Ok, I did a little research and found this in the changelog (http://www.h2database.com/html/changelog.html):
Implicit relative paths are disabled (system property “h2.implicitRelativePath”), so that the database URL jdbc:h2:test now needs to be written as jdbc:h2:./test.
In H2 starting from version 1.4.177 Beta, implicit relative paths are not allowed anymore. Therefore, in your case the url should be written with a explicit relative path: db.default.url="jdbc:h2:./data/db"
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