[JBoss-user] EJB question
Hi all, In my session bean, i have reference to an instance of an entity bean. so, i lookup an instance of the home interface of the entity bean using the bean name or jndi name. The problem is that, with this approach, i have to hardcode the entity bean name or its jndi name within the session bean wich is, IMO, not a very good approach : if the referenced entity bean is deployed with a different name, the session bean directly crashes Any suggestions to avoid this? Does the spec provide some way for the session bean to know the deployed name of an entity bean it's referencing to? --hermann ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB question
You should declare a reference to the entity bean in the deployment descriptor, like this: session ... ejb-ref ejb-ref-nameejb/LogEventInfo/ejb-ref-name ejb-ref-typeEntity/ejb-ref-type homecom.trilogy.tbs.logging.LogEventInfoHome/home remotecom.trilogy.tbs.logging.LogEventInfo/remote ejb-linkLogEventInfo/ejb-link /ejb-ref /session This way, you will code your session bean so that it always does a lookup like: jndiCtx.lookup(java:comp/env/ejb/LogEventInfo); This way, if the entity bean is ever deployed with a different name, all you have to do is change the ejb-link tag to point to the new name. Alex |+-- || Hermann RANGAMANA | || [EMAIL PROTECTED] | || Sent by:| || [EMAIL PROTECTED]| || eforge.net | || | || | || 07/05/01 07:36 AM | || Please respond to jboss-user| || | |+-- ---| | | | To: [EMAIL PROTECTED] | | cc: | | Subject: [JBoss-user] EJB question | ---| Hi all, In my session bean, i have reference to an instance of an entity bean. so, i lookup an instance of the home interface of the entity bean using the bean name or jndi name. The problem is that, with this approach, i have to hardcode the entity bean name or its jndi name within the session bean wich is, IMO, not a very good approach : if the referenced entity bean is deployed with a different name, the session bean directly crashes Any suggestions to avoid this? Does the spec provide some way for the session bean to know the deployed name of an entity bean it's referencing to? --hermann ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB question
Yes, the ejb-link tag is the ejb-name of the referenced bean (as specified in another section of the deployment descriptor). The ejb-ref-name is the jndi name, relative to java:comp/env. Thus, perhaps a better example would have been: ejb-ref-nameejb/WhateverIWant/ejb-ref-name ... ejb-linkOtherEJBName/ejb-link and then in the code jndiCtx.lookup(java:comp/env/ejb/WhateverIWant) will return the home interface of the bean named OtherEJBName. Also note that the ejb/ prefix in the ejb-ref-name is not required, just suggested by the spec. |+-- || danch (Dan Christopherson)| || [EMAIL PROTECTED] | || Sent by:| || [EMAIL PROTECTED]| || eforge.net | || | || | || 07/05/01 02:23 PM | || Please respond to jboss-user| || | |+-- ---| | | | To: [EMAIL PROTECTED] | | cc: | | Subject: Re: [JBoss-user] EJB question | ---| I believe the ejb-link tag is the ejb-name, not necessarily the jndi-name for the bean. [EMAIL PROTECTED] wrote: You should declare a reference to the entity bean in the deployment descriptor, like this: session ... ejb-ref ejb-ref-nameejb/LogEventInfo/ejb-ref-name ejb-ref-typeEntity/ejb-ref-type homecom.trilogy.tbs.logging.LogEventInfoHome/home remotecom.trilogy.tbs.logging.LogEventInfo/remote ejb-linkLogEventInfo/ejb-link /ejb-ref /session This way, you will code your session bean so that it always does a lookup like: jndiCtx.lookup(java:comp/env/ejb/LogEventInfo); This way, if the entity bean is ever deployed with a different name, all you have to do is change the ejb-link tag to point to the new name. Alex ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB question
--On Tuesday, May 08, 2001 11:17 AM +0800 Ralph Jensen [EMAIL PROTECTED] wrote: As danch said: ejbCreate needs to know it, because it must return it, according to spec. What actually happens, if it doesn't? Beats me... In EJB 2.0, we return null, although I think that changed in the latest PFD. So I have never tried it. I was thinking of a function like sendContribution( Object content, clientID, somethingElse ); or possibly two: sendText( String text, clientID, ... ) and sendBinary( Object content, clientID, ... ) if I want to have different tables for text and non-text contributions. The question now is, where these methods should be located. If I understand you correctly, you say that's a session bean. Yes, its become accepted that session beans are generally used to create entity beans and manipulate them and otherwise hole business logic. Of course, there is nothing that stops you from using JDBC to access a database from a session bean if thats the best sollution for your app. Somebody has to create a conference. That is done by entering a record into a database, with fields like topic, starttime, endtime and other configurable items, plus a 'status' column that tells if the conference is in process or not. The collaborative session is then that one record represented by one entity bean. OK, I see. So you mean, the contribution methods would go into a session bean? The session bean would check, if the conference is in process by accessing above ConferenceBean, (then check some other stuff accessing some other beans ...) and THEN: write the contribution into a table without using an entity bean in order to circumvent the primary key issue, which started this discussion. Meaning, if I use and ejbCreate(...) method that ejbCreate needs to return the primary key, but I want the database to asign it and there is no portable way to get it into the bean. This would work. But I would recomend using BMP and dealing with the primary key/sequence issue in the entity bean. I was thinking of two contribution types because a participant can send either text or non-text. Having one contribution type seems to indicate that I each record needs to have columns for text and BLOBs while at any time only one will be used. Makes good sense. As I think about it, I guess all the types of contributions can probably be either binary data or textual data. So, your session bean would be handed the user id of the contributor and the contribution and told to make a new EB to represent the contribution. To make a new EJB representing the contribution created the problem in the first place. I would have to call ContributionHome.create(...) or so, which requires and ejbCreate(...), which needs to return the primary key. So I want to INSERT the contribution without using a bean. If I later need to list contributions I would of course use EJBs with custom finder methods. As we decided above, this would work, but my personal opinion is that two better options are 1) use an EB that uses BMP, or 2) use a unique key generator and not the database sequence type. But reasonable people can certianally disagree. I will use BMP for now. A good choice. Right, but again, for the purpose of creating the data I'd like to do it without an ejbCreate(...). Handling existing data would be done with beans. Yup, that will work. Why would I be tied to a database? All I need is that the database supports something like the autoincrement feature. I don't want to read the key back at creation time, and later I use custom finders with other fields. I just want to avoid the overhead from using multiple fields for the primary key (which is probably impossible anyway due to the nature of the data) or from creating a unique key, when the database can do it best. Well, I have worked mostly with PostgreSQL, MS SQL Server and Oracle. As I recall, all three had a different way of getting the value of the created serial field. But, as you say, your not interesting in reading that data back. I guess as long as your carefull with the BMP SQL, you'll not be tied to a database. Best of luck! Jim ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB question
