java.sql.DriverManager.getCallerClass() exception handling

[Nestor Urquiza]

Hello guys,

I believe the implementation for java.sql.DriverManager.getCallerClass()
has a problem at least in JDK6. Let us see this with the code from "openjdk
6-b14". Swallowing the Exception below is IMO *not good*:
<code>
491        try {
492            callerC = Class.forName(driverClassName, true,
callerClassLoader);
493        }
494        catch (Exception ex) {
495            callerC = null;           // being very careful
496        }
</code>

It becomes clear why with the below code
from java.sql.DriverManager.getConnection(). What happens if the method
above throws a ClassNotFoundException<http://docs.oracle.com/javase/6/docs/api/java/lang/ClassNotFoundException.html>
 ?
<code>
609        for (int i = 0; i < drivers.size(); i++) {
610            DriverInfo di = (DriverInfo)drivers.elementAt(i);
611
612            // If the caller does not have permission to load the driver
then
613            // skip it.
614            if ( getCallerClass(callerCL, di.driverClassName ) !=
di.driverClass ) {
615                println("    skipping: " + di);
616                continue;
617            }
618            try {
619                println("    trying " + di);
620                Connection result = di.driver.connect(url, info);
621                if (result != null) {
622                    // Success!
623                    println("getConnection returning " + di);
624                    return (result);
625                }
626            } catch (SQLException ex) {
627                if (reason == null) {
628                    reason = ex;
629                }
630            }
631        }
632
633        // if we got here nobody could connect.
634        if (reason != null)    {
635            println("getConnection failed: " + reason);
636            throw reason;
637        }
</code>

Basically if there was a previous error like a non suitable inspected
driver we get that as the cause of the failure when in reality we have not
loaded all drivers we intended to load.

I got into this issue after having a random problem (in some Talend jobs if
you mind to know) through which the jtds driver could not be found but
since the sqlite driver was already loaded the error trace looked like if
our code would try to access a MSSQL URL from a sqlite driver:
<quote>
java.sql.SQLException: invalid database address:
jdbc:jtds:sqlserver://mssql.sample.com:1433//Appdata;appName=MyApp;
  at org.sqlite.JDBC.createConnection(JDBC.java:74)
  at org.sqlite.JDBC.connect(JDBC.java:64)
  at java.sql.DriverManager.getConnection(DriverManager.java:582)
  at java.sql.DriverManager.getConnection(DriverManager.java:185)
</quote>

As I said our code does work most of the time but for some reason (probably
related to deployment) we get the alert above from time to time.

Am I missing something or this is indeed a bug which resolution is as
simple as changing the method as below (or just call directly
Class.forName() from the getConnection() method)?:

private static Class
<http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/lang/Class.java#Class>
 <http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/sql/DriverManager.java#>getCallerClass(ClassLoader
<http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/lang/ClassLoader.java#ClassLoader>
callerClassLoader,

<http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/sql/DriverManager.java#>

                                        String
<http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/lang/String.java#String>
driverClassName) throws Exception {

callerC = Class.forName<http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/lang/Class.java#Class.forName%28java.lang.String%2Cboolean%2Cjava.lang.ClassLoader%29>
(driverClassName, true, callerClassLoader);
return callerC;

}


Thanks!
-Nestor
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