Don't consider system ClassLoader in Tomcat

Modify TomcatEmbeddedServletContainerFactory to ensure that the
system ClassLoader is not considered when loading classes.

This is required to fix issues when working with executable JARs
created with the maven plugin.

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

@@ -34,6 +34,7 @@ import org.apache.catalina.core.StandardContext;
 import org.apache.catalina.core.StandardEngine;
 import org.apache.catalina.core.StandardHost;
 import org.apache.catalina.core.StandardService;
+import org.apache.catalina.loader.WebappLoader;
 import org.apache.catalina.startup.Tomcat;
 import org.apache.catalina.startup.Tomcat.FixContextListener;
 import org.apache.coyote.AbstractProtocol;
@@ -139,9 +140,12 @@ public class TomcatEmbeddedServletContainerFactory extends
 		context.setPath(getContextPath());
 		context.setDocBase(docBase.getAbsolutePath());
 		context.addLifecycleListener(new FixContextListener());
-		if (this.resourceLoader != null) {
-			context.setParentClassLoader(this.resourceLoader.getClassLoader());
-		}
+		context.setParentClassLoader(this.resourceLoader != null ? this.resourceLoader
+				.getClassLoader() : ClassUtils.getDefaultClassLoader());
+		WebappLoader loader = new WebappLoader(context.getParentClassLoader());
+		loader.setLoaderClass(TomcatEmbeddedWebappClassLoader.class.getName());
+		context.setLoader(loader);
+
 		if (isRegisterDefaultServlet()) {
 			addDefaultServlet(context);
 		}

spring-bootstrap/src/main/java/org/springframework/bootstrap/context/embedded/tomcat/TomcatEmbeddedWebappClassLoader.java

@@ -0,0 +1,59 @@
+/*
+ * 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.bootstrap.context.embedded.tomcat;
+
+import java.net.URL;
+import java.net.URLClassLoader;
+
+import org.apache.catalina.loader.WebappClassLoader;
+
+/**
+ * Extension of Tomcat's {@link WebappClassLoader} that does not consider the
+ * {@link ClassLoader#getSystemClassLoader() system classloader}. This is required to to
+ * ensure that any custom context classloader is always used (as is the case with some
+ * executable archives).
+ * 
+ * @author Phillip Webb
+ */
+public class TomcatEmbeddedWebappClassLoader extends WebappClassLoader {
+
+	public TomcatEmbeddedWebappClassLoader() {
+		super();
+		this.system = new EmbeddedSystemClassLoader();
+	}
+
+	public TomcatEmbeddedWebappClassLoader(ClassLoader parent) {
+		super(parent);
+		this.system = new EmbeddedSystemClassLoader();
+	}
+
+	private static class EmbeddedSystemClassLoader extends URLClassLoader {
+
+		public EmbeddedSystemClassLoader() {
+			super(new URL[] {});
+		}
+
+		@Override
+		public Class<?> loadClass(String name) throws ClassNotFoundException {
+			throw new ClassNotFoundException(
+					"System ClassLoader disabled for embedded context, unable to load "
+							+ name);
+		}
+
+	}
+
+}