Chatting

Author: Haoyu Wang (王浩羽)

ID: 11911612

Chatting is a simple online-chat application, based on JavaFX and Socket. In this assignment, you will need to implement a WeChat like program, but much simpler.

Exhibition

Introduction

• Server: multithreading + thread pool: 每个线程负责连接一个Client请求
• Client GUI: JavaFX - 前后端分离: 一个fxml文件对应于一个独立的Controller程序.
  • fxml文件为静态文件, 包含GUI的全部组件
  • Controller程序为控制层, 负责处理Client后端和前端GUI的交互逻辑
• Client 后端:
  • Client 类: 该类独立于控制层存在, 其功能包括
    • 连接服务器
    • 发送请求
    • 发送消息
    • 接受信息并处理
    • 安全关闭客户端并与服务器断开连接
  • multithreading: Client类中一个专门的线程负责随时接收Server发送至Client的信息, 并根据消息类型及内容转发给各控制层内的Controller或调用Controller的方法. 其中, 消息的转发使用Pipe Input/Output Stream进行线程间的通讯.
• Communication: 将socket的Input/Output Stream传入Object Input/Output Stream进行通信, 通过对象序列化的方式转递信息.

Assignment Requirement

• Server & Users (70 points)
  • Server maintain a list of users that are currently connected to the Server
  • Client can see a list of other users that are currently available to chat
  • Client can select another user to start a one-to-one chat
  • Client select multiple users to start a group chat
  • Client can send text messages and receive the messages
  • When Client receives new message, it will be a notification in chat list
  • Client can send emojis
• GUI (15 points)
  • Use javafx to implement GUI
  • Main panel to show a list of chats
  • Chat room: a separate chatroom window created for the chat
• Exception Handling (15 points)
  • When one Client is offline, other clients that have chat with the offline client will receive one Server message in his chat content that notifies the client is offline.
  • When Server is offline, all online clients will get a dialog window that notifies the Server is offline. Then the clients can check only history messages of the last chat. He can not begin a one-to-one chat or a group chat.
• Bonus (12 points)
  • Account Management: the server could support user registration and login.
  • Sorted Chat List: user could see a list of available chats, sorted by their recent chat activities
  • Chat History: client can get the chat history.
  • File Transfer

Quick Start

Install the Project

We will define the commonly used constants and models in the chatting-common model, which is the dependency of chatting-client and chatting-server.

Now, the first thing you need to do is to install the parent pom into the local maven repository.

mvn install

If you are a Windows user who has not configured Maven environment variables, you can run this command in IDEA by several ways as below:

• double click the Ctrl key in IDEA to bring up a "Run Anything" pop-up window, then enter the command
• click the "Execute Maven Goal" button on the top of Maven side bar, then enter the command
• simply click on the "install" option in the "Lifecycle" folder of Maven side bar

Each time after modifing the codes in chatting-common, subproject needs to be reinstalled.

mvn install -pl chatting-common

Run the Server

Ffind the Main class under the chatting-server model. Run the main method.

Run the Client

If you are using JDK 1.8 with JavaFX bundled, you may find the Main class under the chatting-client model, and run the main method to start a client. Note that you can start multiple clients by clicking the run button several times.

If you are using JDK in any higher version, please use the javafx plugin to run the client.

mvn javafx:run -pl chatting-client

Alternatively, you can find the goal in the plugin list, and click on it:

Server

properties

• clients: a list that represents current online clients.
• groupsMap: record all chat group, including one-to-one and multi-user. A group uses ID to identify. A chat group object mainly have id, name and maintain a message list.

Behavior

Server receives the Request or Message from a Client, records messary info and returns a response to the Client.

