Feature¶

The Feature term is used to represent functionality or treatment in an application. It is identified by a unique identifier (uid).

Overview¶

A Feature models a unit of application behavior whose state can be changed at runtime. Features can affect any layer of an application, from the user interface to data access. FF4J provides integration points for each layer (see the illustration).

A feature toggle (or feature flag) allows you to enable or disable functionality at runtime, controlling how the code executes without redeploying.

Each feature acts as a flag. For a feature with identifier f1, the code snippet to check its state looks like:

if (ff4j.check("f1")) {
    System.out.println("The feature 'f1' is 'ON'");
} else {
    System.out.println("The feature 'f1' is 'OFF'");
}

Feature object¶

With the library FF4J, a Feature is an object with multiple attributes (not only identifier and state):

• A text description to explain the purpose
• An optional groupName to toggle multiple features at once (see FeatureGroup)
• An optional set of permissions to implement RBAC access. (see Permissions)
• An optional flipping strategy to implement your predicates (see FlippingStrategy)
• A key/value map named customProperties to create some context

classDiagram
    %% FF4J Feature class
    class Feature {
        - String uid
        - boolean enable
        - String description
        - String group
        - Set<String> permissions
        - FlippingStrategy flippingStrategy
        - Map<String, Property> customProperties

        + Feature(String uid)
        + Feature(String uid, boolean penable)
        + Feature(String uid, boolean penable, String description)
        + Feature(String uid, boolean penable, String description, String group)
        + Feature(String uid, boolean penable, String description, String group, Collection<String> auths)
        + Feature(String uid, boolean penable, String description, String group, Collection<String> auths, FlippingStrategy strat)
        + Feature(Feature f)

        + String getUid()
        + void setUid(String uid)

        + boolean isEnable()
        + void setEnable(boolean enable)
        + void enable()
        + void disable()
        + void toggle()

        + String getDescription()
        + void setDescription(String description)

        + String getGroup()
        + void setGroup(String group)

        + Set<String> getPermissions()
        + void setPermissions(Set<String> permissions)

        + FlippingStrategy getFlippingStrategy()
        + void setFlippingStrategy(FlippingStrategy fs)
        + String displayStrategyClassName()

        + Property getProperty(String propId)
        + void addProperty(Property p)

        + Map<String, Property> getCustomProperties()
        + void setCustomProperties(Map<String, Property> props)

        + String toJson()
    }

Examples¶

Create a feature¶

// feature f1 is created with default values (disabled, no description, no group, no permissions, no flipping strategy)
Feature f1 = new Feature("f1");
// feature f2 is created with custom values (enabled, description, no group, no permissions, no flipping strategy)
Feature f2 = new Feature("f2", true, "This is feature f2");

Check the state of a feature¶

if (ff4j.check("f1")) {
    System.out.println("The feature 'f1' is 'ON'");
} else {
    System.out.println("The feature 'f1' is 'OFF'");
}

Enable/Disable a feature¶

// To toggle 'ON' the feature 'f1'
ff4j.enable("f1");
// To toggle 'OFF' the feature 'f1'
ff4j.disable("f1");