add singletons

pom.xml

@@ -33,6 +33,7 @@
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-simple</artifactId>
             <version>1.7.21</version>
+            <scope>provided</scope>
         </dependency>
         <dependency>
             <groupId>junit</groupId>
@@ -46,11 +47,6 @@
             <version>1.3</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>com.google.collections</groupId>
-            <artifactId>google-collections</artifactId>
-            <version>1.0</version>
-        </dependency>
     </dependencies>
 
 

src/main/java/de/joshavg/simpledic/Instantiator.java

@@ -6,9 +6,11 @@ import java.lang.reflect.InvocationTargetException;
 class Instantiator<T> {
 
     private final Class<T> clz;
+    private final SdiContainerInterface container;
 
-    Instantiator(Class<T> clz) {
+    Instantiator(Class<T> clz, SdiContainerInterface container) {
         this.clz = clz;
+        this.container = container;
     }
 
     T createInstance()
@@ -22,10 +24,14 @@ class Instantiator<T> {
         for (int i = 0; i < parameterTypes.length; ++i) {
             @SuppressWarnings("unchecked")
             Class<Object> paramClz = (Class<Object>) parameterTypes[i];
-            parameters[i] = new Instantiator<>(paramClz).createInstance();
+            parameters[i] = container.getInstance(paramClz);
         }
 
         return constructor.newInstance(parameters);
     }
 
+    T createSingleton() {
+        return null;
+    }
+
 }

src/main/java/de/joshavg/simpledic/IntegrityCheck.java

@@ -1,13 +1,14 @@
 package de.joshavg.simpledic;
 
-import com.google.common.annotations.VisibleForTesting;
 import de.joshavg.simpledic.exception.ClassNotRegistered;
 import de.joshavg.simpledic.exception.integrity.DependencyCycleDetected;
 import de.joshavg.simpledic.exception.integrity.DependencyNotSatisfied;
 import de.joshavg.simpledic.exception.integrity.DuplicatedServiceClassesFound;
 import de.joshavg.simpledic.exception.integrity.MoreThanOneConstructor;
+import de.joshavg.simpledic.exception.integrity.NoVisibleConstructor;
 import de.joshavg.simpledic.exception.integrity.SdicClassNotFound;
 import java.lang.reflect.Constructor;
+import java.lang.reflect.Modifier;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -91,10 +92,19 @@ class IntegrityCheck {
     }
 
     private void collectConstructors(ArrayList<Constructor> l, Constructor<?>[] arr) {
+        if(arr.length == 0) {
+            return;
+        }
+
         Class<?> clz = arr[0].getDeclaringClass();
         if (arr.length > 1) {
             throw new MoreThanOneConstructor(clz);
         }
+
+        if(!Modifier.isPublic(arr[0].getModifiers())) {
+            throw new NoVisibleConstructor(clz);
+        }
+
         l.add(arr[0]);
         findDefinition(clz).setConstructor(arr[0]);
     }
@@ -131,9 +141,8 @@ class IntegrityCheck {
         }
     }
 
-    @VisibleForTesting
     static boolean isServiceName(String name) {
-        return !"service.".equals(name) && name.startsWith("service.");
+        return name.matches("service\\.[^.]+");
     }
 
     List<ServiceDefinition> getDefinitions() {

src/main/java/de/joshavg/simpledic/SdiContainer.java

@@ -6,22 +6,27 @@ import de.joshavg.simpledic.exception.SdicInstantiationException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.reflect.InvocationTargetException;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
+import java.util.Objects;
 import java.util.Properties;
 import java.util.stream.Collectors;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-public class SdiContainer {
+public class SdiContainer implements SdiContainerInterface {
 
     private static final Logger LOG = LoggerFactory.getLogger(SdiContainer.class);
 
     private final Properties props;
     private final List<ServiceDefinition> definitions;
+    private final Map<Class<?>, Object> singletons;
 
     private SdiContainer(Properties props, List<ServiceDefinition> definitions) {
         this.props = props;
         this.definitions = definitions;
+        this.singletons = new HashMap<>();
     }
 
     public static SdiContainer load() {
@@ -51,21 +56,40 @@ public class SdiContainer {
         return definitions.stream().map(ServiceDefinition::getClz).collect(Collectors.toList());
     }
 
-    public <T> T createInstance(Class<T> clz) {
-        if (clz == null) {
-            throw new NullPointerException();
-        }
-
+    @Override
+    public <T> T getInstance(Class<T> clz) {
         LOG.trace("instance ordered: ", clz);
         if (!serviceClasses().contains(clz)) {
             throw new ClassNotRegistered(clz);
         }
 
+        if (isStoredAsSingleton(clz)) {
+            return clz.cast(singletons.get(clz));
+        }
+
         try {
-            return new Instantiator<>(clz).createInstance();
+            T instance = new Instantiator<>(clz, this).createInstance();
+            handleSingleton(clz, instance);
+            return instance;
         } catch (IllegalAccessException | InvocationTargetException | InstantiationException e) {
             throw new SdicInstantiationException(e);
         }
     }
 
