reusable SessionBean

3 Message(s) by 2 Author(s) originally posted in java beans

From: Sascha Effert

Date: Friday, October 12, 2007

Hello,

I am writing a Metadata-Server for a Storage virtual

<jargon, architecture> (Via the technical term {virtual
	memory}, probably from the term "virtual image" in optics)
	1. Common alternative to {logical}; often used to refer to the
	artificial objects (like addressable {virtual memory} larger
	than physical memory) created by a computer system to help the
	system control access to shared resources.

	2. Simulated; performing the functions of something that isn't
	really there.  An imaginative child's doll may be a virtual
	playmate.

	Opposite of {real} or physical.

	[{Jargon File}]

	(1994-11-30)

isation using JBoss
4.2.1. There I have a cupple of physical

<jargon> The opposite of {logical} in its jargon sense.
	Compare {real}, {virtual}, and {transparent}.

	It is said that what you can touch and see is real; what you
	can see but not touch is virtual; what you can touch but not
	see is transparent; and what you can neither touch nor see is
	probably imaginary.

	(2001-10-26)

disk

<storage> 1. {magnetic disk}.

	2. {compact disc}.

	3. {optical disk}.

	Note: the american spelling, "disk", is normal for most
	computer disks whereas "compact disc", having come to
	computers via the audio world, is correctly spelled with a
	"c", indeed, this spelling is part of the CD standard.

	(1995-07-30)

s used to build a virtual
disk. There are EntityBeans for the the virtual disks and the physical
disk. Next there exists a SessionBean to be called by the storage

<storage> (Or "memory") A device into which data can be
	entered, in which they can be held, and from which they can be
	retrieved at a later time.

	(1995-12-24)

server

1. A program which provides some service to other ({client})
	programs.  The connection between client and server is
	normally by means of {message passing}, often over a
	{network}, and uses some {protocol} to encode the client's
	requests and the server's responses.  The server may run
	continuously (as a {daemon}), waiting for requests to arrive
	or it may be invoked by some higher level daemon which
	controls a number of specific servers ({inetd} on {Unix}).

	There are many servers associated with the {Internet}, such as
	those for {HTTP}, {Network File System}, {Network Information
	Service} (NIS), {Domain Name System} (DNS), {FTP}, {news},
	{finger}, {Network Time Protocol}.  On Unix, a long list can
	be found in /etc/services or in the {NIS} database "services".
	See {client-server}.

	2. A computer which provides some service for other computers
	connected to it via a network.  The most common example is a
	{file server} which has a local disk and services requests
	from remote clients to read and write files on that disk,
	often using {Sun}'s {Network File System} (NFS) {protocol} or
	{Novell Netware} on {PCs}.  Another common example is a {web
	server}.

	[{Jargon File}]

	(2003-12-29)

s
which decides which physical disk is to be used for a spcified area of the
virtual disk. The askes something like "On which physical Disk schall I
store

[probably from "main store"] In some varieties of Commonwealth
	hackish, the preferred synonym for {core}.  Thus, "bringing a
	program into store" means not that one is returning
	shrink-wrapped software but that a program is being {swap}ped
	in.

	[{Jargon File}]

block

1. <unit> A unit of data or memory, often, but not
	exclusively, on a {magnetic disk} or {magnetic tape}.

	Compare {record}, {sector}.

	(2000-07-17)

	2. <operating system> To delay or sit idle while waiting for
	something.

	Compare {busy-wait}.

	(2000-07-17)

	3. <programming> A delimited section of {source code} in a
	{block-structured} language.

	(2004-09-29)

1234 of Virtual Disk 9876?", the Session Bean initializes a
distribution

1. <software> A software source tree packaged for
	distribution; but see {kit}.

	2. <messaging> A vague term encompassing {mailing lists} and
	{Usenet} {newsgroups} (but not {BBS} {fora}); any
	topic-oriented message channel with multiple recipients.

	3. <messaging> An information-space domain (usually loosely
	correlated with geography) to which propagation of a {Usenet}
	message is restricted; a much-underused feature.

	[{Jargon File}]

algorithm

<algorithm, programming> A detailed sequence of actions to
	perform to accomplish some task.  Named after an Iranian
	mathematician, Al-Khawarizmi.

	Technically, an algorithm must reach a result after a {finite}
	number of steps, thus ruling out {brute force} search methods
	for certain problems, though some might claim that brute force
	search was also a valid (generic) algorithm.  The term is also
	used loosely for any sequence of actions (which may or may not
	terminate).

	{Paul E. Black's Dictionary of Algorithms, Data Structures,
	and Problems (http://www.nist.gov/dads/)}.

	(2002-02-05)

over the physical disks of the virtual disks and
sends back which physical disk is to be used.

Now my problem: The initalisation of the distribution algorithm takes much
time (up to some minutes). The distribution could be reused for every
request to a virtual disk if the instance

<programming> An individual {object} of a certain {class}.
	While a class is just the type definition, an actual usage of
	a class is called "instance".  Each instance of a class can
	have different values for its {instance variables}, i.e. its
	{state}.

