Get messageId in string format (apache#370)

pulsar-client/src/main/java/com/yahoo/pulsar/client/impl/BatchMessageIdImpl.java

@@ -62,8 +62,7 @@ public boolean equals(Object obj) {
 
     @Override
     public String toString() {
-        return Objects.toStringHelper(MessageIdImpl.class).add("ledgerId", ledgerId).add("entryId", entryId)
-                .add("partitionIndex", partitionIndex).add("batchIndex", batchIndex).toString();
+        return String.format("%d:%d:%d:%d", ledgerId, entryId, partitionIndex, batchIndex);
     }
 
     // Serialization

pulsar-client/src/main/java/com/yahoo/pulsar/client/impl/MessageIdImpl.java

@@ -77,8 +77,7 @@ public boolean equals(Object obj) {
 
     @Override
     public String toString() {
-        return Objects.toStringHelper(MessageIdImpl.class).add("ledgerId", ledgerId).add("entryId", entryId)
-                .add("partitionIndex", partitionIndex).toString();
+        return String.format("%d:%d:%d", ledgerId, entryId, partitionIndex);
     }
 
     // / Serialization

pulsar-client/src/test/java/com/yahoo/pulsar/client/api/MessageIdTest.java

@@ -0,0 +1,46 @@
+/**
+ * Copyright 2016 Yahoo Inc.
+ *
+ * Licensed 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 com.yahoo.pulsar.client.api;
+
+import org.testng.annotations.Test;
+
+import com.google.common.base.Objects;
+import com.yahoo.pulsar.client.impl.BatchMessageIdImpl;
+import com.yahoo.pulsar.client.impl.ConsumerId;
+import com.yahoo.pulsar.client.impl.MessageIdImpl;
+
+import static org.testng.Assert.assertEquals;
+
+import org.testng.Assert;
+
+public class MessageIdTest {
+
+    @Test
+    public void messageIdTest() {
+        MessageId mId = new MessageIdImpl(1, 2, 3);
+        assertEquals(mId.toString(), "1:2:3");
+
+        mId = new BatchMessageIdImpl(0, 2, 3, 4);
+        assertEquals(mId.toString(), "0:2:3:4");
+
+        mId = new BatchMessageIdImpl(-1, 2, -3, 4);
+        assertEquals(mId.toString(), "-1:2:-3:4");
+
+        mId = new MessageIdImpl(0, -23, 3);
+        assertEquals(mId.toString(), "0:-23:3");
+    }
+}