ChatApplication


1   /*
2    * Andy John
3    * 2/99
4    * Chat room
5    * andy@enhydra.org
6    * www.enhydra.org
7    * 
8    * Chat - A simple chat room Enhydra application.
9    * 
10   *  The purpose of this program is to demonstrate ways to use the Enhydra
11   *  application framework. Jolt is used for two of the dynamic HTML
12   *  pages. One of the pages is generated by a presentation object written
13   *  by hand.
14   * 
15   *  This application uses what an algorithm I call "on hold push", because
16   *  it gives you the effect of "push technology", but only uses standard
17   *  HTTP. You instantly see when other people send in a message. But it
18   *  will work through proxies and firewalls. It is even applicable to
19   *  applets, which have additional security restrictions (the stand alone
20   *  debugger uses this algorithm to show the requests made to the 
21   *  servlet that is being debugged). See the Discussion object for a
22   *  description of on hold push.
23   *
24   *  www.enhydra.org 
25   */
26  
27  package chat;
28  
29  import com.lutris.appserver.server.*;
30  import com.lutris.appserver.server.httpPresentation.*;
31  import com.lutris.appserver.server.session.*;
32  import com.lutris.util.*;
33  
34  import chat.spec.*;
35  
36  /**
37   * The application object.
38   * Reads all the settings from the config file.
39   */
40  public class ChatApplication extends StandardApplication {
41  
42      private String   roomName = "Chat Room";
43      private String   bgColor = "";
44      private String   clearCommand = "";
45  
46      /**
47       *  Read all the chat room settings at startup time. Some of the
48       *  settings are saved, and the other classes refer to this class when
49       *  they need the values. Some of the settings are only used once to
50       *  initialize parts of the program.
51       */
52      public void startup(Config appConfig) throws ApplicationException {
53          super.startup(appConfig); // Be sure to call this!
54          /*
55           *  Get the title of this chat room from the config file.
56           */
57          try {
58              roomName = appConfig.getString("RoomName", "Chat Room");
59          } catch (ConfigException e) {
60              throw new ApplicationException("Bogus RoomName in config file.", e);
61          }
62          /*
63           *  How long should messages be kept? Get from config file.
64           */
65          int messageLifetimeSecs;
66          try {
67              messageLifetimeSecs = appConfig.getInt("MessageLifetimeSecs", 300);
68          } catch (ConfigException e) {
69              throw new ApplicationException(
70                                  "Bogus MessageLifetimeSecs in config file.", e);
71          }
72          /*
73           *  How often to delete messages that are too old? 
74           */
75          int harvestIntervalSecs;
76          try {
77              harvestIntervalSecs = appConfig.getInt("HarvestIntervalSecs", 55);
78          } catch (ConfigException e) {
79              throw new ApplicationException("Bogus HarvestIntervalSecs in config file.", e);
80          }
81          /*
82           *  Get the max number of messages allowed (if any) from the config
83           *  file. You don't know how many hits you will get. If you allow
84           *  data structures to grow without limit, your application may
85           *  use up all the memory and kill the virtual machine.
86           */
87          int maxQueueSize;
88          try {
89              maxQueueSize = appConfig.getInt("MaxQueueSize", 200);
90          } catch (ConfigException e) {
91              throw new ApplicationException(
92                                         "Bogus MaxQueueSize in config file.", e);
93          }
94          /*
95           *   Get the background color string (if any) from the config file.
96           */
97          try {
98              bgColor = appConfig.getString("BackgroundColor", "#99CCFF");
99          } catch (ConfigException e) {
100             throw new ApplicationException(
101                                     "Bogus BackgroundColor in config file.", e);
102         }
103         /*
104          *  Get the clear command (if any) from the config file.
105          */
106         try {
107             clearCommand = appConfig.getString("ResetCommand", "");
108         } catch (ConfigException e) {
109             throw new ApplicationException(
110                                     "Bogus ResetCommand in config file.", e);
111         }
112         /*
113          *  Configure the DiscussionImpl object.
114          *  Maybe start the message deleting thread.
115          */
116         
117         DiscussionManager discussionManager = DiscussionManagerFactory.getDiscussionManager("chat.business.DiscussionManagerImpl");
118       
119  /*
120  * Catch Null pointer exception ( we canot make a instances of classes from business layer when we run chat_pres )
121  * We need  to allow chat_pres to be functional 
122  */     
123   try{
124         discussionManager.setMaxQueueSize(maxQueueSize);
125       
126         if (harvestIntervalSecs < 1)
127             harvestIntervalSecs = 1;
128         if (messageLifetimeSecs > 0) 
129         
130            discussionManager.startHarvester(messageLifetimeSecs, harvestIntervalSecs);
131  
132     }catch(NullPointerException   e){}
133  
134     }
135 
136  
137     public boolean requestPreprocessor(HttpPresentationComms comms)
138                    throws Exception   {
139         return super.requestPreprocessor(comms);
140     }
141 
142 
143 public void shutdown(){
144    DiscussionManager discussionManager = DiscussionManagerFactory.getDiscussionManager("chat.business.DiscussionManagerImpl");
145     try{
146         discussionManager.stopHarvester();
147     }catch(NullPointerException   e){}
148    }
149     /**
150      *  The title of this chat room.
151      */
152     public String   getRoomName() {
153         return roomName;
154     }
155 
156 
157     /**
158      *  What color should the pages be? This is used by both the entry frame
159      *  and the contents frame.
160      */
161     public String   getBgColor() {
162         return bgColor;
163     }
164 
165     /**
166      *  What's the clear command? This will be "" if there is no command.
167      *  If this string is sent in (in a message), then delete all the 
168      *  messages currently in the queue.
169      */
170     public String   getClearCommand() {
171         return clearCommand;
172     }
173 
174 
175     /**
176      *  This is only called if this application is being run in the
177      *  Enhydra Multiserver. 
178      *  Displays usage stats that an administrator would care about.
179      *  The number of listeners is the number of requets blocked
180      *  on a read, waiting for messages to appear or be deleted (often
181      *  web browsers do "keep alive" behind the scenes, even if the users
182      *  hit "stop", this might not go to zero immediatly).
183      * 
184      * @return HTML that is displayed in the status page of the Multiserver.
185      */
186     public String   toHtml() {
187         String   response;
188         
189       
190         
191          DiscussionManager discussionManager = DiscussionManagerFactory.getDiscussionManager("chat.business.DiscussionManagerImpl");
192          int n = discussionManager.getNumWaiting();
193         
194         if (n == 1)
195             response = "There is 1 person listening.";
196         else
197             response = "There are " + n + " people listening.";
198       
199        long l = discussionManager.getTotalReceived();
200        
201         if (l == 1)
202             response += "<br>A total of 1 message has been received so far.";
203         else
204             response += "<br>A total of " + l + " messages have been received.";
205    
206           l = discussionManager.getCurrentSize();
207         if (l == 1)
208             response += "<br>There is currently 1 message.";
209         else
210             response += "<br>There are currently " + l + " messages.";
211         return response;
212     }
213 
214 }
215 
216
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