Return 0 JMS timestamp if property is null

The property is not supposed to be null in JMS, but it can in AMQP
0.9.1, so JMS messages consumed from AMQP resources can have a null
value. This commit mitigates the issue by returning a timestamp set to 0
in this case, just like the JMS 1.1 specification suggests it when
MessageProducer#setDisableMessageTimestamp(true) is called.

Fixes #126

Author: acogoluegnes

src/main/java/com/rabbitmq/jms/client/RMQMessage.java

@@ -242,7 +242,12 @@ public void setJMSMessageID(String id) throws JMSException {
      */
     @Override
     public long getJMSTimestamp() throws JMSException {
-        return this.getLongProperty(JMS_MESSAGE_TIMESTAMP);
+        Object timestamp = this.getObjectProperty(JMS_MESSAGE_TIMESTAMP);
+        if (timestamp == null) {
+            return 0L;
+        } else {
+            return convertToLong(timestamp);
+        }
     }
 
     /**
@@ -496,7 +501,10 @@ else if (o instanceof String) {
      */
     @Override
     public long getLongProperty(String name) throws JMSException {
-        Object o = this.getObjectProperty(name);
+        return convertToLong(this.getObjectProperty(name));
+    }
+
+    private static long convertToLong(Object o) throws JMSException {
         if (o == null)
             throw new NumberFormatException("Null is not a valid long");
         else if (o instanceof String) {

src/test/java/com/rabbitmq/integration/tests/SimpleAmqpQueueMessageIT.java

@@ -1,6 +1,7 @@
 /* Copyright (c) 2013-2020 VMware, Inc. or its affiliates. All rights reserved. */
 package com.rabbitmq.integration.tests;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
@@ -22,6 +23,7 @@
 import javax.jms.Session;
 import javax.jms.TextMessage;
 
+import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.Test;
 
 import com.rabbitmq.client.AMQP;
@@ -187,6 +189,7 @@ public void testSendFromAmqpAndReceiveBytesMessage() throws Exception {
 
         assertEquals(STRING_PROP_VALUE, message.getStringProperty(USER_STRING_PROPERTY_NAME), "String property not transferred");
         assertEquals("42", message.getStringProperty("DummyProp"), "Numeric property not transferred");
+        assertThat(message.getJMSTimestamp()).isZero();
     }
 
     @Test
@@ -238,6 +241,7 @@ public void testSendFromAmqpAndReceiveTextMessage() throws Exception {
 
         assertEquals(STRING_PROP_VALUE, message.getStringProperty(USER_STRING_PROPERTY_NAME), "String property not transferred");
         assertEquals("42", message.getStringProperty("DummyProp"), "Numeric property not transferred");
+        assertThat(message.getJMSTimestamp()).isZero();
     }
 
     @Test
@@ -274,6 +278,7 @@ public void testSendFromJmsAndReceiveJmsTextMessage() throws Exception {
         assertNotNull(message, "No message received");
         assertEquals(MESSAGE, message.getText(), "Payload doesn't match");
         assertEquals(STRING_PROP_VALUE, message.getStringProperty(USER_STRING_PROPERTY_NAME), "String property not transferred");
+        assertThat(message.getJMSTimestamp()).isGreaterThan(0);
     }
 
 }