Document Information


Part I Introduction

1.  Overview

2.  Using the Tutorial Examples

Part II The Web Tier

3.  Getting Started with Web Applications

4.  JavaServer Faces Technology

5.  Introduction to Facelets

6.  Expression Language

7.  Using JavaServer Faces Technology in Web Pages

8.  Using Converters, Listeners, and Validators

9.  Developing with JavaServer Faces Technology

10.  JavaServer Faces Technology: Advanced Concepts

11.  Using Ajax with JavaServer Faces Technology

12.  Composite Components: Advanced Topics and Example

13.  Creating Custom UI Components and Other Custom Objects

14.  Configuring JavaServer Faces Applications

15.  Java Servlet Technology

16.  Uploading Files with Java Servlet Technology

17.  Internationalizing and Localizing Web Applications

Part III Web Services

18.  Introduction to Web Services

19.  Building Web Services with JAX-WS

20.  Building RESTful Web Services with JAX-RS

21.  JAX-RS: Advanced Topics and Example

Part IV Enterprise Beans

22.  Enterprise Beans

23.  Getting Started with Enterprise Beans

24.  Running the Enterprise Bean Examples

25.  A Message-Driven Bean Example

26.  Using the Embedded Enterprise Bean Container

27.  Using Asynchronous Method Invocation in Session Beans

Part V Contexts and Dependency Injection for the Java EE Platform

28.  Introduction to Contexts and Dependency Injection for the Java EE Platform

29.  Running the Basic Contexts and Dependency Injection Examples

30.  Contexts and Dependency Injection for the Java EE Platform: Advanced Topics

31.  Running the Advanced Contexts and Dependency Injection Examples

Part VI Persistence

32.  Introduction to the Java Persistence API

33.  Running the Persistence Examples

34.  The Java Persistence Query Language

35.  Using the Criteria API to Create Queries

Overview of the Criteria and Metamodel APIs

Using the Criteria API and Metamodel API to Create Basic Typesafe Queries

Creating a Criteria Query

Query Roots

Querying Relationships Using Joins

Path Navigation in Criteria Queries

Restricting Criteria Query Results

The Expression Interface Methods

Expression Methods in the CriteriaBuilder Interface

Managing Criteria Query Results

Ordering Results

Grouping Results

Executing Queries

Single-Valued Query Results

Collection-Valued Query Results

36.  Creating and Using String-Based Criteria Queries

37.  Controlling Concurrent Access to Entity Data with Locking

38.  Using a Second-Level Cache with Java Persistence API Applications

Part VII Security

39.  Introduction to Security in the Java EE Platform

40.  Getting Started Securing Web Applications

41.  Getting Started Securing Enterprise Applications

42.  Java EE Security: Advanced Topics

Part VIII Java EE Supporting Technologies

43.  Introduction to Java EE Supporting Technologies

44.  Transactions

45.  Resources and Resource Adapters

46.  The Resource Adapter Example

47.  Java Message Service Concepts

48.  Java Message Service Examples

49.  Bean Validation: Advanced Topics

50.  Using Java EE Interceptors

Part IX Case Studies

51.  Duke's Bookstore Case Study Example

52.  Duke's Tutoring Case Study Example

53.  Duke's Forest Case Study Example



Using the Metamodel API to Model Entity Classes

The Metamodel API is used to create a metamodel of the managed entities in a particular persistence unit. For each entity class in a particular package, a metamodel class is created with a trailing underscore and with attributes that correspond to the persistent fields or properties of the entity class.

The following entity class, com.example.Pet, has four persistent fields: id, name, color, and owners:

package com.example;


public class Pet {
  protected Long id;
  protected String name;
  protected String color;
  protected Set<Owner> owners;

The corresponding Metamodel class is:

package com.example;


@Static Metamodel(Pet.class)
public class Pet_ {
  public static volatile SingularAttribute<Pet, Long> id;
  public static volatile SingularAttribute<Pet, String> name;
  public static volatile SingularAttribute<Pet, String> color;
  public static volatile SetAttribute<Pet, Owner> owners;

The metamodel class and its attributes are used in Criteria queries to refer to the managed entity classes and their persistent state and relationships.

Using Metamodel Classes

Metamodel classes that correspond to entity classes are of the following type:


Metamodel classes are typically generated by annotation processors either at development time or at runtime. Developers of applications that use Criteria queries may generate static metamodel classes by using the persistence provider’s annotation processor or may obtain the metamodel class by either calling the getModel method on the query root object or first obtaining an instance of the Metamodel interface and then passing the entity type to the instance’s entity method.

The following code snippet shows how to obtain the Pet entity’s metamodel class by calling Root<T>.getModel:

EntityManager em = ...;
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery cq = cb.createQuery(Pet.class);
Root<Pet> pet = cq.from(Pet.class);
EntityType<Pet> Pet_ = pet.getModel();

The following code snippet shows how to obtain the Pet entity’s metamodel class by first obtaining a metamodel instance by using EntityManager.getMetamodel and then calling entity on the metamodel instance:

EntityManager em = ...;
Metamodel m = em.getMetamodel();
EntityType<Pet> Pet_ = m.entity(Pet.class);

Note - The most common use case is to generate type-safe static metamodel classes at development time. Obtaining the metamodel classes dynamically, by calling Root<T>.getModel or EntityManager.getMetamodel and then the entity method, doesn’t allow for type-safety and doesn’t allow the application to call persistent field or property names on the metamodel class.