	(1998-03-06)

could survive between calls. So I
want something like a hashtable where I can store for any virtual disk an
initialised instance of the distribution algorithm. Is there any way to do
this in JBoss? Or do you've any other suggestion what I can do?

tschau

Sascha Effert

From: efriedNoSpam

Date: Saturday, October 13, 2007

wrote in message:

Hello,
I am writing a Metadata-Server for a Storage virtualisation using JBoss
4.2.1. There I have a cupple of physical disks used to build a virtual
disk. There are EntityBeans for the the virtual disks and the physical
disk. Next there exists a SessionBean to be called by the storage servers
which decides which physical disk is to be used for a spcified area of the
virtual disk. The askes something like "On which physical Disk schall I
store block 1234 of Virtual Disk 9876?", the Session Bean initializes a
distribution algorithm over the physical disks of the virtual disks and
sends back which physical disk is to be used.
Now my problem: The initalisation of the distribution algorithm takes much
time (up to some minutes). The distribution could be reused for every
request to a virtual disk if the instance could survive between calls. So I
want something like a hashtable where I can store for any virtual disk an
initialised instance of the distribution algorithm. Is there any way to do
this in JBoss? Or do you've any other suggestion what I can do?
tschau
Sascha Effert

In the past, I had a static member of a SLSB and initialized it if null. This
may not be the best way now.

Someling like:

public class

1. <programming> The prototype for an {object} in an
	{object-oriented language}; analogous to a {derived type} in a
	{procedural language}.  A class may also be considered to be a
	set of objects which share a common structure and behaviour.
	The structure of a class is determined by the {class
	variables} which represent the {state} of an object of that
	class and the behaviour is given by a set of {methods}
	associated with the class.

	Classes are related in a {class hierarchy}.  One class may be
	a specialisation (a "{subclass}") of another (one of its
	"{superclasses}") or it may be composed of other classes or it
	may use other classes in a {client-server} relationship.  A
	class may be an {abstract class} or a {concrete class}.

	See also {signature}.

	2. <programming> See {type class}.

	3. <networking> One of three types of {Internet addresses}
	distinguished by their most significant bits.

	3. <language> A language developed by the {Andrew Project}.
	It was one of the first attempts to add {object-oriented}
	features to {C}.

	(1995-05-01)

MyBean implements SessionBean {
private static Hashtable data

<data, data processing, jargon> /day't*/ (Or "raw data")
	Numbers, {characters}, {images}, or other method of recording,
	in a form which can be assessed by a human or (especially)
	input into a {computer}, stored and {processed} there, or
	transmitted on some {digital channel}.  Computers nearly
	always represent data in {binary}.

	Data on its own has no meaning, only when interpreted by some
	kind of {data processing system} does it take on meaning and
	become {information}.

	People or computers can find patterns in data to perceive
	information, and information can be used to enhance
	{knowledge}.  Since knowledge is prerequisite to wisdom, we
	always want more data and information.  But, as modern
	societies verge on {information overload}, we especially need
	better ways to find patterns.

	1234567.89 is data.

	"Your bank balance has jumped 8087% to $1234567.89" is
	information.

	"Nobody owes me that much money" is knowledge.

	"I'd better talk to the bank before I spend it, because of
	what has happened to other people" is wisdom.

	(1999-04-30)

;

private void init ejbCreate() {
if (data == null)
initdata();
}
....
}

What you mightwant to look at is storing your data using JNDI and populate it
at the server startup. You shoul be able to inject it into your bean

<programming> A {component architecture} for the {Java}
	programming language, developed initially by {Sun}, but now
	available from several other vendors.  JavaBeans components
	are called "{beans}".

	JavaBeans allows developers to create reusable software
	components that can then be assembled together using visual
	application builder tools including {Sybase}'s {PowerJ},
	{Borland}'s {JBuilder}, {IBM}'s {Visual Age for Java},
	{SunSoft}'s {Java Workshop} and {Symantec}'s {Visual Cafe}.

	JavaBeans support Introspection (a builder tool can analyze
	how a Bean works), Customisation (developers can customise the
	appearance and behaviour of a Bean), Events (Beans can
	communicate), Properties (developers can customise and program
	with Beans(?)) and Persistence (customised Beans can be stored
	and reused).

	{Home (http://www.javasoft.com/beans/)}.

	(1997-11-20)

if using
EJB3.

Eric

From: Sascha Effert

Date: Monday, October 15, 2007

wrote in message:

In the past, I had a static member of a SLSB and initialized it if null.
This may not be the best way now.
Someling like:
public class MyBean implements SessionBean {
private static Hashtable data;
private void init ejbCreate() {
if (data == null)
initdata();
}
....
}
What you mightwant to look at is storing your data using JNDI and populate
it at the server startup. You shoul be able to inject it into your bean if
using EJB3.
Eric

Hi,

its so easy... I thought it isn't possible to use static fields in EJBs. I
will try it.

thanks a lot

Sascha Effert

Next Message: Toplink EJB and cascade persistence

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