[Tether07] Migrate Tethering into module

Now tethering would be run in dedicated service.
TetheringManager is the interface used to communicate with
TetheringService. The new call flow would be: ConnectivityManager
-> ConnectivityService -> TetheringManager -> TetheringService.
Note: the return value of #tether(), #untether() and #setUsbTethering()
APIs would always be no error. Client can use #getLastTetherError()
or #getTetheredIfaces or listen tether state change to check
status of corresponding interface.

Bug: 136040414
Bug: 144742179
Test: -build, flash, boot
      -atest TetheringTests
      -atest FrameworksNetTests

Change-Id: I7e78c0e0a3e70f940a749ba2a39ece7c7ec5b9b3
Merged-In: I7e78c0e0a3e70f940a749ba2a39ece7c7ec5b9b3
diff --git a/Tethering/common/TetheringLib/Android.bp b/Tethering/common/TetheringLib/Android.bp
index 5b01b1e..adc5a72 100644
--- a/Tethering/common/TetheringLib/Android.bp
+++ b/Tethering/common/TetheringLib/Android.bp
@@ -18,8 +18,12 @@
 aidl_interface {
     name: "tethering-aidl-interfaces",
     local_include_dir: "src",
+    include_dirs: ["frameworks/base/core/java"], // For framework parcelables.
     srcs: [
+        "src/android/net/ITetherInternalCallback.aidl",
         "src/android/net/ITetheringConnector.aidl",
+        "src/android/net/TetheringConfigurationParcel.aidl",
+        "src/android/net/TetherStatesParcel.aidl",
     ],
     backend: {
         ndk: {
@@ -33,8 +37,15 @@
 
 java_library {
     name: "tethering-client",
-    platform_apis: true,
+    sdk_version: "system_current",
     static_libs: [
         "tethering-aidl-interfaces-java",
     ],
 }
+
+// This is temporary file group which would be removed after TetheringManager is built
+// into tethering-client. Will be done by aosp/1156906.
+filegroup {
+    name: "tethering-manager",
+    srcs: ["src/android/net/TetheringManager.java"],
+}
diff --git a/Tethering/common/TetheringLib/src/android/net/ITetherInternalCallback.aidl b/Tethering/common/TetheringLib/src/android/net/ITetherInternalCallback.aidl
new file mode 100644
index 0000000..abb00e8
--- /dev/null
+++ b/Tethering/common/TetheringLib/src/android/net/ITetherInternalCallback.aidl
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2019 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 android.net;
+
+import android.net.Network;
+import android.net.TetheringConfigurationParcel;
+import android.net.TetherStatesParcel;
+
+/**
+ * Callback class for receiving tethering changed events
+ * @hide
+ */
+oneway interface ITetherInternalCallback
+{
+    void onUpstreamChanged(in Network network);
+    void onConfigurationChanged(in TetheringConfigurationParcel config);
+    void onTetherStatesChanged(in TetherStatesParcel states);
+    void onCallbackCreated(in Network network, in TetheringConfigurationParcel config,
+            in TetherStatesParcel states);
+}
diff --git a/Tethering/common/TetheringLib/src/android/net/ITetheringConnector.aidl b/Tethering/common/TetheringLib/src/android/net/ITetheringConnector.aidl
index 443481e..bfe502f 100644
--- a/Tethering/common/TetheringLib/src/android/net/ITetheringConnector.aidl
+++ b/Tethering/common/TetheringLib/src/android/net/ITetheringConnector.aidl
@@ -15,6 +15,23 @@
  */
 package android.net;
 
+import android.net.ITetherInternalCallback;
+import android.os.ResultReceiver;
+
 /** @hide */
 oneway interface ITetheringConnector {
+    void tether(String iface);
+
+    void untether(String iface);
+
+    void setUsbTethering(boolean enable);
+
+    void startTethering(int type, in ResultReceiver receiver, boolean showProvisioningUi);
+
+    void stopTethering(int type);
+
+    void requestLatestTetheringEntitlementResult(int type, in ResultReceiver receiver,
+            boolean showEntitlementUi);
+
+    void registerTetherInternalCallback(ITetherInternalCallback callback);
 }
diff --git a/Tethering/common/TetheringLib/src/android/net/TetherStatesParcel.aidl b/Tethering/common/TetheringLib/src/android/net/TetherStatesParcel.aidl
new file mode 100644
index 0000000..3d842b3
--- /dev/null
+++ b/Tethering/common/TetheringLib/src/android/net/TetherStatesParcel.aidl
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2019 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 android.net;
+
+/**
+ * Status details for tethering downstream interfaces.
