diff --git a/bundles/io/org.eclipse.smarthome.io.transport.mqtt.test/src/test/java/org/eclipse/smarthome/io/transport/mqtt/MqttServiceTests.java b/bundles/io/org.eclipse.smarthome.io.transport.mqtt.test/src/test/java/org/eclipse/smarthome/io/transport/mqtt/MqttServiceTests.java
index 9688f6805cb..0b2e535f3ae 100644
--- a/bundles/io/org.eclipse.smarthome.io.transport.mqtt.test/src/test/java/org/eclipse/smarthome/io/transport/mqtt/MqttServiceTests.java
+++ b/bundles/io/org.eclipse.smarthome.io.transport.mqtt.test/src/test/java/org/eclipse/smarthome/io/transport/mqtt/MqttServiceTests.java
@@ -59,12 +59,12 @@ public void extractBrokerConfigurationsTests() throws ConfigurationException, Mq
         Map<String, Object> properties = new Hashtable<>();
         properties.put("bam.name", "brokername");
         properties.put("bam.url", "tcp://123.123.123.123");
-        Map<String, Map<String, String>> map = service.extractBrokerConfigurations(properties);
+        Map<String, MqttService.Config> map = service.extractBrokerConfigurations(properties);
         assertEquals(map.size(), 1);
-        Map<String, String> data = map.get("bam");
+        MqttService.Config data = map.get("bam");
         assertNotNull(data);
-        assertEquals("brokername", data.get("name"));
-        assertEquals("tcp://123.123.123.123", data.get("url"));
+        assertEquals("brokername", data.name);
+        assertEquals("tcp://123.123.123.123", data.url);
     }
 
     // Tests if updates to the textual configuration are processed correctly
diff --git a/bundles/io/org.eclipse.smarthome.io.transport.mqtt/src/main/java/org/eclipse/smarthome/io/transport/mqtt/MqttService.java b/bundles/io/org.eclipse.smarthome.io.transport.mqtt/src/main/java/org/eclipse/smarthome/io/transport/mqtt/MqttService.java
index 7d62ced9dc0..0ee65f6baf5 100644
--- a/bundles/io/org.eclipse.smarthome.io.transport.mqtt/src/main/java/org/eclipse/smarthome/io/transport/mqtt/MqttService.java
+++ b/bundles/io/org.eclipse.smarthome.io.transport.mqtt/src/main/java/org/eclipse/smarthome/io/transport/mqtt/MqttService.java
@@ -12,6 +12,7 @@
  */
 package org.eclipse.smarthome.io.transport.mqtt;
 
+import java.nio.charset.StandardCharsets;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Iterator;
@@ -20,6 +21,7 @@
 import java.util.Map.Entry;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.stream.Collectors;
 
 import javax.naming.ConfigurationException;
 
