Known Pitfalls (FAQ)

Annotated classes in dependencies are not found.

hibernate-maven-plugin by default scans dependencies in the scope compile. You can configure it to scan dependencies in other scopes as well. But it scans only direct dependencies. Transitive dependencies are not scanned for annotated classes. If some of your annotated classes are hidden in a transitive dependency, you can simply add that dependency explicitly.

hibernate-maven-plugin always needs a database-connection

The default-configuration exports the created schema to the configured database. Therefore, it needs a valid database-connection and fails, if none is available. If you do not need to export the created schema to a database, you can set the property hibernate.schema.export to false. This can be achieved with the command-line parameter -Dhibernate.schema.export=false or with the following configuration:

<configuration>
  <export>false</export>
</configuration>

But even when no database is to be created, hibernate always needs to know the dialect. Hence, the plugin will still fail, if this parameter is also missing!

Dependency for driver-class XYZ is missing

One regular problem is the scope of the jdbc-driver-dependency. It is very unlikely, that this dependency is needed at compile-time. So a tidy maven-developer would usually scope it for runtime.

But this will break the execution of the hibernate-maven-plugin. Since it will not be able to see the needed dependency, it will fail with an error-message like:

[INFO] Gathered hibernate-configuration (turn on debugging for details):
[INFO]   hibernate.connection.username = sa
[INFO]   hibernate.connection.password = 
[INFO]   hibernate.dialect = org.hibernate.dialect.H2Dialect
[INFO]   hibernate.connection.url = jdbc:h2:file:./db
[INFO]   hibernate.hbm2dll.create_namespaces = false
[INFO]   hibernate.connection.driver_class = org.h2.Driver
[INFO]   hibernate.format_sql = true
[INFO] HHH000412: Hibernate Core {5.0.2.Final}
[INFO] HHH000206: hibernate.properties not found
[INFO] HHH000021: Bytecode provider name : javassist
[INFO] Adding /home/kai/project/target/classes to the list of roots to scan...
[INFO] Adding dependencies from scope compile to the list of roots to scan
[INFO] Adding dependencies from scope org.hibernate:hibernate-core:jar:4.3.0.Final to the list of roots to scan
[INFO] Adding annotated resource: de.juplo.tests.SimplestMavenHib4Test
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.760s
[INFO] Finished at: Mon Mar 07 19:06:54 CET 2016
[INFO] Final Memory: 11M/215M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal de.juplo:hibernate-maven-plugin:2.0.0:drop (default) on project hibernate4-properties-test: Could not open the JDBC-connection: Unable to load class [org.h2.Driver]: Could not load requested class : org.h2.Driver -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

A quick workaround for this error would be, to delete the runtime-constraint for the jdbc-driver-dependency.

A much cleaner way is, to (additionally) ad the dependency, to the plugin-definition:

<plugin>
  <groupId>de.juplo</groupId>
  <artifactId>hibernate-maven-plugin</artifactId>
  <version>2.0.0</version>
  <executions>
    <execution>
      <goals>
        <goal>drop</goal>
        <goal>create</goal>
      </goals>
    </execution>
  </executions>
  <dependencies>
  <dependency>
    <groupId>org.hsqldb</groupId>
    <artifactId>hsqldb</artifactId>
    <version>2.2.8</version>
  </dependency>
  </dependencies>
</plugin>

This is also the best way, if you use a different jdbc-driver for testing, than in production. Because otherwise, this dependency will unnecessarily bloat the runtime-dependencies of your project.

DBUnit fails after execution of hibernate was skipped because nothing has changed

If hibernate-maven-plugin skips its excecution, this may lead to errors in other plugins. For example, when importing sample-data in the automatically created database with the help of the dbunit-plugin, the CLEAN_INSERT-operation may fail because of foreign-key-constraints, if the database was not recreated, because the hibernate-maven-plugin has skipped its excecution.

A quick fix to this problem is, to force hibernate-maven-plugin to export the schema every time it is running. But to recreate the database on every testrun may noticeable slow down your development cycle, if you have to wait for slow IO.

To circumvent this problem, hibernate-maven-plugin signals a skipped excecution by setting the maven property ${hibernate.schema.skipped} to true. You can configure other plugins to react on this signal. For example, the dbunit-plugin can be configured to skip its excecution, if hibernate-maven-plugin was skipped like this:

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>dbunit-maven-plugin</artifactId>
  <configuration>
    <skip>${hibernate.schema.skipped}</skip>
  </configuration>
</plugin>

The database will not be recreated after a manual drop/clean

If one manually drops the database or removes the hsqldb-files, it will not be recreated by the hibernate-maven-plugin, because it cannot detect, that the database needs to be recreated. This happens, because the plugin will not recreate the database if neither the configuration nor the annotated classes have changed, because an unnecessary drop-create-cycle might take a long time. The plugin will report that like this:

[INFO] No modified annotated classes found and dialect unchanged.
[INFO] Skipping schema generation!

If one always uses mvn clean for cleanup, this will not happen. Otherwise the recreation must be forced:

mvn hibernate:create -Dhibernate.schema.force=true

The hibernate:create goal is not executed, when tests are skipped

The hibernate-maven-plugin automatically skips its execution, when maven.test.skip is set to true. If you need it to be always executed, you can configure that explicitly like this:

<plugin>
  <groupId>de.juplo</groupId>
  <artifactId>hibernate-maven-plugin</artifactId>
  ...
  <configuration>
    <skip>false</skip>
  </configuration>
</plugin>

Background-information for this design-decission can be found on the extra page To skip or not to skip: that is the question...

I do not want my dependencies to be scanned for hibernate annotations

If you do not want your dependencies to be scanned for hibernate annotations, you can pass -Dhibernate.schema.scan.dependencies=none to maven or set scanDependencies to none in the configuration of the plugin like this:

<plugin>
  <groupId>de.juplo</groupId>
  <artifactId>hibernate-maven-plugin</artifactId>
  ...
  <configuration>
    <scanDependencies>none</scanDependencies>
  </configuration>
</plugin>

No annotated classes found

If you are working under Windows and get the error-message No annotated classes found in directory C:\projects\X Y Z\path-to-project\target\classes, but you are really sure, that there are annotated classes in that directory, you are expiriencing a bug, in the scannotation-library, that was closed in version 1.1.0 of the hibernate-maven-plugin.

You should consider to upgrade to the latest version of the plugin.