Introduction to Java EE 5 Technology
NetBeans IDE 5.5 has been developed in close cooperation with the Java EE and
Glassfish teams to provide the tightest integration and easiest possible use of the new
Java EE 5 specification. NetBeans IDE 5.5 is the best way to quickly
learn and become productive in Java EE 5 programming.
This document provides an introduction to the major concepts of the Java EE 5 specifications
and how they relate to your hands-on programming. The following topics are covered:
You can find more information about developing and deploying Java EE
5 applications on the Sun Java System Application Server Platform
Edition 9 in the
Java EE 5 Tutorial.
The Java EE 5 platform simplifies deployment by removing the need for deployment descriptors, except
for the deployment descriptor required by the servlet specification, the web.xml file.
Other deployment descriptors, such as ejb-jar.xml and entries related to web services
in web.xml, are obsolete. J2EE 1.4 deployment descriptors were often complex and
it was easy to make mistakes in filling them out. Instead, the Java EE 5 platform makes use of "annotations". Annotations
are Java modifiers, similar to public and private, that you specify in your code. For
example, the EJB 3 specification,
which is a subset of the Java EE 5 specification, defines annotations for the bean type, interface type,
resource references, transaction attributes, security, and more. A similar set of annotations is provided
for web services by the JAX-WS 2.0 specification. Some annotations are used for generating artifacts. Other
annotations are used for documenting your code. Still others provide enhanced services such as security
or runtime-specific logic. In summary, the Java EE 5 platform provides annotations for the following tasks, among others:
Annotations are marked with a @ character. In the IDE, when you create a type
that makes use of annotations in Java EE 5, related placeholders
are provided in the generated code. For example, when you use the IDE to create a stateless session bean,
the following code is generated, which includes the @Stateless() annotation:
package mypackage;
import javax.ejb.*;
@Stateless()
public class HelloWorldSessionBean implements mypackage.HelloWorldSessionLocal {
}
Code completion provides access to annotation attributes specific
to the item under the cursor. For example, when you press Ctrl-Space in the brackets
of a @WebService() annotation, you see the following:

Each attribute has default values. Therefore, you do not need to specify any attributes unless
you want to use a value other than the default value. In simple cases, the default value is sufficient,
which
means that you do not even need to provide attributes at all.
The new EJB 3.0 API makes software development easier by reducing and simplifying the
amount of work required from the developer. In other words, fewer classes and less code.
This is possible because more of the work is now performed by the container.
Here are some of the features and benefits of the new EJB 3.0 API:
In the IDE, you can code enterprise beans just as you would code other Java classes, using
code completion and editor hints to implement the correct methods and keep the classes in synch
with their interfaces. You do not need to use special commands and dialog boxes to generate
things like business methods or web service operations, although the commands are still available
to help acquaint you with the syntax of Java EE 5 code.
Dependency injection enables an object to use annotations to request
external resources directly. This results in cleaner code because you no
longer need to clutter your code with resource creation and lookup code.
You can use resource injection in EJB components, web containers, and clients.
To request injection of a resource, a component uses the @Resource
annotation or, in the case of some specialized resources, the @EJB
and @WebServiceRef
annotations.
Resources that can be injected include:
In the IDE, the Source Editor provides full code completion for resources injection
annotations provided by the Java EE 5 platform. In addition, the IDE automatically
injects resources into your files when you run commands like Call EJB and Use Database.
The Java EE 5 platform introduces the new Java Persistence API, which was developed as part of JSR-220. The Java Persistence
API can also be used outside of EJB components,
for example, in web applications and application clients, and also
outside the Java EE platform, in Java SE applications.
The Java Persistence API has the following key features:
- Entities are POJOs. Unlike EJB components that used container-managed persistence (CMP), entity
objects using the new APIs are no longer components, and they no longer need to be in an EJB module.
- Standardized object-relational mapping. The new specification standardizes how object-relational mapping
is handled, freeing the developer from learning vendor-specific strategies.
The Java Persistence API uses annotations to specify object-relational mapping information, but still support XML descriptors.
- Named queries. A named query is now a static query expressed in metadata. The query can be either
a Java Persistence API query or a native query. This makes reusing queries very simple.
