Implementing the MessageStore class

This class handles the record store. It stores and retrieves the encrypted messages using the local RMS.

To create the class:

1. Assign the class to the package satsa and import the required classes.

   package satsa;
   
   import javax.microedition.lcdui.List;
   import javax.microedition.rms.RecordEnumeration;
   import javax.microedition.rms.RecordStore;
   import javax.microedition.rms.RecordStoreException;

2. Create the class and open the MessageStore.

   // Stores the messages as byte arrays in the RMS
   class MessageStore
   {
     private final SATSAMIDlet midlet;
     private RecordStore recordStore;
     private RecordEnumeration recordEnumeration;
     private int[] messageIdArray;
     private int numberOfMessages;
   
     MessageStore(SATSAMIDlet midlet)
     {
       this.midlet = midlet;
       openMessageStore();
     }
   
     void close()
     {
       try 
       {
         recordStore.closeRecordStore();
       }
       catch (RecordStoreException rse)
       {
         // Ignore, since the application is closing anyway.
       }
     }

3. List all messages in Record Store.

     // List all messages in Record Store
     void fillList(List list)
     {
       list.deleteAll();
   
       try
       {
         numberOfMessages = recordStore.getNumRecords();
         messageIdArray = new int[numberOfMessages+1];
   
         recordEnumeration = recordStore.enumerateRecords(null,
           null,
           false);
         int i=0;
   
         while (recordEnumeration.hasNextElement())
         {
           i++;
           int id=recordEnumeration.nextRecordId();
   
           list.append("Message " + id, null);
           messageIdArray[i]=id;
         }
       }
       catch (RecordStoreException rse)
       {
         midlet.showError("Record Store Exception. " + rse.getMessage());
       }
     }

4. Add a record to Record Store.

     // Add a record to Record Store
     void addMessage(byte[] messageData)
     {
       try
       {
         recordStore.addRecord(messageData, 0, messageData.length);
       }
       catch (RecordStoreException rse)
       {
         midlet.showError("Record Store Exception. " + rse.getMessage());
       }
     }
   
     // Get message from Record Store
     byte[] getMessage(int index)
     {
       try
       {
         byte[] messageData = recordStore.getRecord(messageIdArray[index]);
         return messageData;
       }
       catch (RecordStoreException rse)
       {
         midlet.showError("Record Store Exception. " + rse.getMessage());
         return null;
       }
     }
   
     // Delete a record from Record Store
     void deleteMessage(int index)
     {
       try
       {
         recordStore.deleteRecord(messageIdArray[index]);
       }
       catch (RecordStoreException rse)
       {
         midlet.showError("Record Store Exception. " + rse.getMessage());
       }
     }
     
     private void openMessageStore()
     {
       try 
       {
         recordStore = RecordStore.openRecordStore("SATSA_test", true);
       }
       catch (RecordStoreException rse)
       {
         midlet.showError("Record Store Exception. " + rse.getMessage());
       }
     }
   }