How to save data using PersistentStore in blackberry

This sample explains “How to save data using PersistentStore in blackberry”. Example is a login screen demo implementing single signon method. It saves the username and password once we can log in successfully and retrieve from the database on later attempts.

Step-1:

We need to have a login screen with username and password text field with a submit button. As this is complete basics of UI stuffs. i left this up-to the users. Here I will completely deal with the Database/ Persistence store concepts.

Step-2:

A bean class whose object is used for saving the credentials.

package com.javatechig.data;
public class LoginDetails implements Persistable {
    private String username;
    private String password;

    public LoginDetails(String username, String password) {
        this.username = username;
        this.password = password;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

Step-3:

Now, we can write the class to deal with the Persistence store. Here i am performing the simple operation with DB like adding object, retrieving object and then delete.

package com.javatechig.database;
import java.util.Vector;
import net.rim.device.api.system.CodeSigningKey;
import net.rim.device.api.system.ControlledAccess;
import net.rim.device.api.system.NonPersistableObjectException;
import net.rim.device.api.system.PersistentObject;
import net.rim.device.api.system.PersistentStore;
import net.rim.device.api.ui.component.Dialog;
import com.flurry.blackberry.FlurryAgent;
import com.javatechig.data.LoginDetails;

public class LoginDatabase {

    public final static long key = 0xd3545eeea34045;
    static PersistentObject store;
    Vector objectsList;

    CodeSigningKey codeSigningKey = CodeSigningKey.get("ACME");

    public void reset() {
        try {
            store = PersistentStore.getPersistentObject(key);
            CodeSigningKey codeSigningKey = CodeSigningKey.get("ACME");
            synchronized (store) {
                objectsList = new Vector();
                store.setContents(new ControlledAccess(objectsList, codeSigningKey));
                store.commit();
            }
        }
        catch (Exception e) {
            Dialog.inform(e.toString());
        }
    }

    public LoginDatabase() {
        try {
            store = PersistentStore.getPersistentObject(key);
            CodeSigningKey codeSigningKey = CodeSigningKey.get("ACME");
            try {
                objectsList = (Vector) store.getContents(codeSigningKey);
                try {
                    if (objectsList.equals(null)) {
                        objectsList = new Vector();
                    }
                }
                catch (Exception e) {
                    objectsList = new Vector();
                }
            }
            catch (Exception ne) {
                Dialog.alert("Persistant Store : " + ne.toString());
            }
            synchronized (store) {
                store.setContents(new ControlledAccess(objectsList, codeSigningKey));
                store.commit();
            }
        }
        catch (NonPersistableObjectException e) {
            System.out.println(e.getObject());
            Dialog.alert("Persistant Store : " + e.getObject());
        }
        catch (Exception e) {
            Dialog.inform(e.toString());
        }
    }

    public void addObject(LoginDetails object) {
        try {
            synchronized (store) {
                objectsList = (Vector) store.getContents(codeSigningKey);
            }
            objectsList.addElement(object);
            synchronized (store) {
                store.setContents(new ControlledAccess(objectsList, codeSigningKey));
                store.commit();
            }
        }
        catch (Exception e) {
            Dialog.inform(e.toString());
        }
    }

    public void setCredentials(LoginDetails credentials) {
        try {
            synchronized (store) {
                objectsList = (Vector) store.getContents(codeSigningKey);
            }
            objectsList.removeAllElements();
            objectsList.addElement(credentials);
            synchronized (store) {
                store.setContents(new ControlledAccess(objectsList, codeSigningKey));
                store.commit();
            }
        }
        catch (Exception e) {
            Dialog.inform(e.toString());
        }
    }

    public Vector getObjects() {
        synchronized (store) {
            Vector objectsList = (Vector) store.getContents(codeSigningKey);
            return objectsList;
        }
    }

    public void deleteObject(LoginDetails savedObject) {
        try {
            synchronized (store) {
                Vector objectsList = (Vector) store.getContents(codeSigningKey);
                objectsList.removeElement(savedObject);
            }
            synchronized (store) {
                store.setContents(new ControlledAccess(objectsList, codeSigningKey));
                store.commit();
            }
        }
        catch (Exception e) {           
            Dialog.inform(e.toString());
        }
    }
}

Step-4:

Now we can use this below method to retrieve the data from db and then display it to the UI.

public static LoginDetails getStoredCredentials() {
    LoginDatabase ld = new LoginDatabase();
    Vector v = ld.getObjects();
    LoginDetails loginDetails = null;
    int size = v.size();
    if (size return loginDetails;
}
else {
    loginDetails = (LoginDetails) v.elementAt(0);
    return loginDetails;
}
}

This method returns the LoginDetails object. We can write this method in our UI class and then retrieving the username using getUsername() method and password using getPassword().Here we go!