2009/5/26 Jon Pearson <jon.pear...@sixnet.com>: > I'm having some trouble getting classes loaded by a new classloader to > be able to see classes which should have been loaded automatically from > WEB-INF/lib. All of the documentation that I've seen so far (FAQs, > mailing list searches, ...) describe problems that people have had using > the standard classloader that Tomcat provides, but I have yet to see one > dealing with dynamically loading classes from a new classloader defined > within a webapp. > > More specifically, here is my problem: > > I am developing an application suite involving a database backend which > feeds and is updated by server processes and a Web UI. To support > multiple databases, database modules (JAR files) can simply be dropped > in and loaded by each application dynamically. > > The problem is that when the Web UI loads the database module, that > module is unable to actually load the JDBC driver > (org.postgresql.Driver) which is packaged in > WEB-INF/lib/postgresql-8.3-604.jdbc4.jar (I've checked the case of the > path components). > > This is definitely related to classloaders; I tried placing the database > module directly into my WAR file under > WEB-INF/classes/package/name/PostgreSQLDatabale.class and it worked. But > if I do that, I lose the modularity and easy-upgrading that I achieved > by going with the dynamic loading of classes from JARs. > > I'm using java.net.URLClassLoader with the parent classloader set to the > classloader that loaded my application classes, so it should > theoretically be the same classloader used to load the > postgresql-8.3-604.jdbc4.jar file. > > Has anyone else encountered a problem like this? Any suggestions on what > else I should try? Thanks in advance! > > Jonathan P. Pearson - Software Engineer > --------------------------------------------------
1. What tomcat version? 2. The documentation on classloaders is here: http://tomcat.apache.org/tomcat-6.0-doc/class-loader-howto.html 3. Some JDBC drivers use native code. Those cannot be loaded from different class loaders in the same time. Thus, they cannot be loaded from /WEB-INF/lib, as there will be conflicts between applications, or between several instances of the same application if it is restarted. 4. Put the jar file into WEB-INF/lib, and then restart your web application. (E.g., using Tomcat Manager). Your jar library will be loaded. http://tomcat.apache.org/tomcat-6.0-doc/html-manager-howto.html http://tomcat.apache.org/tomcat-6.0-doc/manager-howto.html Best regards, Konstantin Kolinko --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
