Group items tagged

by the container in order to realize common use cases

An interface becomes a vehicle for encapsulation or abstraction,

“Interfaces are used to encode similarities which the classes of various types share, but do not necessarily constitute a class relationship. For instance, a human and a parrot can both whistle; however, it would not make sense to represent Humans and Parrots as subclasses of a Whistler class. Rather they would most likely be subclasses of an Animal class (likely with intermediate classes), but both would implement the Whistler interface.” [http://en.wikipedia.org/wiki/Java_interface]

Extensive use of interfaces derives from a

Premature Extensibility Is the Root of Some Evil

The number of artifacts will double and you will have to introduce a configuration facility

easy with generics

create

find(

update(

delete(

@TransactionAttribute(TransactionAttributeType.MANDATORY)

this annotation bypasses the management layer and as such it is recommended only for development and testing purposes

Defining a Managed DataSource

Installing a JDBC driver as a deployment

Installing the JDBC Driver

deployment or as a core module

managed by the application server (and thus take advantage of the management and connection pooling facilities it provides), you must perform two tasks.  First, you must make the JDBC driver available to the application server; then you can configure the data source itself.  Once you have performed these tasks you can use the data source via standard JNDI injection.

recommended way to install a JDBC driver into the application server is to simply deploy it as a regular JAR deployment.  The reason for this is that when you run your application server in domain mode, deployments are automatically propagated to all servers to which the deployment applies; thus distribution of the driver JAR is one less thing for administrators to worry about.

Note on MySQL driver and JDBC Type 4 compliance: while the MySQL driver (at least up to 5.1.18) is designed to be a Type 4 driver, its jdbcCompliant() method always return false. The reason is that the driver does not pass SQL 92 full compliance tests, says MySQL. Thus, you will need to install the MySQL JDBC driver as a module (see below).

Installing a JDBC driver as a module

<module xmlns="urn:jboss:module:1.0" name="com.mysql">  <resources>    <resource-root path="mysql-connector-java-5.1.15.jar"/>  </resources>  <dependencies>    <module name="javax.api"/>  </dependencies></module>

jboss-7.0.0.<release>/modules/com/mysql/main

define your module with a module.xml file, and the actual jar file that contains your database driver

content of the module.xml file

Under the root directory of the application server, is a directory called modules

module name, which in this example is com.mysql

where the implementation is, which is the resource-root tag with the path element

define any dependencies you might have.  In this case, as the case with all JDBC data sources, we would be dependent on the Java JDBC API's, which in this case in defined in another module called javax.api, which you can find under modules/javax/api/main as you would expect.

Defining the DataSource itself

   <datasource jndi-name="java:jboss/datasources/MySqlDS" pool-name="MySqlDS">      <connection-url>jdbc:mysql://localhost:3306/EJB3</connection-url>         <driver>com.mysql</driver>

    <drivers>      <driver name="com.mysql" module="com.mysql">        <xa-datasource-class>com.mysql.jdbc.jdbc2.optional.MysqlXADataSource</xa-datasource-class>      </driver>    </drivers>

jboss-7.0.0.<release>/domain/configuration/domain.xml or jboss-7.0.0.<release>/standalone/configuration/standalone.xml

@Inject

CDI managed beans. The @EJB annotation is removed and @Inject is used instead

Annotating the boundary (Cart) with the @Named annotation makes the Cart immediately visible for expression language (EL) expressions in JSP and JSF

@Named annotation takes the simple name of the annotated class, puts the first character in lowercase, and exposes it directly to the JSF pages (or JSP). The Cart bean can be accessed directly, without any backed or managed beans, by the JSF pages: <h:commandButton value="Check out!" action="#{cart.checkout}" />

If there is a need for abstraction, the class can be turned into an interface (or abstract class)

local implementation (with CDI events

@Inject Event<String> event;

event.fire("Order proceeded!");

remote implementation:

javax.enterprise.event.Event belongs to the CDI-implementation

class Event can be considered to be a lightweight alternative to the java.beans.PropertyChangeSupport class

@Inject Event<String> event;

event.fire("Order proceeded!");

event can be received by any managed bean and also by EJB beans

provide a method with a single @Observes annotated parameter

@Observes String event

there is no real event, just the payload:

The during attribute in the @Observes annotation allows you to select in which transactional phase the event gets delivered. The default setting is IN_PROGRESS, which causes an immediate event delivery regardless of the transaction outcome. The AFTER_SUCCESS configuration causes the delivery to occur only after successful transaction completion

Although CDI events work only inside a single process (in the default case, CDI is extensible), they are perfectly suitable for decoupling packages from modules

The method checkout() starts a transaction that gets "reused" by the OrderSystem and CustomerNotification session beans

ordering.placeOrder(); notifier.sendNotification();

EJB beans cannot be directly exposed to JSF or JSP without a little help from CDI

simplified and unofficial UML Profile for EJB 3.0 with support for

Enterprise JavaBeans

session beans

Stateless beans must have a dependent scope while a stateful session bean can have any scope. By default they are transactional, but you can use the transaction attribute annotation.

CDI beans can be injected into EJBs and EJBs can be injected into CDI beans

When to use which bean How do you know when to use which bean? Simple.

In general, you should use CDI beans unless you need the advanced functionality available in the EJBs such as transactional functions. You can write your own interceptor to make CDI beans transactional, but for now, its simpler to use an EJB until CDI gets transactional CDI beans which is just around the corner

Comparing JSF Beans, CDI Beans and EJBs

JSF Managed Beans

In short, don’t use them if you are developing for Java EE 6 and using CDI. They provide a simple mechanism for dependency injection and defining backing beans for web pages, but they are far less powerful than CDI beans.

JSF beans cannot be mixed with other kinds of beans without some kind of manual coding.

CDI Beans

includes a complete, comprehensive managed bean facility

interceptors, conversation scope, Events, type safe injection, decorators, stereotypes and producer methods

JSF-like features, you can define the scope of the CDI bean using one of the scopes defined in the javax.enterprise.context package (namely, request, conversation, session and application scopes). If you want to use the CDI bean from a JSF page, you can give it a name using the javax.inject.Named annotation

Comparing JSF Beans, CDI Beans and EJBs

Comparing JSF Beans, CDI Beans and EJBs

JSF Managed Beans

injected managed beans (controls) results in the simplest possible architecture

Services can remain independent

ServiceFacade combines them