Linux: make davmail notify readyness to systemd

build.xml

@@ -36,6 +36,10 @@
         <available classname="javafx.embed.swing.JFXPanel" classpathref="classpath"/>
     </condition>
 
+    <condition property="is.jna">
+        <available classname="com.sun.jna.Native" classpathref="classpath"/>
+    </condition>
+
     <condition property="is.javafx.message" value="available" else="missing">
         <available classname="javafx.embed.swing.JFXPanel" property="is.javafx" classpathref="classpath"/>
     </condition>
@@ -117,6 +121,7 @@
         <javac srcdir="src/java" destdir="target/classes" source="1.8" target="1.8" debug="on" encoding="UTF-8"
                includeantruntime="false">
             <exclude name="davmail/exchange/auth/*Interactive*" unless="is.javafx"/>
+            <exclude name="davmail/util/SystemdNotify.java" unless="is.jna"/>
             <classpath>
                 <path refid="classpath"/>
             </classpath>

src/init/davmail.service

@@ -6,7 +6,7 @@ Documentation=http://davmail.sourceforge.net/sslsetup.html
 After=network.target
 
 [Service]
-Type=simple
+Type=notify
 User=davmail
 PermissionsStartOnly=true
 AmbientCapabilities=CAP_NET_BIND_SERVICE

src/java/davmail/DavGateway.java

@@ -183,7 +183,16 @@ public static void start() {
         if (showStartupBanner) {
             DavGatewayTray.info(new BundleMessage("LOG_DAVMAIL_GATEWAY_LISTENING", currentVersion, messages));
         }
-        if (!errorMessages.isEmpty()) {
+        if (errorMessages.isEmpty()) {
+            if (System.getenv("INVOCATION_ID") != null) {
+                // we are run by systemd
+                try {
+                    Class.forName("davmail.util.SystemdNotify").getMethod("ready").invoke(null);
+                } catch (Exception e) {
+                    LOGGER.warn("Running on a host with systemd but could not notify readiness.");
+                }
+            }
+        } else {
             DavGatewayTray.error(new BundleMessage("LOG_MESSAGE", errorMessages));
         }
 

src/java/davmail/util/SystemdNotify.java

@@ -0,0 +1,95 @@
+// Based on this answer https://stackoverflow.com/a/36945256/784804
+
+/*
+ * Copyright (c) 2018 Ian Kirk
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package davmail.util;
+
+import com.sun.jna.Library;
+import com.sun.jna.Native;
+
+public final class SystemdNotify {
+
+  interface SystemD extends Library {
+    final SystemD INSTANCE = Native.load(SYSTEMD_SO, SystemD.class);
+
+    int sd_notify(int unset_environment, String state);
+  }
+
+  private static final String SYSTEMD_SO = "systemd";
+  private static final String READY      = "READY=1";
+  private static final String RELOADING  = "RELOADING=1";
+  private static final String STOPPING   = "STOPPING=1";
+  private static final String STATUS     = "STATUS=%s";
+  private static final String WATCHDOG   = "WATCHDOG=1";
+  private static final String MAINPID    = "MAINPID=%d";
+  private static final String ERRNO      = "ERRNO=%d";
+  private static final String BUSERROR   = "BUSERROR=%s";
+
+  public static void busError(final String error) {
+    notify(String.format(BUSERROR, error));
+  }
+
+  public static void errno(final int errno) {
+    notify(String.format(ERRNO, errno));
+  }
+
+  public static void mainPid(final long pid) {
+    notify(String.format(MAINPID, pid));
+  }
+
+  public static void notify(final String message) {
+    try {
+      final int returnCode = SystemD.INSTANCE.sd_notify(0, message);
+      if (returnCode < 0)
+        throw new RuntimeException(
+          String.format("sd_notify returned %d", returnCode));
+    } catch (UnsatisfiedLinkError e) {
+      // libsystemd could not be loaded, ignore and do nothing
+    } catch (final Exception e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  public static void ready() {
+    notify(READY);
+  }
+
+  public static void reloading() {
+    notify(RELOADING);
+  }
+
+  public static void status(final String text) {
+    notify(String.format(STATUS, text));
+  }
+
+  public static void stopping() {
+    notify(STOPPING);
+  }
+
+  public static void watchdog() {
+    notify(WATCHDOG);
+  }
+
+  private SystemdNotify() {
+    throw new RuntimeException("This class should not be instantiated");
+  }
+}