Re: Extensions

From:

Thomas Fritsch <i.dont.like.spam@invalid.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 14 Jun 2007 10:55:58 GMT

Message-ID:

<newscache$a1hmjj$y9h$1@news.ops.de>

Click wrote:

try
{
     CExtClassLoader loader=new CExtClassLoader(extPath);
     Class c=Class.forName(extName, false, loader);
     CEditExtension object = (CEditExtension)c.newInstance();
     return object;
}
catch (LinkageError e)
{...}
catch (ClassNotFoundException e)
{...}
catch (InstantiationException e)
{...}
catch (IllegalAccessException e)
{...}

If you write
  catch (IllegalAccessException e) {
    e.printStackTrace();
  }
what exactly do get ?

My class loader locates the class file in the extension folder, creates a
byte array and calls defineClass as explained in the javadoc. It
successfully loads the file.

The problem is that I have a IllegalAccessException in the Class.forName
method. I do not know why. The doc on this exception says :

"An IllegalAccessException is thrown when an application tries to
reflectively create an instance (other than an array), set or get a field,
or invoke a method, but the currently executing method does not have
access to the definition of the specified class, field, method or
constructor."
So obviously, it does not find something when instanciating my extension.
It is true that the extension imports some of the packages defined in my
main project. But it compiles fine (as soon as I declared the jar file as
a library).

What am I doing wrong?

The API doc at
<http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Class.html#newInstance()>
says:
"IllegalAccessException - if the class or its nullary constructor is not
accessible."
Therefore I would guess that
(1) your class doesn't not have a no-arguments constructor
or (2) your class does have that constructor, but it is not public

--
Thomas