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From Gary Gregory <garydgreg...@gmail.com>
Subject Re: ClassNotFoundException trying to use JDBC appender
Date Wed, 30 Nov 2016 00:48:30 GMT
OSGi and class loaders make for complications and tricky debugging sessions
:-(

Gary

On Tue, Nov 29, 2016 at 2:08 PM, Michael Carman <michael.j.carman@gmail.com>
wrote:

> To try to tease out whether my problem is at the Eclipse level or the Log4j
> level I experimented with loading my class via reflection.
>
> static {
> try {
> Class<?>   clazz      = Class.forName("x.y.z.LogDB");
> Method     method     = clazz.getMethod("getConnection");
> Connection connection = (Connection) method.invoke(clazz);
> connection.close();
> } catch (Exception e) {
> e.printStackTrace();
> }
> logger = LogManager.getLogger();
> }
>
> My attempt at reflection is successful. The call to LogManager.getLogger()
> results in a ClassNotFoundException. This implies that my problem is that
> Log4j isn't picking up on the class path used within my plugin. Is there a
> way to configure that? Searching for "log4j classpath" turns up lots of
> things about where to put the log4j.properties file.
>
> I can't be the first person to try to use a JDBC appender with Eclipse RCP.
>
> -Mike
>
>
> On Tue, Nov 29, 2016 at 3:27 PM Michael Carman <michael.j.carman@gmail.com
> >
> wrote:
>
> > Yes, getConnection() is static. Log4j isn't getting far enough to attempt
> > calling it, though. An explicit call to LogDB.getConnection()  is
> > successful but Log4j's attempts to invoke it via reflection fails trying
> to
> > load the class. That holds true even if I move my LogDB into the plug-in
> > for my application and pre-load it! e.g., in the Activator for my main
> > plug-in:
> >
> > static {
> > try {
> > LogDB.getConnection(); // succeeds
> > } catch (SQLException e) {
> > e.printStackTrace();
> > }
> > LogManager.getLogger(); // throws ClassNotFoundException
> > }
> >
> > It seems like some sort of class path configuration problem, but I can't
> > figure out what to set.
> >
> > -Mike
> >
> > On Tue, Nov 29, 2016 at 2:43 PM Gary Gregory <garydgregory@gmail.com>
> > wrote:
> >
> > Is your getConnection() method static?
> >
> > Gary
> >
> > On Tue, Nov 29, 2016 at 9:04 AM, Michael Carman <
> > michael.j.carman@gmail.com>
> > wrote:
> >
> > > I'm using Log4j2 in an Eclipse RCP application. I've been using a
> > > RollingFileAppender and am trying to switch to a JDBC appender backed
> by
> > a
> > > ConnectionFactory. I've implemented this using the examples at
> > > https://logging.apache.org/log4j/2.x/manual/appenders.
> html#JDBCAppender
> > as
> > > a guide but get a ClassNotFoundException at each call to
> > > LogManager.getLogger(). e.g.
> > >
> > > 2016-11-29 10:23:06,233 main ERROR java.lang.ClassNotFoundException:
> > > x.y.z.LogDB java.lang.ClassNotFoundException: x.y.z.LogDB
> > >     at
> > > org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(
> > > BundleLoader.java:506)
> > >     at
> > > org.eclipse.osgi.internal.loader.BundleLoader.findClass(
> > > BundleLoader.java:422)
> > >     at
> > > org.eclipse.osgi.internal.loader.BundleLoader.findClass(
> > > BundleLoader.java:410)
> > >     at
> > > org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(
> > > DefaultClassLoader.java:107)
> > >     at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
> > >     at java.lang.Class.forName0(Native Method)
> > >     at java.lang.Class.forName(Class.java:264)
> > >     at
> > > org.apache.logging.log4j.util.LoaderUtil.loadClass(
> LoaderUtil.java:141)
> > >     at
> > > org.apache.logging.log4j.core.appender.db.jdbc.
> > > FactoryMethodConnectionSource.createConnectionSource(
> > > FactoryMethodConnectionSource.java:82)
> > >     ...
> > >
> > > My log4j2.xml defines the appender as:
> > >
> > > <JDBC name="DB" tableName="APP_LOG">
> > >   <ConnectionFactory class="x.y.z.LogDB" method="getConnection" />
> > >   <Column name="TIMESTAMP" isEventTimestamp="true"    />
> > >   <Column name="PID"       pattern="%X{pid}"          />
> > >   <Column name="THREAD"    pattern="%thread"          />
> > >   <Column name="USERNAME"  pattern="${env:USERNAME}"  />
> > >   <Column name="SEVERITY"  pattern="%level"           />
> > >   <Column name="LOGGER"    pattern="%logger{1.1.1.*}" />
> > >   <Column name="MESSAGE"   pattern="%message"         />
> > >   <Column name="EXCEPTION" pattern="%exception" isClob="true" />
> > > </JDBC>
> > >
> > > I've looked at the obvious things: the name of my factory class matches
> > > between my code and config file, it's declared public, and its package
> is
> > > exported by the parent plug-in. (The parent plug-in is also required by
> > > other plugins via their manifests.) I can't see why the class loader
> > > shouldn't be able to find it. I assume there's something simple and
> > stupid
> > > that I'm missing.
> > >
> > > I'm using Eclipse 3.6.2 (Helios) and Log4j 2.7.
> > >
> > > -Mike
> > >
> >
> >
> >
> > --
> > E-Mail: garydgregory@gmail.com | ggregory@apache.org
> > Java Persistence with Hibernate, Second Edition
> > <
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> > >
> >
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>



-- 
E-Mail: garydgregory@gmail.com | ggregory@apache.org
Java Persistence with Hibernate, Second Edition
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JUnit in Action, Second Edition
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Spring Batch in Action
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