java - Native Library sqljdbc_auth.dll already loaded in another classloader

Question

I have 2 java web apps that need to connect to SQL Server Database using Windows Integrated Authentication.

The first one that is loaded works fine but the second one throws the exception:

Native Library sqljdbc_auth.dll already loaded in another classloader

The error above occurs when I place the sqljdbc_auth.dll in one of the folders:

• C:WINDOWSsystem32
• C:Program FilesApache Software FoundationTomcat 7.0in

If I place the sqljdbc_auth.dll in one of the folders below:

• /WEB-INF/lib directory of each web application
• C:Program FilesApache Software FoundationTomcat 7.0lib

Both apps throw the exception:

Failed to load the sqljdbc_auth.dll cause :- no sqljdbc_auth in java.library.path

I am using this code to load the driver:

Class.forName("jdbc:sqlserver://<HOST>;databaseName=<DBNAME>;integratedSecurity=true;");

How can I solve it?

Answer 1

Each web application has its own Classloader (isolating them). When you call the Class.forName() method, there is a static block which is trying to load the shared library (dll file) - so both your web apps are trying to load the shared lib, hence the error message when the second one attempts to load.

The JDBC jar you have for sqlserver should be moved from being bundled with your wars, to the tomcat 7.0/lib folder and copy the sqljdbc_auth.dll to tomcat/bin folder - this way it will be in the tomcat parent classloader, and the class will only be loaded once.

|----------------------------------|
| sqljdbc*.jar     --> tomcat*/lib |
|----------------------------------|
| sqljdbc_auth.dll --> tomcat*/bin |
|----------------------------------|