Spring boot starter for Unleash Client SDK for Java

This provides a springboot starter for the official Unleash Client SDK for Java. This takes care of the required bootstrapping and creation of Unleash client. This also provides a annotation based approach to feature toggling similar to the functionality provided by FF4J client library. This also takes care of adding the unleash sdk as a transitive dependency.

Getting started

The following dependency needs to be added to the springboot project pom.

<dependency>
    <groupId>io.getunleash</groupId>
    <artifactId>springboot-unleash-starter</artifactId>
    <version>Latest version here</version>
</dependency>

Add the following to application.yaml

io:
  getunleashed:
    app-name: <application-name>
    instance-id: <instance-id>
    environment: <environment>
    api-url: <url>
    api-token: <token>

ex:

io:
  getunleashed:
    app-name: springboot-test
    instance-id: instance x
    environment: development
    api-url: http://unleash.herokuapp.com/api/
    api-token: '*:development.21a0a7f37e3ee92a0e601560808894ee242544996cdsdsdefgsfgdf'

The configuration takes care of creating configuring UnleashConfig and creating an instance of io.getunleash.Unleash.
This takes care of binding all strategy instances (in-built and custom) to the Unleash instance.

Including Spring Security Details in the Unleash Context

Provide an UnleashContextProvider bean to add details that Unleash can leverage when evaluating toggle strategies:

@Bean
@ConditionalOnMissingBean
public UnleashContextProvider unleashContextProvider(final UnleashProperties unleashProperties) {
    return () -> {
        UnleashContext.Builder builder = UnleashContext.builder();
        Object principal = SecurityContextHolder.getContext().getAuthentication().getPrincipal();
        if (principal instanceof User) {
            builder.userId((((User)principal).getUsername());
        }
        
        return builder
            .appName(unleashProperties.getAppName())
            .environment(unleashProperties.getEnvironment())
            .build();
    };
}

Usage

Create a feature toggle demo-toggle on unleash server and enabled it.
Create an interface FeatureDemoService and 2 implementation

public interface FeatureDemoService {
    String getDemoString(String name);
}

@Service("featureOldService")
public class FeatureDemoOldServiceImpl implements FeatureDemoService {
    public String getDemoString(String name) {
        return "old implementation";
    }
}

@Service("featureNewService")
public class FeatureDemoNewServiceImpl implements FeatureDemoService {
    public String getDemoString(String name) {
        return "New implementation";
    }
}

The requirement is that if the feature is enabled on the server, the new service implementation is used.
To get the above functionality add the @Toggle annotation to the interface,
If Context annotation is not used and UnleashContext is explicitly passed as a method parameter

import io.getunleash.UnleashContext;
import org.unleash.features.annotation.Toggle;

public interface FeatureDemoService {
    @Toggle(name="demo-toggle", alterBean="featureNewService")
    String getDemoString(String name, UnleashContext context);
}

If @Context annotation is used to set UnleashContext

import io.getunleash.UnleashContext;
import org.unleash.features.annotation.Toggle;

public interface FeatureDemoService {
    @Toggle(name="demo-toggle", alterBean="featureNewService")
    String getDemoString(String name);
}

FeatureDemoService is injected where required.

If Context annotation is not used and UnleashContext is explicitly passed as a method parameter

import io.getunleash.UnleashContext;
import org.unleash.features.annotation.Toggle;

public interface FeatureDemoService {
    @Toggle(name="demo-toggle", alterBean="featureNewService")
    String getDemoString(String name, UnleashContext context);
}

@RestController
@RequestMapping("/feature")
public class FeatureDemoController {
    private final FeatureDemoService featureDemoService;
    
    public FeatureDemoController(@Qualifier("featureOldService") final FeatureDemoService featureDemoService) {
        this.featureDemoService = featureDemoService;
    }
    
    @GetMapping
    public String feature(@RequestMapping final String name) {
        return featureDemoService.getDemoString(name, UnleashContext.builder().addProperty("name", name).build());
    }
}

If @Context annotation is used to set UnleashContext

import io.getunleash.UnleashContext;
import org.unleash.features.annotation.Toggle;

public interface FeatureDemoService {
    @Toggle(name="demo-toggle", alterBean="featureNewService")
    String getDemoString(String name);
}

@RestController
@RequestMapping("/feature")
public class FeatureDemoController {
    private final FeatureDemoService featureDemoService;
    
    public FeatureDemoController(@Qualifier("featureOldService") final FeatureDemoService featureDemoService) {
        this.featureDemoService = featureDemoService;
    }
    
    @GetMapping
    public String feature(@RequestMapping @Context(name = "name") final String name) {
        return featureDemoService.getDemoString(name);
    }
}

With the above, if the demo-toggle feature is enabled, the featureNewService is called even though featureOldService was injected.

Example for variants

Toggle annotation has support for variants. It can be used as follows:

  @Toggle(name = "background-color-feature",
          variants = @FeatureVariants(
                  fallbackBean = "noBackgroundColorService",
                  variants = {
                          @FeatureVariant(name = "green-background-variant", variantBean = "greenBackgroundColorService"),
                          @FeatureVariant(name = "red-background-variant", variantBean = "redBackgroundColorService")
                  }))

In the above example, there are 2 variants green-background-variant and red-background-variant defined in unleash. Here the implementation to be used for each variant is defined. fallbackBean is the implementation that will be used if a variant to bean mapping is not found.