net.jini.space

Interface JavaSpace

All Known Subinterfaces:

JavaSpace05

public interface JavaSpace

This interface is implemented by servers that export a JavaSpaces technology service. The operations in this interface are the public methods that all such spaces support.

Author:

Sun Microsystems, Inc.

See Also:

Entry

Field Summary

Fields

Modifier and Type	Field and Description
static long	NO_WAIT Wait for no time at all.

Method Summary

Modifier and Type	Method and Description
EventRegistration	notify(Entry tmpl, Transaction txn, RemoteEventListener listener, long lease, MarshalledObject handback) When entries are written that match this template notify the given listener with a RemoteEvent that includes the handback object.
Entry	read(Entry tmpl, Transaction txn, long timeout) Read any matching entry from the space, blocking until one exists.
Entry	readIfExists(Entry tmpl, Transaction txn, long timeout) Read any matching entry from the space, returning null if there is currently is none.
Entry	snapshot(Entry e) The process of serializing an entry for transmission to a JavaSpaces service will be identical if the same entry is used twice.
Entry	take(Entry tmpl, Transaction txn, long timeout) Take a matching entry from the space, waiting until one exists.
Entry	takeIfExists(Entry tmpl, Transaction txn, long timeout) Take a matching entry from the space, returning null if there is currently is none.
Lease	write(Entry entry, Transaction txn, long lease) Write a new entry into the space.

Field Detail

NO_WAIT

static final long NO_WAIT

Wait for no time at all. This is used as a timeout value in various read and take calls.

See Also:

read(net.jini.core.entry.Entry, net.jini.core.transaction.Transaction, long), readIfExists(net.jini.core.entry.Entry, net.jini.core.transaction.Transaction, long), take(net.jini.core.entry.Entry, net.jini.core.transaction.Transaction, long), takeIfExists(net.jini.core.entry.Entry, net.jini.core.transaction.Transaction, long), Constant Field Values

Method Detail

write

Lease write(Entry entry,
            Transaction txn,
            long lease)
     throws TransactionException,
            RemoteException

Write a new entry into the space.

Parameters:

entry - the entry to write

txn - the transaction object, if any, under which to perform the write

lease - the requested lease time, in milliseconds

Returns:

a lease for the entry that was written to the space

Throws:

TransactionException - if a transaction error occurs

RemoteException - if a communication error occurs

read

Entry read(Entry tmpl,
           Transaction txn,
           long timeout)
    throws UnusableEntryException,
           TransactionException,
           InterruptedException,
           RemoteException

Read any matching entry from the space, blocking until one exists. Return null if the timeout expires.

Parameters:

tmpl - The template used for matching. Matching is done against tmpl with null fields being wildcards ("match anything") other fields being values ("match exactly on the serialized form").

txn - The transaction (if any) under which to work.

timeout - How long the client is willing to wait for a transactionally proper matching entry. A timeout of NO_WAIT means to wait no time at all; this is equivalent to a wait of zero.

Returns:

a copy of the entry read from the space

Throws:

UnusableEntryException - if any serialized field of the entry being read cannot be deserialized for any reason

TransactionException - if a transaction error occurs

InterruptedException - if the thread in which the read occurs is interrupted

RemoteException - if a communication error occurs

IllegalArgumentException - if a negative timeout value is used

readIfExists

Entry readIfExists(Entry tmpl,
                   Transaction txn,
                   long timeout)
            throws UnusableEntryException,
                   TransactionException,
                   InterruptedException,
                   RemoteException

Read any matching entry from the space, returning null if there is currently is none. Matching and timeouts are done as in read, except that blocking in this call is done only if necessary to wait for transactional state to settle.

Parameters:

tmpl - The template used for matching. Matching is done against tmpl with null fields being wildcards ("match anything") other fields being values ("match exactly on the serialized form").

txn - The transaction (if any) under which to work.

timeout - How long the client is willing to wait for a transactionally proper matching entry. A timeout of NO_WAIT means to wait no time at all; this is equivalent to a wait of zero.

Returns:

a copy of the entry read from the space

Throws:

UnusableEntryException - if any serialized field of the entry being read cannot be deserialized for any reason

TransactionException - if a transaction error occurs

InterruptedException - if the thread in which the read occurs is interrupted

RemoteException - if a communication error occurs

IllegalArgumentException - if a negative timeout value is used

See Also:

read(net.jini.core.entry.Entry, net.jini.core.transaction.Transaction, long)

take

Entry take(Entry tmpl,
           Transaction txn,
           long timeout)
    throws UnusableEntryException,
           TransactionException,
           InterruptedException,
           RemoteException

Take a matching entry from the space, waiting until one exists. Matching is and timeout done as for read.

