Reflection on uninitialized fields

I did a quick test and found out that if you call get() on a Field to get its value and that field is not initialized, you get 0 for integers and null for objects. Is this something I can rely on in my program or are there JVMs for which the reflection mechanism can return garbage for uninitialized values? I want to check if the fields in some user-generated class are initialized.

Yes, they're all initialized to null/zero:
From the JLS: [4.12.5 Initial Values of Variables|http://java.sun.com/docs/books/jls/third_edition/html/typesValues.html#4.12.5]

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Hello Experts,
How can i reflect a new field (payment reference) in bank data while making payment through F-53?
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I tried it at both level,fsg anf posting key,But no use.
Is there any other process to make available and required field in BANK DATA of vendor payment?
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Regards,
Sumeya offrin

Hello Sumeya,
Please consider note 145864 which explains what you have to do to
make this field visible in your selection criteria:
"In Transaction FB00 (Financial Accounting Editing Options -> Open items
activate the flag 'Payment reference as selection criterion'.
This is valid for incoming payment; please test if the same procedure
is valid for outgoing payment as well.
I check the issue, and unfortunately these function seems to not be supported for vendor open items.
When you try to select the 'Payment Reference' in Additional selections
the following messages is arised:
'No account specified, items selected via document no. or reference'
That means,when you do not specify an account in F-53 you can only
via Reference and/or document. This is not a bug but system design.
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Reflecting a synchronized field

If I have a class which defines a synchronized field, and I use reflection to get the corresponding Field object, do the set and get methods of that Field object acquire the appropriate locks (on the object or class, depending on whether it is an instance or a static field) before setting and getting? I haven't found anything helpful here or via Google.

From the 1.4.2 JLS (I suspect little has changed)
8.3.1 Field Modifiers
FieldModifiers:
     FieldModifier
     FieldModifiers FieldModifier
FieldModifier: one of
     public protected private
     static final transient volatile
There is no synchronized keyword here. That modifying a field with synchronized does not cause the compiler to choke I don't know.
In response to the poster who said that the volatile modifier renders concurrent access to a field impossible, this is completely untrue. The volatile modifier tells the VM that a primitive value should always be stored in main memory and not in a Thread Local cache. This ensures that concurrent access of such variables is always done on the one "copy" available and not on a possibly out-of-synch version local to the Thread.
I am not certain if JLS and the VMS together enforce VM's to ensure that Object references are not cached although this would make sense. In any event it does not hurt performance if you make reference variables volatile because the actual Object is always to be found on the heap.

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Hello Experts,
I have a script that does some validation in the Field Data Edit Scripting context of the "Line Item" class, and I have "MATERIAL" as my target. when i try throwing an Application Exception in this context I get a reflection error message box instead of the message I have passed to the Application Exception constructor.
your help will be greatly appreciated.
kind regards,

One thing to be aware of is that no matter how you choose to construct your exception in field, field data edit and collection scripts, the attribute is always set to the be the taget field/collection. Have you noticed that? The script designers made things that way. What's going on here is that the exception raised in the Interprer is caught by the Script Manager and rethrown with the script target as the attribute and your raised exception as the exception.
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So, for your particular problem, you may want to rethink your strategy and see if you can get things to work for you bypassing that reflection issue. If you still can't raise the exception on MATERIAL, maybe you can raise it on another field, because another advantage of this approach is that you have full control to raise any error on any field on the Line Items.

Reflection and the field.set method

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this.getClass().getName()
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field.set(this, null)
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Class ClearParent can not access a member of class
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import java.lang.reflect.*;
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super();
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It is an instance of ClearChild that is being used so
that class name is ClearChild. However, the method
exists in the parent class and thus cannot act upon a
private field of another class (even if it happens to
be a subclass).Ahh...makes sense.
Why don't you just override clear in the child?We were trying to avoid this because we run into problems in the past of people adding fields to the class, but not adding to the clear, and things not being cleared properly.
I talked it over with the guys here and they have no problem making the fields protected instead of private. If it's protected, then the parent has access to it and my sample code works.
Thanks for your help KPSeal!
Jes

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I doubt anyone knows how but I'll try my luck. Is there an (+elegant+?) way of accessing private fields of superclass? My intention is something like the following
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import java.lang.reflect.Field;
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stefan.schulz wrote:
Well, getDeclaredField/getDeclaredFields return direct members of a class. You will have to ask the (proper) superclass for its private members.
For example:
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Dear SAP Gurus,
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Regards

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Re: BADI for Claims search in trade promotion management
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Regards,
Bhushan

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can u pls expond the procedure... )
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iMac Intel Duo-Core; Intel Mac mini single-core Mac OS X (10.4.6)
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How to track the change of an asset via field ANLC-KANSW?

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regards Bernhard
Edited by: Bernhard Kirchner on Nov 19, 2010 9:13 AM

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Reflection on uninitialized fields

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