Why annotations?

Generally we use annotation to facilitate the development and to make the code more clear and clean.

What are annotations?

Java 5 annotations provide standardization of metadata in a general goal. This metadata associated with Java features can be exploited in the compilation or execution.

Java was modified to allow the implementation of annotations:

• A dedicated syntax was added in Java to allow the definition and use of annotations.
• bytecode is enhanced to allow storage of annotations.

Where can annotations be used?

Annotations can be used with :

packages, classes, interfaces, constructors, methods, fields, parameters, variables or annotations themselves.

Categories of annotation

There are three categories of annotation:

• Markers: These annotations do not have an attribute

For example @Deprecated, @Override ...

• Single value annotation: these annotations have only one attribute

For example @MyAnnotation ( "test")

• Full annotations: these annotations have multiple attributes

For example @MyAnnotation (arg1 = "test 3", arg2 = "test 2", arg3 = "test3")

Like we see before you can create your own annotation

Create managed bean

To create a manage bean you need the annotation @ManagedBean

for example:

@ManagedBean
public class Example {}

You need the package:

import javax.faces.bean.ManagedBean;

Managed bean Scope

We use annotations to define the scope in which the bean will be stored.

There are many scope of managed bean: @NoneScoped, @RequestScoped, @ViewScoped, @SessionScoped, @ApplicationScoped, ...

• Application (@ApplicationScoped): Application scope persists across all users’ interactions with a web application.
• Session (@SessionScoped): Session scope persists across multiple HTTP requests in a web application.
• View (@ViewScoped): View scope persists during a user’s interaction with a single page (view) of a web application.
• Request (@RequestScoped): Request scope persists during a single HTTP request in a web application.
• None (@NoneScoped): Indicates a scope is not defined for the application.
• Custom (@CustomScoped): A user-defined, nonstandard scope. Its value must be configured as a java.util.Map. Custom scopes are used infrequently.