Client

properties

• currentUsername: username is unique
• onlineUserCnt: current online user number(contain current user himself)
• userList: other current online user list (not contain current user himself)
• chatGroupList (id, group name): all of the current chat groups, contain one-to-one and multi-user chat group. 无论是一对一的聊天还是多人聊天，处理方式均相同，放在同一列表中
• currentChatId: the id of current chat. 当前打开的聊天的id，使用id来确定唯一聊天，而不是聊天名字或群内用户
• chatContentList: the content of current chat

Operation

1. create one-to-one chat
   • select one user and click button "ok" to try to create one-to-one chat
     • if chat has existed in chatGroupList : set currentChatId
     • else: send CreateChatGroup Request to Server, when get return message, set currentChatId
   • your chat content will focus on the one-to-one chat you want immediately.
2. create group chat
   • input group chat name, select several users and click button "ok" to create a multi-user chat
   • you can always create group chat successfully, including the same group name or the same group users
   • send CreateChatGroup Request to Server, when get return message, set currentChatId
   • your chat content will focus on the group chat you created immediately
3. select a chat
   • select a chat in chatGroupList, set currentChatId
   • update content when next "Request to Server"
4. send message
   • send a Message to Server
   • text can't be empty
5. Request to Server periodically
   • online user list (and number)
   • chat group list: other user may start a new chat with current user
   • chat content list: update chat content (1. other user may send new message; 2. current user may open another chat)

Exceptions and Functions

Connect

1. Connecting Server is failed

   

Login

1. username or password is empty

   

2. username does not exist

   

3. password is wrong

   

4. user has already been online

   

5. if use can login, he will go to the Chat GUI:

   

Signup

1. username has already exists

   

2. signup successfully

   

emoji

sorted chat list

1. User a send a message "A" in group chat xxx, then xxx will be the first chat in the chat list:

2. Then user a send another message "B" in one-to-one chat with user b. This private chat becomes the last active chat and be the first chat.

chat history

1. User a is offline

2. User a is online again, and he can get history messages.

New Message Notify

Design

1. Message对象: 该对象专门用于储存一条消息, 其属性包含:

   • timestamp: 时间戳, 记录发出消息时的时间
   • sentBy: String类型, 发送者. 可为某个用户的名称或"Server"
   • sendTo: int类型, 表示想要发送到的聊天id, 每一个Server中维护的聊天都用id唯一表示
   • data: 信息内容

2. 将私聊和群聊视为近乎相同的对象, 称为ChatGroup. 它仅通过一个属性加以区分私聊和群聊, 而在行为上没有区别. 所有ChatGroup都会被维护在服务器端. 当用户向服务器申请开通任意一类聊天时, 服务器端将创建一个新的ChatGroup对象, 该对象包含属性如下:

   • id: 用以唯一确定一个聊天
   • name: 对于群聊, 储存自定义的群聊名称; 对于私聊, 不储存内容
   • owner: 群主, 即申请创建聊天的用户
   • users: 参与该聊天的用户列表
   • type: 该聊天的类型时私聊或群聊
   • record: 消息记录, 以Message对象储存
   • lastActiveTime: 最后一个消息的时间, 用以在用户界面以聊天活跃时间为顺序进行排序

3. 请求与回应: 为完成聊天功能, 客户端将根据需求向服务器端发送一系列的请求, 服务器收到请求后会做出回应. 整个过程通过java socket完成. 建立连接后, 客户端可能发出的请求类型及对应的回应分为以下数种:

   • signup: 申请注册

   • login: 申请登录

   • UserList: 申请在线用户列表. 服务器将返回所有在线用户列表

   • ChatGroupList: 申请本用户所在的全部聊天(包括私聊和群聊), 服务器将以LocalGroup的数据类型返回聊天列表. LocalGroup仅包含以下属性:

     • id: 识别聊天的唯一标识符, 在用户向某个聊天发送消息时, 将指定该参数

     • name: 用于显示在GUI上的聊天名称, 私聊将显示另一个用户的名称, 群聊直接显示群名

     • type: 用于辨别该聊天是私聊还是群聊

     服务器在发送LocalGroup列表时, 将会把列表的顺序以及这三个属性均维护正确.

     只传递一个聊天的部分信息而不是完整信息的原因是: 用户每次都会请求全部聊天列表, 若此时将全部聊天的全部聊天记录发送, 会传递大量数据且很多数据是冗余的. 因此, 用户维护聊天信息的部分, 并不在该请求中实现.