@@ -51,6 +53,70 @@
                 "service.pid=org.eclipse.smarthome.mqtt" })
 @NonNullByDefault
 public class MqttService {
+    public static class Config {
+        public final @Nullable String name;
+        public final @Nullable String url;
+        public final @Nullable String user;
+        public final @Nullable String pwd;
+        public final @Nullable String clientId;
+        public final @Nullable Integer keepAlive;
+        public final @Nullable Integer qos;
+        public final @Nullable Boolean retain;
+        public final @Nullable String lwt;
+        public final @Nullable String lwtTopic;
+        public final byte @Nullable [] lwtMessage;
+        public final @Nullable Integer lwtQos;
+        public final @Nullable Boolean lwtRetain;
+
+        public Config(final Map<String, String> cfg) {
+            name = cfg.get(NAME_PROPERTY);
+            url = cfg.get("url");
+            user = cfg.get("user");
+            pwd = cfg.get("pwd");
+            clientId = cfg.get("clientId");
+            keepAlive = asInt(cfg.get("keepAlive"));
+            qos = asInt(cfg.get("qos"));
+            retain = asBool(cfg.get("retain"));
+
+            // Check for Last Will and Testament
+            lwt = cfg.get("lwt");
+
+            // Inspect explicit given LWT values
+            lwtTopic = cfg.get("lwtTopic");
+            String tmp = cfg.get("lwtMessage");
+            if (tmp != null) {
+                lwtMessage = tmp.getBytes(StandardCharsets.UTF_8);
+            } else {
+                lwtMessage = null;
+            }
+            Integer tmpInt = asInt(cfg.get("lwtQos"));
+            if (tmpInt != null && tmpInt >= 0 && tmpInt <= 2) {
+                lwtQos = tmpInt;
+            } else {
+                lwtQos = null;
+            }
+            lwtRetain = asBool(cfg.get("lwtRetain"));
+        }
+
+        private static @Nullable Integer asInt(final @Nullable String value) {
+            if (value == null || value.isEmpty()) {
+                return null;
+            }
+            try {
+                return Integer.valueOf(value);
+            } catch (final NumberFormatException ex) {
+                return null;
+            }
+        }
+
+        private static @Nullable Boolean asBool(final @Nullable String value) {
+            if (value == null || value.isEmpty()) {
+                return null;
+            }
+            return Boolean.valueOf(value);
+        }
+    }
+
     private static final String NAME_PROPERTY = "name";
     private final Logger logger = LoggerFactory.getLogger(MqttService.class);
     private final Map<String, MqttBrokerConnection> brokerConnections = new ConcurrentHashMap<String, MqttBrokerConnection>();
@@ -71,7 +137,7 @@ public class MqttService {
      * @param properties Service configuration
      * @return A 'list' of broker configurations as key-value maps. A configuration map at least contains a "name".
      */
-    public Map<String, Map<String, String>> extractBrokerConfigurations(Map<String, Object> properties) {
+    public Map<String, Config> extractBrokerConfigurations(Map<String, Object> properties) {
         Map<String, Map<String, String>> configPerBroker = new HashMap<String, Map<String, String>>();
         for (Entry<String, Object> entry : properties.entrySet()) {
             String key = entry.getKey();
@@ -106,7 +172,8 @@ public Map<String, Map<String, String>> extractBrokerConfigurations(Map<String,
             brokerConfig.put(subkeys[1], value);
         }
 
-        return configPerBroker;
+        return configPerBroker.entrySet().stream()
+                .collect(Collectors.toMap(entry -> entry.getKey(), entry -> new Config(entry.getValue())));
     }
 
     /**
@@ -133,9 +200,9 @@ public void modified(Map<String, Object> config) {
             return;
         }
 
-        Map<String, Map<String, String>> brokerConfigs = extractBrokerConfigurations(config);
+        Map<String, Config> brokerConfigs = extractBrokerConfigurations(config);
 
-        for (Map<String, String> brokerConfig : brokerConfigs.values()) {
+        for (Config brokerConfig : brokerConfigs.values()) {
             try {
                 final MqttBrokerConnection conn = addBrokerConnection(brokerConfig);
                 if (conn == null) {
@@ -228,28 +295,31 @@ public boolean addBrokerConnection(MqttBrokerConnection connection) {
     }
 
     /**
-     * Add a broker by a configuration key-value map. You need to provide at least a "name" and an "url".
+     * Add a broker by a configuration.
+     *
+     * <p>
+     * You need to provide at least a "name" and an "url".
      * Additional properties are "user","pwd","qos","retain","lwt","keepAlive","clientId", please read the
      * service configuration documentation for a detailed description.
      *
-     * @param brokerConnectionConfig The configuration key-value map.
+     * @param cfg The configuration key-value map.
      * @return Returns the created broker connection or null if there is already a connection with the same name.
      * @throws ConfigurationException Most likely your provided name and url are invalid.
      * @throws MqttException
      */
-    public @Nullable MqttBrokerConnection addBrokerConnection(Map<String, String> brokerConnectionConfig)
-            throws ConfigurationException, MqttException {
+    public @Nullable MqttBrokerConnection addBrokerConnection(Config cfg) throws ConfigurationException, MqttException {
         // Extract mandatory fields
-        String brokerID = brokerConnectionConfig.get(NAME_PROPERTY);
+        String brokerID = cfg.name;
         if (brokerID == null || brokerID.isEmpty()) {
             throw new ConfigurationException("MQTT Broker property 'name' is not provided");
         }
         brokerID = brokerID.toLowerCase();
 