For all that it's worth - I certainly appreciate this jBoss unrelated discussion and the help I received. There is a lot of expertise bundled in this newsgroup. Does anybody know of groups where these kind of discussions are on topic? I've tried the SUN discussion forums but that wasn't exciting. Ralph - Original Message - From: Jim Archer [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Thursday, May 10, 2001 3:57 AM Subject: Re: [JBoss-user] EJB question Best of luck! Jim ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
RE: [JBoss-user] EJB question
Hal, were you able to find the actual source for this? I searched and searched last week with no luck... Jim --On Friday, May 04, 2001 8:33 AM -0400 Deadman, Hal [EMAIL PROTECTED] wrote: Take a look at the key generator that comes with Exolab's Castor (open-source). http://castor.exolab.org/key-generator.html You probably want something like their HIGH/LOW generator. I haven't used it but I use a similiar technique that I wrote myself. I like their implementation better because they let you use different key gen techniques that you can specify in the config file without changing code. They offer a max+1 option which you should stay away from b/c I don't see how that could guarantee uniqueness. The castor high/low generator uses a database but it grabs a range of values with each db hit so you don't hit the db everytime. Hal -Original Message- From: Ralph Jensen [mailto:[EMAIL PROTECTED]] Sent: Friday, May 04, 2001 7:27 AM To: [EMAIL PROTECTED] Subject: Re: [JBoss-user] EJB question Thanks. But that is actually much more than I want. I only need a unique INT for primary keys. For the moment I will try this: In the sql-script: create table uniqueInteger( pk INTEGER constraint pk_unique primary key, uniqueID INTEGER ); insert into uniqueInteger VALUES( 1, 1 ); Then in the bean: SELECT uniqueID from uniqeInteger; save uniqueID in variable ( let's call it 'uniqueVar' ) then: UPDATE uniqueInteger SET uniqueID = uniqueVar+1 WHERE pk = 1; I think that's basically Vinay's suggestion. Does that look reasonable? That's a lot of database access to get a unique primary key, just to be able to return it from ejbCreate() - especially in light of the fact, that databases do it automatically, if the table is created accordingly. Isn't this kind of thing done regularly? I know this has nothing to do with jBoss. Thank you. :-) Ralph - Original Message - From: Jim Downing [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 5:47 PM Subject: Re: [JBoss-user] EJB question Check out www.activescript.co.uk for a non-free ($99) component to generate unique ids. The author has also posted the pattern on theserverside.com, so you have something to work to if you want to implement it yourself. jim - Original Message - From: Ralph Jensen [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 10:25 AM Subject: Re: [JBoss-user] EJB question The portability would be there in terms of data access. How to tell the database to autoincrement when I create a table is probably always database specific. Or not? I'm not good at SQL. So how would your suggestion look in code? What would the key generator bean look like? Off which table would it work? Ralph - Original Message - From: Vinay Menon [EMAIL PROTECTED] To: JBOSS [EMAIL PROTECTED] Sent: Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB question Why don't you just use a primary key generator bean to encapsulate the key genaration? The ejbCreate can then work off that ejb and assign the primary key field to the primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a different one and the primary key generator will work off that table. [Also makes sure that you have complete protability in terms of the database server!] Vinay - Original Message - From: Ralph Jensen Sent: Friday, May 04, 2001 8:52 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB question I asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key. That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating a table with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: How do I know that value in order to return it? Is that possible? Thanks Ralph Jensen ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-userbr clear=allhrGet your FREE download of MSN Explorer at a href=http://explorer.msn.com;http://explorer.msn.com/abr/p
Re: [JBoss-user] EJB question
- Original Message -
From: Jim Archer [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Monday, May 07, 2001 3:28 PM
Subject: Re: [JBoss-user] EJB question
Or, if you want a sollution thats free and lots easier, look at your java
SDK docs at java.rmi.server.UID class.
One of the major critisims of EJB as it currently exists is that it can't
take advantage of a databases serial or autoincrement field. Of
course,
these all vary from database to database anyhow, and EJB is not even tied
to a relational database.
That probably means that java.sql can't do it. Even if it could, that
wouldn't solve the problem with non-relational databases.
So using a primary key generator is a necessity if you can't create your
PK
from your data (maybe by combining other fields).
Good luck!
Jim
Actually, the original question came up in this context:
I am developing a collaborative application which stores the contributions
of participants in a database. These contributions could be text messages
or other objects, stored as blobs. None of the individual elements will be
useful as a primary key and thus I thought, why not let the database create
a unique key. My original question arose from the fact that an EJB needs to
know the primary key in order to return it and my assumption that I have to
call create(...) on an EJB in order to insert new data.
But I could also do it this way:
I have an EJB which represents one collaborative session - let's call it a
Conference. It represents a record in a table called conferenceTable. In
creation of this conference, all the issues discussed concerning uniqueness
of keys are relevant. But because I create that only once I may even
trouble the creator to enter a unique conference id. (Don't we all know it:
Your userid isnt unique. Try again. Suggestion: 'mk$rtio237k'. :-). Then,
during the session, participants will add a lot of information and that's
where I want to minimize the effort for creating unique keys.
