Two questions
1) How can I get sysinfo if Derby is loaded in a custom Class Loader?
2) Will DERBY-668 mean that it won't print the right information
anyway, even if I get the coding right?
Below are some details.
I have a custom ClassLoader DerbyURLClassLoader and am trying to add a
getSysinfo method to access sysinfo based on the version loaded. The
code below does not work because the constructor for sysinfo is not
public. I could not see how to access the static method with reflection
without instantiating the class and I think need to use reflection so
that it gets loaded from the right place.
getSysinfo method in DerbyURLClassLoader:
/**
* Print sysinfo. Any exceptions will go to out and not be thrown
* like in sysinfo's getInfo method
*
* @param out PrintWriter for sysinfo output
*/
public void getSysinfo(PrintWriter out)
{
try {
System.out.println("printSysinfo");
Object mysysinfo =
loadClass("org.apache.derby.tools.sysinfo").newInstance();
Class[] argType = {PrintWriter.class};
Object[] args = new Object[] { out};
Method sh = mysysinfo.getClass().getMethod("getInfo",argType);
sh.invoke(mysysinfo,args);
} catch (Exception e)
{
out.println("Unexpected exception printing sysinfo");
e.printStackTrace(out);
}
}
calling code:
DerbyURLClassLoader loader1 =new DerbyURLClassLoader(urls);
loader1.getSysinfo(new PrintWriter(System.out,true));
Exception that occurs because sysinfo constructor is not public.
Unexpected exception printing sysinfo
java.lang.IllegalAccessException: Class DerbyURLClassLoader can not
access a member of class org.apache.derby.tools.sysinfo with modifiers
"private"
at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:57)
at java.lang.Class.newInstance0(Class.java:302)
at java.lang.Class.newInstance(Class.java:261)
at DerbyURLClassLoader.getSysinfo(DerbyURLClassLoader.java:86)
at DerbyLoaderApp.main(DerbyLoaderApp.java:32)
Possible workarounds I thought might work but haven't tried
1) Extend sysinfo and provide a constructor.
2) Create a DerbyUtil class that is instantiated in the loader and make
a getSysinfo method that would then (hopefully) load things from the
right place.
Neither solution seemed right to me, so I thought I would ask.
Kathey
