#9 sample invocation strategy is in place

microservices/src/main/java/org/silverware/microservices/annotations/InvocationPolicy.java

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+/*
+ * -----------------------------------------------------------------------\
+ * SilverWare
+ *  
+ * Copyright (C) 2010 - 2013 the original author or authors.
+ *  
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * -----------------------------------------------------------------------/
+ */
+package org.silverware.microservices.annotations;
+
+import org.silverware.microservices.silver.services.LookupStrategy;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * @author Martin Večeřa <[email protected]>
+ */
+@Target(ElementType.FIELD)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface InvocationPolicy {
+
+   Class<LookupStrategy> lookupStrategy();
+}

microservices/src/main/java/org/silverware/microservices/silver/services/LookupStrategyFactory.java

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+/*
+ * -----------------------------------------------------------------------\
+ * SilverWare
+ *  
+ * Copyright (C) 2010 - 2013 the original author or authors.
+ *  
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * -----------------------------------------------------------------------/
+ */
+package org.silverware.microservices.silver.services;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.silverware.microservices.Context;
+import org.silverware.microservices.MicroserviceMetaData;
+import org.silverware.microservices.annotations.InvocationPolicy;
+
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Constructor;
+import java.util.Set;
+
+/**
+ * @author Martin Večeřa <[email protected]>
+ */
+public class LookupStrategyFactory {
+
+   /**
+    * Logger.
+    */
+   private static Logger log = LogManager.getLogger(LookupStrategyFactory.class);
+
+   public static LookupStrategy getStrategy(final Context context, final MicroserviceMetaData metaData, final Set<Annotation> options) {
+      LookupStrategy strategy = null;
+
+      for (Annotation option: options) {
+         if (option.annotationType().isAssignableFrom(InvocationPolicy.class)) {
+            InvocationPolicy policy = (InvocationPolicy) option;
+            Class<LookupStrategy> clazz = policy.lookupStrategy();
+
+            try {
+               Constructor c = clazz.getConstructor();
+               strategy = (LookupStrategy) c.newInstance();
+               strategy.initialize(context, metaData, options);
+               break;
+            } catch (Exception e) {
+               log.warn(String.format("Could not instantiate lookup strategy class %s:", clazz.getName()), e);
+            }
+         }
+      }
+
+      return strategy;
+   }
+}

microservices/src/main/java/org/silverware/microservices/silver/services/lookup/AbstractLookupStrategy.java

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+/*
+ * -----------------------------------------------------------------------\
+ * SilverWare
+ *  
+ * Copyright (C) 2010 - 2013 the original author or authors.
+ *  
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * -----------------------------------------------------------------------/
+ */
+package org.silverware.microservices.silver.services.lookup;
+
+import org.silverware.microservices.Context;
+import org.silverware.microservices.MicroserviceMetaData;
+import org.silverware.microservices.silver.services.LookupStrategy;
+
+import java.lang.annotation.Annotation;
+import java.util.Set;
+
+/**
+ * @author Martin Večeřa <[email protected]>
+ */
+abstract public class AbstractLookupStrategy implements LookupStrategy {
+
+   protected Context context;
+   protected MicroserviceMetaData metaData;
+   protected Set<Annotation> options;
+
+   @Override
+   public void initialize(final Context context, final MicroserviceMetaData metaData, final Set<Annotation> options) {
+      this.context = context;
+      this.metaData = metaData;
+      this.options = options;
+   }
+}

microservices/src/main/java/org/silverware/microservices/silver/services/lookup/RandomRobinLookupStrategy.java

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+/*
+ * -----------------------------------------------------------------------\
+ * SilverWare
+ *  
+ * Copyright (C) 2010 - 2013 the original author or authors.
+ *  
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * -----------------------------------------------------------------------/
+ */
+package org.silverware.microservices.silver.services.lookup;
+
+import java.util.Random;
+
+/**
+ * @author Martin Večeřa <[email protected]>
+ */
+public class RandomRobinLookupStrategy extends AbstractLookupStrategy {
+
+   private Random rnd = new Random();
+
+   @Override
+   public Object getService() {
+      final Object[] services = context.lookupMicroservice(metaData).toArray();
+      return services[rnd.nextInt(services.length)];
+   }
+}