I can add methods to my Conference bean like Conference.sendText( text,
client ) or Conference.sendOtherStuff( blob, client ) and then within these
methods do INSERTs into another table which hold the contributions of
participants, somehow like this:
Conference.sendText( text, client ){
...
t_stamp = System.currentTimeMillis();
INSERT INTO contributions( confID, text, client, timestamp ) VALUES
conferenceID, text, client, t_stamp );
...
}
That means my ConferenceBean - which represents a record from the
conferenceTable - INSERTs data into another table.
That table could be created with an AUTOINCREMENT (or similar, depending on
the database) for the primary key and thus primary keys are generated
transparently by the database during the INSERT. But I don't need to know
it, because the INSERT is not performed in an ejbCreate() method and
doesn't need to be returned.
(In reality I will probably write a second EJB, which participants can use
but which does not allow access to all fields of the Conference record.)
Does that sound reasonable or am I in for trouble somewhere else?
Ralph
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RE: [JBoss-user] EJB question
It looks like the code is in this distribution: ftp://ftp.exolab.org/pub/castor/castor_0.9.2/castor-0.9.2-src.zip from this page http://castor.exolab.org/download.html Look for *KeyGen*.java. I haven't had a chance to try to use it and I don't know if you can use it with CMP entity beans. Hal -Original Message- From: Jim Archer [mailto:[EMAIL PROTECTED]] Sent: Monday, May 07, 2001 3:30 AM To: [EMAIL PROTECTED] Subject: RE: [JBoss-user] EJB question Hal, were you able to find the actual source for this? I searched and searched last week with no luck... Jim --On Friday, May 04, 2001 8:33 AM -0400 Deadman, Hal [EMAIL PROTECTED] wrote: Take a look at the key generator that comes with Exolab's Castor (open-source). http://castor.exolab.org/key-generator.html You probably want something like their HIGH/LOW generator. I haven't used it but I use a similiar technique that I wrote myself. I like their implementation better because they let you use different key gen techniques that you can specify in the config file without changing code. They offer a max+1 option which you should stay away from b/c I don't see how that could guarantee uniqueness. The castor high/low generator uses a database but it grabs a range of values with each db hit so you don't hit the db everytime. Hal -Original Message- From: Ralph Jensen [mailto:[EMAIL PROTECTED]] Sent: Friday, May 04, 2001 7:27 AM To: [EMAIL PROTECTED] Subject: Re: [JBoss-user] EJB question Thanks. But that is actually much more than I want. I only need a unique INT for primary keys. For the moment I will try this: In the sql-script: create table uniqueInteger( pk INTEGER constraint pk_unique primary key, uniqueID INTEGER ); insert into uniqueInteger VALUES( 1, 1 ); Then in the bean: SELECT uniqueID from uniqeInteger; save uniqueID in variable ( let's call it 'uniqueVar' ) then: UPDATE uniqueInteger SET uniqueID = uniqueVar+1 WHERE pk = 1; I think that's basically Vinay's suggestion. Does that look reasonable? That's a lot of database access to get a unique primary key, just to be able to return it from ejbCreate() - especially in light of the fact, that databases do it automatically, if the table is created accordingly. Isn't this kind of thing done regularly? I know this has nothing to do with jBoss. Thank you. :-) Ralph - Original Message - From: Jim Downing [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 5:47 PM Subject: Re: [JBoss-user] EJB question Check out www.activescript.co.uk for a non-free ($99) component to generate unique ids. The author has also posted the pattern on theserverside.com, so you have something to work to if you want to implement it yourself. jim - Original Message - From: Ralph Jensen [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 10:25 AM Subject: Re: [JBoss-user] EJB question The portability would be there in terms of data access. How to tell the database to autoincrement when I create a table is probably always database specific. Or not? I'm not good at SQL. So how would your suggestion look in code? What would the key generator bean look like? Off which table would it work? Ralph - Original Message - From: Vinay Menon [EMAIL PROTECTED] To: JBOSS [EMAIL PROTECTED] Sent: Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB question Why don't you just use a primary key generator bean to encapsulate the key genaration? The ejbCreate can then work off that ejb and assign the primary key field to the primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a different one and the primary key generator will work off that table. [Also makes sure that you have complete protability in terms of the database server!] Vinay - Original Message - From: Ralph Jensen Sent: Friday, May 04, 2001 8:52 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB question I asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key. That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating a table with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable
Re: [JBoss-user] EJB question
Hi Ralph... --On Monday, May 07, 2001 4:36 PM +0800 Ralph Jensen [EMAIL PROTECTED] wrote: That probably means that java.sql can't do it. Even if it could, that wouldn't solve the problem with non-relational databases. Right. Actually, the original question came up in this context: I am developing a collaborative application which stores the contributions of participants in a database. These contributions could be text messages or other objects, stored as blobs. None of the individual elements will be useful as a primary key and thus I thought, why not let the database create a unique key. My original question arose from the fact that an EJB needs to know the primary key in order to return it and my assumption that I have to call create(...) on an EJB in order to insert new data. I'm not sure what you mean by the EJB needs to know the primark key to return it... All your entity beans need to have a primary key, but your home interface can have finder methods that don't need the primary key. If you have different people making contributions, then you are probably (my poor assumption) going to need a way to tell who made what? So you can search by the username field or something like that to get vack a COllection of all the entity beans that have that username. You can do this with ny field, of course, although I'm not exactly sure how it would work with a BLOB. But I could also do it this way: I have an EJB which represents one collaborative session - let's call it a I'm not sure what a collaborative session is - one record or many? I think you mean it would be a bunch of entity beans... Conference. It represents a record in a table called conferenceTable. In creation of this conference, all the issues discussed concerning uniqueness of keys are relevant. But because I create that only once I may even trouble the creator to enter a unique conference id. (Don't we all know it: Your userid isnt unique. Try again. Suggestion: 'mk$rtio237k'. :-). Then, during the session, participants will add a lot of information and that's where I want to minimize the effort for creating unique keys. I can add methods to my Conference bean like Conference.sendText( text, client ) or Conference.sendOtherStuff( blob, client ) and then within these methods do INSERTs into another table which hold the contributions of participants, somehow like this: First, the issue of an API for the other code. Generally, a good EJB design will use a session bean to access entity beans. Your busines logic would go into the session bean, so methods that create new data, manipulate existing data and so on would go here. This presents a nice API to the rest of the code that you can change the implementation of. So the session bean might have a method like sendText(text, client) Now, the issue of the data and how its related. It seems like you are talking about having two entity beans. One to represent the person (or client?) making the contribution. This EB might have fields to identify that person. Next, you have an EB to represent the contribution. This EB might have a field to home the contribution, like a BLOB field. It would be easy if you hade only one contributiun type, but if you have multiple types (text, binary) you may want to look at multiple EBs for each type. So, your session bean would be handed the user id of the contributor and the