The Mobile Information Device Profile --
the platform for mobile Java applications -- provides a mechanism for MIDP
applications to persistently store data locally, across multiple invocations
and retrieve it later.
This persistent storage mechanism can be
viewed as a simple record-oriented database model and is called the record
management system (RMS).
The
javax.microedition.rms.RecordStore class represents a RMS record store, called otherwise a database
table. It provides several methods to manage as well as insert, update, and
delete records in a record store.
The record store is created in
platform-dependent locations, like nonvolatile device memory.
I implemented a simple java class working with
RMS, that we can use in our j2me application:
|
1 package mobileapplicationdb; 2 3 import javax.microedition.rms.RecordStore; 4 5 public class RmsDb { 6 private RecordStore rmsDb = null; 7 static final String LOCAL_DB_NAME = "rms_db_example"; 8 9 public RmsDb() { 10 } 11 12 public void openRecStore() { 13 try { 14 // The second parameter indicates that the record store 15 // should be created if it does not exist 16 rmsDb = RecordStore.openRecordStore(LOCAL_DB_NAME, true ); 17 } 18 catch (Exception e) { 19 System.out.println(e.toString()); 20 } 21 } 22 23 public void closeRecStore() { 24 try { 25 rmsDb.closeRecordStore(); 26 } 27 catch (Exception e) { 28 System.out.println(e.toString()); 29 } 30 } 31 32 public void deleteRecStore() { 33 if (RecordStore.listRecordStores() != null) { 34 try { 35 RecordStore.deleteRecordStore(LOCAL_DB_NAME); 36 } 37 catch (Exception e) { 38 System.out.println(e.toString()); 39 } 40 } 41 } 42 43 public void writeRecord(String str) { 44 byte[] record = str.getBytes(); 45 try { 46 rmsDb.addRecord(record, 0, record.length); 47 } 48 catch (Exception e) { 49 System.out.println(e.toString()); 50 } 51 } 52 53 public String readRecords() { 54 String res = ""; 55 StringBuffer buf = new StringBuffer(); 56 try { 57 byte[] recData = null; 58 int intLen; 59 60 for (int i = 1; i <= rmsDb.getNumRecords(); i++) { 61 recData = new byte[rmsDb.getRecordSize(i)]; 62 intLen = rmsDb.getRecord(i, recData, 0); 63 res = "Record no." + i + ": " + new String(recData, 0, intLen)+"\n"; 64 buf.append(res); 65 } 66 res = buf.toString(); 67 } 68 catch (Exception e) { 69 System.out.println(e.toString()); 70 } 71 return res; 72 } 73 74 }-->
No comments:
Post a Comment