简单封装MIDP RMS操作

许多MIDP应用程序需要简单的存储配置信息，对此，简单封装一个RMSHandler，实现一条记录的读写：

package com.crackj2ee.midp.rms;

import java.io.*;

import javax.microedition.rms.*;

public final class RMSHandler {

 private static final String RECORD_STORE_NAME = "RmsDaTa";

 public static boolean loadUniqueRecord(Persistentable p) {
 byte[] data = loadUniqueRecord();
 if(data==null)
 return false;
 DataInputStream input = null;
 try {
 input = new DataInputStream(new ByteArrayInputStream(data));
 p.load(input);
 return true;
 }
 catch(IOException ioe) {
 return false;
 }
 finally {
 try {
 input.close();
 }
 catch (Exception e) {}
 }
 }

 public static boolean saveUniqueRecord(Persistentable p) {
 DataOutputStream output = null;
 try {
 ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 output = new DataOutputStream(bytes);
 p.save(output);
 return saveUniqueRecord(bytes.toByteArray());
 }
 catch(IOException ioe) {
 return false;
 }
 finally {
 if(output!=null)
 try {
 output.close();
 }
 catch (Exception e) {}
 }
 }

 private static byte[] loadUniqueRecord() {
 RecordStore rs = null;
 RecordEnumeration re = null;
 try {
 rs = RecordStore.openRecordStore(RECORD_STORE_NAME, true);
 if(rs.getNumRecords()==0)
 return null;
 re = rs.enumerateRecords(null, null, false);
 if(re.hasNextElement())
 return re.nextRecord();
 return null;
 }
 catch(RecordStoreException rse) {
 return null;
 }
 finally {
 if(re!=null) {
 re.destroy();
 }
 if(rs!=null) {
 try {
 rs.closeRecordStore();
 }
 catch (Exception e) {}
 }
 }
 }

 private static boolean saveUniqueRecord(byte[] data) {
 RecordStore rs = null;
 RecordEnumeration re = null;
 try {
 rs = RecordStore.openRecordStore(RECORD_STORE_NAME, true);
 re = rs.enumerateRecords(null, null, false);
 if(re.hasNextElement()) {
 rs.setRecord(re.nextRecordId(), data, 0, data.length);
 }
 else {
 rs.addRecord(data, 0, data.length);
 }
 return true;
 }
 catch(RecordStoreException rse) {
 return false;
 }
 finally {
 if(re!=null) {
 re.destroy();
 }
 if(rs!=null) {
 try {
 rs.closeRecordStore();
 }
 catch (Exception e) {}
 }
 }
 }
}

需要持久化的类实现一个Persistentable接口：

package com.crackj2ee.midp.rms;

import java.io.*;

public interface Persistentable {

 void save(DataOutputStream output) throws IOException;

 void load(DataInputStream input) throws IOException;

}

读写数据时，按照顺序依次读写即可，例如：

class MyForm extends Form implements Persistentable {

 private int score;
 private String username;


public MyForm() {
 super("Test");
 load(this);
 }



 public void save(DataOutputStream output) throws IOException {
 output.writeInt(score);
 output.writeUTF8(username);
 }

 public void load(DataInputStream input) throws IOException {
score = input.readInt();
username = input.readUTF8();
 }

}