Roundtrip engineering with Hibernate is possible using a set of Eclipse plugins, commandline tools, as well as Ant tasks. The Hibernate Tools currently include plugins for the Eclipse IDE as well as Ant tasks for reverse engineering of existing databases: Mapping Editor: An editor for Hibernate XML mapping files, supporting auto-completion and syntax highlighting. It also supports semantic auto-completion for class names and property/field names, making it much more versatile than a normal XML editor. Console: The console is a new view in Eclipse. In addition to a tree overview of your console configurations, you also get an interactive view of your persistent classes and their relationships. The console allows you to execute HQL queries against your database and browse the result directly in Eclipse. Development Wizards: Several wizards are provided with the Hibernate Eclipse tools; you can use a wizard to quickly generate Hibernate configuration (cfg.xml) files, or you may even completely reverse engineer an existing database schema into POJO source files and Hibernate mapping files. The reverse engineering wizard supports customizable templates. Ant Tasks: Please refer to the Hibernate Tools package and it's documentation for more information. However, the Hibernate main package comes bundled with an integrated tool (it can even be used from "inside" Hibernate on-the-fly): SchemaExport aka hbm2ddl. DDL may be generated from your mapping files by a Hibernate utility. The generated schema includes referential integrity constraints (primary and foreign keys) for entity and collection tables. Tables and sequences are also created for mapped identifier generators. You must specify a SQL Dialect via the hibernate.dialect property when using this tool, as DDL is highly vendor specific. First, customize your mapping files to improve the generated schema. Many Hibernate mapping elements define optional attributes named length, precision and scale. You may set the length, precision and scale of a column with this attribute. ]]> ]]> Some tags also accept a not-null attribute (for generating a NOT NULL constraint on table columns) and a unique attribute (for generating UNIQUE constraint on table columns). ]]> ]]> A unique-key attribute may be used to group columns in a single unique key constraint. Currently, the specified value of the unique-key attribute is not used to name the constraint in the generated DDL, only to group the columns in the mapping file. ]]> An index attribute specifies the name of an index that will be created using the mapped column or columns. Multiple columns may be grouped into the same index, simply by specifying the same index name. ]]> A foreign-key attribute may be used to override the name of any generated foreign key constraint. ]]> Many mapping elements also accept a child <column> element. This is particularly useful for mapping multi-column types: ]]> The default attribute lets you specify a default value for a column (you should assign the same value to the mapped property before saving a new instance of the mapped class). ]]> ]]> The sql-type attribute allows the user to override the default mapping of a Hibernate type to SQL datatype. ]]> The check attribute allows you to specify a check constraint. ]]> ... ]]> Attribute Values Interpretation length number column length precision number column decimal precision scale number column decimal scale not-null true|false specfies that the column should be non-nullable unique true|false specifies that the column should have a unique constraint index index_name specifies the name of a (multi-column) index unique-key unique_key_name specifies the name of a multi-column unique constraint foreign-key foreign_key_name specifies the name of the foreign key constraint generated for an association, for a <one-to-one>, <many-to-one>, <key>, or <many-to-many> mapping element. Note that inverse="true" sides will not be considered by SchemaExport. sql-type SQL column type overrides the default column type (attribute of <column> element only) default SQL expression specify a default value for the column check SQL expression create an SQL check constraint on either column or table The <comment> element allows you to specify comments for the generated schema. Current customers only ... ]]> Balance in USD ]]> This results in a comment on table or comment on column statement in the generated DDL (where supported). The SchemaExport tool writes a DDL script to standard out and/or executes the DDL statements. java -cp hibernate_classpaths org.hibernate.tool.hbm2ddl.SchemaExport options mapping_files Option Description --quiet don't output the script to stdout --drop only drop the tables --create only create the tables --text don't export to the database --output=my_schema.ddl output the ddl script to a file --naming=eg.MyNamingStrategy select a NamingStrategy --config=hibernate.cfg.xml read Hibernate configuration from an XML file --properties=hibernate.properties read database properties from a file --format format the generated SQL nicely in the script --delimiter=; set an end of line delimiter for the script You may even embed SchemaExport in your application: Database properties may be specified as system properties with -D<property> in hibernate.properties in a named properties file with --properties The needed properties are: Property Name Description hibernate.connection.driver_class jdbc driver class hibernate.connection.url jdbc url hibernate.connection.username database user hibernate.connection.password user password hibernate.dialect dialect You can call SchemaExport from your Ant build script: ]]> The SchemaUpdate tool will update an existing schema with "incremental" changes. Note that SchemaUpdate depends heavily upon the JDBC metadata API, so it will not work with all JDBC drivers. java -cp hibernate_classpaths org.hibernate.tool.hbm2ddl.SchemaUpdate options mapping_files Option Description --quiet don't output the script to stdout --text don't export the script to the database --naming=eg.MyNamingStrategy select a NamingStrategy --properties=hibernate.properties read database properties from a file --config=hibernate.cfg.xml specify a .cfg.xml file You may embed SchemaUpdate in your application: You can call SchemaUpdate from the Ant script: ]]> The SchemaValidator tool will validate that the existing database schema "matches" your mapping documents. Note that SchemaValidator depends heavily upon the JDBC metadata API, so it will not work with all JDBC drivers. This tool is extremely useful for testing. java -cp hibernate_classpaths org.hibernate.tool.hbm2ddl.SchemaValidator options mapping_files Option Description --naming=eg.MyNamingStrategy select a NamingStrategy --properties=hibernate.properties read database properties from a file --config=hibernate.cfg.xml specify a .cfg.xml file You may embed SchemaValidator in your application: You can call SchemaValidator from the Ant script: ]]>