reconnection to the mqtt server if failed on startup

src/java/com/wasteinformationserver/Main.kt

@@ -1,4 +1,5 @@
 @file:JvmName("Main")
+
 package com.wasteinformationserver
 
 import com.wasteinformationserver.basicutils.Info
@@ -7,7 +8,6 @@ import com.wasteinformationserver.basicutils.Storage
 import com.wasteinformationserver.db.JDBC
 import com.wasteinformationserver.mqtt.MqttService
 import com.wasteinformationserver.website.Webserver
-import java.io.IOException
 
 /**
  * application entry point
@@ -22,14 +22,9 @@ fun main() {
     Log.info("startup of WasteInformationServer")
 
     Runtime.getRuntime().addShutdownHook(Thread(Runnable {
-        try {
-            Thread.sleep(200)
+        // shutdown routine
         Log.warning("Shutting down ...")
         JDBC.getInstance().disconnect();
-            //shutdown routine
-        } catch (e: InterruptedException) {
-            e.printStackTrace()
-        }
     }))
 
     Log.info("Server version: " + Info.getVersion())
@@ -49,10 +44,7 @@ fun main() {
     //startup mqtt service
     Log.message("starting mqtt service")
 
-    if (JDBC.isConnected()) {
-        val m = MqttService(Storage.getInstance().mqttServer, Storage.getInstance().mqttPort.toString())
+    val m = MqttService.getInstance()
+    m.init(Storage.getInstance().mqttServer, Storage.getInstance().mqttPort.toString())
     m.startupService()
-    }else{
-        Log.error("could't start mqtt service because of missing db connection!")
-    }
 }

src/java/com/wasteinformationserver/db/JDBC.java

@@ -1,8 +1,8 @@
 package com.wasteinformationserver.db;
 
-import com.mysql.cj.exceptions.ConnectionIsClosedException;
 import com.wasteinformationserver.basicutils.Log;
 import com.wasteinformationserver.basicutils.Storage;
+import com.wasteinformationserver.mqtt.MqttService;
 
 import java.io.IOException;
 import java.sql.*;
@@ -116,6 +116,12 @@ public class JDBC {
                     portc = st.getDbPort();
                     Log.Log.info("Retry connection");
                     loggedin = logintodb(usernamec, passwordc, dbnamec, ipc, portc);
+                    if (loggedin) {
+                        // startup mqtt service if successfully connected
+                        MqttService srvc = MqttService.Companion.getInstance();
+                        srvc.init(st.getMqttServer(), String.valueOf(st.getMqttPort()));
+                        srvc.startupService();
+                    }
                 }
             }).start();
         }
@@ -141,7 +147,7 @@ public class JDBC {
             conn.isValid(5);
             PreparedStatement stmt = conn.prepareStatement(sql);
             return stmt.executeQuery();
-        } catch (SQLNonTransientConnectionException ee){
+        } catch (SQLNonTransientConnectionException ee) {
             if (logintodb(usernamec, passwordc, dbnamec, ipc, portc)) {
                 return this.executeQuery(sql);
             } else {
@@ -165,13 +171,13 @@ public class JDBC {
             conn.isValid(5);
             PreparedStatement stmt = conn.prepareStatement(sql);
             return stmt.executeUpdate();
-        } catch (SQLNonTransientConnectionException ee){
+        } catch (SQLNonTransientConnectionException ee) {
             if (logintodb(usernamec, passwordc, dbnamec, ipc, portc)) {
                 return this.executeUpdate(sql);
             } else {
                 throw new SQLException();
             }
-        } catch (SQLException e){
+        } catch (SQLException e) {
             throw new SQLException();
         }
     }

src/java/com/wasteinformationserver/mqtt/MqttService.kt

@@ -1,5 +1,6 @@
 package com.wasteinformationserver.mqtt
 
+import com.wasteinformationserver.basicutils.Log
 import com.wasteinformationserver.basicutils.Log.Log.debug
 import com.wasteinformationserver.basicutils.Log.Log.error
 import com.wasteinformationserver.basicutils.Log.Log.info
@@ -19,31 +20,38 @@ import java.util.*
  * @author Lukas Heiligenbrunner
  * @author Gregor Dutzler
  */
-class MqttService(serverurl: String, port: String) {
-    private val serveruri: String = "tcp://$serverurl:$port"
-    private var client: MqttClient = MqttClient(serveruri, "JavaSample42")
+class MqttService {
+    private var serveruri: String = "";
+    private lateinit var client: MqttClient;
     private var db: JDBC = JDBC.getInstance()
 
