In this guide we explain how to use feature toggles in a Java application using Unleash-hostd. We will be using the open source Unleash Java Client SDK.

    Important details

    Make sure your have the following details available:

    • API URL – Where you should connect your client SDK
    • API Secret – Your API secret required to connect to your instance. 
    You can find this information in your “Instance admin”. 

    Step 1: Install client SDK

    First we must add Unleash Client SDK as a dependency to your project. Below is an example of how you would add it to your pom.xml in Java:

    <dependency>
        <groupId>no.finn.unleash</groupId>
        <artifactId>unleash-client-java</artifactId>
        <version>Latest version here</version>
    </dependency>
    

    Step 2: Create a new Unleash Instance

    Next must must initialize a new instance of the Unleash Client.

    UnleashConfig unleashConfig = UnleashConfig.builder()
            .appName("my.java-app")
            .instanceId("your-instance-1")
            .environment(System.getenv("APP_ENV"))
            .unleashAPI("API URL")
            .customHttpHeader("Authorization", "API Secret")
            .build();
    
    Unleash unleash = new DefaultUnleash(config);
          
    

    In your app you typically just want one instance of Unleash, and inject that where you need it. You will typically use a dependency injection frameworks such as Spring or Guice to manage this.

    You should change the URL and the Authorization header (API secret) with the correct values for your instance, which you may locate under “Instance admin” in the menu.

    Step 3: Use the feature toggle

    Now that we have initialized the client SDK we can start using feature toggles defined in Unleash in our application. To achieve this we have the “isEnabled” method available, which will allow us to check the value of a feature toggle. This method will return true or false based on whether the feature should be enabled or disabled for the current request. 

    if(unleash.isEnabled("AwesomeFeature")) {
      //do some magic
    } else {
      //do old boring stuff
    }
    

    Pleas note the client SDK will synchronize with the Unleash-hosted API on initialization, and thus it can take a few milliseconds the first time before the client has the correct state. You can use the synchronousFetchOnInitialisation option to block the client until it has successfully synced with the server. 

    Read more about the Unleash architecture to learn how it works in more details

    Step 4: Provide Unleash Context

    It is the client SDK that computes whether a feature toggle should be considered enabled or disabled for  specific use request. This is the job of the activation strategies, which are implemented in the client SDK.

    The activation strategies is an implementation of rules based on data, which you provide as part of the Unleash Context.

    a) As argument to the isEnabled call

    The simplest way to provide the Unleash Context is as part of the “isEnabled” call:

    UnleashContext context = UnleashContext.builder()
      .userId("user@mail.com").build();
    
    unleash.isEnabled("someToggle", context);
    

    b) Via a UnleashContextProvider

    This is a bit more advanced approach, where you configure a unleash-context provider. By doing this you do not have rebuild or pass the unleash-context object to every place you are calling unleash.isEnabled.

    The provider typically binds the context to the same thread as the request. If you are using Spring the UnleashContextProvider will typically be a ‘request scoped’ bean.

    UnleashContextProvider contextProvider = new MyAwesomeContextProvider();
    
    UnleashConfig config = new UnleashConfig.Builder()
                .appName("java-test")
                .instanceId("instance x")
                .unleashAPI("http://unleash.herokuapp.com/api/")
                .unleashContextProvider(contextProvider)
                .build();
    
    Unleash unleash = new DefaultUnleash(config);
    
    // Anywhere in the code unleash will get the unleash context from your registered provider. 
    unleash.isEnabled("someToggle");