Re: entity beans within an Action
So would I have to do a setAttribute to store every session? Is there someway to uniquely identify each session by it's attribute name, or how is that often handled, since I think I'm going to have to give it a unique name for each setAttribute.? Thnxs for the responses. - Original Message - From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Tuesday, April 03, 2001 8:54 AM Subject: RE: entity beans within an Action > Hi Gary, > > To keep track of a stateful session bean (or any other object for that > matter) across multiple requests, you will need to store its reference in > the session using setAttribute(). You will also need to perform a check in > the Action each time a request is processed to see if that object already > exists- use getAttribute() and see if it returns null, and if so then create > it. I suppose there are other ways to do this, but this is probably the most > direct way to do it. Keep in mind that stateful session EJBs might be > overkill for what you are trying to accomplish. You could just gather input > and populate your same ActionForm using multiple input forms- then when the > last form is submitted write the changes to the entity EJB. You will still > need a session EJB to do this properly, with methods like saveUser() and > getUser(), but there is no need to make it stateful. You should consider > stateful if you need to write the changes after each input form is > completed- if you can't wait until the last page is submitted. > > Regarding the field-to-field copies from an ActionForm to an Entity bean. > This is the way I am doing things and it is working out nicely. Just make > sure you name your fields the same and use the Struts > PropertyUtils.copyProperties() method to do this work for you if possible. > It would work even better if copyProperties could make simple type > conversions :) Some may oppose this design- having the session EJB be aware > of the ActionForm- since it somewhat couples the presentation to business, > so if this bugs you then you could use an interface instead- let the session > EJB be aware of the interface instead of a specific ActionForm (more details > on this were posted by someone else a while back- last week I think). One > thing you should not do is perform the copy operations from within the > Action. Make sure you pass the entire data structure (i.e. the ActionForm) > to a session EJB and let the session EJB invoke all the setters/getters on > the entity EJB- either directly or via the Struts copy util. > > One short note on stateful session EJBs too... Some avoid using them for > performance reasons. If you are building a high demand site then you may > want to avoid using them. They can't be shared and pooled the same way > stateless beans can- just make sure you really understand the lifecycle > before you use them. I can't speak from personal experience on this, perhaps > someone else can, but this is just what I hear through the grapevine. I am > sure a lot depends on what EJB container you use as well. > > -Bob > > > > -----Original Message- > From: G.L. Grobe [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, April 03, 2001 1:43 AM > To: [EMAIL PROTECTED] > Subject: Re: entity beans within an Action > > > Comments and questions below. > > - Original Message - > From: <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Monday, April 02, 2001 10:23 PM > Subject: RE: entity beans within an Action > > > Creation of EJBs is really the job of the EJB container. The container > > manages the creation, passivation, destruction, etc... of the EJBs. When > you > > "create" an EJB from your Action for example, you are just asking the > > container for a reference. Of course there is some overhead with looking > up > > the bean's home interface and creating the stubs- but this should be > > negligible (compared with instantiation of the actual entity bean). > However, > > If you know that many requests within the same session will need access to > > the same entity bean(s), you could create a stateful session bean and keep > > track of its reference in the session. > > I have an Action that spans multiple pages. I have only one ActionForm class > to go w/ this Action for the multiple pages, so the user makes multiple > submits on the same ActionForm. > > This part I don't get. If I've done a lookup and gotten the reference of > this stateful session bean, how is that returned reference kept for the next > time the Action is called, afterall, the Action was destroyed. Must I do > another lookup everytime the Action is called to get the reference to the > session bean? I can
RE: entity beans within an Action
Hi Gary, To keep track of a stateful session bean (or any other object for that matter) across multiple requests, you will need to store its reference in the session using setAttribute(). You will also need to perform a check in the Action each time a request is processed to see if that object already exists- use getAttribute() and see if it returns null, and if so then create it. I suppose there are other ways to do this, but this is probably the most direct way to do it. Keep in mind that stateful session EJBs might be overkill for what you are trying to accomplish. You could just gather input and populate your same ActionForm using multiple input forms- then when the last form is submitted write the changes to the entity EJB. You will still need a session EJB to do this properly, with methods like saveUser() and getUser(), but there is no need to make it stateful. You should consider stateful if you need to write the changes after each input form is completed- if you can't wait until the last page is submitted. Regarding the field-to-field copies from an ActionForm to an Entity bean. This is the way I am doing things and it is working out nicely. Just make sure you name your fields the same and use the Struts PropertyUtils.copyProperties() method to do this work for you if possible. It would work even better if copyProperties could make simple type conversions :) Some may oppose this design- having the session EJB be aware of the ActionForm- since it somewhat couples the presentation to business, so if this bugs you then you could use an interface instead- let the session EJB be aware of the interface instead of a specific ActionForm (more details on this were posted by someone else a while back- last week I think). One thing you should not do is perform the copy operations from within the Action. Make sure you pass the entire data structure (i.e. the ActionForm) to a session EJB and let the session EJB invoke all the setters/getters on the entity EJB- either directly or via the Struts copy util. One short note on stateful session EJBs too... Some avoid using them for performance reasons. If you are building a high demand site then you may want to avoid using them. They can't be shared and pooled the same way stateless beans can- just make sure you really understand the lifecycle before you use them. I can't speak from personal experience on this, perhaps someone else can, but this is just what I hear through the grapevine. I am sure a lot depends on what EJB container you use as well. -Bob -Original Message- From: G.L. Grobe [mailto:[EMAIL PROTECTED]] Sent: Tuesday, April 03, 2001 1:43 AM To: [EMAIL PROTECTED] Subject: Re: entity beans within an Action Comments and