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Michael Bouschen

Michael Bouschen is a software engineer and architect at Tech@Spree in Berlin, Germany. He has a long time Java experience and is working in the area of persistence, mapping Java objects to a database. His main focus is on query languages including Java Persistence Query Language, EJBQL, JDOQL, SQL)and persistence metadata. Michael is member of the JDO expert group (JSR-12 and JSR-243).

 

mb124283's blog

Java Persistence Query Return Types

Posted by mb124283 on April 25, 2007 at 3:08 PM EDT

The Java Persistence API (JPA) defines a query language that allows to define queries over entities and their persistent state. In this weblog I would like to point out what determines the type of the query result, such as the method to execute the query and the structure of the query SELECT clause.

Query API execution methods

Using relationships in the Java Persistence Query Language

Posted by mb124283 on July 5, 2006 at 6:07 PM EDT

The Java Persistence Query Language supports using relationships as defined in the object model in the query. The syntax of a relationship access expression is the same as in Java: a navigational expression using a dot as in o.customer. Please note, the query does not depend on the mapping of the relationship field to tables, columns and foreign keys in the underlying database schema.