android - Database locked exception

Question

I have created a database in my application with 5 tables. my database is being updated from different threads. When i see the log i can see that there are database locked exception while opening the database if it is already open.

One of my friend suggested me to always use content provider to avoid this issue. According to him content provider manages concurrency issues on its own?

Is it a good practice to use content provider if we don't want to share data to other applications?

Answer 1

I think using a read-write lock is enough in most cases.

Suppose you have written the following,

import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class MyDatabase extends SQLiteOpenHelper
{
    private static final ReadWriteLock rwLock = new ReentrantReadWriteLock(true);

    private static void beginReadLock()
    {
        rwLock.readLock().lock();
    }

    private static void endReadLock()
    {
        rwLock.readLock().unlock();
    }

    private static void beginWriteLock()
    {
        rwLock.writeLock().lock();
    }

    private static void endWriteLock()
    {
        rwLock.writeLock().unlock();
    }

then you can do your task like the following.

    public static void doSomething()
    {
        SQLiteDatabase sldb = null;

        try
        {
            beginReadLock();

            MyDatabase mydb = new MyDatabase();
            sldb = mldb.getReadableDatabase();
            ......
        }
        catch (Exception e)
        {
            ......
        }
        finally
        {
            if (sldb != null)
            {
                try
                {
                    sldb.close();
                }
                catch (Exception e) {}
            }

            endReadLock();
        }
    }

Enclose read operations with beginReadLock() and endReadLock(). Likewise, enclose write operations with beginWriteLock() and endWriteLock().

Months ago, by the solution described above, I could solve my own database-lock issue where multiple threads were trying to read/write-open a database simultaneously.