应用RMS实现用户自动登陆功能

    MIDP的子系统Record Management System提供了MIDlet的持久性存储,精通MIDP子系统RMS系列文章对其使用进行了详细介绍。本文讲述如何使用RMS提供的功能实现应用程序的定制功能——自动登陆。

    我们的设计思路非常简单，在RecordStore中存储用户的设置和用户的信息（用户名和密码），如果用户选择自动登陆的话，那么下次当用户想联网的时候将跳过登陆界面，系统会从RecordStore中读取用户和密码，经过服务器的验证后转入到适当的界面。我对整个程序进行了简化，我们不进行联网，对信息的存储也都从简，只是为了说明RMS实现应用程序定制的思路，因此给出的代码并没有全面测试和优化。下面是程序的截图

   

 

 

 

 

 

 

     我们用Account和Preference分别存储用户信息和用户的个性化设置，同样在这两个类中提供序列化的方法，这样方便我们从RecordStore中读取和写入。这里只给出Preference类的代码，Account类似。
package com.j2medev.autologin;

import java.io.*;

public class Preference
{
    private boolean autoLogin;

    public Preference(boolean _autoLogin)
    {
        this.autoLogin = _autoLogin;
    }

    public Preference()
    {
    }

    public void serialize(DataOutputStream dos) throws IOException
    {
        dos.writeBoolean(autoLogin);
    }

    public static Preference deserialize(DataInputStream dis)
            throws IOException
    {
        Preference preference = new Preference();
        preference.setAutoLogin(dis.readBoolean());

        return preference;
    }

    public boolean isAutoLogin()
    {
        return autoLogin;
    }

    public void setAutoLogin(boolean autoLogin)
    {
        this.autoLogin = autoLogin;
    }
}

    我们需要一个Model类来处理读取和写入RecordStore数据的逻辑，它也非常简单。为了简化程序我们规定首先写入Account然后写入Preference，这样我们读取的时候只要通过recordID分别为1和2来读取了，在实际使用的时候通常会比较复杂，我们要借助过滤器等查找，可以参考我的基于MIDP1.0实现个人通讯录。

package com.j2medev.autologin;

import javax.microedition.rms.*;
import java.io.*;

public class Model
{
    private RecordStore accountStore;
    public static final String RNAME = "accountstore";

    public Model()
    {
        try
        {
            accountStore = RecordStore.openRecordStore(RNAME, true);
        } catch (RecordStoreException e)
        {
            e.printStackTrace();
        }
    }

    public void closeRecordStore()
    {
        try
        {
            accountStore.closeRecordStore();
        } catch (RecordStoreException e)
        {
            e.printStackTrace();
        }
    }

    public void saveAccount(Account account)
    {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        try
        {
            account.serialize(dos);
            byte[] data = baos.toByteArray();
            accountStore.addRecord(data, 0, data.length);
            baos.close();
        } catch (IOException e)
        {
            e.printStackTrace();
        } catch (RecordStoreException e)
        {
            e.printStackTrace();
        }

    }

    public Account getAccount(int recordID)
    {

        try
        {
            if (accountStore.getNumRecords() > 0)
            {
                byte[] data = accountStore.getRecord(recordID);
                ByteArrayInputStream bais = new ByteArrayInputStream(data);
                DataInputStream dis = new DataInputStream(bais);
                Account account = Account.deserialize(dis);
                bais.close();
                return account;
            }
            return null;

        } catch (IOException e)
        {
            return null;
        } catch (RecordStoreException e)
        {
            return null;
        }
    }

    public void savePreference(Preference preference)
    {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        try
        {
            preference.serialize(dos);
            byte[] data = baos.toByteArray();
            accountStore.addRecord(data, 0, data.length);
            baos.close();
           
        } catch (IOException e)
        {
            e.printStackTrace();
        } catch (RecordStoreException e)
        {
            e.printStackTrace();
        }

    }

    public Preference getPreference(int recordID)
    {
        try
        {
            if (accountStore.getNumRecords() > 0)
            {
                byte[] data = accountStore.getRecord(recordID);
                ByteArrayInputStream bais = new ByteArrayInputStream(data);
                DataInputStream dis = new DataInputStream(bais);
                Preference preference = Preference.deserialize(dis);
                bais.close();
                return preference;
            }
            return null;
        } catch (IOException e)
        {
            return null;
        } catch (RecordStoreException e)
        {
            return null;
        }
    }

}

    MIDlet的设计同样很简单，直接给出代码。整个程序的代码可以从这里下载

package com.j2medev.autologin;

import javax.microedition.lcdui.*;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class LoginMIDlet extends MIDlet implements CommandListener
{

    private Display display;
    private Form loginForm;
    private Form successForm;
    private TextField userName;
    private TextField password;
    private ChoiceGroup autoLogin;
    private Model model;
    public static final Command ConnCMD = new Command("Connect", Command.OK, 1);

    protected void startApp() throws MIDletStateChangeException
    {
        initMIDlet();
        Preference p = model.getPreference(2);
        if (p == null || !p.isAutoLogin())
        {
            display.setCurrent(loginForm);
        } else if (p.isAutoLogin())
        {
            Account account = model.getAccount(1);
            System.out.println("username:" + account.getUsrName() + "password:"
                    + account.getPassword());
            display.setCurrent(successForm);

        }

    }

    public void initMIDlet()
    {
        model = new Model();
        display = Display.getDisplay(this);
        loginForm = new Form("LoginForm");
        userName = new TextField("username", null, 20, TextField.ANY);
        password = new TextField("password", null, 20, TextField.PASSWORD);
        autoLogin = new ChoiceGroup("AutoLogin", Choice.MULTIPLE,
                new String[] { "remember me" }, null);
        loginForm.append(userName);
        loginForm.append(password);
        loginForm.append(autoLogin);
        loginForm.addCommand(ConnCMD);
        loginForm.setCommandListener(this);
        successForm = new Form("OK");
        successForm.append("Ok you have connected to server");
    }

    protected void pauseApp()
    {
     
    }

    protected void destroyApp(boolean arg0) throws MIDletStateChangeException
    {

    }

    public void commandAction(Command arg0, Displayable arg1)
    {
        String _userName;
        String _password;
        boolean auto = false;

        if (arg0 == ConnCMD)
        {
            _userName = userName.getString();
            _password = password.getString();
            auto = autoLogin.isSelected(0);
            System.out.println(_userName + _password + auto);
            if (auto)
            {
                Account account = new Account(_userName, _password);
                model.saveAccount(account);
                Preference preference = new Preference(auto);
                model.savePreference(preference);

            }
            display.setCurrent(successForm);
        }
    }

}