contribution and told to make a new EB to represent the contribution. You would then find the EB for the contributor, get its remote inteface (using a finder from its home object) and give the remote interfce to the contribution EB to relate the two. EJB 1.1 does not handle these things very well if your using CMP, but thats being fixed in EJB 2.0. That table could be created with an AUTOINCREMENT (or similar, depending on the database) for the primary key and thus primary keys are generated transparently by the database during the INSERT. But I don't need to know it, because the INSERT is not performed in an ejbCreate() method and doesn't need to be returned. Probably, you might want to look at using BMP for this contribution bean. Under BMP, you write all the database code with JDBC. When the bean is created the create method you wrote is called. You could create the record and let your database init the autoincrement field, then read it back. Also, you would handle the relationship using the PK rather than a serialized remote interface. But I would not recomend that at all. I would recomend that you use a unique key genertor to create your key. If you don't you'll be heavily tied to whatever database you write this for. The java.rmi.server.UID class will generate a unique key for the machine your using, and you can add the IP address for global uniqueness. If your just starting pout with this, you may want to look at EJB 2.0. The spec is not final yet, but its close. EJB 2.0 CMP has vastly improved support for
Re: [JBoss-user] EJB question
- Original Message - From: Jim Archer [EMAIL PROTECTED] To: [EMAIL PROTECTED] Cc: Ralph Jensen [EMAIL PROTECTED] Sent: Tuesday, May 08, 2001 4:03 AM Subject: Re: [JBoss-user] EJB question Hi Ralph... ... Actually, the original question came up in this context: I am developing a collaborative application which stores the contributions of participants in a database. These contributions could be text messages or other objects, stored as blobs. None of the individual elements will be useful as a primary key and thus I thought, why not let the database create a unique key. My original question arose from the fact that an EJB needs to know the primary key in order to return it and my assumption that I have to call create(...) on an EJB in order to insert new data. I'm not sure what you mean by the EJB needs to know the primark key to return it... All your entity beans need to have a primary key, but your home interface can have finder methods that don't need the primary key. As danch said: ejbCreate needs to know it, because it must return it, according to spec. What actually happens, if it doesn't? If you have different people making contributions, then you are probably (my poor assumption) going to need a way to tell who made what? So you can search by the username field or something like that to get vack a COllection of all the entity beans that have that username. I was thinking of a function like sendContribution( Object content, clientID, somethingElse ); or possibly two: sendText( String text, clientID, ... ) and sendBinary( Object content, clientID, ... ) if I want to have different tables for text and non-text contributions. The question now is, where these methods should be located. If I understand you correctly, you say that's a session bean. You can do this with ny field, of course, although I'm not exactly sure how it would work with a BLOB. The searching then would have to be done depending on the choice above. But I could also do it this way: I have an EJB which represents one collaborative session - let's call it a I'm not sure what a collaborative session is - one record or many? I think you mean it would be a bunch of entity beans... Somebody has to create a conference. That is done by entering a record into a database, with fields like topic, starttime, endtime and other configurable items, plus a 'status' column that tells if the conference is in process or not. The collaborative session is then that one record represented by one entity bean. Conference. It represents a record in a table called conferenceTable. ... I can add methods to my Conference bean like Conference.sendText( text, client ) or Conference.sendOtherStuff( blob, client ) and then within these methods do INSERTs into another table which hold the contributions of participants, somehow like this: I meant to add the one or two contribution methods to the above entity bean representing the conference. First, the issue of an API for the other code. Generally, a good EJB design will use a session bean to access entity beans. Your busines logic would go into the session bean, so methods that create new data, manipulate existing data and so on would go here. This presents a nice API to the rest of the code that you can change the implementation of. So the session bean might have a method like sendText(text, client) So you mean, the contribution methods would go into a session bean? The session bean would check, if the conference is in process by accessing above ConferenceBean, (then check some other stuff accessing some other beans ...) and THEN: write the contribution into a table without using an entity bean in order to circumvent the primary key issue, which started this discussion. Meaning, if I use and ejbCreate(...) method that ejbCreate needs to return the primary key, but I want the database to asign it and there is no portable way to get it into the bean. Now, the issue of the data and how its related. It seems like you are talking about having two entity beans. One to represent the person (or client?) making the contribution. This EB might have fields to identify that person. Next, you have an EB to represent the contribution. This EB might have a field to home the contribution, like a BLOB field. It would be easy if you hade only one contributiun type, but if you have multiple types (text, binary) you may want to look at multiple EBs for each type. I was thinking of two contribution types because a participant can send either text or non-text. Having one contribution type seems to indicate that I each record needs to have columns for text and BLOBs while at any time only one will be used. So, your session bean would be handed the user id of the contributor and the contribution and told to make a new EB to represent the contribution. To make a new EJB representing the contribution created the problem in the first place. I would
[JBoss-user] EJB question
I asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key. That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating a table with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: How do I know that value in order to return it? Is that possible? Thanks Ralph Jensen ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB question
Why don't you just use a primary key generator bean to encapsulate the key genaration? The ejbCreate can then work off that ejb and assign the primary key field tothe primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a different one and the primary key generator will work off that table. [Also makes sure that you have complete protability in terms of the database server!] Vinay - Original Message - From:Ralph Jensen Sent:Friday, May 04, 2001 8:52 AM To:[EMAIL PROTECTED] Subject:[JBoss-user] EJB question I asked this question elsewhere, but didn't get an answer. So:An entity bean's ejbCreate(...) method MUST return the primary key. That isnot a problem, if I specify the primary key myself and pass it to thecreate(...) method.But I want to let the database assign the primary key by creating a tablewith an AUTOINCREMENT default for the primary key column, like in thisexample using Cloudscape (part of SUN's J2EE v1.3):create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc.);Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' );The database then assigns a unique value to the id column of that newrecord.If I do this in the ejbCreate(...) method of my bean my problem is: How doI know that value in order to return it? Is that possible?ThanksRalph Jensen___JBoss-user mailing list[EMAIL PROTECTED]http://lists.sourceforge.net/lists/listinfo/jboss-user Get your FREE download of MSN Explorer at http://explorer.msn.com
RE: [JBoss-user] EJB question
