I have a jsp page that lists all of my objects, say "students" for the sake of arguement
I want to have a form, where I can enter various information such as first name, last name, reference number etc, and to "search" based on the provided criteria, and display a list of results.
From a top level I know I need to do the following
1. Create a form containing all of the search fields
2. On my controller, take in this information and pass it through to the service layer
3. Service layer calls DAO with data and hopefully returns something
4. DAO layer should query to find the objects (this is the bit I'm stuck on)
5. Return all this (or null) back up the stack and redirect to results page
I'm using JPA, with a hibernate implemenation (also using Spring and StripesMVC)
Would it be best, when doing this search, to initialise a "dummy" student domain object, populate the fields from the form, and try to query this?
I'm not asking anyone to do this for me, I would just like some pointers as to where to start. Is there functionality provided by JPA to do what I'm after? Am I on the right lines?
I will now go and read JPA api docs and see what I can find
What's up, J.
Keep in mind that this is just my opinion, ok?
I'd say that depends of the amount of queries you want to perform in an entity. In my opinion, one of the best way to search objects is using NamedQueries. You can type a name for it and a query in JPQL (not very different from SQL). Than, in your DAO, you would create that NamedQuery and get the result.
Something like this
In your DAO, you can have something like this:
Of course, this is a very resumed version of the code. I omitted great part of it. Checkout this doc for more details. In my opinion, it's the best documentation for JPA.
There's other ways to do it. You can create only the JPQL and store it in a class and, when you need it, you can get that JPQL sentence. I don't recommend for you to do only one thing: don't ever write the JPQL code in a class like a DAO. It's very nice to find all the queries in a class (or in the class that refers to that entity or something like that). Another thing you should study is Criteria.
About the 'flow' you said, I guess it's ok. I'd just add a few throws exceptions with the message to present in the screen. Something like... "Oh, we don't have an entity with that name.".
By the way, I'm sorry my english. It's late in Brazil and I'm tired =) Bad day at the office.