ApplicationScoped annotation indicate

The @ApplicationScoped annotation in JavaServer Faces (JSF) indicates that a managed bean instance should be shared among all users (sessions) of an application. It ensures that only one instance of the managed bean is created and shared across the entire application context. Here’s an explanation followed by a Java example:

Explanation

• 1.  Singleton Scope:
  • Managed beans annotated with @ApplicationScoped behave like singleton objects in the context of a web application.
  • There is only one instance of the bean throughout the lifespan of the application, regardless of how many users (sessions) are using it.
• 2.  Shared State:
  • Use @ApplicationScoped for beans that manage application-wide state or resources that should be accessible to all users.
  • These beans are initialized when the application starts and are available until the application shuts down.
• 3.  Concurrency Considerations:
  • Since @ApplicationScoped beans are shared among all users, developers must ensure thread safety if the bean’s properties or methods are accessed and modified concurrently.

Java Example

Here’s an example demonstrating the use of @ApplicationScoped annotation in JSF:

java
package com.example.beans;

import javax.faces.bean.ApplicationScoped;
import javax.faces.bean.ManagedBean;

@ManagedBean
@ApplicationScoped
public class ApplicationSettings {
    private String appName = "MyApp";
    private String adminEmail = "admin@example.com";

    // Getter and Setter for appName and adminEmail
    public String getAppName() {
        return appName;
    }

    public void setAppName(String appName) {
        this.appName = appName;
    }

    public String getAdminEmail() {
        return adminEmail;
    }

    public void setAdminEmail(String adminEmail) {
        this.adminEmail = adminEmail;
    }
}

Explanation of Example

• ApplicationSettings (ApplicationSettings.java):  This managed bean is annotated with @ManagedBean to indicate it is a managed bean and @ApplicationScoped to specify its scope. The ApplicationSettings bean manages application-wide settings (appName and adminEmail).
• Usage:  In a JSF application, ApplicationSettings can be injected into other managed beans or accessed directly from JSF pages to retrieve or modify application settings. Since it is @ApplicationScoped, there will be only one instance of ApplicationSettings throughout the application lifecycle.

Using @ApplicationScoped ensures that application-wide data or configuration settings are centrally managed and available to all users of the application. It simplifies sharing of resources and helps in maintaining consistent application state across sessions.