Build: Fix hang with Tomcat 8.5.33+ (ticket #2307)

apps/jetty/java/src/net/i2p/servlet/util/JspC.java

@@ -0,0 +1,34 @@
+package net.i2p.servlet.util;
+
+import java.lang.reflect.Method;
+
+/**
+ *  Simply call org.apache.jasper.JspC, then exit.
+ *
+ *  As of Tomcat 8.5.33, forking their JspC won't complete,
+ *  because the JspC compilation is now threaded and the thread pool workers aren't daemons.
+ *  May be fixed in a future release, maybe not, but we don't know what version distros may have.
+ *
+ *  https://tomcat.apache.org/tomcat-8.5-doc/changelog.html
+ *  https://bz.apache.org/bugzilla/show_bug.cgi?id=53492
+ *
+ *  We could set fork=false in build.xml, but then the paths are all wrong.
+ *  Only for use in build scripts, obviously not a public API.
+ *  See apps/routerconsole/java/build.xml for more information.
+ *
+ *  @since 0.9.37
+ */
+public class JspC {
+    public static void main(String args[]) {
+       try {
+           String cls = "org.apache.jasper.JspC";
+           Class<?> c = Class.forName(cls, true, ClassLoader.getSystemClassLoader());
+           Method main = c.getMethod("main", String[].class);
+           main.invoke(null, (Object) args);
+           System.exit(0);
+       } catch (Exception e) {
+           e.printStackTrace();
+           System.exit(1);
+       }
+    }
+}