2. Using the Tutorial Examples
3. Getting Started with Web Applications
5. JavaServer Pages Technology
7. JavaServer Pages Standard Tag Library
10. JavaServer Faces Technology
11. Using JavaServer Faces Technology in JSP Pages
12. Developing with JavaServer Faces Technology
13. Creating Custom UI Components
14. Configuring JavaServer Faces Applications
15. Internationalizing and Localizing Web Applications
16. Building Web Services with JAX-WS
17. Binding between XML Schema and Java Classes
19. SOAP with Attachments API for Java
21. Getting Started with Enterprise Beans
23. A Message-Driven Bean Example
24. Introduction to the Java Persistence API
25. Persistence in the Web Tier
26. Persistence in the EJB Tier
Simplified Query Language Syntax
Queries That Navigate to Related Entities
A Simple Query with Relationships
Navigating to Single-Valued Relationship Fields
Traversing Relationships with an Input Parameter
Traversing Multiple Relationships
Navigating According to Related Fields
Queries with Other Conditional Expressions
BNF Grammar of the Java Persistence Query Language
Operators and Their Precedence
Empty Collection Comparison Expressions
28. Introduction to Security in the Java EE Platform
29. Securing Java EE Applications
31. The Java Message Service API
32. Java EE Examples Using the JMS API
36. The Coffee Break Application
Chapter 27
The Java Persistence Query Language
The Java Persistence query language defines queries for entities and their persistent state.The query language allows you to write portable queries that work regardless ofthe underlying data store.
The query language uses the abstract persistence schemas of entities, including their relationships,for its data model, and it defines operators and expressions based on thisdata model. The scope of a query spans the abstract schemas of relatedentities that are packaged in the same persistence unit. The query language usesa SQL-like syntax to select objects or values based on entity abstract schema typesand relationships among them.
This chapter relies on the material presented in earlier chapters. For conceptual information,seeChapter 24, Introduction to the Java Persistence API. For code examples, see ChaptersThepersistence.xml File andUpdating Data in the Database.
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