+ * {@hide}
+ */
+parcelable TetherStatesParcel {
+    String[] availableList;
+    String[] tetheredList;
+    String[] localOnlyList;
+    String[] erroredIfaceList;
+    // List of Last error code corresponding to each errored iface in erroredIfaceList. */
+    // TODO: Improve this as b/143122247.
+    int[] lastErrorList;
+}
diff --git a/Tethering/common/TetheringLib/src/android/net/TetheringConfigurationParcel.aidl b/Tethering/common/TetheringLib/src/android/net/TetheringConfigurationParcel.aidl
new file mode 100644
index 0000000..fdf0d16
--- /dev/null
+++ b/Tethering/common/TetheringLib/src/android/net/TetheringConfigurationParcel.aidl
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2019 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 android.net;
+
+/**
+ * Configuration details for a tethering.
+ * @hide
+ */
+parcelable TetheringConfigurationParcel {
+    int subId;
+    String[] tetherableUsbRegexs;
+    String[] tetherableWifiRegexs;
+    String[] tetherableBluetoothRegexs;
+    boolean isDunRequired;
+    boolean chooseUpstreamAutomatically;
+    int[] preferredUpstreamIfaceTypes;
+    String[] legacyDhcpRanges;
+    String[] defaultIPv4DNS;
+    boolean enableLegacyDhcpServer;
+    String[] provisioningApp;
+    String provisioningAppNoUi;
+    int provisioningCheckPeriod;
+}
diff --git a/Tethering/common/TetheringLib/src/android/net/TetheringManager.java b/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
new file mode 100644
index 0000000..9e8726e
--- /dev/null
+++ b/Tethering/common/TetheringLib/src/android/net/TetheringManager.java
@@ -0,0 +1,507 @@
+/*
+ * Copyright (C) 2019 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 android.net;
+
+import static android.Manifest.permission.NETWORK_STACK;
+import static android.net.ConnectivityManager.TETHER_ERROR_NO_ERROR;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.net.util.SharedLog;
+import android.os.ConditionVariable;
+import android.os.IBinder;
+import android.os.RemoteCallbackList;
+import android.os.RemoteException;
+import android.os.ResultReceiver;
+import android.util.Slog;
+
+import com.android.internal.annotations.GuardedBy;
+
+import java.io.PrintWriter;
+import java.util.StringJoiner;
+
+/**
+ * Service used to communicate with the tethering, which is running in a separate module.
+ * @hide
+ */
+public class TetheringManager {
+    private static final String TAG = TetheringManager.class.getSimpleName();
+
+    private static TetheringManager sInstance;
+
+    @Nullable
+    private ITetheringConnector mConnector;
+    private TetherInternalCallback mCallback;
+    private Network mTetherUpstream;
+    private TetheringConfigurationParcel mTetheringConfiguration;
+    private TetherStatesParcel mTetherStatesParcel;
+
+    private final RemoteCallbackList<ITetheringEventCallback> mTetheringEventCallbacks =
+            new RemoteCallbackList<>();
+    @GuardedBy("mLog")
+    private final SharedLog mLog = new SharedLog(TAG);
+
+    private TetheringManager() { }
+
+    /**
+     * Get the TetheringManager singleton instance.
+     */
+    public static synchronized TetheringManager getInstance() {
+        if (sInstance == null) {
+            sInstance = new TetheringManager();
+        }
+        return sInstance;
+    }
+
+    private class TetheringConnection implements
+            ConnectivityModuleConnector.ModuleServiceCallback {
+        @Override
+        public void onModuleServiceConnected(@NonNull IBinder service) {
+            logi("Tethering service connected");
+            registerTetheringService(service);
+        }
+    }
+
+    private void registerTetheringService(@NonNull IBinder service) {
+        final ITetheringConnector connector = ITetheringConnector.Stub.asInterface(service);
+
+        log("Tethering service registered");
+
+        // Currently TetheringManager instance is only used by ConnectivityService and mConnector
+        // only expect to assign once when system server start and bind tethering service.
+        // STOPSHIP: Change mConnector to final before TetheringManager put into boot classpath.
