Dissolve gerrit-server top-level directory

Change-Id: I538512dfe0f1bea774c01fdd45fa410a45634011

java/com/google/gerrit/server/LibModuleLoader.java

@@ -0,0 +1,61 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// 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 com.google.gerrit.server;
+
+import static java.util.stream.Collectors.toList;
+
+import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.inject.Injector;
+import com.google.inject.Key;
+import com.google.inject.Module;
+import com.google.inject.ProvisionException;
+import java.util.Arrays;
+import java.util.List;
+import org.eclipse.jgit.lib.Config;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/** Loads configured Guice modules from {@code gerrit.installModule}. */
+public class LibModuleLoader {
+  private static final Logger log = LoggerFactory.getLogger(LibModuleLoader.class);
+
+  public static List<Module> loadModules(Injector parent) {
+    Config cfg = getConfig(parent);
+    return Arrays.stream(cfg.getStringList("gerrit", null, "installModule"))
+        .map(m -> createModule(parent, m))
+        .collect(toList());
+  }
+
+  private static Config getConfig(Injector i) {
+    return i.getInstance(Key.get(Config.class, GerritServerConfig.class));
+  }
+
+  private static Module createModule(Injector injector, String className) {
+    Module m = injector.getInstance(loadModule(className));
+    log.info("Installed module {}", className);
+    return m;
+  }
+
+  @SuppressWarnings("unchecked")
+  private static Class<Module> loadModule(String className) {
+    try {
+      return (Class<Module>) Class.forName(className);
+    } catch (ClassNotFoundException | LinkageError e) {
+      String msg = "Cannot load LibModule " + className;
+      log.error(msg, e);
+      throw new ProvisionException(msg, e);
+    }
+  }
+}