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();
    }

}