finder-methods

How do clients locate existing entity beans representing database records? Unlike session beans, entity beans persist beyond a single client interaction, so they need methods to find and load existing data.

Finder methods are special methods on entity beans that search the database and return one or more primary keys of matching entity records. They don’t create new data—they locate existing records.

• Defined on Home Interface (e.g., findByPrimaryKey(String id))
• Implemented in bean class with ejb prefix: ejbFindByPrimaryKey(AccountPK key)
• Bean executes SQL SELECT query using JDBC
• Returns primary key to container, container creates EJB Object (proxy)
• Can return single key or Collection of keys

• Must begin with ejbFind prefix
• Must implement at minimum ejbFindByPrimaryKey() — required
• Return type: Primary Key object or Collection of Primary Keys
• Container generates for CMP, developer writes for BMP

• Built from: Entity Bean, Home Interface
• Builds into: Primary Key, Bean-Managed Persistence
• Contrasts with: ejbCreate() (creates new vs finds existing)
• Related: FinderException

• Finder methods run while bean is still in the pool—before acquiring specific data
• Don’t confuse with ejbCreate() which inserts new records
• Can return empty Collection but typically throw FinderException if not found
• Must NOT call getPrimaryKey() in finders—bean has no identity yet