如何保持应用程序引擎的Servlet听火力地堡 [英] How to keep App Engine Servlet Listening to Firebase

问题描述

的https：

我在下面的教程//云.google.com /解决方案/移动/火力-APP-引擎机器人工作室

我拥有的一切工作和电子邮件每隔2分钟，因为它应该发送。不过，我现在想扩大这种触发只有在得到火力地堡节点上的数据变化，不可以发送邮件每2分钟发送电子邮件。

要测试我更换了 cron.xml 文件
来自：

 ＆LT;？XML版本=1.0编码=UTF-8＆GT？;
＆LT; cronentries＆GT;
   ＆LT;＆cron的GT;
       ＆LT; URL＆GT; /你好＆LT; / URL＆GT;
       ＆LT;描述＆GT;送我早上＆LT优秀项目的电子邮件; /描述＆GT;
       ＆LT;＆时间表GT;每2分钟＆LT; /时间表＆GT;
   ＆LT; / cron的＆GT;
＆LT; / cronentries＆GT;
 

到

 ＆LT;？XML版本=1.0编码=UTF-8＆GT？;
＆LT; cronentries /＆GT;
 

要清除出计划任务。

但是，现在在做的火力地堡分贝的改变，邮件永远不会发送....

的如何将我的应用程序引擎服务器监听保持到了火力点，随后产生 onDataChanged 实时给出一个动作？的

MyServlet类：

 公共类MyServlet延伸的HttpServlet {
    静态记录器记录= Logger.getLogger（com.example.username.myapplication.backend.MyServlet）;    @覆盖
    公共无效的doGet（HttpServletRequest的REQ，HttpServletResponse的RESP）
            抛出IOException
        Log.info（拿到的cron信息，构建邮件。）;        //创建一个新的火力地堡实例，并认购儿童的事件。
        火力地堡火力点=新的火力点（[火力参考]）;
        firebase.addValueEventListener（新ValueEventListener（）{
            @覆盖
            公共无效onDataChange（DataSnapshot dataSnapshot）{
                //生成使用各个领域，从火力地堡电子邮件内容。
                最后StringBuilder的newItemMessage =新的StringBuilder（）;
                newItemMessage.append（这应该非常密切地改变数据后抵达）;
                //现在发送电子邮件
                属性道具=新特性（）;
                会话的会话=作为Session.getDefaultInstance（道具，NULL）;
                尝试{
                    消息味精=新的MimeMessage（会话）;
                    //确保您替换您的项目-ID在电子邮件From字段
                    msg.setFrom（新网际地址（任何@ [应用引擎] .appspotmail.com
                            藤堂Nagger））;
                    msg.addRecipient（Message.RecipientType.TO，
                            新的网际地址（[e-mail]，收件人））;
                    msg.setSubject（盛宴电子邮件测试）;
                    msg.setText（newItemMessage.toString（））;
                    Transport.send（MSG）;
                }赶上（MessagingException | UnsupportedEncodingException五）{
                    Log.warning（e.getMessage（））;
                }
            }            公共无效onCancelled（FirebaseError firebaseError）{
            }
        }）;
    }}
 

解决方案

您的问题实际上是一个有关的AppEngine以及如何创建自动启动并自动执行一些初始化一个Servlet的问题。

您想保留手动缩放比例，但按照下列步骤进行：
的https://cloud.google.com/appengine/docs/java/config/appconfig#using_a_load-on-startup_servlet

有关初始化设置你的听众（），而不是一个HTTP请求。
你正在尝试绝对是可能的，看到它在其他地方运行。

I am following the tutorial at: https://cloud.google.com/solutions/mobile/firebase-app-engine-android-studio

I have everything working and the email is sending every 2 minutes as it should. However, I now wish to extend this to trigger sending an email only upon data change on the Firebase node, not sending a message every 2 minutes.

To test I replaced the cron.xml file from:

<?xml version="1.0" encoding="UTF-8"?>
<cronentries>
   <cron>
       <url>/hello</url>
       <description>Send me an email of outstanding items in the morning</description>
       <schedule>every 2 minutes</schedule>
   </cron>
</cronentries>

to:

<?xml version="1.0" encoding="UTF-8"?>
<cronentries/>

To clear out the scheduled tasks.

But now upon making a change in the Firebase db, the email is never sent....

How can I keep my app engine server "listening" to the firebase node and subsequently produce an action given onDataChanged in real-time?

MyServlet class:

public class MyServlet extends HttpServlet {
    static Logger Log = Logger.getLogger("com.example.username.myapplication.backend.MyServlet");

    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {
        Log.info("Got cron message, constructing email.");

        //Create a new Firebase instance and subscribe on child events.
        Firebase firebase = new Firebase("[firebase ref]");
        firebase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                // Build the email message contents using every field from Firebase.
                final StringBuilder newItemMessage = new StringBuilder();
                newItemMessage.append("This should arrive very closely after changing the data");


                //Now Send the email
                Properties props = new Properties();
                Session session = Session.getDefaultInstance(props, null);
                try {
                    Message msg = new MimeMessage(session);
                    //Make sure you substitute your project-id in the email From field
                    msg.setFrom(new InternetAddress("anything@[app-engine].appspotmail.com",
                            "Todo Nagger"));
                    msg.addRecipient(Message.RecipientType.TO,
                            new InternetAddress("[e-mail]", "Recipient"));
                    msg.setSubject("Feast Email Test");
                    msg.setText(newItemMessage.toString());
                    Transport.send(msg);
                } catch (MessagingException | UnsupportedEncodingException e) {
                    Log.warning(e.getMessage());
                }
            }

            public void onCancelled(FirebaseError firebaseError) {
            }
        });
    }

}

解决方案

Your question is actually a question about AppEngine and how to create a Servlet that starts automatically and automatically performs some initialization.

You will want to keep manual scaling on, but follow the steps here: https://cloud.google.com/appengine/docs/java/config/appconfig#using_a_load-on-startup_servlet

for setting up your listeners on init() instead of an http request. What you are trying is definitely possible and have seen it run elsewhere.

这篇关于如何保持应用程序引擎的Servlet听火力地堡的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！