Hack around with Tomcat resource paths

Tomcat 8 has different APIs again so it was quite difficult to
get it working and test it. The test is manual anyway (multi-module
project with JSPs in /META-INF/resources, not part of the samples),
and requires you to build a war and execute it (since the resource
paths are different when it's an archive).

Fixes gh-1131

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

@@ -20,6 +20,9 @@ import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.reflect.Method;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -37,10 +40,12 @@ import org.apache.catalina.LifecycleListener;
 import org.apache.catalina.Valve;
 import org.apache.catalina.Wrapper;
 import org.apache.catalina.connector.Connector;
+import org.apache.catalina.core.StandardContext;
 import org.apache.catalina.loader.WebappLoader;
 import org.apache.catalina.startup.Tomcat;
 import org.apache.catalina.startup.Tomcat.FixContextListener;
 import org.apache.coyote.AbstractProtocol;
+import org.apache.naming.resources.FileDirContext;
 import org.springframework.beans.BeanUtils;
 import org.springframework.boot.context.embedded.AbstractEmbeddedServletContainerFactory;
 import org.springframework.boot.context.embedded.EmbeddedServletContainer;
@@ -584,6 +589,95 @@ public class TomcatEmbeddedServletContainerFactory extends
 			if (servletContext.getAttribute(this.MERGED_WEB_XML) == null) {
 				servletContext.setAttribute(this.MERGED_WEB_XML, getEmptyWebXml());
 			}
+			addClasspathResources(context);
+		}
+
+		private void addClasspathResources(Context context) {
+			ClassLoader loader = getClass().getClassLoader();
+			if (loader instanceof URLClassLoader) {
+				for (URL url : ((URLClassLoader) loader).getURLs()) {
+					String file = url.getFile();
+					if (file.endsWith(".jar") || file.endsWith(".jar!/")) {
+						addJarContext(context, url);
+					}
+					else if (url.toString().startsWith("file:")) {
+						addDirContext(context, url);
+					}
+				}
+			}
+		}
+
+		private void addJarContext(Context context, URL url) {
+			String jar = url.toString();
+			if (!jar.startsWith("jar:")) {
+				// A jar file in the file system. Convert to Jar URL.
+				jar = "jar:" + jar + "!/";
+			}
+			if (ClassUtils.isPresent("org.apache.catalina.deploy.ErrorPage", null)) {
+				// Tomcat 7
+				try {
+					context.addResourceJarUrl(new URL(jar));
+				}
+				catch (MalformedURLException e) {
+					// Ignore?
+				}
+			}
+			else {
+				// Tomcat 8
+				addResourceSet(context, "RESOURCE_JAR", jar);
+			}
+		}
+
+		private void addDirContext(Context context, URL url) {
+			String dir = url.toString().substring("file:".length());
+			if (new File(dir).isDirectory()) {
+				if (ClassUtils.isPresent("org.apache.catalina.deploy.ErrorPage", null)) {
+					// Tomcat 7
+					if (context instanceof StandardContext) {
+						FileDirContext files = new FileDirContext();
+						files.setDocBase(dir);
+						((StandardContext) context).addResourcesDirContext(files);
+					}
+				}
+				else {
+					// Tomcat 8
+					addResourceSet(context, "RESOURCE_JAR", url.toString());
+				}
+			}
+		}
+
+		@SuppressWarnings({ "rawtypes", "unchecked" })
+		private void addResourceSet(Context context, String name, String dir) {
+			Object resources;
+			Method create;
+			Class type;
+			try {
+				Method getResources = ReflectionUtils.findMethod(context.getClass(),
+						"getResources");
+				resources = getResources.invoke(context);
+				type = ClassUtils.resolveClassName(
+						"org.apache.catalina.WebResourceRoot.ResourceSetType", null);
+				create = ReflectionUtils.findMethod(resources.getClass(),
+						"createWebResourceSet", type, String.class, URL.class,
+						String.class);
+			}
+			catch (Exception e) {
+				throw new IllegalStateException("Tomcat 8 reflection failed", e);
+			}
+			try {
+				if (dir.indexOf("!/") < dir.lastIndexOf("!/")) {
+					// It's a nested jar but we now don't want the suffix because Tomcat
+					// is going to try and locate it as a root URL (not the resource
+					// inside it)
+					dir = dir.substring(0, dir.length() - 2);
+				}
+				URL url = new URL(dir);
+				String path = "/META-INF/resources";
+				create.invoke(resources, Enum.valueOf(type, name), "/", url, path);
+			}
+			catch (Exception e) {
+				// Ignore (probably not a directory)
+			}
 		}
 
 		private String getEmptyWebXml() {