How to lock a record in a database using java

Question

hi,
i want to lock a record in a database. how could it be done.
if any body has idea pls share with me

Answer 1

Ok, then you can create a simple lock:
The idea is same, but this allow you to lock multiple id at the same time:
static Object LOCK_FLAG = new Object();
static Object[] locker = new Object[1000]; // assuming you have id 0-999 to lock
    this function will wait until current thread succesfully
    locks all the ids to lock.
public void lock( int[] idsToLock) {
   while (true) {
       synchronized(locker) {
          boolean success = true;
          for(int i=0; i<idsToLock.length; i++) {
              if (locker[ idsToLock[ i ] ] != null )
                 success=false;
              if (!success) break;
          if (success) {
              for(int i=0; i<idsToLock.length; i++)
                 locker[ idsToLock[ i ] ] = LOCK_FLAG;
              locker.notify();
              return;
          locker.notify();
       try {  Thread.sleep(100); } catch (Exception ex) { }
    this function will wait until all locks are released
public void releaseLock( int[] idsToLock) {
   synchronized(locker) {
       for(int i=0; i<idsToLock.length; i++)
             locker[ idsToLock[ i ] ] = null;
       locker.notify();
}How to use:
int[] recordToLock = new int[] { 1, 100, 55, 32, 25 };
lock(recordToLock); // lock before modify ..
try {
   // do anything with your records ...
} catch (Throwable t) {
   // if any exception ...
} finally {
   releaseLock(recordToLock);  // make sure this will always be executed
}rgds,
Alex