+ hibernate4-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.
+
+ The default-configuration uses the EXPORT-target of the SchemaExport-Tool.
+ If you do not need to create a database with the evaluated schema, you can
+ use the NONE- or the SCRIPT-target.
+ This can be achieved with the command-line parameter
+ -Dhibernate.export.target=SCRIPT or with the following configuration:
+
+<configuration> + <target>SCRIPT</target> +</configuration>+
+ But even when no database is to be created, hibernate always needs to know + the dialect. Hence, the plugin will fail if this parameter 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 hibernate4-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.HSQLDialect +[INFO] hibernate.connection.url = jdbc:hsqldb:/home/kai/mmf/target/mmf;shutdown=true +[INFO] hibernate.connection.driver_class = org.hsqldb.jdbcDriver +[ERROR] Dependency for driver-class org.hsqldb.jdbcDriver is missing! +[INFO] ------------------------------------------------------------------------ +[ERROR] BUILD ERROR +[INFO] ------------------------------------------------------------------------ +[INFO] org.hsqldb.jdbcDriver +[INFO] ------------------------------------------------------------------------ +[INFO] For more information, run Maven with the -e switch +[INFO] ------------------------------------------------------------------------ +[INFO] Total time: 2 seconds +[INFO] Finished at: Thu Nov 29 11:31:14 CET 2012 +[INFO] Final Memory: 32M/342M +[INFO] ------------------------------------------------------------------------+
+ 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>hibernate4-maven-plugin</artifactId>
+ <version>${project.version}</version>
+ <executions>
+ <execution>
+ <goals>
+ <goal>export</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. +
+
+ If hibernate4-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 hibernate4-maven-plugin has
+ skipped its excecution.
+
+ A quick fix to this problem is, to force + hibernate4-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, hibernate4-maven-plugin signals a skipped
+ excecution by setting the maven property $\{hibernate.export.skipped\} to
+ true.
+ You can configure other plugins to react on this signal.
+ For example, the dbunit-plugin can be configured to skip its excecution, if
+ hibernate4-maven-plugin was skipped like this:
+
+<plugin>
+ <groupId>org.codehaus.mojo</groupId>
+ <artifactId>dbunit-maven-plugin</artifactId>
+ <configuration>
+ <skip>${hibernate.export.skipped}</skip>
+ </configuration>
+</plugin>
+ + If one manually drops the database or removes the hsqldb-files, it will not + be recreated by the hibernate4-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 hibernate4:export -Dhibernate.export.force=true+
+ The hibernate4-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>hibernate4-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... +
+ +