implemented restarter to move control over the restart process to the core

scm-webapp/src/main/java/sonia/scm/lifecycle/DefaultRestarter.java

@@ -0,0 +1,41 @@
+package sonia.scm.lifecycle;
+
+import com.google.common.annotations.VisibleForTesting;
+import sonia.scm.event.ScmEventBus;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+@Singleton
+public class DefaultRestarter implements Restarter {
+
+  private ScmEventBus eventBus;
+  private RestartStrategy strategy;
+
+  @Inject
+  public DefaultRestarter() {
+    this(
+      ScmEventBus.getInstance(),
+      RestartStrategy.get(Thread.currentThread().getContextClassLoader()).orElse(null)
+    );
+  }
+
+  @VisibleForTesting
+  DefaultRestarter(ScmEventBus eventBus, RestartStrategy strategy) {
+    this.eventBus = eventBus;
+    this.strategy = strategy;
+  }
+
+  @Override
+  public boolean isSupported() {
+    return strategy != null;
+  }
+
+  @Override
+  public void restart(Class<?> cause, String reason) {
+    if (!isSupported()) {
+      throw new RestartNotSupportedException("restarting is not supported");
+    }
+    eventBus.post(new RestartEvent(cause, reason));
+  }
+}