-    /**
-     * initial login to db
-     */
-    init {
-        connectToDb()
+    companion object {
+        private val obj = MqttService()
+        fun getInstance(): MqttService {
+            return obj;
+        }
+    }
+
+    fun init(serverurl: String, port: String){
+        serveruri = "tcp://$serverurl:$port"
     }
 
     /**
      * startup of the mqtt service
      */
     fun startupService() {
+        if(JDBC.isConnected()) {
             try {
-            client = MqttClient(serveruri, "JavaSample42")
+                client = MqttClient(serveruri, "WasteInformationServerID")
                 val connOpts = MqttConnectOptions()
                 connOpts.isCleanSession = true
                 client.connect(connOpts)
                 client.setCallback(object : MqttCallback {
                     override fun connectionLost(throwable: Throwable) {
                         error("connection lost")
-                    connectToDb()
+                        Thread.sleep(500)
+                        // restart service
+                        startupService()
                     }
 
                     override fun messageArrived(s: String, mqttMessage: MqttMessage) {
@@ -52,11 +60,13 @@ class MqttService(serverurl: String, port: String) {
                         val res = db.executeQuery("SELECT * from devices WHERE DeviceID=$deviceid")
                         try {
                             res.last()
-                        if (res.row != 0) { //existing device
+                            if (res.row != 0) {
+                                // existing device
                                 res.first()
                                 val devicecities = db.executeQuery("SELECT * from device_city WHERE DeviceID='$deviceid'")
                                 devicecities.last()
-                            if (devicecities.row == 0) { //not configured
+                                if (devicecities.row == 0) {
+                                    // not configured
                                     tramsmitMessage("$deviceid,-1")
                                 }
                                 else {
@@ -69,7 +79,8 @@ class MqttService(serverurl: String, port: String) {
                                     }
                                 }
                             }
-                        else { //new device
+                            else {
+                                // new device
                                 db.executeUpdate("INSERT INTO devices (DeviceID) VALUES ($deviceid)")
                                 info("new device registered to server")
                                 tramsmitMessage("$deviceid,-1")
@@ -85,6 +96,9 @@ class MqttService(serverurl: String, port: String) {
             } catch (e: MqttException) {
                 error("Connection to the Broker failed")
             }
+        }else{
+            Log.error("could't start mqtt service because of missing db connection!")
+        }
     }
 
     /**
@@ -98,7 +112,8 @@ class MqttService(serverurl: String, port: String) {
         val set2 = db.executeQuery("SELECT * FROM cities WHERE `id`='$citywastezoneid'")
         try {
             set2.last()
-            if (set2.row != 1) { //error
+            if (set2.row != 1) {
+                //error
                 warning("multiple Rows with same city id found - DB Error")
             }
             else {
@@ -111,7 +126,8 @@ class MqttService(serverurl: String, port: String) {
         val result = db.executeQuery("SELECT pickupdates.pickupdate FROM pickupdates WHERE pickupdates.citywastezoneid=$citywastezoneid")
         try {
             result.last()
-            if (result.row == 0) { //if not found in db --> send zero
+            if (result.row == 0) {
+                //if not found in db --> send zero
                 debug("not found in db")
                 tramsmitMessage("$deviceid,$wastetype,0")
             }
@@ -130,7 +146,8 @@ class MqttService(serverurl: String, port: String) {
                         return
                     }
                 } while (result.next())
-                tramsmitMessage("$deviceid,$wastetype,0") //transmit zero if not returned before
+                tramsmitMessage("$deviceid,$wastetype,0")
+                //transmit zero if not returned before
             }
         } catch (e: SQLException) {
             e.printStackTrace()
@@ -165,11 +182,4 @@ class MqttService(serverurl: String, port: String) {
             else -> 0
         }
     }
-
-    /**
-     * receives connection object and initial connection to db
-     */
-    private fun connectToDb() {
-        db = JDBC.getInstance()
-    }
 }