I believe this is dependent upon the underlying database implementation. For instance, in Informix, if you have an autoincrement (called SERIAL type in Informix), you could make the function call DBINFO( 'sqlca.sqlerrd1' ) to get the last value of a serial type that was created by the database thread. There's probably a way to do this in the database you're using (I'm not familiar with Cloudscape). -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Ralph Jensen Sent: Friday, May 04, 2001 12:09 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB question I asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key. That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating a table with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: How do I know that value in order to return it? Is that possible? Thanks Ralph Jensen ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB question
The portability would be there in terms of data access. How to tell the database to autoincrement when I create a table is probably always database specific. Or not? I'm not good at SQL. So how would your suggestion look in code? What would the key generator bean look like? Off which table would it work? Ralph - Original Message - From: Vinay Menon [EMAIL PROTECTED] To: JBOSS [EMAIL PROTECTED] Sent: Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB question Why don't you just use a primary key generator bean to encapsulate the key genaration? The ejbCreate can then work off that ejb and assign the primary key field to the primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a different one and the primary key generator will work off that table. [Also makes sure that you have complete protability in terms of the database server!] Vinay - Original Message - From: Ralph Jensen Sent: Friday, May 04, 2001 8:52 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB question I asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key. That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating a table with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: How do I know that value in order to return it? Is that possible? Thanks Ralph Jensen ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-userbr clear=allhrGet your FREE download of MSN Explorer at a href=http://explorer.msn.com;http://explorer.msn.com/abr/p ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB question
Check out www.activescript.co.uk for a non-free ($99) component to generate unique ids. The author has also posted the pattern on theserverside.com, so you have something to work to if you want to implement it yourself. jim - Original Message - From: Ralph Jensen [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 10:25 AM Subject: Re: [JBoss-user] EJB question The portability would be there in terms of data access. How to tell the database to autoincrement when I create a table is probably always database specific. Or not? I'm not good at SQL. So how would your suggestion look in code? What would the key generator bean look like? Off which table would it work? Ralph - Original Message - From: Vinay Menon [EMAIL PROTECTED] To: JBOSS [EMAIL PROTECTED] Sent: Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB question Why don't you just use a primary key generator bean to encapsulate the key genaration? The ejbCreate can then work off that ejb and assign the primary key field to the primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a different one and the primary key generator will work off that table. [Also makes sure that you have complete protability in terms of the database server!] Vinay - Original Message - From: Ralph Jensen Sent: Friday, May 04, 2001 8:52 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB question I asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key. That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating a table with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: How do I know that value in order to return it? Is that possible? Thanks Ralph Jensen ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-userbr clear=allhrGet your FREE download of MSN Explorer at a href=http://explorer.msn.com;http://explorer.msn.com/abr/p ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB question
Thanks. But that is actually much more than I want. I only need a unique INT for primary keys. For the moment I will try this: In the sql-script: create table uniqueInteger( pk INTEGER constraint pk_unique primary key, uniqueID INTEGER ); insert into uniqueInteger VALUES( 1, 1 ); Then in the bean: SELECT uniqueID from uniqeInteger; save uniqueID in variable ( let's call it 'uniqueVar' ) then: UPDATE uniqueInteger SET uniqueID = uniqueVar+1 WHERE pk = 1; I think that's basically Vinay's suggestion. Does that look reasonable? That's a lot of database access to get a unique primary key, just to be able to return it from ejbCreate() - especially in light of the fact, that databases do it automatically, if the table is created accordingly. Isn't this kind of thing done regularly? I know this has nothing to do with jBoss. Thank you. :-) Ralph - Original Message - From: Jim Downing [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 5:47 PM Subject: Re: [JBoss-user] EJB question Check out www.activescript.co.uk for a non-free ($99) component to generate unique ids. The author has also posted the pattern on theserverside.com, so you have something to work to if you want to implement it yourself. jim - Original Message - From: Ralph Jensen [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 10:25 AM Subject: Re: [JBoss-user] EJB question The portability would be there in terms of data access. How to tell the database to autoincrement when I create a table is probably always database specific. Or not? I'm not good at SQL. So how would your suggestion look in code? What would the key generator bean look like? Off which table would it work? Ralph - Original Message - From: Vinay Menon [EMAIL PROTECTED] To: JBOSS [EMAIL PROTECTED] Sent: Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB question Why don't you just use a primary key generator bean to encapsulate the key genaration? The ejbCreate can then work off that ejb and assign the primary key field to the primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a different one and the primary key generator will work off that table. [Also makes sure that you have complete protability in terms of the database server!] Vinay - Original Message - From: Ralph Jensen Sent: Friday, May 04, 2001 8:52 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB question I asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key. That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating a table with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: How do I know that value in order to return it? Is that possible? Thanks Ralph Jensen ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-userbr clear=allhrGet your FREE download of MSN Explorer at a href=http://explorer.msn.com;http://explorer.msn.com/abr/p ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
RE: [JBoss-user] EJB question
Take a look at the key generator that comes with Exolab's Castor (open-source). http://castor.exolab.org/key-generator.html You probably want something like their HIGH/LOW generator. I haven't used it but I use a similiar technique that I wrote myself. I like their implementation better because they let you use different key gen techniques that you can specify in the config file without changing code. They offer a max+1 option which you should stay away from b/c I don't see how that could guarantee uniqueness. The castor high/low generator uses a database but it grabs a range of values with each db hit so you don't hit the db everytime. Hal -Original Message- From: Ralph Jensen [mailto:[EMAIL PROTECTED]] Sent: Friday, May 04, 2001 7:27 AM To: [EMAIL PROTECTED] Subject: Re: [JBoss-user] EJB question Thanks. But that is actually much more than I want. I only need a unique INT for primary keys. For the moment I will try this: In the sql-script: create table uniqueInteger( pk INTEGER constraint pk_unique primary key, uniqueID INTEGER ); insert into uniqueInteger VALUES( 1, 1 ); Then in the bean: SELECT uniqueID from uniqeInteger; save uniqueID in variable ( let's call it 'uniqueVar' ) then: UPDATE uniqueInteger SET uniqueID = uniqueVar+1 WHERE pk = 1; I think that's basically Vinay's suggestion. Does that look reasonable? That's a lot of database access to get a unique primary key, just to be able to return it from ejbCreate() - especially in light of the fact, that databases do it automatically, if the table is created accordingly. Isn't this kind of thing done regularly? I know this has nothing to do with jBoss. Thank you. :-) Ralph - Original Message - From: Jim Downing [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 5:47 PM Subject: Re: [JBoss-user] EJB question Check out www.activescript.co.uk for a non-free ($99) component to generate unique ids. The author has also posted the pattern on theserverside.com, so you have something to work to if you want to implement it yourself. jim - Original Message - From: Ralph Jensen [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 10:25 AM Subject: Re: [JBoss-user] EJB question The portability would be there in terms of data access. How to tell the database to autoincrement when I create a table is probably always database specific. Or not? I'm not good at SQL. So how would your suggestion look in code? What would the key generator bean look like? Off which table would it work? Ralph - Original Message - From: Vinay Menon [EMAIL PROTECTED] To: JBOSS [EMAIL PROTECTED] Sent: Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB question Why don't you just use a primary key generator bean to encapsulate the key genaration? The ejbCreate can then work off that ejb and assign the primary key field to the primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a different one and the primary key generator will work off that table. [Also makes sure that you have complete protability in terms of the database server!] Vinay - Original Message - From: Ralph Jensen Sent: Friday, May 04, 2001 8:52 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB question I asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key. That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating a table with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: How do I know that value in order to return it? Is that possible? Thanks Ralph Jensen ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-userbr clear=allhrGet your FREE download of MSN Explorer at a href=http://explorer.msn.com;http://explorer.msn.com/abr/p ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list
Re: [JBoss-user] EJB question
- Original Message - From: Ralph Jensen [EMAIL PROTECTED] For the moment I will try this: In the sql-script: create table uniqueInteger( pk INTEGER constraint pk_unique primary key, uniqueID INTEGER ); insert into uniqueInteger VALUES( 1, 1 ); Then in the bean: SELECT uniqueID from uniqeInteger; save uniqueID in variable ( let's call it 'uniqueVar' ) then: UPDATE uniqueInteger SET uniqueID = uniqueVar+1 WHERE pk = 1; I think that's basically Vinay's suggestion. Does that look reasonable? Nope. It doesn't handle concurrent access. Anytime you separate your read from your update you are open to concurrency issues. If you are going to take this route, you will have to obtain a table lock...which is going to be db specific. There is much discussion on this topic in most SQL books, and also on theserverside.com are a few threads. jim - Original Message - From: Jim Downing [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 5:47 PM Subject: Re: [JBoss-user] EJB question Check out www.activescript.co.uk for a non-free ($99) component to generate unique ids. The author has also posted the pattern on theserverside.com, so you have something to work to if you want to implement it yourself. jim - Original Message - From: Ralph Jensen [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 10:25 AM Subject: Re: [JBoss-user] EJB question The portability would be there in terms of data access. How to tell the database to autoincrement when I create a table is probably always database specific. Or not? I'm not good at SQL. So how would your suggestion look in code? What would the key generator bean look like? Off which table would it work? Ralph - Original Message - From: Vinay Menon [EMAIL PROTECTED] To: JBOSS [EMAIL PROTECTED] Sent: Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB question Why don't you just use a primary key generator bean to encapsulate the key genaration? The ejbCreate can then work off that ejb and assign the primary key field to the primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a different one and the primary key generator will work off that table. [Also makes sure that you have complete protability in terms of the database server!] Vinay - Original Message - From: Ralph Jensen Sent: Friday, May 04, 2001 8:52 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB question I asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key. That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating a table with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: How do I know that value in order to return it? Is that possible? Thanks Ralph Jensen ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-userbr clear=allhrGet your FREE download of MSN Explorer at a href=http://explorer.msn.com;http://explorer.msn.com/abr/p ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB question
Ralph, Just to add that the autoincrement needn't be database specific... your ejb could just have keyValue = keyValue+1; where keyValue maps to the underlying column in the database table. That way autoincrement is not database specific! If you want to use to the database specific primary key generation you could do so. regards. Vinay - Original Message - From:Ralph Jensen Sent:Friday, May 04, 2001 1:09 PM To:[EMAIL PROTECTED] Subject:Re: [JBoss-user] EJB question Thanks. But that is actually much more than I want. I only need a uniqueINT for primary keys.For the moment I will try this:In the sql-script:create table uniqueInteger( pk INTEGER constraint pk_unique primary key, uniqueID INTEGER);insert into uniqueInteger VALUES( 1, 1 );Then in the bean:SELECT uniqueID from uniqeInteger;save uniqueID in variable ( let's call it 'uniqueVar' )then:UPDATE uniqueInteger SET uniqueID = uniqueVar+1 WHERE pk = 1;I think that's basically Vinay's suggestion. Does that look reasonable?That's a lot of database access to get a unique primary key, just to beable to return it from ejbCreate() - especially in light of the fact, thatdatabases do it automatically, if the table is created accordingly. Isn'tthis kind of thing done regularly?I know this has nothing to do with jBoss. Thank you. :-)Ralph- Original Message -From: Jim Downing [EMAIL PROTECTED]To: [EMAIL PROTECTED]Sent: Friday, May 04, 2001 5:47 PMSubject: Re: [JBoss-user] EJB question Check out www.activescript.co.uk for a non-free ($99) component togenerate unique ids. The author has also posted the pattern on theserverside.com,so you have something to work to if you want to implement it yourself. jim - Original Message - From: "Ralph Jensen" [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 10:25 AM Subject: Re: [JBoss-user] EJB question The portability would be there in terms of data access. How to tell the database to autoincrement when I create a table is probably always database specific. Or not? I'm not good at SQL. So how would your suggestion look in code? Whatwould the key generator bean look like? Off which table would it work? Ralph - Original Message - From: Vinay Menon [EMAIL PROTECTED] To: JBOSS [EMAIL PROTECTED] Sent: Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB questionWhy don't you just use a primary key generator bean to encapsulate thekey genaration? The ejbCreate can then work off that ejb and assign the primary key field to the primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a differentone and the primary key generator will work off that table. [Also makessure that you have complete protability in terms of the database server!] Vinay - Original Message - From: Ralph Jensen Sent: Friday, May 04, 2001 8:52 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB questionI asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key.That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating atable with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: Howdo I know that value in order to return it? Is that possible? Thanks Ralph Jensen___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-userbr clear=allhrGet your FREE download of MSN Explorer at a href="http://explorer.msn.com"http://explorer.msn.com/abr/p ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user___JBoss-user mailing list[EMAIL PROTECTED]http://lists.sourceforge.net/lists/listinfo/jboss-user Get your FREE download of MSN Explorer at http://explorer.msn.com
RE: [JBoss-user] EJB question
I don't think this will
work unless you are willing to lock the entire table before you execute
this. Otherwise, you will have a race condition for the unique
key.
Jim
-Original Message-From:
[EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Vinay
MenonSent: Friday, May 04, 2001 2:21 PMTo:
JBOSSSubject: Re: [JBoss-user] EJB question
Ralph,
Just to add that the autoincrement needn't be database
specific... your ejb could just have
keyValue = keyValue+1;
where keyValue maps to the underlying column in the database
table.
That way autoincrement is not database specific! If you want to use to
the database specific primary key generation you could do so.
regards.
Vinay
- Original Message -
From:Ralph
Jensen
Sent:Friday, May 04, 2001 1:09
PM
To:[EMAIL PROTECTED]
Subject:Re: [JBoss-user] EJB
question
Thanks. But that is actually much more than I want. I only
need a uniqueINT for primary keys.For the moment I will try
this:In the sql-script:create table
uniqueInteger( pk INTEGER constraint pk_unique primary
key, uniqueID INTEGER);insert into
uniqueInteger VALUES( 1, 1 );Then in the bean:SELECT
uniqueID from uniqeInteger;save uniqueID in variable ( let's call it
'uniqueVar' )then:UPDATE uniqueInteger SET uniqueID =
uniqueVar+1 WHERE pk = 1;I think that's basically Vinay's
suggestion. Does that look reasonable?That's a lot of database access to
get a unique primary key, just to beable to return it from ejbCreate() -
especially in light of the fact, thatdatabases do it automatically, if
the table is created accordingly. Isn'tthis kind of thing done
regularly?I know this has nothing to do with jBoss. Thank
you. :-)Ralph- Original Message -From: Jim
Downing [EMAIL PROTECTED]To:
[EMAIL PROTECTED]Sent: Friday, May 04, 2001 5:47
PMSubject: Re: [JBoss-user] EJB question Check out
www.activescript.co.uk for a non-free ($99) component togenerate
unique ids. The author has also posted the pattern on
theserverside.com,so you have something to work to if you want
to implement it yourself. jim - Original
Message - From: "Ralph Jensen" [EMAIL PROTECTED]
To: [EMAIL PROTECTED] Sent: Friday, May 04,
2001 10:25 AM Subject: Re: [JBoss-user] EJB
question The portability would be there in
terms of data access. How to tell the database to autoincrement
when I create a table is probably always database
specific. Or not? I'm not good at SQL. So how
would your suggestion look in code? Whatwould the key
generator bean look like? Off which table would it work?
Ralph - Original Message
- From: Vinay Menon [EMAIL PROTECTED]
To: JBOSS [EMAIL PROTECTED] Sent:
Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB
questionWhy don't you just use a
primary key generator bean to encapsulate thekey
genaration? The ejbCreate can then work off that ejb and assign the
primary key field to the primary key generated field? so your
autoincrement essentially will not be on the same table as the
ejb but a differentone and the primary key generator will
work off that table. [Also makessure that you have complete
protability in terms of the database server!]
Vinay - Original
Message - From: Ralph Jensen Sent: Friday, May
04, 2001 8:52 AM To: [EMAIL PROTECTED]
Subject: [JBoss-user] EJB question
I asked this question elsewhere, but didn't get an answer. So:
An entity bean's ejbCreate(...) method MUST return the
primary key.That is not a problem, if I specify the
primary key myself and pass it to the create(...)
