Load real driver class before use

[CadenP]

Issue #, if available: #26

Description of changes:
Load the real driver before it is used by calling Class.forName(this.realDriverClass). This ensures that the real driver has an opportunity to be registered.

If the real driver class does not exist, an IllegalStateException is thrown. This exception matches the assertThrows tested by AWSSecretsManagerDriverTest.test_getWrappedDriver_throws_badDriver.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[CadenP]

I am using this change on a project which uses AWSSecretsManagerPostgreSQLDriver with the default org.postgresql.Driver and can confirm it worked, at least in my environment.

Note that I have not tested it with any other drivers. However, the tests run as part of the install script all passed.

[zhaidw]

main branch already has called getDefaultDriverClass(); in Line 195 of AWSSecretsManagerDriver.java

[CadenP]

main branch already has called getDefaultDriverClass(); in Line 195 of AWSSecretsManagerDriver.java

Yep! And the addition in this pull request makes use of this knowledge, and that the result of that call is put into this.realDriverClass, and so calls Class.forName with it.

getDefaultDriverClass() does not call Class.forName, except for some variant of the MySQL driver. Other than that one exception it just returns a string, and does not do anything to ensure that the driver has been registered.

It's been a while since I created this pull request, and my mind has been elsewhere since. If I miss something simple, let me know! Also, I am no longer working on the project in which I came across this issue, so I will be unable to test any changes within that context.

[tuannguyent20]

One year later... confirm this commit resolve my same issue today.