-        final String brokerURL = brokerConnectionConfig.get("url");
+        final String brokerURL = cfg.url;
         if (brokerURL == null || brokerURL.isEmpty()) {
             throw new ConfigurationException("MQTT Broker property 'url' is not provided");
         }
+
         // Add the connection
         MqttBrokerConnection connection;
         synchronized (brokerConnections) {
@@ -262,21 +332,19 @@ public boolean addBrokerConnection(MqttBrokerConnection connection) {
         }
 
         // Extract further configurations
-        connection.setCredentials(brokerConnectionConfig.get("user"), brokerConnectionConfig.get("pwd"));
-        connection.setClientId(brokerConnectionConfig.get("clientId"));
-        String property = brokerConnectionConfig.get("keepAlive");
-        if (!StringUtils.isBlank(property)) {
-            connection.setKeepAliveInterval(Integer.valueOf(property));
+        connection.setCredentials(cfg.user, cfg.pwd);
+        connection.setClientId(cfg.clientId);
+        if (cfg.keepAlive != null) {
+            connection.setKeepAliveInterval(cfg.keepAlive);
         }
-        property = brokerConnectionConfig.get("qos");
-        if (!StringUtils.isBlank(property)) {
-            connection.setQos(Integer.valueOf(property));
+        if (cfg.qos != null) {
+            connection.setQos(cfg.qos);
         }
-        property = brokerConnectionConfig.get("retain");
-        if (!StringUtils.isBlank(property)) {
-            connection.setRetain(Boolean.valueOf(property));
+        if (cfg.retain != null) {
+            connection.setRetain(cfg.retain);
         }
-        MqttWillAndTestament will = MqttWillAndTestament.fromString(brokerConnectionConfig.get("lwt"));
+        MqttWillAndTestament will = MqttWillAndTestament.fromString(cfg.lwt, cfg.lwtTopic, cfg.lwtMessage, cfg.lwtQos,
+                cfg.lwtRetain);
         if (will != null) {
             logger.debug("Setting last will: {}", will);
             connection.setLastWill(will);
diff --git a/bundles/io/org.eclipse.smarthome.io.transport.mqtt/src/main/java/org/eclipse/smarthome/io/transport/mqtt/MqttWillAndTestament.java b/bundles/io/org.eclipse.smarthome.io.transport.mqtt/src/main/java/org/eclipse/smarthome/io/transport/mqtt/MqttWillAndTestament.java
index 8f50103ac4e..383b5bcec66 100644
--- a/bundles/io/org.eclipse.smarthome.io.transport.mqtt/src/main/java/org/eclipse/smarthome/io/transport/mqtt/MqttWillAndTestament.java
+++ b/bundles/io/org.eclipse.smarthome.io.transport.mqtt/src/main/java/org/eclipse/smarthome/io/transport/mqtt/MqttWillAndTestament.java
@@ -12,7 +12,11 @@
  */
 package org.eclipse.smarthome.io.transport.mqtt;
 
+import java.nio.charset.StandardCharsets;
+
 import org.apache.commons.lang.StringUtils;
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
 
 /**
  * Class encapsulating the last will and testament that is published after the client has gone offline.
@@ -20,11 +24,15 @@
  * @author Markus Mann
  *
  */
+@NonNullByDefault
 public class MqttWillAndTestament {
-    private String topic;
-    private byte[] payload;
-    private int qos = 0;
-    private boolean retain = false;
+    private static final int DFL_QOS = 0;
+    private static final boolean DFL_RETAIN = false;
+
+    private final String topic;
+    private final byte @Nullable [] payload;
+    private final int qos;
+    private final boolean retain;
 