+        mConnector = connector;
+        mCallback = new TetherInternalCallback();
+        try {
+            mConnector.registerTetherInternalCallback(mCallback);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+    }
+
+    private class TetherInternalCallback extends ITetherInternalCallback.Stub {
+        private final ConditionVariable mWaitForCallback = new ConditionVariable(false);
+        private static final int EVENT_CALLBACK_TIMEOUT_MS = 60_000;
+
+        @Override
+        public void onUpstreamChanged(Network network) {
+            mTetherUpstream = network;
+            reportUpstreamChanged(network);
+        }
+
+        @Override
+        public void onConfigurationChanged(TetheringConfigurationParcel config) {
+            mTetheringConfiguration = config;
+        }
+
+        @Override
+        public void onTetherStatesChanged(TetherStatesParcel states) {
+            mTetherStatesParcel = states;
+        }
+
+        @Override
+        public void onCallbackCreated(Network network, TetheringConfigurationParcel config,
+                TetherStatesParcel states) {
+            mTetherUpstream = network;
+            mTetheringConfiguration = config;
+            mTetherStatesParcel = states;
+            mWaitForCallback.open();
+        }
+
+        boolean awaitCallbackCreation() {
+            return mWaitForCallback.block(EVENT_CALLBACK_TIMEOUT_MS);
+        }
+    }
+
+    private void reportUpstreamChanged(Network network) {
+        final int length = mTetheringEventCallbacks.beginBroadcast();
+        try {
+            for (int i = 0; i < length; i++) {
+                try {
+                    mTetheringEventCallbacks.getBroadcastItem(i).onUpstreamChanged(network);
+                } catch (RemoteException e) {
+                    // Not really very much to do here.
+                }
+            }
+        } finally {
+            mTetheringEventCallbacks.finishBroadcast();
+        }
+    }
+
+    /**
+     * Start the tethering service. Should be called only once on device startup.
+     *
+     * <p>This method will start the tethering service either in the network stack process,
+     * or inside the system server on devices that do not support the tethering module.
+     *
+     * {@hide}
+     */
+    public void start() {
+        // Using MAINLINE_NETWORK_STACK permission after cutting off the dpendency of system server.
+        ConnectivityModuleConnector.getInstance().startModuleService(
+                ITetheringConnector.class.getName(), NETWORK_STACK,
+                new TetheringConnection());
+        log("Tethering service start requested");
+    }
+
+    /**
+     * Attempt to tether the named interface.  This will setup a dhcp server
+     * on the interface, forward and NAT IP v4 packets and forward DNS requests
+     * to the best active upstream network interface.  Note that if no upstream
+     * IP network interface is available, dhcp will still run and traffic will be
+     * allowed between the tethered devices and this device, though upstream net
+     * access will of course fail until an upstream network interface becomes
+     * active. Note: return value do not have any meaning. It is better to use
+     * #getTetherableIfaces() to ensure corresponding interface is available for
+     * tethering before calling #tether().
+     *
+     * TODO: Deprecate this API. The only usages should be in PanService and Wifi P2P which
+     * need direct access.
+     *
+     * {@hide}
+     */
+    public int tether(@NonNull String iface) {
+        try {
+            mConnector.tether(iface);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+        return TETHER_ERROR_NO_ERROR;
+    }
+
+    /**
+     * Stop tethering the named interface.
+     *
+     * {@hide}
+     */
+    public int untether(@NonNull String iface) {
+        try {
+            mConnector.untether(iface);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+        return TETHER_ERROR_NO_ERROR;
+    }
+
+    /**
+     * Attempt to both alter the mode of USB and Tethering of USB. WARNING: New client should not
+     * use this API anymore. All clients should use #startTethering or #stopTethering which
+     * encapsulate proper entitlement logic. If the API is used and an entitlement check is needed,
+     * downstream USB tethering will be enabled but will not have any upstream.
+     *
+     * @Deprecated
+     * {@hide}
+     */
+    public int setUsbTethering(boolean enable) {
+        try {
+            mConnector.setUsbTethering(enable);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+        return TETHER_ERROR_NO_ERROR;
+    }
+
+    /**
+     * Starts tethering and runs tether provisioning for the given type if needed. If provisioning
+     * fails, stopTethering will be called automatically.
+     *
+     * {@hide}
+     */
+    // TODO: improve the usage of ResultReceiver, b/145096122
+    public void startTethering(int type, @NonNull ResultReceiver receiver,
+            boolean showProvisioningUi) {
+        try {
+            mConnector.startTethering(type, receiver, showProvisioningUi);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+    }
+
+    /**
+     * Stops tethering for the given type. Also cancels any provisioning rechecks for that type if
+     * applicable.
