RMS - Record Management System

1. RMS - Record Management System

2. Record Store • En Record er et bytearray af vilkårlig størrelse • En RecordStore er et antal Records nummerede 1, 2, 3, ... • Når en ny Record indsættes anvendes næste endnu ikke anvendte index (ingen genbrug af indexværdier)

3. Oprette en RecordStore ... // Create a record store RecordStore rs = null; try { rs = RecordStore.openRecordStore( "myrs", true ); } catch( RecordStoreException e ){ // couldn't open it or create it } ...

4. Indsætte og opdatere Records // Indsætte en ny Record byte[] data = new byte[]{0, 1, 2, 3 }; int recordID; recordID = rs.addRecord(data, 0, data.length); // Opdatere en eksisterende Record int recordID = ...; // some record ID byte[] data = new byte[]{ 0, 10, 20, 30}; rs.setRecord(recordID, data, 1, 2); // replaces all data in record with 10, 20

5. Læse og fjerne Records ... int recordID = .... // some record ID byte[] data = rs.getRecord(recordID); ... ... int recordID = ...; // some record ID rs.deleteRecord(recordID); ... Once a record is deleted, any attempt to use it throws an InvalidRecordIDException.

6. Slette en RecordStore ... try { RecordStore.deleteRecordStore("myrs"); } catch(RecordStoreNotFoundException e){ // no such record store } catch(RecordStoreException e){ // somebody has it open } ...

7. Flere RecordStore operationer • getLastModified() returns the time of the last modification • getName() returns the name of the record store. • getNumRecords() returns the number of records in the record store. • getSize() returns the total size of the record store, in bytes. • getSizeAvailable() returns the number of bytes available for growth. • getVersion() returns the version number of the record store.

8. RMS Exceptions • InvalidRecordIDException is thrown when an operation cannot be performed because the record ID is invalid. • RecordStoreFullException is thrown when no more space is available in the record store. • RecordStoreNotFoundException is thrown when the application tries to open a non-existent record store. • RecordStoreNotOpenException is thrown when an application tries to access a record store that has already been closed. • RecordStoreException is the superclass of the other four, and is thrown for general errors they don't cover.

9. Datamapping 1

10. Datamapping 2 public void fromByteArray(byte[] data) throws IOException { ByteArrayInputStream bin = new ByteArrayInputStream(data); DataInputStream din = new DataInputStream(bin); _firstName = din.readUTF(); _lastName = din.readUTF(); _phoneNumber = din.readUTF(); din.close(); } public byte[] toByteArray() throws IOException { ByteArrayOutputStream bout = new ByteArrayOutputStream(); DataOutputStream dout = new DataOutputStream(bout); dout.writeUTF(getFirstName()); dout.writeUTF(getLastName()); dout.writeUTF(getPhoneNumber()); dout.close(); return bout.toByteArray(); }

11. Enumerations 1 RecordStore rs = ... // an open record store RecordEnumeration enum = rs.enumerateRecords( filter, comperator, tracking_updates ); ... // use the enumeration here enum.destroy(); // always clean it up! enum.hasNextElement() enum.nextRecordId() enum.nextRecord() osv Rækkefølgen i enum er udefineret

12. Enumerations 2 RecordFilter public class MyFilter implements RecordFilter { public boolean matches( byte[] recordData ) { ... // matching code here } }

13. Enumerations 3 RecordComparator public class MyComparator implements RecordComparator { public int compare(byte[] r1, byte[] r2){ int salary1 = getSalary(r1); int salary2 = getSalary(r2); if(salary1 < salary2){ return PRECEDES; } else if(salary1 == salary2){ return EQUIVALENT; } else { return FOLLOWS; } } }

14. Alternativer • RMS • Filsystem (FileConnection API) • PIM (Personal Information Management API) RMS er tilgængelig på de fleste apparater Filesystem og PIM er ikke så tilgængelige som RMS, og kræver endvidere certificering

15. Afsluttende bemærkninger • Alle RMS operationer er trådsikre • Attributten MIDlet-Data-Size (minimumsværdi) bør sættes i såvel jad som manifest filer • Det vil være rart at kunne arbejde på "objektniveau" • Der er behov for at kunne søge effektivt i en RecordStore