sunlabs.brazil.template

Class QueueTemplate

public class QueueTemplate extends Template

Template class for Managing simple Queues, allowing text communication among sessions. The "name" attribute names the Q. When enqueueing messages, "name" is a white space separated list of queue recipients. When Dequeueing Messages, "name" is the recipient Queue.

The following tags are recognized.

This format is supported for backward compatibility with the old behavior. (Just in case the compatibility isn't quite right, see QueueTemplateOld).

Version: @(#)QueueTemplate.java 1.5 1.5

Author: Stephen Uhler

Nested Class Summary
static classQueueTemplate.Queue
Create an object queue.
static classQueueTemplate.QueueItem
A bag of items to keep on the Q.
Field Summary
static StringQ_ID
Method Summary
static QueueTemplate.QueueItemdequeue(String name, int timelimit)
Program access to the Q.
static voiddestroyQueue(String name)
Remove a Queue, freeing its resources.
static booleanenqueue(String to, String from, String message, String meta, boolean noCreate, boolean force)
Allow a message to be enqueued from java code.
static booleanenqueue(String to, String from, Dictionary data, boolean noCreate, boolean force)
Allow a message to be enqueued from java code.
static QueueTemplate.QueuegetQ(String name, boolean create)
Return a Q.
static QueueTemplate.QueuegetQ(String name)
voidtag_dequeue(RewriteContext hr)
Remove an item from the queue, and generate the appropriate properties.
voidtag_enqueue(RewriteContext hr)
Add a text message onto a named queue.
voidtag_queueinfo(RewriteContext hr)
Return info about the Q, and optionally clear or remove it.

Field Detail

Q_ID

public static final String Q_ID

Method Detail

dequeue

public static QueueTemplate.QueueItem dequeue(String name, int timelimit)
Program access to the Q.

Parameters: name; The name of the Q. A new Q will be created if it doesn't already exist. timelimit: how long (in ms) to wait before returning

Returns: The Queue item, or Null if no item is available.

destroyQueue

public static void destroyQueue(String name)
Remove a Queue, freeing its resources.

enqueue

public static boolean enqueue(String to, String from, String message, String meta, boolean noCreate, boolean force)

Deprecated:

Allow a message to be enqueued from java code. Use the {@link #enqueue(String to, String from, Dictionary data, boolean noCreate, boolean force)} method instead.

Parameters: to: The queue name from: The sender of the data message: The message to enqueue meta: The meta data, if any noCreate: If true, don't create a Q if it doesn't already exist force: Force item onto Q even if it is closed

Returns: True, if the data was enqueued

enqueue

public static boolean enqueue(String to, String from, Dictionary data, boolean noCreate, boolean force)
Allow a message to be enqueued from java code.

Parameters: to: The queue name (only a single q) from: The sender of the data data: a dictionary f name/value pairs noCreate: If true, don't create a Q if it doesn'a already exist force: Force item onto Q even if it is closed

Returns: True, if the data was enqueued

getQ

public static QueueTemplate.Queue getQ(String name, boolean create)
Return a Q. All calls to the session manager go through here, so we can reap old queues some day.

getQ

public static QueueTemplate.Queue getQ(String name)

tag_dequeue

public void tag_dequeue(RewriteContext hr)
Remove an item from the queue, and generate the appropriate properties. Attributes:
name
The name of the queue to examine
prepend
The prefix in the properties table to use to set the results. Defaults to our prefix.
timelimit
how long to wait for an item to appear, in sec. Defaults to 30.
If an item is retrieved, the following request properties are set (preceded by prepend):
age
Set how long the message has been q's (in seconds)
sent
Set the timestamp (in sec) of when the item was q'd.
items
Set the number of Q'd items.
from
Set the (unauthenticated) sender.
error
Something went wrong. Set an error message.
In addition, all name/value pairs send as part of the message will be set as well. (In prewvious versions of this template, that consists of "message" and (optionally) "meta".)

Note: this tag blocks until an item is received in the Queue (or a timelimit expires). As template processing is synchronized based on sessions, care should be taken to avoid blocking other (unrelated) session based requests while waiting on the queue.

tag_enqueue

public void tag_enqueue(RewriteContext hr)
Add a text message onto a named queue. Attributes:
- name: the name of the queue (required). "name" is a delim list of queues to send the data too.
- from: the sender name
- data: a set of property names to send as name/value pairs. If Names provided of the form nnn#vvv, then "vvv" is taken as the value to use if it is not already set, otherwise the empty string is used as the value.
- nocreate: If set, The item will not be Queued if the Q for that recipient does not already exist.
- force: put to the queue even if its closed
- delim: The delimiter character for the list of names. (It defaults to " " for backward compatibility with the previous behavior)

The property "count" contains the number of recipients for which the message was successfully Queued. The property "error.name" will contain an error message if Queueing failed. In both cases, the template prefix will be prepended. It is not considered an error condition for a message not to be delivered to a non existent Queue if "nocreate" is set.

The experimental attribute "glob" may be used instead of "name", in which case name is taken as the list of "delim" separated tokens named by the first wildcard substring of the matching glob pattern.

tag_queueinfo

public void tag_queueinfo(RewriteContext hr)
Return info about the Q, and optionally clear or remove it. If the queue doesn't already exist, it is created. Attributes:
name
The name of the queue to examine
prepend
The prefix in the properties table to use to set the results. Defaults to our prefix.
clear
If set, then clear the queue
remove
If set, then remove the queue
closed=[true|false]
set the closed state of the Q
create=[true|false]
Should the Q be created if it doesn't already exist (defaults to true).
The following request properties are set (preceded by prepend):
lastIn
The timestamp (ms) of the last Q insert attempt.
lastOut
The timestamp (ms) of the last Q retrieval attempt.
size
The number of items in the Q.
count
The total number of items inserted into the Q
created
The timestamp (in ms) of the Q's creation
expires
The Q's expiration period (in ms)
If the Q doesn't exist (e.g. create=false), then the property "error" is set.