5 Replies Latest reply on Mar 20, 2009 11:15 AM by buckmin.erdem.agaoglu.gmail.com

Map, new-Operator and In

nimo22 Mar 20, 2009 8:57 AM

In Seam, you should not instantiate a Object via the new-Operator. But what about this:

@In(required=false, create=true) @Out(required=false) private Map<String, String> myMap;

You see, I want seam to create a new Instance if no is available. But this does not work.

When I want to use my Map I get a NPE. For example, in the GUI:

<h:inputText value="#{myMap['test']} .../>

This returns:

value="#{myMap['test']}": Target Unreachable, identifier 'myMap' resolved to null

It works, only when I instantiate my Map with the new-Operator:

@In(required=false, create=true) @Out(required=false) private Map<String, String> myMap = new HashMap<String, String>();

But I have thougth, I should not use the new-Operator in SEAM. So what I make wrong?

1. Re: Map, new-Operator and In

oguzyalcin.oguzhanyalcin.gazi.edu.tr Mar 20, 2009 9:41 AM (in response to nimo22)
Could you please try the code below. Maybe seam tries to create an instance using ...myMap=new Map<String,String>; ...so in this situation it is impossible to create an instance.

@In(required=false, create=true) @Out(required=false) private HashMap<String, String> myMap;
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2. Re: Map, new-Operator and In

nimo22 Mar 20, 2009 10:13 AM (in response to nimo22)
I have tried it with HashMap

@In(required=false, create=true) @Out(required=false) private HashMap<String, String> myMap;

but the same failure occurs:

Caused by: javax.el.PropertyNotFoundException: /mySite.xhtml @111,79 value="#{myMap['test']}": Target Unreachable, identifier 'myMap' resolved to null

I solved it via new-Operator even Seam does not allow to use it.
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3. Re: Map, new-Operator and In

buckmin.erdem.agaoglu.gmail.com Mar 20, 2009 10:29 AM (in response to nimo22)

First of all, i am not much of a expert but @In(required=false, create=true) seems a little weird. By required=false you tell seam that if there is no var named myMap in any context, then it is not a problem. By create=true you tell seam if there is no var myMap, then it should try to create it.

i don't know the exact order but i think seam tries to create because of create=true but since there is no component definition for "myMap" it cant and gives no problem because of required=false. hence you get el exception.

i often use @Factory for non-javabean non-ejb context variable initialization. so if you have

@Factory("myMap")
public void initMyMap(){
    myMap = new HashMap<String, String>();
    // population of that map, or whatever
}

or

@Factory("myMap")
public Map<String, String> initMyMap(){
    // create map as you'd like or simply
    return new HashMap<String, String>();
}

seam will now how to initialize myMap.
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4. Re: Map, new-Operator and In

nimo22 Mar 20, 2009 10:58 AM (in response to nimo22)

I have done that also with a Factory all the time (which works), but I wanted to be conform with SEAM which does not allow the new-Operator.
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5. Re: Map, new-Operator and In

buckmin.erdem.agaoglu.gmail.com Mar 20, 2009 11:15 AM (in response to nimo22)

it only applies to @Name defined javabeans and ejbs. it is not restricted anyway, but if you create them with new-operator, seam is not able to manage them efficiently (you have to @Out them which will probably overwrite any configuration around @Name definition). but since List and Map like objects are not defined anywhere seam provides @Factory and @Unwrap components for that matter. more information.
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