org.apache.curator.framework.recipes.shared

Class SharedValue

java.lang.Object

org.apache.curator.framework.recipes.shared.SharedValue

All Implemented Interfaces:

Closeable, AutoCloseable, SharedValueReader

public class SharedValue
extends Object
implements Closeable, SharedValueReader

Manages a shared value. All clients watching the same path will have the up-to-date value (considering ZK's normal consistency guarantees).

Constructor Summary

Constructors

Constructor and Description
SharedValue(org.apache.curator.framework.CuratorFramework client, String path, byte[] seedValue)

Method Summary

Modifier and Type	Method and Description
void	close()
org.apache.curator.framework.listen.ListenerContainer<SharedValueListener>	getListenable() Returns the listenable
byte[]	getValue() Return the current value of the count
VersionedValue<byte[]>	getVersionedValue() Return the current version and value
void	setValue(byte[] newValue) Change the shared value value irrespective of its previous state
void	start() The shared value must be started before it can be used.
boolean	trySetValue(byte[] newValue) Deprecated. use trySetValue(VersionedValue, byte[]) for stronger atomicity guarantees. Even if this object's internal state is up-to-date, the caller has no way to ensure that they've read the most recently seen value.
boolean	trySetValue(VersionedValue<byte[]> previous, byte[] newValue) Changes the shared value only if its value has not changed since the version specified by newValue.

Methods inherited from class java.lang.Object

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

Constructor Detail

SharedValue

public SharedValue(org.apache.curator.framework.CuratorFramework client,
                   String path,
                   byte[] seedValue)

Parameters:

client - the client

path - the shared path - i.e. where the shared value is stored

seedValue - the initial value for the value if/f the path has not yet been created

Method Detail

getValue

public byte[] getValue()

Description copied from interface: SharedValueReader

Return the current value of the count

Specified by:

getValue in interface SharedValueReader

Returns:

count

getVersionedValue

public VersionedValue<byte[]> getVersionedValue()

Description copied from interface: SharedValueReader

Return the current version and value

Specified by:

getVersionedValue in interface SharedValueReader

Returns:

version/value

setValue

public void setValue(byte[] newValue)
              throws Exception

Change the shared value value irrespective of its previous state

Parameters:

newValue - new value

Throws:

Exception - ZK errors, interruptions, etc.

trySetValue

@Deprecated
public boolean trySetValue(byte[] newValue)
                                throws Exception

Deprecated. use trySetValue(VersionedValue, byte[]) for stronger atomicity guarantees. Even if this object's internal state is up-to-date, the caller has no way to ensure that they've read the most recently seen value.

Changes the shared value only if its value has not changed since this client last read it. If the value has changed, the value is not set and this client's view of the value is updated. i.e. if the value is not successful you can get the updated value by calling getValue().

Parameters:

newValue - the new value to attempt

Returns:

true if the change attempt was successful, false if not. If the change was not successful, getValue() will return the updated value

Throws:

Exception - ZK errors, interruptions, etc.

trySetValue

public boolean trySetValue(VersionedValue<byte[]> previous,
                           byte[] newValue)
                    throws Exception

Changes the shared value only if its value has not changed since the version specified by newValue. If the value has changed, the value is not set and this client's view of the value is updated. i.e. if the value is not successful you can get the updated value by calling getValue().

Parameters:

newValue - the new value to attempt

Returns:

true if the change attempt was successful, false if not. If the change was not successful, getValue() will return the updated value

Throws:

Exception - ZK errors, interruptions, etc.

getListenable

public org.apache.curator.framework.listen.ListenerContainer<SharedValueListener> getListenable()

Returns the listenable

Specified by:

getListenable in interface SharedValueReader

Returns:

listenable

start

public void start()
           throws Exception

The shared value must be started before it can be used. Call close() when you are finished with the shared value

Throws:

Exception - ZK errors, interruptions, etc.

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException