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How to get one instance of list using select statement in EJB 3 and JSF

Answer 1

+1 A:

Try using getSingleResult method and get your "retrieveAllAbout" method to return "About" object instead of List. In case there are more rows in database and you are trying to get the first one use getFirstResult. Otherwise you would have to be more specific when defining the query.

javax.persistence.Query

cbaby 2010-10-04 00:55:35

i try using getSingleResult method but not work for me, in JSF ManagedBean i create new instance in constructor of JSF Manage bean sample `public Constructor(){ About = new About(statelessbean.retreiveAllAbout)}` in about entity i create constructor sample `public About(String value){ this.value = value}` please help me

MYE 2010-10-04 01:39:44

@MYE: About is not a String, so your constructor is never getting called. Besides, there is no need to call a constructor. In Java all variables are passed by value, but all object variables are actually references. There are a few things wrong with your code: "About" is your class name and therefor cannot be used as a variable; There is no need to call a constructor as your function is returning an object reference. So your code should look something like this: public Constructor(){ about = statelessbean.retriveAllAbout;}. You need to have default constructor in your bean.

cbaby 2010-10-04 08:51:49

@MYE: changing `getResultList()` to `getFirstResult()` in the code as you posted in the question will work. If you'd like to call it only once, use `@PostConstruct`, because `em` is not yet injected when constructed is called. If still in vain, ask a new question. This is unrelated to the problem as in the current question.

BalusC 2010-10-06 03:00:08

thank two you i can do it :D but i have new question i will post it , please help me :D with new question

MYE 2010-10-06 12:02:01

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How to get one instance of list using select statement in EJB 3 and JSF

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