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 java.net.URLStreamHandlerFactory;
 
 import javax.servlet.ServletContainerInitializer;
 
+import org.apache.catalina.webresources.TomcatURLStreamHandlerFactory;
 import org.eclipse.jetty.util.component.AbstractLifeCycle;
 import org.eclipse.jetty.webapp.WebAppContext;
 
@@ -69,12 +70,19 @@ class JasperInitializer extends AbstractLifeCycle {
 		if (this.initializer == null) {
 			return;
 		}
+		if (ClassUtils.isPresent(
+				"org.apache.catalina.webresources.TomcatURLStreamHandlerFactory",
+				getClass().getClassLoader())) {
+			TomcatURLStreamHandlerFactory.register();
+		}
+		else {
 			try {
 				URL.setURLStreamHandlerFactory(new WarUrlStreamHandlerFactory());
 			}
 			catch (Error ex) {
 				// Ignore
 			}
+		}
 		ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
 		try {
 			Thread.currentThread().setContextClassLoader(this.context.getClassLoader());