Introduce a Lifecycle for system services

Provide an abstract class for system services to extend from,
similar to the android.app.Service.

This will allow services to receive events in a uniform way,
and will allow services to be created and started in the
correct order regardless of whether or not a particular
service exists.

Similar to android.app.Service, services are meant to implement
Binder interfaces as inner classes. This prevents services from
having incestuous access to each other and makes them use the
public API.

Change-Id: Iaacfee8d5f080a28d7cc606761f4624673ed390f

1 files changed, 141 insertions, 0 deletions

diff --git a/services/java/com/android/server/SystemServiceManager.java b/services/java/com/android/server/SystemServiceManager.java
new file mode 100644
index 000000000000..648975a9b7ca
--- /dev/null
+++ b/services/java/com/android/server/SystemServiceManager.java
@@ -0,0 +1,141 @@
+/*
+ * Copyright (C) 2013 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.android.server;
+
+import android.content.Context;
+import android.util.Log;
+import android.util.Slog;
+
+import java.util.ArrayList;
+
+/**
+ * Manages creating, starting, and other lifecycle events of system services.
+ */
+public class SystemServiceManager {
+    private static final String TAG = "SystemServiceManager";
+
+    private final Context mContext;
+
+    // Services that should receive lifecycle events.
+    private final ArrayList<SystemService> mServices = new ArrayList<SystemService>();
+
+    private int mCurrentPhase = -1;
+
+    public SystemServiceManager(Context context) {
+        mContext = context;
+    }
+
+    /**
+     * Creates and starts a system service. The class must be a subclass of
+     * {@link com.android.server.SystemService}.
+     *
+     * @param serviceClass A Java class that implements the SystemService interface.
+     * @throws RuntimeException if the service fails to start.
+     */
+    public void startService(Class<?> serviceClass) {
+        final SystemService serviceInstance = createInstance(serviceClass);
+        try {
+            Slog.i(TAG, "Creating " + serviceClass.getSimpleName());
+            serviceInstance.init(mContext, this);
+        } catch (Throwable e) {
+            throw new RuntimeException("Failed to create service " + serviceClass.getName(), e);
+        }
+
+        mServices.add(serviceInstance);
+
+        try {
+            Slog.i(TAG, "Starting " + serviceClass.getSimpleName());
+            serviceInstance.onStart();
+        } catch (Throwable e) {
+            throw new RuntimeException("Failed to start service " + serviceClass.getName(), e);
+        }
+    }
+
+    /**
+     * Starts the specified boot phase for all system services that have been started up to
+     * this point.
+     *
+     * @param phase The boot phase to start.
+     */
+    public void startBootPhase(final int phase) {
+        if (phase <= mCurrentPhase) {
+            throw new IllegalArgumentException("Next phase must be larger than previous");
+        }
+        mCurrentPhase = phase;
+
+        Slog.i(TAG, "Starting phase " + mCurrentPhase);
+
+        final int serviceLen = mServices.size();
+        for (int i = 0; i < serviceLen; i++) {
+            final SystemService service = mServices.get(i);
+            try {
+                service.onBootPhase(mCurrentPhase);
+            } catch (Throwable e) {
+                reportWtf("Service " + service.getClass().getName() +
+                        " threw an Exception processing boot phase " + mCurrentPhase, e);
+            }
+        }
+    }
+
+    /**
+     * Outputs the state of this manager to the System log.
+     */
+    public void dump() {
+        StringBuilder builder = new StringBuilder();
+        builder.append("Current phase: ").append(mCurrentPhase).append("\n");
+        builder.append("Services:\n");
+        final int startedLen = mServices.size();
+        for (int i = 0; i < startedLen; i++) {
+            final SystemService service = mServices.get(i);
+            builder.append("\t")
+                    .append(service.getClass().getSimpleName())
+                    .append("\n");
+        }
+
+        Slog.e(TAG, builder.toString());
+    }
+
+    private SystemService createInstance(Class<?> clazz) {
+        // Make sure it's a type we expect
+        if (!SystemService.class.isAssignableFrom(clazz)) {
+            reportWtf("Class " + clazz.getName() + " does not extend " +
+                    SystemService.class.getName());
+        }
+
+        try {
+            return (SystemService) clazz.newInstance();
+        } catch (InstantiationException e) {
+            reportWtf("Class " + clazz.getName() + " is abstract", e);
+        } catch (IllegalAccessException e) {
+            reportWtf("Class " + clazz.getName() +
+                    " must have a public no-arg constructor", e);
+        }
+        return null;
+    }
+
+    private static void reportWtf(String message) {
+        reportWtf(message, null);
+    }
+
+    private static void reportWtf(String message, Throwable e) {
+        Slog.i(TAG, "******************************");
+        Log.wtf(TAG, message, e);
+
+        // Make sure we die
+        throw new RuntimeException(message, e);
+    }
+}