psdi.server

Class SharedSpace

java.lang.Object

psdi.server.SharedSpace

public class SharedSpace
extends java.lang.Object

A shared space is an object that provides an object for two or more threads to rondezvous to exchnage data. The way in which objects indicate their interest in a particular piece of data is by using a common key known by the producer of the data and the consumer of the data. Objects can be placed in the shared space using the put(key) method. Another thread can attempt to get the object by using the get(key) method. If the desired data has not been placed in the shared space, at the time of the get(key) call, the caller will be blocked until the data is placed in the space. The caller can specify a maximum time for the get() call to wait for the data. The class is thread safe. Note that the order in which threads get the data from the space is not guarenteed. This is important when more than one thread is waiting on the same data. The first to be woken up (which is undefined) will get the data and remove it from the space, the other threads remain blocked until more data with the same key arrives.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	SharedSpace.Reaper Class that cleans up the space of expired data

Constructor Summary

Constructors

Constructor and Description
SharedSpace()

Method Summary

Methods

Modifier and Type	Method and Description
boolean	containsKey(java.lang.Object key) Does data for the specified key exist in the space at the current time ?
java.lang.Object	createKey() Creates a key that is unique for this space.
void	finalize()
java.lang.Object	get(java.lang.Object key) Get an object from the space.
java.lang.Object	get(java.lang.Object key, long timeout) Get and object from the space with the specified key.
void	put(java.lang.Object key, java.lang.Object data) Place an object in the space.
void	put(java.lang.Object key, java.lang.Object data, long time) Place an object in the space.
java.lang.String	toString() Only shows the entries in the space hashtable

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SharedSpace

public SharedSpace()

Method Detail

toString

public java.lang.String toString()

Only shows the entries in the space hashtable

Overrides:

toString in class java.lang.Object

put

public void put(java.lang.Object key,
       java.lang.Object data)

Place an object in the space.

put

public void put(java.lang.Object key,
       java.lang.Object data,
       long time)

Place an object in the space. The object remains available to others for the specified time. If the time expires, the data is removed. Time is specified in seconds.

get

public java.lang.Object get(java.lang.Object key)

Get an object from the space. If the object is not available, it will wait forever until the data arrives.

get

public java.lang.Object get(java.lang.Object key,
                   long timeout)

Get and object from the space with the specified key. The timeout specifies how long (in seconds) to wait before returning. If data did not arrive in the specified time out, null is returned. Due to the way that Java threading works, it is not guarenteed that the timeout time will not be exceeded as there may be a wait to reaquire the monitor lock for the synchronized method.

createKey

public java.lang.Object createKey()

Creates a key that is unique for this space.

containsKey

public boolean containsKey(java.lang.Object key)

Does data for the specified key exist in the space at the current time ?

finalize

public void finalize()
              throws java.lang.Throwable

Overrides:

finalize in class java.lang.Object

Throws:

java.lang.Throwable