questions below. - Original Message - From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, April 02, 2001 10:23 PM Subject: RE: entity beans within an Action > Creation of EJBs is really the job of the EJB container. The container > manages the creation, passivation, destruction, etc... of the EJBs. When you > "create" an EJB from your Action for example, you are just asking the > container for a reference. Of course there is some overhead with looking up > the bean's home interface and creating the stubs- but this should be > negligible (compared with instantiation of the actual entity bean). However, > If you know that many requests within the same session will need access to > the same entity bean(s), you could create a stateful session bean and keep > track of its reference in the session. I have an Action that spans multiple pages. I have only one ActionForm class to go w/ this Action for the multiple pages, so the user makes multiple submits on the same ActionForm. This part I don't get. If I've done a lookup and gotten the reference of this stateful session bean, how is that returned reference kept for the next time the Action is called, afterall, the Action was destroyed. Must I do another lookup everytime the Action is called to get the reference to the session bean? I can understand how the session bean itself can hold a reference to the entity bean, since the stateful session bean itself persists. Also, I guess as the last step in my conversation it's ok to do regular field-to-field copies of the ActionForm data into the entity bean. After writing all this out trying to explain it to you guys, I think I've just answered my question and am looking for a "yes, you're on the right track" or "no, it's usually done like this" kind of answer. I only need to lookup and create the entity bean at the very end of the session, all in one method, so after the session ends, my entity beans info will still be around for use for the backend servers part of my application. Now I'm just wondering where I'd put the business logic to handle those beans once they get status c
Re: entity beans within an Action
Comments and questions below. - Original Message - From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, April 02, 2001 10:23 PM Subject: RE: entity beans within an Action > Creation of EJBs is really the job of the EJB container. The container > manages the creation, passivation, destruction, etc... of the EJBs. When you > "create" an EJB from your Action for example, you are just asking the > container for a reference. Of course there is some overhead with looking up > the bean's home interface and creating the stubs- but this should be > negligible (compared with instantiation of the actual entity bean). However, > If you know that many requests within the same session will need access to > the same entity bean(s), you could create a stateful session bean and keep > track of its reference in the session. I have an Action that spans multiple pages. I have only one ActionForm class to go w/ this Action for the multiple pages, so the user makes multiple submits on the same ActionForm. This part I don't get. If I've done a lookup and gotten the reference of this stateful session bean, how is that returned reference kept for the next time the Action is called, afterall, the Action was destroyed. Must I do another lookup everytime the Action is called to get the reference to the session bean? I can understand how the session bean itself can hold a reference to the entity bean, since the stateful session bean itself persists. Also, I guess as the last step in my conversation it's ok to do regular field-to-field copies of the ActionForm data into the entity bean. After writing all this out trying to explain it to you guys, I think I've just answered my question and am looking for a "yes, you're on the right track" or "no, it's usually done like this" kind of answer. I only need to lookup and create the entity bean at the very end of the session, all in one method, so after the session ends, my entity beans info will still be around for use for the backend servers part of my application. Now I'm just wondering where I'd put the business logic to handle those beans once they get status changes from backend servers since I no longer have user Actions? It seems like there would be so many exampes of what I'm trying to do, but I've seen no full examples of *both* session beans implementing entity beans within an Action. (i.e. A user goes shopping (session) and puts is stuff in a cart (entity)). > From within the stateful session bean > you can create once and keep track of the entity beans and won't need to do > JNDI lookups, etc... for each request... At least that is the way I would do > it :) > > -Bob > > > > -Original Message- > From: G.L. Grobe [mailto:[EMAIL PROTECTED]] > Sent: Monday, April 02, 2001 7:12 PM > To: [EMAIL PROTECTED] > Subject: entity beans within an Action > > > If the life-span of an Action is only when that Action is being exec'd > (which is also where I implemented my session bean since it's life-span is > also not neccesary to hang around), where should entity beans be initialized > and populated by data held in the ActionForm bean? Seems if I init'd them > within the Action, I'd be creating a new Bean everytime it ran through that > Action, same w/ the session. Am I going about this wrong? > > Any help much appreciated. >
RE: entity beans within an Action
Creation of EJBs is really the job of the EJB container. The container manages the creation, passivation, destruction, etc... of the EJBs. When you "create" an EJB from your Action for example, you are just asking the container for a reference. Of course there is some overhead with looking up the bean's home interface and creating the stubs- but this should be negligible (compared with instantiation of the actual entity bean). However, If you know that many requests within the same session will need access to the same entity bean(s), you could create a stateful session bean and keep track of its reference in the session. From within the stateful session bean you can create once and keep track of the entity beans and won't need to do JNDI lookups, etc... for each request... At least that is the way I would do it :) -Bob -Original Message- From: G.L. Grobe [mailto:[EMAIL PROTECTED]] Sent: Monday, April 02, 2001 7:12 PM To: [EMAIL PROTECTED] Subject: entity beans within an Action If the life-span of an Action is only when that Action is being exec'd (which is also where I implemented my session bean since it's life-span is also not neccesary to hang around), where should entity beans be initialized and populated by data held in the ActionForm bean? Seems if I init'd them within the Action, I'd be creating a new Bean everytime it ran through that Action, same w/ the session. Am I going about this wrong? Any help much appreciated.
entity beans within an Action
If the life-span of an Action is only when that Action is being exec'd (which is also where I implemented my session bean since it's life-span is also not neccesary to hang around), where should entity beans be initialized and populated by data held in the ActionForm bean? Seems if I init'd them within the Action, I'd be creating a new Bean everytime it ran through that Action, same w/ the session. Am I going about this wrong? Any help much appreciated.
