Avoid a clash with TomcatURLStreamHandlerFactory

In the unlikely (outside the tests of a number of Spring Boot's
modules) event that both Tomcat and Jetty are on the classpath,
there's a risk that Tomcat will try to register its
URLStreamHandlerFactory after JasperInitializer has registered its
WarUrlStreamHandlerFactory. Should this happen, Tomcat will fail to
start.

TomcatURLStreamHandlerFactory registers a handler for the war: URLs
produced by org.apache.tomcat.util.scan.JarFactory that's used by
both Tomcat and Jetty's Jasper integration. This makes it a suitable
replacement for WarUrlStreamHandlerFactory so this commit updates
JasperIntializer to register TomcatURLStreamHandlerFactory when it's
available, falling back to WarUrlStreamHandlerFactory when it's not.

Closes gh-8622

spring-boot/src/main/java/org/springframework/boot/web/embedded/jetty/JasperInitializer.java

@@ -25,6 +25,7 @@
 
 import javax.servlet.ServletContainerInitializer;
 
+import org.apache.catalina.webresources.TomcatURLStreamHandlerFactory;
 import org.eclipse.jetty.util.component.AbstractLifeCycle;
 import org.eclipse.jetty.webapp.WebAppContext;
 
@@ -69,11 +70,18 @@ protected void doStart() throws Exception {
 		if (this.initializer == null) {
 			return;
 		}
-		try {
-			URL.setURLStreamHandlerFactory(new WarUrlStreamHandlerFactory());
+		if (ClassUtils.isPresent(
+				"org.apache.catalina.webresources.TomcatURLStreamHandlerFactory",
+				getClass().getClassLoader())) {
+			TomcatURLStreamHandlerFactory.register();
 		}
-		catch (Error ex) {
-			// Ignore
+		else {
+			try {
+				URL.setURLStreamHandlerFactory(new WarUrlStreamHandlerFactory());
+			}
+			catch (Error ex) {
+				// Ignore
+			}
 		}
 		ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
 		try {