- Simple packaging rules. Because entity beans are simple Java technology classes, they can be
packaged virtually anywhere in a Java EE application. For example, entity beans can be part of an EJB
JAR
, application-client JAR
, WEB-INF/lib
,
WEB-INF/classes
, or even part of a utility JAR
in an enterprise application
archive (EAR) file. With these simple packaging rules, you no longer have to make an EAR file to use entity
beans from a web application or application client.
- Detached entities. Because entity beans are POJOs, they can be serialized and sent across the
network to a different address space and used in a persistence-unaware environment. As a result, you no
longer need to use data transfer objects (DTOs).
- EntityManager API. Application programmers now use a standard EntityManager API to perform
Create Read Update Delete
(CRUD) operations that involve entities.
The IDE provides tools to work with the new Java Persistence API. You can generate entity classes
automatically from a database, or code entity classes by hand.
The IDE also provides templates and graphic editors for creating and maintaining
persistence units. See Java Persistence in the Java EE 5 Platform for more
information on using the new Java Persistence API.
In the Java EE 5 platform, the use of annotations has greatly improved and simplified web services support.
The following specifications contributed to this area: JSR 224, Java API for XML-Based Web Services (JAX-WS)
2.0; JSR 222, Java Architecture for XML Binding (JAXB) 2.0; and JSR 181, Web Services Metadata for the Java
Platform.
JAX-WS 2.0 is the new API for web services in the Java EE 5 platform. As a successor to JAX-RPC 1.1,
JAX-WS 2.0 retains the natural RPC programming model while improving on several fronts: data binding,
protocol and transport independence, support for the REST
style of web services, and ease of
development.
A crucial difference from JAX-RPC 1.1 is that all data binding has now been delegated to JAXB 2.0.
This allows JAX-WS-based web services to use 100 percent of XML Schema, which results in improved
interoperability and ease of use. The two technologies are well integrated, so users no longer have
to juggle two sets of tools. When starting from Java technology classes, JAXB 2.0 can generate XML
Schema documents that are automatically embedded inside a Web Service Description Language (WSDL)
document, saving users from performing this error-prone integration manually.
Out of the box, JAX-WS 2.0 supports the SOAP 1.1, SOAP 1.2, and XML/HTTP protocols. Protocol extensibility
has been a goal from the very beginning, and JAX-WS 2.0 allows vendors to support additional protocols and
encodings for better performance -- for example, the FAST Infoset -- or for specialized applications. Web
services that use attachments to optimize the sending and receiving of large binary data can take advantage
of the MTOM/XOP (short for message transmission optimization mechanism/XML-binary optimized packaging)
standard from W3C without any adverse effect on the programming model. (See this page for information
on MTOM/XOP.)
Before Java EE 5 technology, defining a web service required long, unwieldy descriptors. Now it's
as easy as placing the @WebService
annotation on a Java technology class. All the
public methods on the class are automatically published as web service operations, and all their
arguments are mapped to XML Schema data types using JAXB 2.0.
Asynchronous Web Services
Because web service invocations take place over a network, such calls can take unpredictable lengths of
time. Many clients, especially interactive ones such as JFC/Swing-based desktop applications, experience
serious performance degradation from having to wait for a server's response. To avoid such performance
degradation, JAX-WS 2.0 provides a new asynchronous client API. With this API, application programmers no
longer have to create threads on their own. Instead, they can rely on the JAX-WS runtime to manage
long-running remote invocations for them.
Asynchronous methods can be used in conjunction with any WSDL-generated interfaces as well as with the more
dynamic Dispatch
API. For your convenience, when importing a WSDL document, you can require
asynchronous methods to be generated for any of the operations defined by the web service.
There are two usage models:
- In the polling model, you make a call. When you're ready, you request the results.
- In the callback model, you register a handler. As soon as the response arrives, you are notified.
Note that asynchronous invocation support is entirely implemented on the client side, so no changes are
required to the target web service.
The IDE provides tools to work with JAX-WS. You can use templates in the New File wizard
to generate JAX-WS artifacts. Asynchronous web services can be created by means of a Web Service Customization editor.
The code completion functionality includes annotations that you can use in your web services.
Next Steps
For more information about using NetBeans IDE 5.5 to develop Java EE applications, see the following resources:
To send comments and suggestions, get support, and keep informed on the latest
developments on the NetBeans IDE Java EE development features, join
the nbj2ee@netbeans.org mailing list.
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