org.jsimpledb

Class Counter

java.lang.Object

org.jsimpledb.Counter

public class Counter
extends Object

Represents a 64-bit counter value that can be adjusted concurrently by multiple transactions, typically without locking (depending on the underlying key/value store).

To define a field of type Counter, annotate the field's getter method as a normal field using @JField. No setter method should be defined. Counter fields do not support indexing or change listeners.

Note: during schema version change notification, counter field values appear as plain long values.

Method Summary

Modifier and Type	Method and Description
void	adjust(long offset) Adjust this counter's value by the specified amount.
void	decrement() Decrement this counter's value by one.
long	get() Read this counter's current value.
void	increment() Increment this counter's value by one.
void	set(long value) Set this counter's value.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

get

public long get()

Read this counter's current value. Invoking this method will typically disable the lock-free behavior of adjust() in the current transaction.

Returns:

current value of the counter

Throws:

StaleTransactionException - if the transaction from which this instance was read is no longer usable

DeletedObjectException - if the object from which this instance was read no longer exists

set

public void set(long value)

Set this counter's value. Invoking this method will typically disable the lock-free behavior of adjust() in the current transaction.

Parameters:

value - new value for the counter

Throws:

StaleTransactionException - if the transaction from which this instance was read is no longer usable

DeletedObjectException - if the object from which this instance was read no longer exists

adjust

public void adjust(long offset)

Adjust this counter's value by the specified amount.

Parameters:

offset - amount to add to counter

Throws:

StaleTransactionException - if the transaction from which this instance was read is no longer usable

DeletedObjectException - if the object from which this instance was read no longer exists

increment

public void increment()

Increment this counter's value by one.

Throws:

StaleTransactionException - if the transaction from which this instance was read is no longer usable

DeletedObjectException - if the object from which this instance was read no longer exists

decrement

public void decrement()

Decrement this counter's value by one.

Throws:

StaleTransactionException - if the transaction from which this instance was read is no longer usable

DeletedObjectException - if the object from which this instance was read no longer exists