Move signal handling into its own class (#754)

This opens some room to per-jdk implementation

common/src/main/java/org/mvndaemon/mvnd/common/SignalHelper.java

@@ -0,0 +1,32 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.mvndaemon.mvnd.common;
+
+public class SignalHelper {
+
+    /**
+     * Ignore signals to that stopping the mvnd client won't stop the daemon
+     */
+    public static void ignoreStopSignals() throws Exception {
+        sun.misc.Signal.handle(new sun.misc.Signal("INT"), sun.misc.SignalHandler.SIG_IGN);
+        if (Os.current() != Os.WINDOWS) {
+            sun.misc.Signal.handle(new sun.misc.Signal("TSTP"), sun.misc.SignalHandler.SIG_IGN);
+        }
+    }
+}

daemon/src/main/java/org/mvndaemon/mvnd/daemon/Server.java

@@ -67,8 +67,8 @@ import org.mvndaemon.mvnd.common.DaemonStopEvent;
 import org.mvndaemon.mvnd.common.Environment;
 import org.mvndaemon.mvnd.common.Message;
 import org.mvndaemon.mvnd.common.Message.BuildRequest;
-import org.mvndaemon.mvnd.common.Os;
 import org.mvndaemon.mvnd.common.ProcessHelper;
+import org.mvndaemon.mvnd.common.SignalHelper;
 import org.mvndaemon.mvnd.common.SocketFamily;
 import org.mvndaemon.mvnd.daemon.DaemonExpiration.DaemonExpirationResult;
 import org.mvndaemon.mvnd.daemon.DaemonExpiration.DaemonExpirationStrategy;
@@ -77,8 +77,6 @@ import org.mvndaemon.mvnd.logging.smart.LoggingOutputStream;
 import org.mvndaemon.mvnd.logging.smart.ProjectBuildLogAppender;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import sun.misc.Signal;
-import sun.misc.SignalHandler;
 
 public class Server implements AutoCloseable, Runnable {
 
@@ -110,10 +108,7 @@ public class Server implements AutoCloseable, Runnable {
         // without ignoring those signals, a client being interrupted will
         // also interrupt and kill the daemon.
         try {
-            Signal.handle(new Signal("INT"), SignalHandler.SIG_IGN);
+            SignalHelper.ignoreStopSignals();
-            if (Os.current() != Os.WINDOWS) {
-                Signal.handle(new Signal("TSTP"), SignalHandler.SIG_IGN);
-            }
         } catch (Throwable t) {
             LOGGER.warn("Unable to ignore INT and TSTP signals", t);
         }