   • MessageList: 申请给定聊天id的全部聊天内容. 服务器将返回Message列表

   • CreateChatGroup: 申请开一个新的聊天(包括私聊和群聊), 服务器会判断是否允许开启新聊天 (开群聊没有限制, 可以开重名群聊, 也可以开多个包含相同用户的群聊; 开私聊的情况, 两个用户之间仅能存在一个私聊). 最终, 服务器返回一个聊天id (新聊天id或已存在的老聊天id).

   • Disconnect: 通知服务器断开连接, 服务器将安全地回收各种资源, 维护用户列表, 通知各群聊或其他用户该用户下线.

   为保证客户端始终能够获取最新的数据, 本工程的实现方式为, 客户端周期性地向服务器发出UserList, ChatGroupList, MessageList三个申请, 并将服务器返回的信息展示在GUI上.

4. 线程间通信: 用户接受消息的线程和javafx的线程之间常常需要进行通信, 这里根据需求采用了两种方式:

   • 直接转发收到的信息: 采用java中的Pipe Input/Output Stream直接将收到的信息转发给指定线程, 在Connect, Signup, Login阶段多采用这种方式.
   • 调用其他线程的方法: java多线程中, 对象是可以共享的, 因此只要维护好共享对象, 就可以直接调用该对象中需要的方法, 在Chat阶段采用该方式.

Exception

处理在使用过程中, 因为网络问题所导致的一些异常. 期望在这些异常发生时, 程序可以优雅地将它们反馈给用户. 避免程序突然退出, 或者爆出很多红色地异常提示.

1. One Client is offline: Server will give all chats of this offline user a extra message to notify he is offline

   

   If the offline client is online again, all his chat will get an extra message from Server: "User 'x' is online":

   

2. Server is down: all user will be notified. User can quit by himself elegantly. User can only check the last chat messages. He can not create a new one-to-one chat or group chat.

   

   If Client sends message, he will get:

   

   And Online User is set to be zero.

Difficulty

1. ListView 控件, 在被选中时, 会发生高频刷新闪烁问题: C#有double buffer的解决措施, 但是javafx没找到好办法. 暂且使用0.5s进行一次刷新的方式缓解.

2. javafx的fxml文件编写较复杂: 采用图形化界面 javafx Scene Builder 进行界面构建, 非常高效.

3. 客户端GUI界面关闭后, 该用户仍然在连接着服务器, 原因是仍有未处理的线程占用系统资源或占用端口: 在类Client中增加close()方法, 当负责GUI界面的线程关闭时, 需要执行该close()方法, 将其他必要的线程也全部终止, 并向Server发出Disconnect请求.

4. 回车发送消息：JavaFX 实现回车发送信息，Ctrl+Enter换行

   为TextArea添加key press监听器, 当收到Enter后, 将判定发送消息或换行.

5. 发表情: 使用依赖emoji-java处理表情, 非常方便.

   emoji-java: The missing emoji library for Java

   轻量级工具emoji-java处理emoji表情字符

6. 发文件/收文件: 使用javafx.stage的FileChooser和DirectoryChooser

7. 其他设计思路及优化:

   • 对于私聊, 在两个用户之间建立管道进行通讯. 这种方式有更快的通讯速度和安全性, 即使服务器因为请求多而迟缓, 私聊的通讯也可以不受影响;
   • 客户端在本地储存全部群聊的聊天记录, 而不是仅当前群聊的聊天记录. 这样在离线时, 客户端仍然可以查看所有的聊天记录. 但这可能涉及到了各个用户端聊天记录与服务器端的同步问题.
   • 目前的设计中, 在更新聊天记录时, 服务端会发送全部聊天记录. 可以通过客户端申请聊天记录时, 增加参数时间戳, 表示仅申请该时间后的聊天记录, 服务器将发送这一小部分聊天记录, 效率更高.

GUI Color Design

License

This project is licensed under the MIT License - see the LICENSE file for details.