     /**
      * Create an instance of the last will using a string with the following format:<br/>
@@ -40,42 +48,65 @@ public class MqttWillAndTestament {
      * @param string the string to parse. If null, null is returned
      * @return the will instance, will be null only if parameter is null
      */
-    public static MqttWillAndTestament fromString(String string) {
-        if (string == null) {
-            return null;
-        }
-        MqttWillAndTestament result = new MqttWillAndTestament();
-        String[] components = string.split(":");
-        for (int i = 0; i < Math.min(components.length, 4); i++) {
-            String value = StringUtils.trimToEmpty(components[i]);
-            switch (i) {
-                case 0:
-                    result.topic = value;
-                    break;
-                case 1:
-                    result.payload = value.getBytes();
-                    break;
-                case 2:
-                    if (!"".equals(value)) {
-                        int qos = Integer.valueOf(value);
-                        if (qos >= 0 && qos <= 2) {
-                            result.qos = qos;
+    public static @Nullable MqttWillAndTestament fromString(@Nullable String string) {
+        return fromString(string, null, null, null, null);
+    }
+
+    public static @Nullable MqttWillAndTestament fromString(@Nullable String string, @Nullable String topic,
+            byte @Nullable [] payload, @Nullable Integer qos, @Nullable Boolean retain) {
+        String tmpTopic = null;
+        byte[] tmpPayload = null;
+        int tmpQos = DFL_QOS;
+        boolean tmpRetain = DFL_RETAIN;
+
+        // Parse string if given.
+        if (string != null) {
+            String[] components = string.split(":");
+            for (int i = 0; i < Math.min(components.length, 4); i++) {
+                String value = StringUtils.trimToEmpty(components[i]);
+                switch (i) {
+                    case 0:
+                        tmpTopic = value;
+                        break;
+                    case 1:
+                        tmpPayload = value.getBytes(StandardCharsets.UTF_8);
+                        break;
+                    case 2:
+                        if (!"".equals(value)) {
+                            int tmp = Integer.valueOf(value);
+                            if (tmp >= 0 && tmp <= 2) {
+                                tmpQos = tmp;
+                            }
                         }
-                    }
-                    break;
-                case 3:
-                    result.retain = Boolean.valueOf(value);
-                    break;
+                        break;
+                    case 3:
+                        tmpRetain = Boolean.valueOf(value);
+                        break;
+                }
             }
         }
-        return result.isValid() ? result : null;
-    }
 
-    /**
-     * Hide the constructor and force consumers to use the fromString() method or the
-     * constructor requiring all field parameters to be set.
-     */
-    private MqttWillAndTestament() {
+        // Use explicit given values.
+        if (topic != null) {
+            tmpTopic = topic;
+        }
+        if (payload != null) {
+            tmpPayload = payload;
+        }
+        if (qos != null) {
+            tmpQos = qos;
+        }
+        if (retain != null) {
+            tmpRetain = retain;
+        }
+
+        // Check if valid
+        if (tmpTopic == null || tmpTopic.isEmpty()) {
+            return null;
+        }
+
+        // Create MQTT Last Will and Testament object
+        return new MqttWillAndTestament(tmpTopic, tmpPayload, tmpQos, tmpRetain);
     }
 
     /**
@@ -86,7 +117,7 @@ private MqttWillAndTestament() {
      * @param qos Valid values are 0 (Deliver at most once),1 (Deliver at least once) or 2</li>
      * @param retain true if messages shall be retained
      */
-    public MqttWillAndTestament(String topic, byte[] payload, int qos, boolean retain) {
+    public MqttWillAndTestament(String topic, byte @Nullable [] payload, int qos, boolean retain) {
         if (StringUtils.isBlank(topic)) {
             throw new IllegalArgumentException("Topic must be set");
         }
@@ -96,13 +127,6 @@ public MqttWillAndTestament(String topic, byte[] payload, int qos, boolean retai
         this.retain = retain;
     }
 
-    /**
-     * Return true if the last will and testament object is valid.
-     */
-    private boolean isValid() {
-        return !StringUtils.isBlank(topic);
-    }
-
     /**
      * @return the topic for the last will.
      */
@@ -113,7 +137,7 @@ public String getTopic() {
     /**
      * @return the payload of the last will.
      */
-    public byte[] getPayload() {
+    public byte @Nullable [] getPayload() {
         return payload;
     }