AW: PooledConnection#connectUsingDriver, Thread.currentThread().getContextClassLoader() is null

[Clemens Wyss DEV]

Note: I have moved this "issue" over to the tomcat-dev mailinglist ...

-----Ursprüngliche Nachricht-----
Von: Clemens Wyss DEV <clemens...@mysign.ch> 
Gesendet: Mittwoch, 24. Juli 2019 11:07
An: 'Tomcat Users List' <users@tomcat.apache.org>
Betreff: PooledConnection#connectUsingDriver, 
Thread.currentThread().getContextClassLoader() is null

Context:
Debian GNU/Linux 9 \n \l
java version 1.8.0_162
Tomcat 8.5.35

From time to time we are facing the follwing exception (call stack):
...
Caused by: java.sql.SQLException: Unable to load class: org.mariadb.jdbc.Driver 
from ClassLoader:java.net.URLClassLoader@4c873330;ClassLoader:null
        at 
org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:292)
        at 
org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:212)
        at 
org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:736)
        at 
org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:668)
        at 
org.apache.tomcat.jdbc.pool.ConnectionPool.getConnection(ConnectionPool.java:198)
        at 
org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:132)
        at org.apache.torque.Torque.getConnection(Torque.java:924)
        ... 53 common frames omitted
Caused by: java.lang.ClassNotFoundException: Unable to load class: 
org.mariadb.jdbc.Driver from 
ClassLoader:java.net.URLClassLoader@4c873330;ClassLoader:null
        at 
org.apache.tomcat.jdbc.pool.ClassLoaderUtil.loadClass(ClassLoaderUtil.java:56)
        at 
org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:280)
        ... 59 common frames omitted
Caused by: java.lang.ClassNotFoundException: Classloader is null
        at 
org.apache.tomcat.jdbc.pool.ClassLoaderUtil.loadClass(ClassLoaderUtil.java:40)
        ... 60 common frames omitted

According to the code (in PooledConnection# connectUsingDriver) 
Thread.currentThread().getContextClassLoader() returns null

Googling for " Thread.currentThread().getContextClassLoader() is null" the 
common demoniator seems to be `getContextClassLoader can be null`. If this is 
true there should be
a) a null-check in PooledConnection# connectUsingDriver
b) if null, then there should be a fallback-Classloader (the system class 
laoder?)

WDYT ?

Or any ideas why the given exception pops up from time to time

Thx
Clemens
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