+    private <T> void handleSingleton(Class<T> clz, T instance) {
+        String key = props.entrySet().stream()
+            .filter(e -> Objects.equals(clz.getName(), String.valueOf(e.getValue())))
+            .map(e -> e.getKey().toString())
+            .findFirst()
+            .orElse("");
+
+        if (props.containsKey(key + ".singleton") && "true".equals(props.get(key + ".singleton"))) {
+            singletons.put(clz, instance);
+        }
+    }
+
+    private <T> boolean isStoredAsSingleton(Class<T> clz) {
+        return singletons.containsKey(clz);
+    }
+
 }

src/main/java/de/joshavg/simpledic/SdiContainerInterface.java

@@ -0,0 +1,6 @@
+package de.joshavg.simpledic;
+
+public interface SdiContainerInterface {
+
+    <T> T getInstance(Class<T> clz);
+}

src/main/java/de/joshavg/simpledic/exception/integrity/NoVisibleConstructor.java

@@ -0,0 +1,8 @@
+package de.joshavg.simpledic.exception.integrity;
+
+public class NoVisibleConstructor extends RuntimeException {
+
+    public NoVisibleConstructor(Class<?> clz) {
+        super(String.format("%s has no visible constructor", clz));
+    }
+}

src/test/java/de/joshavg/simpledic/ErrorTests.java

@@ -2,10 +2,10 @@ package de.joshavg.simpledic;
 
 import de.joshavg.simpledic.exception.ClassNotRegistered;
 import de.joshavg.simpledic.exception.ContainerInitException;
-import de.joshavg.simpledic.exception.SdicInstantiationException;
 import de.joshavg.simpledic.exception.integrity.DependencyCycleDetected;
 import de.joshavg.simpledic.exception.integrity.DependencyNotSatisfied;
 import de.joshavg.simpledic.exception.integrity.DuplicatedServiceClassesFound;
+import de.joshavg.simpledic.exception.integrity.NoVisibleConstructor;
 import de.joshavg.simpledic.services.Depends1;
 import de.joshavg.simpledic.services.PrivateConstructor;
 import java.util.Map;
@@ -20,27 +20,22 @@ public class ErrorTests {
 
     @Test(expected = DependencyCycleDetected.class)
     public void testCycleDetection() {
-        SdiContainer.load("cycle.properties").createInstance(Depends1.class);
+        SdiContainer.load("cycle.properties").getInstance(Depends1.class);
     }
 
     @Test(expected = ClassNotRegistered.class)
     public void requestUnknownClass() {
-        SdiContainer.load("almostsane.properties").createInstance(Map.class);
+        SdiContainer.load("sane.properties").getInstance(Map.class);
     }
 
     @Test(expected = DependencyNotSatisfied.class)
     public void requestServiceWithUnregisteredDependency() {
-        SdiContainer.load("unknowndep.properties").createInstance(Depends1.class);
+        SdiContainer.load("unknowndep.properties").getInstance(Depends1.class);
     }
 
-    @Test(expected = SdicInstantiationException.class)
+    @Test(expected = NoVisibleConstructor.class)
     public void privateConstructor() {
-        SdiContainer.load("almostsane.properties").createInstance(PrivateConstructor.class);
-    }
-
-    @Test(expected = NullPointerException.class)
-    public void requestNull() {
-        SdiContainer.load("almostsane.properties").createInstance(null);
+        SdiContainer.load("invisible.properties").getInstance(PrivateConstructor.class);
     }
 
     @Test(expected = ContainerInitException.class)

src/test/java/de/joshavg/simpledic/IntegrityCheckTest.java

@@ -13,6 +13,7 @@ public class IntegrityCheckTest {
         assertThat(IntegrityCheck.isServiceName("service"), is(false));
         assertThat(IntegrityCheck.isServiceName("service."), is(false));
         assertThat(IntegrityCheck.isServiceName("service.a"), is(true));
+        assertThat(IntegrityCheck.isServiceName("service.a.singleton"), is(false));
     }
 
 }

src/test/java/de/joshavg/simpledic/SimpleDependenciesTest.java

@@ -5,7 +5,7 @@ import org.junit.Test;
 
 public class SimpleDependenciesTest {
 
-    private static final String FILENAME = "almostsane.properties";
+    private static final String FILENAME = "sane.properties";
 
     @Test
     public void testIntegrityCheck() {
@@ -15,6 +15,6 @@ public class SimpleDependenciesTest {
     @Test
     public void createOneDependencyService() {
         SdiContainer container = SdiContainer.load(FILENAME);
-        container.createInstance(DependsOnNoDependencies.class);
+        container.getInstance(DependsOnNoDependencies.class);
     }
 }

src/test/java/de/joshavg/simpledic/SingletonTest.java

@@ -0,0 +1,18 @@
+package de.joshavg.simpledic;
+
+import static org.hamcrest.CoreMatchers.sameInstance;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import de.joshavg.simpledic.services.NoDependencies;
+import org.junit.Test;
+
+public class SingletonTest {
+
+    @Test
+    public void sameInstances() {
+        SdiContainer container = SdiContainer.load("singleton.properties");
+        assertThat(container.getInstance(NoDependencies.class),
+            sameInstance(container.getInstance(NoDependencies.class)));
+    }
+
+}

src/test/resources/invisible.properties

@@ -0,0 +1 @@
+service.private: de.joshavg.simpledic.services.PrivateConstructor

src/test/resources/sane.properties

@@ -1,3 +1,2 @@
 service.one: de.joshavg.simpledic.services.DependsOnNoDependencies
 service.nodeps: de.joshavg.simpledic.services.NoDependencies
-service.private: de.joshavg.simpledic.services.PrivateConstructor

src/test/resources/singleton.properties

@@ -0,0 +1,2 @@
+service.one: de.joshavg.simpledic.services.NoDependencies
+service.one.singleton: true