+     *
+     * {@hide}
+     */
+    public void stopTethering(int type) {
+        try {
+            mConnector.stopTethering(type);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+    }
+
+    /**
+     * Request the latest value of the tethering entitlement check.
+     *
+     * Note: Allow privileged apps who have TETHER_PRIVILEGED permission to access. If it turns
+     * out some such apps are observed to abuse this API, change to per-UID limits on this API
+     * if it's really needed.
+     */
+    // TODO: improve the usage of ResultReceiver, b/145096122
+    public void requestLatestTetheringEntitlementResult(int type, @NonNull ResultReceiver receiver,
+            boolean showEntitlementUi) {
+        try {
+            mConnector.requestLatestTetheringEntitlementResult(type, receiver, showEntitlementUi);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+    }
+
+    /**
+     * Register tethering event callback.
+     *
+     * {@hide}
+     */
+    public void registerTetheringEventCallback(@NonNull ITetheringEventCallback callback) {
+        mTetheringEventCallbacks.register(callback);
+    }
+
+    /**
+     * Unregister tethering event callback.
+     *
+     * {@hide}
+     */
+    public void unregisterTetheringEventCallback(@NonNull ITetheringEventCallback callback) {
+        mTetheringEventCallbacks.unregister(callback);
+    }
+
+    /**
+     * Get a more detailed error code after a Tethering or Untethering
+     * request asynchronously failed.
+     *
+     * {@hide}
+     */
+    public int getLastTetherError(@NonNull String iface) {
+        if (!mCallback.awaitCallbackCreation()) {
+            throw new NullPointerException("callback was not ready yet");
+        }
+        if (mTetherStatesParcel == null) return TETHER_ERROR_NO_ERROR;
+
+        int i = 0;
+        for (String errored : mTetherStatesParcel.erroredIfaceList) {
+            if (iface.equals(errored)) return mTetherStatesParcel.lastErrorList[i];
+
+            i++;
+        }
+        return TETHER_ERROR_NO_ERROR;
+    }
+
+    /**
+     * Get the list of regular expressions that define any tetherable
+     * USB network interfaces.  If USB tethering is not supported by the
+     * device, this list should be empty.
+     *
+     * {@hide}
+     */
+    public @NonNull String[] getTetherableUsbRegexs() {
+        if (!mCallback.awaitCallbackCreation()) {
+            throw new NullPointerException("callback was not ready yet");
+        }
+        return mTetheringConfiguration.tetherableUsbRegexs;
+    }
+
+    /**
+     * Get the list of regular expressions that define any tetherable
+     * Wifi network interfaces.  If Wifi tethering is not supported by the
+     * device, this list should be empty.
+     *
+     * {@hide}
+     */
+    public @NonNull String[] getTetherableWifiRegexs() {
+        if (!mCallback.awaitCallbackCreation()) {
+            throw new NullPointerException("callback was not ready yet");
+        }
+        return mTetheringConfiguration.tetherableWifiRegexs;
+    }
+
+    /**
+     * Get the list of regular expressions that define any tetherable
+     * Bluetooth network interfaces.  If Bluetooth tethering is not supported by the
+     * device, this list should be empty.
+     *
+     * {@hide}
+     */
+    public @NonNull String[] getTetherableBluetoothRegexs() {
+        if (!mCallback.awaitCallbackCreation()) {
+            throw new NullPointerException("callback was not ready yet");
+        }
+        return mTetheringConfiguration.tetherableBluetoothRegexs;
+    }
+
+    /**
+     * Get the set of tetherable, available interfaces.  This list is limited by
+     * device configuration and current interface existence.
+     *
+     * {@hide}
+     */
+    public @NonNull String[] getTetherableIfaces() {
+        if (!mCallback.awaitCallbackCreation()) {
+            throw new NullPointerException("callback was not ready yet");
+        }
+        if (mTetherStatesParcel == null) return new String[0];
+        return mTetherStatesParcel.availableList;
+    }
+
+    /**
+     * Get the set of tethered interfaces.
+     *
+     * {@hide}
+     */
+    public @NonNull String[] getTetheredIfaces() {
+        if (!mCallback.awaitCallbackCreation()) {
+            throw new NullPointerException("callback was not ready yet");
+        }
+        if (mTetherStatesParcel == null) return new String[0];
+        return mTetherStatesParcel.tetheredList;
+    }
+
+    /**
+     * Get the set of interface names which attempted to tether but
+     * failed.
