implemented optional injection of ServletContextListeners

scm-webapp/src/main/java/sonia/scm/ServletContextListenerHolder.java

@@ -39,6 +39,7 @@ import com.google.inject.Singleton;
 
 //~--- JDK imports ------------------------------------------------------------
 
+import java.util.Collections;
 import java.util.Set;
 
 import javax.servlet.ServletContextEvent;
@@ -49,55 +50,36 @@ import javax.servlet.ServletContextListener;
  * @author Sebastian Sdorra
  */
 @Singleton
-public class ServletContextListenerHolder implements ServletContextListener
-{
+public class ServletContextListenerHolder implements ServletContextListener {
 
-  /**
-   * Constructs ...
-   *
-   *
-   * @param listenerSet
-   */
-  @Inject
-  public ServletContextListenerHolder(Set<ServletContextListener> listenerSet)
-  {
-    this.listenerSet = listenerSet;
-  }
-
-  //~--- methods --------------------------------------------------------------
-
-  /**
-   * Method description
-   *
-   *
-   * @param sce
-   */
-  @Override
-  public void contextDestroyed(ServletContextEvent sce)
-  {
-    for (ServletContextListener listener : listenerSet)
-    {
-      listener.contextDestroyed(sce);
-    }
-  }
-
-  /**
-   * Method description
-   *
-   *
-   * @param sce
-   */
-  @Override
-  public void contextInitialized(ServletContextEvent sce)
-  {
-    for (ServletContextListener listener : listenerSet)
-    {
-      listener.contextInitialized(sce);
-    }
-  }
-
-  //~--- fields ---------------------------------------------------------------
-
-  /** Field description */
+  static class ListenerHolder {
+    @Inject(optional = true)
     private Set<ServletContextListener> listenerSet;
+
+    private Set<ServletContextListener> getListenerSet() {
+      if (listenerSet == null) {
+        return Collections.emptySet();
+      }
+      return listenerSet;
+    }
+  }
+
+  private final Set<ServletContextListener> listenerSet;
+
+  @Inject
+  public ServletContextListenerHolder(ListenerHolder listeners)
+  {
+    this.listenerSet = listeners.getListenerSet();
+  }
+
+
+  @Override
+  public void contextInitialized(ServletContextEvent sce) {
+    listenerSet.forEach(listener -> listener.contextInitialized(sce));
+  }
+
+  @Override
+  public void contextDestroyed(ServletContextEvent sce) {
+    listenerSet.forEach(listener -> listener.contextDestroyed(sce));
+  }
 }

scm-webapp/src/test/java/sonia/scm/ServletContextListenerHolderTest.java

@@ -0,0 +1,91 @@
+package sonia.scm;
+
+import com.google.inject.AbstractModule;
+import com.google.inject.Guice;
+import com.google.inject.Injector;
+import com.google.inject.Key;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@ExtendWith(MockitoExtension.class)
+class ServletContextListenerHolderTest {
+
+  @Test
+  void shouldInitializeEveryContextListener() {
+    CountingListener one = new CountingListener(41);
+    CountingListener two = new CountingListener(41);
+
+    ServletContextListenerHolder holder = createHolder(one, two);
+    holder.contextInitialized(null);
+
+    assertThat(one.counter).isEqualTo(42);
+    assertThat(one.counter).isEqualTo(42);
+  }
+
+  @Test
+  void shouldDestroyEveryContextListener() {
+    CountingListener one = new CountingListener(43);
+    CountingListener two = new CountingListener(43);
+
+    ServletContextListenerHolder holder = createHolder(one, two);
+    holder.contextDestroyed(null);
+
+    assertThat(one.counter).isEqualTo(42);
+    assertThat(one.counter).isEqualTo(42);
+  }
+
+  @Test
+  void shouldNotFailWithoutServletContextListenerBound(){
+    Injector injector = Guice.createInjector();
+    ServletContextListenerHolder holder = injector.getInstance(ServletContextListenerHolder.class);
+    holder.contextInitialized(null);
+    holder.contextDestroyed(null);
+  }
+
+  private ServletContextListenerHolder createHolder(CountingListener one, CountingListener two) {
+    Injector injector = Guice.createInjector(new ListenerModule(one, two));
+    return injector.getInstance(ServletContextListenerHolder.class);
+  }
+
+  public static class ListenerModule extends AbstractModule {
+
+    private final Set<ServletContextListener> listeners;
+
+    ListenerModule(ServletContextListener... listeners) {
+      this.listeners = new HashSet<>(Arrays.asList(listeners));
+    }
+
+    @Override
+    protected void configure() {
+      bind(new Key<Set<ServletContextListener>>(){}).toInstance(listeners);
+    }
+  }
+
+  public static class CountingListener implements ServletContextListener {
+
+    private int counter;
+
+    CountingListener(int counter) {
+      this.counter = counter;
+    }
+
+    @Override
+    public void contextInitialized(ServletContextEvent sce) {
+      counter++;
+    }
+
+    @Override
+    public void contextDestroyed(ServletContextEvent sce) {
+      counter--;
+    }
+  }
+}