNotNull(this.context.getBean(DispatcherServlet.class));
 		ServletRegistrationBean registration = this.context
 				.getBean(ServletRegistrationBean.class);
-		assertEquals("[/spring]", registration.getUrlMappings().toString());
+		assertEquals("[/spring/*]", registration.getUrlMappings().toString());
 		assertNull(registration.getMultipartConfig());
 	}
 

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/RemappedErrorViewIntegrationTests.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2012-2013 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.boot.autoconfigure.web;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.RemappedErrorViewIntegrationTests.TestConfiguration;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;
+import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;
+import org.springframework.boot.context.embedded.ErrorPage;
+import org.springframework.boot.test.IntegrationTest;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.boot.test.TestRestTemplate;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.stereotype.Controller;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.web.WebAppConfiguration;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.client.RestTemplate;
+
+import static org.junit.Assert.assertTrue;
+
+/**
+ * @author Dave Syer
+ */
+@SpringApplicationConfiguration(classes = TestConfiguration.class)
+@RunWith(SpringJUnit4ClassRunner.class)
+@WebAppConfiguration
+@IntegrationTest({ "server.servletPath:/spring/*", "server.port:0" })
+@DirtiesContext
+public class RemappedErrorViewIntegrationTests {
+
+	@Value("${local.server.port}")
+	private int port;
+
+	private RestTemplate template = new TestRestTemplate();
+
+	@Test
+	public void directAccessToErrorPage() throws Exception {
+		String content = this.template.getForObject("http://localhost:" + this.port
+				+ "/spring/error", String.class);
+		assertTrue("Wrong content: " + content, content.contains("error"));
+		assertTrue("Wrong content: " + content, content.contains("999"));
+	}
+
+	@Test
+	public void forwardToErrorPage() throws Exception {
+		String content = this.template.getForObject("http://localhost:" + this.port
+				+ "/spring/", String.class);
+		assertTrue("Wrong content: " + content, content.contains("error"));
+		assertTrue("Wrong content: " + content, content.contains("500"));
+	}
+
+	@Configuration
+	@Import({ PropertyPlaceholderAutoConfiguration.class,
+			ServerPropertiesAutoConfiguration.class, WebMvcAutoConfiguration.class,
+			HttpMessageConvertersAutoConfiguration.class,
+			EmbeddedServletContainerAutoConfiguration.class,
+			DispatcherServletAutoConfiguration.class, ErrorMvcAutoConfiguration.class })
+	@Controller
+	public static class TestConfiguration implements EmbeddedServletContainerCustomizer {
+
+		@RequestMapping("/")
+		public String home() {
+			throw new RuntimeException("Planned!");
+		}
+
+		@Override
+		public void customize(ConfigurableEmbeddedServletContainer container) {
+			container.addErrorPages(new ErrorPage("/spring/error"));
+		}
+
+		// For manual testing
+		public static void main(String[] args) {
+			new SpringApplicationBuilder(TestConfiguration.class).properties(
+					"server.servletPath:spring/*").run(args);
+		}
+
+	}
+
+}