Enable structured types as config values

README.md

@@ -51,13 +51,22 @@ And the _@ConfigurationServiceScan_ annotation hints the Baigan registrar to loo
 	@BaiganConfig
 	public interface ExpressFeature {
 
-	    public Boolean enabled();
+	    Boolean enabled();
 
-	    public String serviceUrl();
+	    String serviceUrl();
 
+        SomeStructuredConfigClass complexConfiguration();
+
+        List<String> configList();
+
+		Map<UUID, List<SomeConfigObject>> nestedGenericConfiguration();
 	}
 ```
 
+The individual methods may have arbitrary classes as return types, in particular complex structured types are supported, including Generics.
+
+**Note**: Primitives are not supported as return types as they cannot be null and therefore cannot express a missing configuration value.
+
 The above example code enables the application to inject _ExpressFeature_ spring bean into any other Spring bean:
 
 ```Java
@@ -84,13 +93,20 @@ This is done using the Spring Bean of type `RepositoryFactory`, which allows cre
 types. The following example shows how to configure a filesystem based repository.
 
 ```Java
-	@Bean
-	public ConfigurationRepository configurationRepository(RepositoryFactory factory) {
-		return factory.fileSystemConfigurationRepository()
-					  .fileName("configs.json");
+	@Configuration
+	public class ApplicationConfiguration {
+
+    	@Bean
+		public ConfigurationRepository configurationRepository(RepositoryFactory factory){
+			return factory.fileSystemConfigurationRepository()
+						  .fileName("configs.json");
+		}
 	}
 ``` 
 
+Check the documentation of the builders for details on how to configure the repositories. In particular, all
+repositories can be configured with a Jackson `ObjectMapper` used to deserialize the configuration.
+
 ### Creating configurations
 Baigan configurations follow a specific schema and can be stored on any of the supported repositories.
 

src/main/java/org/zalando/baigan/model/In.java

@@ -16,7 +16,9 @@
 
 package org.zalando.baigan.model;
 
+import java.util.Objects;
 import java.util.Set;
+import java.util.StringJoiner;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -45,4 +47,23 @@ public boolean eval(final String forValue) {
         return inValue.contains(forValue);
     }
 
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        In in = (In) o;
+        return Objects.equals(inValue, in.inValue);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(inValue);
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", In.class.getSimpleName() + "[", "]")
+                .add("inValue=" + inValue)
+                .toString();
+    }
 }

src/main/java/org/zalando/baigan/proxy/BaiganConfigClasses.java

@@ -0,0 +1,23 @@
+package org.zalando.baigan.proxy;
+
+import java.lang.reflect.Type;
+import java.util.Map;
+
+public class BaiganConfigClasses {
+    private Map<String, Type> configTypesByKey;
+
+    public BaiganConfigClasses() {}
+
+    public void setConfigTypesByKey(Map<String, Type> configTypesByKey) {
+        configTypesByKey.forEach((key, value) -> {
+            if (value.getClass().isPrimitive()) {
+                throw new IllegalArgumentException("Config " + key + " has an illegal return type " + value + ". Primitives are not supported as return type.");
+            }
+        });
+        this.configTypesByKey = configTypesByKey;
+    }
+
+    public Map<String, Type> getConfigTypesByKey() {
+        return configTypesByKey;
+    }
+}

src/main/java/org/zalando/baigan/proxy/ConfigurationBeanDefinitionRegistrar.java

@@ -31,21 +31,25 @@
 import org.zalando.baigan.annotation.BaiganConfig;
 import org.zalando.baigan.annotation.ConfigurationServiceScan;
 
+import java.lang.reflect.Type;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.stream.Collectors;
 
