Add broker version condition when checking x-death headers

Those headers have been introduced in RabbitMQ 3.7, so
checking them against earlier versions doesn't make sense.

References rabbitmq/rabbitmq-server#1332

Author: acogoluegnes

src/test/java/com/rabbitmq/client/test/TestUtils.java

@@ -44,4 +44,34 @@ public static void close(Connection connection) {
         }
     }
 
+    public static boolean isVersion37orLater(Connection connection) {
+        String currentVersion = connection.getServerProperties().get("version").toString();
+        if (currentVersion.contains("+")) {
+            currentVersion = currentVersion.substring(0, currentVersion.indexOf("+"));
+        }
+        return "0.0.0".equals(currentVersion) ? true : versionCompare(currentVersion, "3.7.0") >= 0;
+    }
+
+    /**
+     * http://stackoverflow.com/questions/6701948/efficient-way-to-compare-version-strings-in-java
+     *
+     */
+    static int versionCompare(String str1, String str2) {
+        String[] vals1 = str1.split("\\.");
+        String[] vals2 = str2.split("\\.");
+        int i = 0;
+        // set index to first non-equal ordinal or length of shortest version string
+        while (i < vals1.length && i < vals2.length && vals1[i].equals(vals2[i])) {
+            i++;
+        }
+        // compare first non-equal ordinal number
+        if (i < vals1.length && i < vals2.length) {
+            int diff = Integer.valueOf(vals1[i]).compareTo(Integer.valueOf(vals2[i]));
+            return Integer.signum(diff);
+        }
+        // the strings are equal or one string is a substring of the other
+        // e.g. "1.2.3" = "1.2.3" or "1.2.3" < "1.2.3.4"
+        return Integer.signum(vals1.length - vals2.length);
+    }
+
 }

src/test/java/com/rabbitmq/client/test/functional/DeadLetterExchange.java

@@ -18,6 +18,7 @@
 import com.rabbitmq.client.*;
 import com.rabbitmq.client.AMQP.BasicProperties;
 import com.rabbitmq.client.test.BrokerTestCase;
+import com.rabbitmq.client.test.TestUtils;
 import org.junit.Test;
 
 import java.io.IOException;
@@ -536,9 +537,14 @@ public void process(GetResponse getResponse) {
                 assertNotNull(headers);
                 ArrayList<Object> death = (ArrayList<Object>) headers.get("x-death");
                 assertNotNull(death);
-                assertNotNull(headers.get("x-first-death-queue"));
-                assertNotNull(headers.get("x-first-death-reason"));
-                assertNotNull(headers.get("x-first-death-exchange"));
+                // the following assertions shouldn't be checked on version lower than 3.7
+                // as the headers are new in 3.7
+                // see https://github.com/rabbitmq/rabbitmq-server/issues/1332
+                if(TestUtils.isVersion37orLater(channel.getConnection())) {
+                    assertNotNull(headers.get("x-first-death-queue"));
+                    assertNotNull(headers.get("x-first-death-reason"));
+                    assertNotNull(headers.get("x-first-death-exchange"));
+                }
                 assertEquals(1, death.size());
                 assertDeathReason(death, 0, TEST_QUEUE_NAME, reason,
                         "amq.direct",