method. But I want to let the database assign the
primary key by creating atable with an AUTOINCREMENT
default for the primary key column, like in this example using
Cloudscape (part of SUN's J2EE v1.3): create table
myTable( id INT DEFAULT AUTOINCREMENT
CONSTRAINT pk_id PRIMARY KEY, someString
VARCHAR(6), etc. );
Then I can use INSERT like this:
INSERT INTO mytable ( someString ) VALUES ( 'Hello'
); The database then assigns a unique value to the
id column of that new record. If I do
this in the ejbCreate(...) method of my bean my problem is:
Howdo I know that value in order to return it? Is that
possible? Thanks Ralph
Jensen
___ JBoss-user
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Re: [JBoss-user] EJB question
Am assuming a. Number of inserts into a table is usually low as compared to reads and updates. b. Read is a fairly lightweight operation. All this is if portability is required! And needless to say there is a price to pay! Of course, do let me know you are aware of any other options. Vinay - Original Message - From:Jim Brownfield Sent:Saturday, May 05, 2001 12:02 AM To:[EMAIL PROTECTED] Subject:RE: [JBoss-user] EJB question I don't think this will work unless you are willing to lock the entire table before you execute this. Otherwise, you will have a race condition for the unique key. Jim -Original Message-From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Vinay MenonSent: Friday, May 04, 2001 2:21 PMTo: JBOSSSubject: Re: [JBoss-user] EJB question Ralph, Just to add that the autoincrement needn't be database specific... your ejb could just have keyValue = keyValue+1; where keyValue maps to the underlying column in the database table. That way autoincrement is not database specific! If you want to use to the database specific primary key generation you could do so. regards. Vinay - Original Message - From:Ralph Jensen Sent:Friday, May 04, 2001 1:09 PM To:[EMAIL PROTECTED] Subject:Re: [JBoss-user] EJB question Thanks. But that is actually much more than I want. I only need a uniqueINT for primary keys.For the moment I will try this:In the sql-script:create table uniqueInteger( pk INTEGER constraint pk_unique primary key, uniqueID INTEGER);insert into uniqueInteger VALUES( 1, 1 );Then in the bean:SELECT uniqueID from uniqeInteger;save uniqueID in variable ( let's call it 'uniqueVar' )then:UPDATE uniqueInteger SET uniqueID = uniqueVar+1 WHERE pk = 1;I think that's basically Vinay's suggestion. Does that look reasonable?That's a lot of database access to get a unique primary key, just to beable to return it from ejbCreate() - especially in light of the fact, thatdatabases do it automatically, if the table is created accordingly. Isn'tthis kind of thing done regularly?I know this has nothing to do with jBoss. Thank you. :-)Ralph- Original Message -From: Jim Downing [EMAIL PROTECTED]To: [EMAIL PROTECTED]Sent: Friday, May 04, 2001 5:47 PMSubject: Re: [JBoss-user] EJB question Check out www.activescript.co.uk for a non-free ($99) component togenerate unique ids. The author has also posted the pattern on theserverside.com,so you have something to work to if you want to implement it yourself. jim - Original Message - From: "Ralph Jensen" [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 04, 2001 10:25 AM Subject: Re: [JBoss-user] EJB question The portability would be there in terms of data access. How to tell the database to autoincrement when I create a table is probably always database specific. Or not? I'm not good at SQL. So how would your suggestion look in code? Whatwould the key generator bean look like? Off which table would it work? Ralph - Original Message - From: Vinay Menon [EMAIL PROTECTED] To: JBOSS [EMAIL PROTECTED] Sent: Friday, May 04, 2001 4:29 PM Subject: Re: [JBoss-user] EJB questionWhy don't you just use a primary key generator bean to encapsulate thekey genaration? The ejbCreate can then work off that ejb and assign the primary key field to the primary key generated field? so your autoincrement essentially will not be on the same table as the ejb but a differentone and the primary key generator will work off that table. [Also makessure that you have complete protability in terms of the database server!] Vinay - Original Message - From: Ralph Jensen Sent: Friday, May 04, 2001 8:52 AM To: [EMAIL PROTECTED] Subject: [JBoss-user] EJB questionI asked this question elsewhere, but didn't get an answer. So: An entity bean's ejbCreate(...) method MUST return the primary key.That is not a problem, if I specify the primary key myself and pass it to the create(...) method. But I want to let the database assign the primary key by creating atable with an AUTOINCREMENT default for the primary key column, like in this example using Cloudscape (part of SUN's J2EE v1.3): create table myTable( id INT DEFAULT AUTOINCREMENT CONSTRAINT pk_id PRIMARY KEY, someString VARCHAR(6), etc. ); Then I can use INSERT like this: INSERT INTO mytable ( someString ) VALUES ( 'Hello' ); The database then assigns a unique value to the id column of that new record. If I do this in the ejbCreate(...) method of my bean my problem is: Howdo I know that value in order to return it? Is that possible? Thanks Ralph Jensen___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-userbr clear=allhrGet your FREE download of MSN Explorer at a href="http://explorer.msn.com"http://explorer.msn.com/abr/p ___ JBoss-user mailing li
Re: [JBoss-user] EJB Question
Daniel Cardin wrote: I am definitely not an expert on that topic, but I'd like to add my comments :) For one, beans have the advantage of running in the context of the server. So you can assume that JBoss will manage security and transactions if you so desire. This by itself is already worth something, IMHO. Especially the transaction support. You have also access to all internal ressources like DataSources (not available outside the context of the server). As well, if your session bean (implementing business code) needs to use Entity beans, they could run within the same JVM. This sort of intra-JVM type of communication is optimized in JBoss, so that calls that would go through RMI are handled as normal method calls. (This is how I understand it... hope it's correct :)) Nearly as a normal method call. The spec dictates that the method calls always behave as though they're remote insofar as passing of references go. This can be turned off for performance reasons. If you use stateless session beans, code can be pooled and reused by the server to serve many clients in succession. Comparing this to a non-ejb helper that's used (for example) as a bean on a JSP page, you should save a lot of memory and garbage collection overhead. -danch ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] EJB Question
Hi, From a practical standpoint, usually entity beans have 'individual field' data access methods, and usually when you have a business process step, more than one field is affected. To get all the modifications in one transaction without jumping through external transaction control hoops and obviating the main reason you got an app server in the first place, put a method that does all the changes at once in a session bean. Automatically ( unless you mess with the transaction attributes of the methods) everything is in one transaction. From an architectural standpoint, the entity beans pretty much represent a data access layer, session beans expose a business process interface, the flow control outside the ejb container a presentation manager, and what actually makes the ui such as jsps a presentation layer. Mixing up any of these layers, such as exposing the data access interface to the presentation manager layer, means _much_ more difficulty when it comes time to extend or replace a layer. Hope this helps david jencks On 2001.04.26 16:17:56 -0400 Michael Hustler wrote: I have a general (and likely simple) question about EJB's - session beans in particular. What are the advantages of a stateless session bean over a non EJB helper class provided to clients. Thanks, -mike. ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