+import static java.util.stream.Collectors.toMap;
+import static org.zalando.baigan.proxy.ProxyUtils.createKey;
+
 /**
  * ImportBeanDefinitionRegistrar implementation that finds the
  * {@link ConfigurationServiceScan} annotations, delegates the scanning of
  * packages and proxy bean creation further down to the corresponding
  * implementations.
  *
- * @see ConfigurationServiceBeanFactory
- *
  * @author mchand
- *
+ * @see ConfigurationServiceBeanFactory
  */
 public class ConfigurationBeanDefinitionRegistrar
         implements ImportBeanDefinitionRegistrar {
@@ -83,38 +87,49 @@ private void createAndRegisterBeanDefinitions(final Set<String> packages,
         final ClassPathScanningCandidateComponentProvider scanner = new ClassPathScanningCandidateInterfaceProvider();
         scanner.addIncludeFilter(new AnnotationTypeFilter(BaiganConfig.class));
 
+        List<Class<?>> baiganConfigClasses = new ArrayList<>();
+
         for (final String singlePackage : packages) {
             final Set<BeanDefinition> candidates = scanner.findCandidateComponents(singlePackage);
             for (BeanDefinition definition : candidates) {
                 if (definition instanceof GenericBeanDefinition) {
                     final GenericBeanDefinition genericDefinition = (GenericBeanDefinition) definition;
-                    registerAsBean(registry, genericDefinition);
+                    final Class<?> baiganConfigClass = registerAsBean(registry, genericDefinition);
+                    baiganConfigClasses.add(baiganConfigClass);
                 } else {
                     throw new IllegalStateException(
-                        String.format(
-                            "Unable to read required metadata of configuration candidate [%s]",
-                            definition
-                        )
+                            String.format(
+                                    "Unable to read required metadata of configuration candidate [%s]",
+                                    definition
+                            )
                     );
                 }
             }
         }
+        Map<String, Type> configTypesByKey = baiganConfigClasses.stream().flatMap(clazz ->
+                Arrays.stream(clazz.getMethods()).map(method -> new ConfigType(createKey(clazz, method), method.getGenericReturnType()))
+        ).collect(toMap(c -> c.key, c -> c.type));
+        GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
+        beanDefinition.setBeanClass(BaiganConfigClasses.class);
+        beanDefinition.getPropertyValues().add("configTypesByKey", configTypesByKey);
+        registry.registerBeanDefinition("baiganConfigClasses", beanDefinition);
     }
 
-    private void registerAsBean(final BeanDefinitionRegistry registry, final GenericBeanDefinition genericDefinition) {
+    private Class<?> registerAsBean(final BeanDefinitionRegistry registry, final GenericBeanDefinition genericDefinition) {
         try {
             final Class<?> interfaceToImplement = genericDefinition.resolveBeanClass(
-                registry.getClass().getClassLoader()
+                    registry.getClass().getClassLoader()
             );
             registerAsBean(registry, interfaceToImplement);
+            return interfaceToImplement;
         } catch (final ClassNotFoundException e) {
             throw new IllegalStateException("Unable to register annotated interface as configuration bean", e);
         }
     }
 
     private void registerAsBean(final BeanDefinitionRegistry registry, final Class<?> interfaceToImplement) {
         final BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(
-            ConfigurationServiceBeanFactory.class
+                ConfigurationServiceBeanFactory.class
         );
         builder.addPropertyValue("candidateInterface", interfaceToImplement);
 
@@ -123,7 +138,7 @@ private void registerAsBean(final BeanDefinitionRegistry registry, final Class<?
     }
 
     private static class ClassPathScanningCandidateInterfaceProvider
-        extends ClassPathScanningCandidateComponentProvider {
+            extends ClassPathScanningCandidateComponentProvider {
 
         public ClassPathScanningCandidateInterfaceProvider() {
             super(false);
@@ -136,4 +151,13 @@ protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
         }
     }
 
+    private static class ConfigType {
+        private final String key;
+        private final Type type;
+
+        public ConfigType(String key, Type type) {
+            this.key = key;
+            this.type = type;
+        }
+    }
 }

src/main/java/org/zalando/baigan/proxy/ProxyUtils.java

@@ -19,6 +19,8 @@
 import com.google.common.base.CaseFormat;
 import com.google.common.base.Strings;
 
+import java.lang.reflect.Method;
+
 /**
  * The class to contain utility methods used in proxying configuration beans.
  *
@@ -28,7 +30,15 @@
 public class ProxyUtils {
     private static final String NAMESPACE_SEPARATOR = ".";
 
