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Key: CAY-457
Summary: Cayenne Naming and Sequence Generator Configuration
Type: New Feature
Status: Unassigned
Priority: Major
Project: Cayenne
Components:
Cayenne Core Library
Versions:
1.2 [DEV]
Assignee:
Reporter: Heiko Erhardt
Created: Sun, 19 Feb 2006 7:08 PM
Updated: Sun, 19 Feb 2006 7:08 PM
Description:
Here is an excerpt from the feature descritpion of the Cayenne xdocs file.
I felt this becomes important when reengineering databases or creating new objects in the Modeler, so I placed it in the Modeler guide though the implementation resides in the Cayenne core.
I couldn't place it in the Wiki because the common-tasks-section has not been entered there yet.
Heiko Erhardt
----When reverse engineering a database or synchronizing object entities with database entities, Cayenne applies various rules for converting database names to object, member and relationship names. Also, a sequence generator definition may be created automatically for each reverse-engineered database entitiy. The file cayenne-naming.properties in the .cayenne directory in the classpath allows for customizing the behavior of the Cayenne modeler and the database loader to some extent.
The .cayenne/cayenne-naming.properties will be searched in the classpath. Just like the cayenne-log.properties file, You may copy the file from within the cayenne.jar archive and place it into an archive or folder that will be prepended to the classpath. Cayenne will read the contents of this file only once, so note that you must restart the Cayenne modeler if you change the file's contents.
Strategies. The naming algorithm is implemented using the strategy pattern, which allows you to plug in your own naming implementations. The naming strategy must implement the org.objectstyle.cayenne.util.NamingStrategy interface and can extend from the default naming strategy org.objectstyle.cayenne.util.DefaultNamingStrategy class. You may specify the strategy class name in the cayenne-naming.properties file.
Likewise, a key generator strategy may be specified. It must implement org.objectstyle.cayenne.access.DbLoaderKeyGeneratorStrategy and may extend from DbLoaderPropertyBasedKeyGeneratorStrategy.
Name Conversion. In general, names of object entities or object members are generated by converting the underscore-based database names to proper Java names. This behaviour is hard-coded at the moment. However, before this conversion is performed, some modifications may be applied.
Entity Naming. Sometimes, database tables are named in a plural form whereas Java class names reflect the singular form if a term. If your set the <code>Naming.SingularizeObjEntities</code> property to true, the database entity name will be converted to its singular form by stripping the traling "s". For exceptions to this rule where this simple operation won't do (e. g. "ADDRESSES"), you may specify the singular form of the entity using the <code>Naming.Singular.</code> property prefix (e. g. <code>Naming.Singular.ADDRESSES=ADDRESS</code>). object entities or object members are generated by converting the underscore-based database names to proper Java names. This behaviour is hard-coded at the moment. However, before this conversion is performed, some modifications may be applied.
Attribute Naming. It may be desirable to remove an auto-generated prefix from database column names before converting the to Java member names in order to generate object property names. The <code>Naming.DbAttributeNamePrefixToRemove</code> property supports this. If specified, any text up to (and including) the specified prefix will be removed. For example, some database design tools automatically add a table-specific prefix to all column names of the table like "PERS_FIRST_NAME". The property entry <code>Naming.DbAttributeNamePrefixToRemove=_</code> will remove everything up to the first underscore, leaving "FIRST_NAME" for generating the object attribute name.
Relationship Naming. The relationship naming controls the names of the generated relationship getter, setter, addition and removal methods of a data object class. The default naming strategy of the cayenne-naming.properties file supports specifying prefixes and postfixes for to-one and to-many relations. By default, to-one relations will be prefixed by "TO_", resuling in the method prefix "to" (e. g. a relation to the "PAINTING" entity will result in a "setToPainting" setter method. To-many relations will have the postfix "_ARRAY", resuling in "addToPaintingArray" adder methods.
Setting for example <code>Naming.ToOneRelationPrefix=</code> and <code>Naming.ToManyRelationSuffix=_LIST</code> will remove the "to" prefix from to-one relations and change the to-many postfix to "List".
The <code>org.objectstyle.cayenne.util.RelationsshipFkNamingStrategy</code> naming strategy extends the default naming strategy. It will add the name of the foreign key of a relationship before the target entity name to the relationsship name. This has two advantages: 1. Relations between the same entities (e. g. two relations between entity A and entity B) will have a speaking difference instead of merely a running number appended in order to make the unique (e. g. "goodPainting" and "badPainting" instead of "painting" and "painting1"). 2. It might be more descriptive than just using the target entity name. Similar to <code>Naming.DbAttributeNamePrefixToRemove</code>, the Similar to <code>Naming.Relationship.AttrNamePrefixToRemove</code> allows to remove a prefix from the foreign key before applying it to the name conversion. For example, for foreign keys like "PAINTING_ID_GOOD", the property entry <code>Naming.Relationship.AttrNamePrefixToRemove=_ID_</code> will leave the "GOOD" text for relationship name generation, resulting in a method name like "setGoodPainting".
Key Generator Settings. As with Cayenne object naming, a key generator definition can be bound to each reverse-engineered database entity using a pluggable strategy class, which must implement the org.objectstyle.cayenne.access.DbLoaderKeyGeneratorStrategy interface. The default implementation is the org.objectstyle.cayenne.access.DbLoaderPropertyBasedKeyGeneratorStrategy class. The properties of the cayenne-naming.properties file allow to specify the generator type, key cache size and the name of the generator (i. e. the name of the sequence). It may be generated from the table name or the entire name or a prefix of the key attribute.
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