-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Chuck,
On 5/22/13 1:42 PM, Caldarale, Charles R wrote: >> From: Christopher Schultz [mailto:ch...@christopherschultz.net] >> Subject: Re: Follow-up: Possible false-postive with >> JreMemoryLeakPreventionListener and Tomcat's JDBC Pool and >> OracleTimeoutPollingThread > >> I suspect that the DriverManager will always be loaded by the >> boot ClassLoader, since the default-dispatch for ClassLoaders is >> to chekc the parent first, then check "yourself". The >> DriverManager is at the top-level (well, there is primordial, but >> that doesn't really count) ClassLoader so you'll always get >> that. > > Terminology alert: you're confusing the boot class loader with the > system class loader, and have erroneously labeled the actual boot > class loader as "primordial". Generally speaking, the boot class > loader is responsible for extracting JRE classes from rt.jar (and > others that come with the JRE), while the system class loader > deals with those specified by the java.class.path setting > (CLASSPATH for those still stuck on environment variables). Thanks for the pedantry: I was in fact ignoring the difference between the system and boot ClassLoaders. However, the primordial ClassLoader does in fact exist, and does in fact load classes, and is not called the "boot" ClassLoader. Oracle describes the primordial ClassLoader as that which loads pretty much everything in the java.* package space. Oracle also describes the "system" ClassLoader as the "delegation root ancestor of all class loaders".[1] In practice, the primordial class loader is identified by a "null" reference (and is this difficult to inspect) and the system class loader is represented by an "ExtClassLoader". On top of that is an AppClassLoader. I'll have to play around with some classes loaded via endorsed directories to see if I can nail-down how to get a Class with the "ExtClassLoader" as its class loader instead of AppClassLoader. DriverManager's ClassLoader is in fact null, the primordial class loader. You can test it yourself, and discover the ClassLoader hierarchy in play with a simple program: public class ClassLoaderTest { public static void main(String[] args) { printClassLoaders(ClassLoaderTest.class); printClassLoaders(Thread.class); printClassLoaders(Object.class); printClassLoaders(java.sql.DriverManager.class); } public static void printClassLoaders(Class cls) { ClassLoader cl = cls.getClassLoader(); System.out.println("*** ClassLoaders for " + cls.getName() + " ***"); while(null != cl) { System.out.println("ClassLoader[" + cls.getName() + "]: " + cl); cl = cl.getParent(); } System.out.println("ClassLoader[" + cls.getName() + "]: " + cl); } } Run under two different JVMs on my laptop, I get: $ java -showversion ClassLoaderTest java version "1.7.0_17" Java(TM) SE Runtime Environment (build 1.7.0_17-b02) Java HotSpot(TM) 64-Bit Server VM (build 23.7-b01, mixed mode) *** ClassLoaders for ClassLoaderTest *** ClassLoader[ClassLoaderTest]: sun.misc.Launcher$AppClassLoader@63644028 ClassLoader[ClassLoaderTest]: sun.misc.Launcher$ExtClassLoader@4ab03512 ClassLoader[ClassLoaderTest]: null *** ClassLoaders for java.lang.Thread *** ClassLoader[java.lang.Thread]: null *** ClassLoaders for java.lang.Object *** ClassLoader[java.lang.Object]: null *** ClassLoaders for java.sql.DriverManager *** ClassLoader[java.sql.DriverManager]: null $ java ClassLoaderTest java version "1.6.0_45" Java(TM) SE Runtime Environment (build 1.6.0_45-b06-451-11M4406) Java HotSpot(TM) 64-Bit Server VM (build 20.45-b01-451, mixed mode) *** ClassLoaders for ClassLoaderTest *** ClassLoader[ClassLoaderTest]: sun.misc.Launcher$AppClassLoader@a6eb38a ClassLoader[ClassLoaderTest]: sun.misc.Launcher$ExtClassLoader@69cd2e5f ClassLoader[ClassLoaderTest]: null *** ClassLoaders for java.lang.Thread *** ClassLoader[java.lang.Thread]: null *** ClassLoaders for java.lang.Object *** ClassLoader[java.lang.Object]: null *** ClassLoaders for java.sql.DriverManager *** ClassLoader[java.sql.DriverManager]: null $ java -showversion ClassLoaderTest java version "1.6.0_45" Java(TM) SE Runtime Environment (build 1.6.0_45-b06-451-11M4406) Java HotSpot(TM) Client VM (build 20.45-b01-451, mixed mode) *** ClassLoaders for ClassLoaderTest *** ClassLoader[ClassLoaderTest]: sun.misc.Launcher$AppClassLoader@cf2c80 ClassLoader[ClassLoaderTest]: sun.misc.Launcher$ExtClassLoader@1729854 ClassLoader[ClassLoaderTest]: null *** ClassLoaders for java.lang.Thread *** ClassLoader[java.lang.Thread]: null *** ClassLoaders for java.lang.Object *** ClassLoader[java.lang.Object]: null *** ClassLoaders for java.sql.DriverManager *** ClassLoader[java.sql.DriverManager]: null - -chris -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.17 (Darwin) Comment: GPGTools - http://gpgtools.org Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIbBAEBCAAGBQJRnipcAAoJEBzwKT+lPKRYVHIP90ZDie3fKOS+pM9rjMah95/6 M4ZLz/QjPTNylZDvXCR6uNHygv2ubSEwzTAoE77QwCO0IVxwV0wsPfKLKE2mULQc ZKD1pRJSWBWeHJhzIRlVSlOIPkXdu3jc9+AZV94VCn7pwsXLCKZnlGU2GKKf91cD yrA2OMwkwC98b6XvVYE5dPQuPJibN2S5A0Iy9f7eLOgFaJh9Cl6ldMFxRaZ206k4 b+huVAkOjZMvjZJ1ugDw3MJluED7/opvZiTtuyCq1PyvDB0pR3xsjvzUOR/MoCxR BmLH4SrfwVPt+gBOJZOqeMdKfR8xXohJfEov39ABgYpegl0DsaeHO58m612GQ1IZ /AIc3f8bgNlgjKCLp2+QeCw0SUqPAmOdRUDUOCJc82Z0flUmc4Z0wGn+Q4TsOL7d Ntu7w1X9ASO9De54GFcpnjPoyQqj6adf6fsOgQprOuV9fDTo2a/Gc48WnGpBzSJl v6WjZSspEPcNGFg/r0S5N6dNY4hOZYdnhSb6F3z1EwD1dnpOyIV3LrePytn5iGac nKyqJfm1kZUATR+KPPjUJEQEG2yoo9H3pHbtJAP8bgU1uJQiAMmilsin+Vt1avWW tv7SXjA4WkhyajKItm84QTbFHwSX+xaKcgqyoh/r83i9Nlqyzh6Ry3QSw7gNB3lB BY9Lqxc4HOXqr8lyIQQ= =S6U6 -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
