Add new message type :: Watcher message, this class will wrapp zeppelin ws message and add extra information such as noteId and user

zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/socket/WatcherMessage.java

@@ -0,0 +1,73 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.zeppelin.notebook.socket;
+
+import com.google.gson.Gson;
+
+/**
+ * Zeppelin websocket massage template class for watcher socket.
+ */
+public class WatcherMessage {
+
+  private String message;
+  private String noteId;
+  private String subject;
+  
+  private static final Gson gson = new Gson();
+  
+  public static Builder builder(String noteId) {
+    return new Builder(noteId);
+  }
+  
+  private WatcherMessage(Builder builder) {
+    this.noteId = builder.noteId;
+    this.message = builder.message;
+    this.subject = builder.subject;
+  }
+  
+  public String serialize() {
+    return gson.toJson(this);
+  }
+  
+  /**
+   * Simple builder.
+   */
+  public static class Builder {
+    private final String noteId;
+    private String subject;
+    private String message;
+    
+    public Builder(String noteId) {
+      this.noteId = noteId;
+    }
+    
+    public Builder subject(String subject) {
+      this.subject = subject;
+      return this;
+    }
+    
+    public Builder message(String message) {
+      this.message = message;
+      return this;
+    }
+
+    public WatcherMessage build() {
+      return new WatcherMessage(this);
+    }
+  }
+  
+}