Explanation

When starting XWiki with PostgreSQL, you may encounter the following error:

Method org.postgresql.jdbc4.Jdbc4Connection.isValid(int) is not yet implemented

Cause

This error occurs when using an outdated PostgreSQL JDBC driver version. Versions older than PostgreSQL JDBC 9.2 do not implement the isValid(int) method required by newer servlet containers and connection pools.

Solution

To resolve the issue, update the PostgreSQL JDBC driver to a newer version.

Possible approaches:

• If installed from a Debian package:
  1. Upgrade to a newer JDBC package version (at least the version shipped with Debian Jessie).
  2. Download a newer package.
  3. Install it using:

     dpkg --install libpostgresql-jdbc-java_9.2-1002-1_all.deb

• Alternatively, locate the existing postgresql-*.jar file in your servlet container or XWiki installation and replace it with a newer PostgreSQL JDBC driver downloaded from https://jdbc.postgresql.org/download/.

After updating the JDBC driver, restart the servlet container or application server to apply the changes.