-    public static String dottify(final String text) {
+    public static String createKey(final Class<?> clazz, Method method) {
+        final String methodName = method.getName();
+        final String nameSpace = clazz.getSimpleName();
+
+        return ProxyUtils.dottify(nameSpace) + "."
+                + ProxyUtils.dottify(methodName);
+    }
+
+    private static String dottify(final String text) {
 
         if (Strings.isNullOrEmpty(text)) {
             return NAMESPACE_SEPARATOR;

src/main/java/org/zalando/baigan/proxy/handler/ContextAwareConfigurationMethodInvocationHandler.java

@@ -1,7 +1,6 @@
 package org.zalando.baigan.proxy.handler;
 
 import com.google.common.base.Supplier;
-import com.google.common.primitives.Primitives;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.BeansException;
@@ -12,19 +11,17 @@
 import org.zalando.baigan.context.ContextProviderRetriever;
 import org.zalando.baigan.model.Configuration;
 import org.zalando.baigan.context.ContextProvider;
-import org.zalando.baigan.proxy.ProxyUtils;
 import org.zalando.baigan.repository.ConfigurationRepository;
 
-import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
 
 import static com.google.common.base.Preconditions.checkState;
 import static com.google.common.base.Suppliers.memoize;
+import static org.zalando.baigan.proxy.ProxyUtils.createKey;
 
 /**
  * This class provides a concrete implementation for the Method invocation
@@ -58,58 +55,25 @@ public void setBeanFactory(final BeanFactory beanFactory) throws BeansException
     }
 
     @Override
-    protected Object handleInvocation(Object proxy, Method method,
-            Object[] args) throws Throwable {
-        final String methodName = method.getName();
-        final String nameSpace = getNamespace(proxy);
-
-        final String key = ProxyUtils.dottify(nameSpace) + "."
-                + ProxyUtils.dottify(methodName);
+    protected Object handleInvocation(Object proxy, Method method, Object[] args) {
+        final String key = createKey(getClass(proxy), method);
         final Object result = getConfig(key);
         if (result == null) {
             LOG.warn("Configuration not found for key: {}", key);
             return null;
         }
-
-        final Class<?> declaredReturnType = method.getReturnType();
-
-        try {
-
-            Constructor<?> constructor;
-            if (declaredReturnType.isInstance(result)) {
-                return result;
-            } else if (declaredReturnType.isPrimitive()) {
-                final Class<?> resultClass = result.getClass();
-                constructor = Primitives.wrap(declaredReturnType)
-                        .getDeclaredConstructor(resultClass);
-            } else if (declaredReturnType.isEnum()) {
-                for (Object t : Arrays
-                        .asList(declaredReturnType.getEnumConstants())) {
-                    if (result.toString().equalsIgnoreCase(t.toString())) {
-                        return t;
-                    }
-                }
-                LOG.warn("Unable to map [{}] to enum type [{}].", result, declaredReturnType.getName());
-                return null;
-            } else {
-                constructor = declaredReturnType
-                        .getDeclaredConstructor(result.getClass());
-            }
-            return constructor.newInstance(result);
-        } catch (Exception exception) {
-            LOG.warn(
-                    "Wrong or Incompatible configuration. Cannot find a constructor to create object of type "
-                            + declaredReturnType
-                            + " for value of the configuration key " + key,
-                    exception);
+        if (!method.getReturnType().isInstance(result)) {
+            LOG.error("Configuration repository returned object of wrong type. Expected: {}, actual: {}", method.getReturnType(), result.getClass());
+            return null;
         }
-        return null;
+
+        return result;
     }
 
-    private String getNamespace(final Object proxy) {
+    private Class<?> getClass(final Object proxy) {
         final Class<?>[] interfaces = proxy.getClass().getInterfaces();
         checkState(interfaces.length == 1, "Expected exactly one interface on proxy object.");
-        return interfaces[0].getSimpleName();
+        return interfaces[0];
     }
 
     private Object getConfig(final String key) {