feature flag patterns

Author: thombergs

spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/patterns/replacebean/FeatureFlagEvaluation.java

@@ -4,15 +4,16 @@
 
 import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.Proxy;
+import java.util.function.Supplier;
 
-public class FeatureFlaggedBean<T> implements FactoryBean<T> {
+public class FeatureFlagFactoryBean<T> implements FactoryBean<T> {
 
     private final Class<T> targetClass;
-    private final FeatureFlagEvaluation featureFlagEvaluation;
+    private final Supplier<Boolean> featureFlagEvaluation;
     private final T beanWhenTrue;
     private final T beanWhenFalse;
 
-    public FeatureFlaggedBean(Class<T> targetClass, FeatureFlagEvaluation featureFlagEvaluation, T beanWhenTrue, T beanWhenFalse) {
+    public FeatureFlagFactoryBean(Class<T> targetClass, Supplier<Boolean> featureFlagEvaluation, T beanWhenTrue, T beanWhenFalse) {
         this.targetClass = targetClass;
         this.featureFlagEvaluation = featureFlagEvaluation;
         this.beanWhenTrue = beanWhenTrue;
@@ -21,9 +22,8 @@ public FeatureFlaggedBean(Class<T> targetClass, FeatureFlagEvaluation featureFla
 
     @Override
     public T getObject() {
-
         InvocationHandler invocationHandler = (proxy, method, args) -> {
-            if (featureFlagEvaluation.evaluate()) {
+            if (featureFlagEvaluation.get()) {
                 return method.invoke(beanWhenTrue, args);
             } else {
                 return method.invoke(beanWhenFalse, args);

spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/patterns/replacebean/FeatureFlaggedBean.java renamed to spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/patterns/replacebean/FeatureFlagFactoryBean.java

@@ -4,9 +4,13 @@
 import org.springframework.stereotype.Component;
 
 @Component("replaceBeanFeatureFlaggedService")
-class FeatureFlaggedService extends FeatureFlaggedBean<Service> {
+class FeatureFlaggedService extends FeatureFlagFactoryBean<Service> {
 
     public FeatureFlaggedService(FeatureFlagService featureFlagService) {
-        super(Service.class, featureFlagService::isNewServiceEnabled, new NewService(), new OldService());
+        super(
+                Service.class,
+                featureFlagService::isNewServiceEnabled,
+                new NewService(),
+                new OldService());
     }
 }

spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/patterns/replacebean/FeatureFlaggedService.java

@@ -26,4 +26,5 @@ public int doSomething() {
             return oldService.doSomething();
         }
     }
+
 }

spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/patterns/replacemethod/FeatureFlaggedService.java

@@ -8,4 +8,5 @@ class NewService implements Service {
     public int doSomething() {
         return 42;
     }
+
 }

spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/patterns/replacemethod/NewService.java

@@ -8,4 +8,9 @@ class OldService implements Service {
     public int doSomething() {
         return 1;
     }
+
+    public int doSomethingElse(){
+        return 2;
+    }
+
 }

spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/patterns/replacemethod/OldService.java

@@ -1,7 +1,7 @@
 package io.reflectoring.featureflags.patterns.replacemodule;
 
 import io.reflectoring.featureflags.FeatureFlagService;
-import io.reflectoring.featureflags.patterns.replacebean.FeatureFlaggedBean;
+import io.reflectoring.featureflags.patterns.replacebean.FeatureFlagFactoryBean;
 import io.reflectoring.featureflags.patterns.replacemodule.newmodule.NewService1;
 import io.reflectoring.featureflags.patterns.replacemodule.newmodule.NewService2;
 import io.reflectoring.featureflags.patterns.replacemodule.oldmodule.OldService1;
@@ -19,13 +19,13 @@ public FeatureFlaggedServiceModule(FeatureFlagService featureFlagService) {
     }
 
     @Bean("replaceModuleService1")
-    FeatureFlaggedBean<Service1> service1() {
-        return new FeatureFlaggedBean<>(Service1.class, featureFlagService::isNewServiceEnabled, new NewService1(), new OldService1());
+    FeatureFlagFactoryBean<Service1> service1() {
+        return new FeatureFlagFactoryBean<>(Service1.class, featureFlagService::isNewServiceEnabled, new NewService1(), new OldService1());
     }
 
     @Bean("replaceModuleService2")
-    FeatureFlaggedBean<Service2> service2() {
-        return new FeatureFlaggedBean<>(Service2.class, featureFlagService::isNewServiceEnabled, new NewService2(), new OldService2());
+    FeatureFlagFactoryBean<Service2> service2() {
+        return new FeatureFlagFactoryBean<>(Service2.class, featureFlagService::isNewServiceEnabled, new NewService2(), new OldService2());
     }
 
 }

spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/patterns/replacemodule/FeatureFlaggedServiceModule.java

@@ -20,6 +20,9 @@ public class ReplaceMethodTest {
     @Autowired
     private Service service;
 
+    @Autowired
+    private OldService oldService;
+
     @BeforeEach
     void resetMocks() {
         Mockito.reset(featureFlagService);
@@ -29,12 +32,15 @@ void resetMocks() {
     void oldServiceTest() {
         given(featureFlagService.isNewServiceEnabled()).willReturn(false);
         assertThat(service.doSomething()).isEqualTo(1);
+        assertThat(oldService.doSomethingElse()).isEqualTo(2);
     }
 
     @Test
     void newServiceTest() {
         given(featureFlagService.isNewServiceEnabled()).willReturn(true);
         assertThat(service.doSomething()).isEqualTo(42);
+        // doSomethingElse() is not behind a feature flag, so it should return the same value independant of the feature flag
+        assertThat(oldService.doSomethingElse()).isEqualTo(2);
     }
 
 }