I'm guessing that Class.newInstance()'s constructor call doesn't have a
caller on the stack. So log4j throws this exception because it can't
find it's caller. Looks like the convienient "LogManager.getLogger()"
can't be used in a component's constructor/static-init if that component
is going to be used as a gui bean. Sigh!
-ernie
On 2/26/22 1:15 PM, Ernie Rael wrote:
Hi all,
I'm looking at a problem between log4j and gui builder (not Matisse)
for someone.
NB13-rc3, jdk-17 (also fails with NB-12.2, jdk-15)
The following trivial and tiny NB project runs fine (for example under
the debugger).
https://github.com/bpangburn/swingset/files/8146641/GuiFormTest.zip
Comment out this line (log4j stuff) in the play.MyTextField
constructor and all is well.
final Logger logger = LogManager.getLogger();
One way to reproduce the problem (if it doesn't just happen). Open
NewJFrame.jav in the designer
ContextMenu: AddFromPalette > Beans > ChooseBean
enter: play.MyTextField
Get the exception seen at the end of this message. Seems that log4j is
doing something weird that NB detects as a problem (security manager?).
I took a quick look at CreationFactory.createDefaultInstance(Class) it
does a weird dance with classloaders (yes plural), but there's
CreationDescriptor cd = getDescriptor(cls);
...
Object instance = cd != null ?
cd.createDefaultInstance() :
cls.newInstance();
And I was hoping there would be a way to get some BeanInfo thing (I
don't really know about BeanInfo's) as the CreationDescriptor but I
didn't find anything like that. And I don't really think that's the
problem.
-ernie
This project was created with beanbinding plugin, but that's not
required to get the exception.
INFO [org.netbeans.modules.form.MetaComponentCreator]: Failed to
create an instance of play.MyTextField class.
The class itself was loaded, but instantiating failed.
This typically happens due to an exception in constructor/initializer
code, or failure in loading an additional class needed by the
component. Check the attached exception.
java.lang.UnsupportedOperationException: No class provided, and an
appropriate one cannot be found.
at
org.apache.logging.log4j.LogManager.callerClass(LogManager.java:573)
at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:598)
at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:585)
at play.MyTextField.<init>(MyTextField.java:15)
at
java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native
Method)
at
java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)
at
java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at
java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
at
java.base/java.lang.reflect.ReflectAccess.newInstance(ReflectAccess.java:128)
at
java.base/jdk.internal.reflect.ReflectionFactory.newInstance(ReflectionFactory.java:347)
at java.base/java.lang.Class.newInstance(Class.java:645)
at
org.netbeans.modules.form.CreationFactory.createDefaultInstance(CreationFactory.java:155)
at
org.netbeans.modules.form.RADComponent.createBeanInstance(RADComponent.java:227)
at
org.netbeans.modules.form.RADComponent.initInstance(RADComponent.java:166)
The above stack is consistent no matter how the exception is exactly
generated (RADComponent.initInstance) get called from multiple places.
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