ARQ-117 Added more descriptive exception messages

impl-base/src/main/java/org/jboss/arquillian/impl/DynamicServiceLoader.java

@@ -17,6 +17,7 @@
 package org.jboss.arquillian.impl;
 
 import java.util.Collection;
+import java.util.logging.Logger;
 
 import org.jboss.arquillian.spi.ServiceLoader;
 import org.jboss.arquillian.spi.util.DefaultServiceLoader;
@@ -29,24 +30,81 @@
  */
 public class DynamicServiceLoader implements ServiceLoader
 {
+   private static Logger logger = Logger.getLogger(DynamicServiceLoader.class.getName());
 
+   /* (non-Javadoc)
+    * @see org.jboss.arquillian.spi.ServiceLoader#all(java.lang.Class)
+    */
    public <T> Collection<T> all(Class<T> serviceClass)
    {
       return DefaultServiceLoader.load(serviceClass).getProviders();
    }
 
+   /* (non-Javadoc)
+    * @see org.jboss.arquillian.spi.ServiceLoader#onlyOne(java.lang.Class)
+    */
    public <T> T onlyOne(Class<T> serviceClass)
    {
       Collection<T> providers = DefaultServiceLoader.load(serviceClass).getProviders();
+      verifyOnlyOneOrSameImplementation(serviceClass, providers);
+
+      return providers.iterator().next();
+   }
+
+   private void verifyOnlyOneOrSameImplementation(Class<?> serviceClass, Collection<?> providers)
+   {
       if(providers == null || providers.size() == 0)
       {
-         throw new IllegalStateException("No implementation found for: " + serviceClass.getName() + ", check classpath");
+         throw new IllegalStateException(
+               "No implementation found for " + 
+               serviceClass.getName() + ", please check your classpath");
       }
       if(providers.size() > 1)
       {
-         throw new IllegalStateException("Mutiple implementations found for: " + serviceClass.getName() + ", check classpath");
+         // verify that they all point to the same implementation, if not throw exception
+         verifySameImplementation(serviceClass, providers);
       }
-      return providers.iterator().next();
    }
-
+
+   private void verifySameImplementation(Class<?> serviceClass, Collection<?> providers)
+   {
+      boolean providersAreTheSame = false;
+      Class<?> firstProvider = null;
+      for(Object provider : providers)
+      {
+         if(firstProvider == null)
+         {
+            // set the class to match
+            firstProvider = provider.getClass();
+            continue;
+         }
+         if(firstProvider == provider.getClass()) 
+         {
+            providersAreTheSame = true;
+         } 
+         else
+         {
+            throw new IllegalStateException(
+                  "More then one implementation found for " 
+                  + serviceClass.getName() + ", " +
+                  "please check your classpath. The found implementations are " + toClassString(providers));            
+         }
+      }
+      if(providersAreTheSame)
+      {
+         logger.warning(
+               "More then one reference to the same implementation was found for " + 
+               serviceClass.getName() + ", please verify you classpath");
+      }
+   }
+
+   private String toClassString(Collection<?> providers)
+   {
+      StringBuilder sb = new StringBuilder();
+      for(Object provider : providers)
+      {
+         sb.append(provider.getClass().getName()).append(", ");
+      }
+      return sb.subSequence(0, sb.length()-2).toString();
+   }
 }

impl-base/src/test/java/org/jboss/arquillian/impl/DynamicServiceLoaderTestCase.java

@@ -0,0 +1,64 @@
+/*
+ * JBoss, Home of Professional Open Source
+ * Copyright 2009, Red Hat Middleware LLC, and individual contributors
+ * by the @authors tag. See the copyright.txt in the distribution for a
+ * full listing of individual contributors.
+ *
+ * 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.jboss.arquillian.impl;
+
+import java.util.Collection;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Verify the behavior of the Dynamic Service Loader 
+ *
+ * @author <a href="mailto:aknutsen@redhat.com">Aslak Knutsen</a>
+ * @version $Revision: $
+ */
+public class DynamicServiceLoaderTestCase
+{
+
+   @Test(expected = IllegalStateException.class)
+   public void shouldFailIfMultipleProvidersFound() throws Exception 
+   {
+      new DynamicServiceLoader().onlyOne(Service.class);
+   }
+
+   @Test
+   public void shouldNotFailIfMultipleProvidersFoundPointingToSameImpl() throws Exception 
+   {
+      Service2 service = new DynamicServiceLoader().onlyOne(Service2.class);
+
+      Assert.assertTrue(
+            "verify that a instance of Service2Impl was loaded",
+            service.getClass() == Service2Impl.class);
+   }
+
+   @Test
+   public void shouldLoadAllInstances() throws Exception { 
+      Collection<Service> services = new DynamicServiceLoader().all(Service.class);
+
+      Assert.assertEquals(
+            "verify that all services where found and loaded",
+            2, services.size());
+   }
+
+   public interface Service {}
+   public static class ServiceImpl1 implements Service {}
+   public static class ServiceImpl2 implements Service {}
+
+   public interface Service2 {}
+   public static class Service2Impl implements Service2 {}
+}

impl-base/src/test/resources/META-INF/services/org.jboss.arquillian.impl.DynamicServiceLoaderTestCase$Service

@@ -0,0 +1,2 @@
+org.jboss.arquillian.impl.DynamicServiceLoaderTestCase$ServiceImpl1
+org.jboss.arquillian.impl.DynamicServiceLoaderTestCase$ServiceImpl2

impl-base/src/test/resources/META-INF/services/org.jboss.arquillian.impl.DynamicServiceLoaderTestCase$Service2

@@ -0,0 +1,2 @@
+org.jboss.arquillian.impl.DynamicServiceLoaderTestCase$Service2Impl
+org.jboss.arquillian.impl.DynamicServiceLoaderTestCase$Service2Impl

spi/src/main/java/org/jboss/arquillian/spi/util/DefaultServiceLoader.java

@@ -197,7 +197,7 @@ public void reload()
                            }
                            catch (ClassCastException e)
                            {
-                              throw new IllegalStateException("Extension " + line + " does not implement Extension");
+                              throw new IllegalStateException(line + " does not implement " + expectedType);
                            }
                            Constructor<? extends S> constructor = serviceClass.getConstructor();
                            if(!constructor.isAccessible()) {