+     *
+     * {@hide}
+     */
+    public @NonNull String[] getTetheringErroredIfaces() {
+        if (!mCallback.awaitCallbackCreation()) {
+            throw new NullPointerException("callback was not ready yet");
+        }
+        if (mTetherStatesParcel == null) return new String[0];
+        return mTetherStatesParcel.erroredIfaceList;
+    }
+
+    /**
+     * Get the set of tethered dhcp ranges.
+     *
+     * {@hide}
+     */
+    public @NonNull String[] getTetheredDhcpRanges() {
+        if (!mCallback.awaitCallbackCreation()) {
+            throw new NullPointerException("callback was not ready yet");
+        }
+        return mTetheringConfiguration.legacyDhcpRanges;
+    }
+
+    /**
+     * Check if the device allows for tethering.
+     *
+     * {@hide}
+     */
+    public boolean hasTetherableConfiguration() {
+        if (!mCallback.awaitCallbackCreation()) {
+            throw new NullPointerException("callback was not ready yet");
+        }
+        final boolean hasDownstreamConfiguration =
+                (mTetheringConfiguration.tetherableUsbRegexs.length != 0)
+                || (mTetheringConfiguration.tetherableWifiRegexs.length != 0)
+                || (mTetheringConfiguration.tetherableBluetoothRegexs.length != 0);
+        final boolean hasUpstreamConfiguration =
+                (mTetheringConfiguration.preferredUpstreamIfaceTypes.length != 0)
+                || mTetheringConfiguration.chooseUpstreamAutomatically;
+
+        return hasDownstreamConfiguration && hasUpstreamConfiguration;
+    }
+
+    /**
+     * Log a message in the local log.
+     */
+    private void log(@NonNull String message) {
+        synchronized (mLog) {
+            mLog.log(message);
+        }
+    }
+
+    /**
+     * Log a condition that should never happen.
+     */
+    private void logWtf(@NonNull String message, @Nullable Throwable e) {
+        Slog.wtf(TAG, message);
+        synchronized (mLog) {
+            mLog.e(message, e);
+        }
+    }
+
+    /**
+     * Log a ERROR level message in the local and system logs.
+     */
+    private void loge(@NonNull String message, @Nullable Throwable e) {
+        synchronized (mLog) {
+            mLog.e(message, e);
+        }
+    }
+
+    /**
+     * Log a INFO level message in the local and system logs.
+     */
+    private void logi(@NonNull String message) {
+        synchronized (mLog) {
+            mLog.i(message);
+        }
+    }
+
+    /**
+     * Dump TetheringManager logs to the specified {@link PrintWriter}.
+     */
+    public void dump(@NonNull PrintWriter pw) {
+        // dump is thread-safe on SharedLog
+        mLog.dump(null, pw, null);
+
+        pw.print("subId: ");
+        pw.println(mTetheringConfiguration.subId);
+
+        dumpStringArray(pw, "tetherableUsbRegexs",
+                mTetheringConfiguration.tetherableUsbRegexs);
+        dumpStringArray(pw, "tetherableWifiRegexs",
+                mTetheringConfiguration.tetherableWifiRegexs);
+        dumpStringArray(pw, "tetherableBluetoothRegexs",
+                mTetheringConfiguration.tetherableBluetoothRegexs);
+
+        pw.print("isDunRequired: ");
+        pw.println(mTetheringConfiguration.isDunRequired);
+
+        pw.print("chooseUpstreamAutomatically: ");
+        pw.println(mTetheringConfiguration.chooseUpstreamAutomatically);
+
+        dumpStringArray(pw, "legacyDhcpRanges", mTetheringConfiguration.legacyDhcpRanges);
+        dumpStringArray(pw, "defaultIPv4DNS", mTetheringConfiguration.defaultIPv4DNS);
+
+        dumpStringArray(pw, "provisioningApp", mTetheringConfiguration.provisioningApp);
+        pw.print("provisioningAppNoUi: ");
+        pw.println(mTetheringConfiguration.provisioningAppNoUi);
+
+        pw.print("enableLegacyDhcpServer: ");
+        pw.println(mTetheringConfiguration.enableLegacyDhcpServer);
+
+        pw.println();
+    }
+
+    private static void dumpStringArray(@NonNull PrintWriter pw, @NonNull String label,
+            @Nullable String[] values) {
+        pw.print(label);
+        pw.print(": ");
+
+        if (values != null) {
+            final StringJoiner sj = new StringJoiner(", ", "[", "]");
+            for (String value : values) sj.add(value);
+
+            pw.print(sj.toString());
+        } else {
+            pw.print("null");
+        }
+
+        pw.println();
+    }
+}