Parameters:

tmpl - The template used for matching. Matching is done against tmpl with null fields being wildcards ("match anything") other fields being values ("match exactly on the serialized form").

txn - The transaction (if any) under which to work.

timeout - How long the client is willing to wait for a transactionally proper matching entry. A timeout of NO_WAIT means to wait no time at all; this is equivalent to a wait of zero.

Returns:

the entry taken from the space

Throws:

UnusableEntryException - if any serialized field of the entry being read cannot be deserialized for any reason

TransactionException - if a transaction error occurs

InterruptedException - if the thread in which the take occurs is interrupted

RemoteException - if a communication error occurs

IllegalArgumentException - if a negative timeout value is used

See Also:

read(net.jini.core.entry.Entry, net.jini.core.transaction.Transaction, long)

takeIfExists

Entry takeIfExists(Entry tmpl,
                   Transaction txn,
                   long timeout)
            throws UnusableEntryException,
                   TransactionException,
                   InterruptedException,
                   RemoteException

Take a matching entry from the space, returning null if there is currently is none. Matching is and timeout done as for read, except that blocking in this call is done only if necessary to wait for transactional state to settle.

Parameters:

tmpl - The template used for matching. Matching is done against tmpl with null fields being wildcards ("match anything") other fields being values ("match exactly on the serialized form").

txn - The transaction (if any) under which to work.

timeout - How long the client is willing to wait for a transactionally proper matching entry. A timeout of NO_WAIT means to wait no time at all; this is equivalent to a wait of zero.

Returns:

the entry taken from the space

Throws:

UnusableEntryException - if any serialized field of the entry being read cannot be deserialized for any reason

TransactionException - if a transaction error occurs

InterruptedException - if the thread in which the take occurs is interrupted

RemoteException - if a communication error occurs

IllegalArgumentException - if a negative timeout value is used

See Also:

read(net.jini.core.entry.Entry, net.jini.core.transaction.Transaction, long)

notify

EventRegistration notify(Entry tmpl,
                         Transaction txn,
                         RemoteEventListener listener,
                         long lease,
                         MarshalledObject handback)
                  throws TransactionException,
                         RemoteException

When entries are written that match this template notify the given listener with a RemoteEvent that includes the handback object. Matching is done as for read.

Parameters:

tmpl - The template used for matching. Matching is done against tmpl with null fields being wildcards ("match anything") other fields being values ("match exactly on the serialized form").

txn - The transaction (if any) under which to work.

listener - The remote event listener to notify.

lease - the requested lease time, in milliseconds

handback - An object to send to the listener as part of the event notification.

Returns:

the event registration to the the registrant

Throws:

TransactionException - if a transaction error occurs

RemoteException - if a communication error occurs

IllegalArgumentException - if the lease time requested is not Lease.ANY and is negative

See Also:

read(net.jini.core.entry.Entry, net.jini.core.transaction.Transaction, long), EventRegistration

snapshot

Entry snapshot(Entry e)
        throws RemoteException

The process of serializing an entry for transmission to a JavaSpaces service will be identical if the same entry is used twice. This is most likely to be an issue with templates that are used repeatedly to search for entries with read or take. The client-side implementations of read and take cannot reasonably avoid this duplicated effort, since they have no efficient way of checking whether the same template is being used without intervening modification. The snapshot method gives the JavaSpaces service implementor a way to reduce the impact of repeated use of the same entry. Invoking snapshot with an Entry will return another Entry object that contains a snapshot of the original entry. Using the returned snapshot entry is equivalent to using the unmodified original entry in all operations on the same JavaSpaces service. Modifications to the original entry will not affect the snapshot. You can snapshot a null template; snapshot may or may not return null given a null template. The entry returned from snapshot will be guaranteed equivalent to the original unmodified object only when used with the space. Using the snapshot with any other JavaSpaces service will generate an IllegalArgumentException unless the other space can use it because of knowledge about the JavaSpaces service that generated the snapshot. The snapshot will be a different object from the original, may or may not have the same hash code, and equals may or may not return true when invoked with the original object, even if the original object is unmodified. A snapshot is guaranteed to work only within the virtual machine in which it was generated. If a snapshot is passed to another virtual machine (for example, in a parameter of an RMI call), using it--even with the same JavaSpaces service--may generate an IllegalArgumentException.

Parameters:

e - the entry to take a snapshot of.

Returns:

a snapshot of the entry.

Throws:

RemoteException - if a communication error occurs