Java Reference
In-Depth Information
You can get the parent class loader from the method
getParent
. If the
class loader's parent is the bootstrap class loader,
getParent
may return
null
.
Class loaders are an integral part of the security architecturesee "
Se-
class loader are checked operations that may throw a
SecurityException
.
The primary method of
ClassLoader
is
loadClass
:
public Class<?>
loadClass(String name)
tHRows ClassNotFoundException
Returns the
Class
object for the class with the specified binary
name, loading the class if necessary. If the class cannot be
loaded you will get a
ClassNotFoundException
.
The default implementation of
loadClass
, which is not usually overridden,
attempts to load a class as follows:
1.
It checks to see if the class has already been loaded by invoking
findLoadedClass
.
ClassLoader
maintains a table of
Class
objects for
all the classes loaded by the current class loader. If a class has
been previously loaded
findLoadedClass
will return the existing
Class
object.
2.
If the class has not been loaded it invokes
loadClass
on the parent
class loader. If the current class loader does not have a parent,
the bootstrap class loader is used.
3.
If the class still has not been loaded,
findClass
is invoked to locate
and load the class.
Note that the parent class loader is always given the chance to load the
class first; only if the bootstrap loader and the system class loader fail
to load a given class will your custom class loader be given the oppor-
tunity to do so. The implication is that your custom class loader must
search for classes in places that are different from those searched by
the system or bootstrap class loaders.
