java.net
public class URLClassLoader extends SecureClassLoader
URLs this class
loader will retrieve classes and resources by fetching them from
possible remote locations. Each URL is searched in
order in which it was added. If the file portion of the
URL ends with a '/' character then it is interpreted
as a base directory, otherwise it is interpreted as a jar file from
which the classes/resources are resolved.
New instances can be created by two static
newInstance() methods or by three public
contructors. Both ways give the option to supply an initial array
of URLs and (optionally) a parent classloader (that is
different from the standard system class loader).
Normally creating a URLClassLoader throws a
SecurityException if a SecurityManager is
installed and the checkCreateClassLoader() method does
not return true. But the newInstance() methods may be
used by any code as long as it has permission to acces the given
URLs. URLClassLoaders created by the
newInstance() methods also explicitly call the
checkPackageAccess() method of
SecurityManager if one is installed before trying to
load a class. Note that only subclasses of
URLClassLoader can add new URLs after the
URLClassLoader had been created. But it is always possible to get
an array of all URLs that the class loader uses to resolve classes
and resources by way of the getURLs() method.
Open issues:
definePackage() and sealing work
precisely?newInstance() but do we have to use it in more
places?URLStreamHandlers has not been tested.Since: 1.2
| Constructor Summary | |
|---|---|
| URLClassLoader(URL[] urls)
Creates a URLClassLoader that gets classes from the supplied URLs.
| |
| URLClassLoader(URL[] urls, ClassLoader parent)
Creates a URLClassLoader that gets classes from the supplied
URLs.
| |
| URLClassLoader(URL[] urls, ClassLoader parent, URLStreamHandlerFactory factory)
Creates a URLClassLoader that gets classes from the supplied URLs.
| |
| Method Summary | |
|---|---|
| protected void | addURL(URL newUrl)
Adds a new location to the end of the internal URL store. |
| protected Package | definePackage(String name, Manifest manifest, URL url)
Defines a Package based on the given name and the supplied manifest
information. |
| protected Class<?> | findClass(String className)
Finds (the first) class by name from one of the locations. |
| URL | findResource(String resourceName)
Finds the first occurrence of a resource that can be found.
|
| Enumeration<URL> | findResources(String resourceName)
Finds all the resources with a particular name from all the locations.
|
| protected PermissionCollection | getPermissions(CodeSource source)
Returns the permissions needed to access a particular code
source. |
| URL[] | getURLs()
Returns all the locations that this class loader currently uses the
resolve classes and resource. |
| static URLClassLoader | newInstance(URL[] urls)
Creates a new instance of a URLClassLoader that gets
classes from the supplied URLs. |
| static URLClassLoader | newInstance(URL[] urls, ClassLoader parent)
Creates a new instance of a URLClassLoader that gets
classes from the supplied URLs and with the supplied
loader as parent class loader.
|
| String | toString()
Returns a String representation of this URLClassLoader giving the
actual Class name, the URLs that are searched and the parent
ClassLoader. |
SecureClassLoader) is called first, which
can throw a SecurityException. Then the supplied URLs are added
in the order given to the URLClassLoader which uses these URLs to
load classes and resources (after using the default parent ClassLoader).
Parameters: urls Locations that should be searched by this ClassLoader when resolving Classes or Resources.
Throws: SecurityException if the SecurityManager disallows the creation of a ClassLoader.
See Also: SecureClassLoader
URLClassLoader that gets classes from the supplied
URLs.
To determine if this classloader may be created the constructor of
the super class (SecureClassLoader) is called first, which
can throw a SecurityException. Then the supplied URLs are added
in the order given to the URLClassLoader which uses these URLs to
load classes and resources (after using the supplied parent ClassLoader).Parameters: urls Locations that should be searched by this ClassLoader when resolving Classes or Resources. parent The parent class loader used before trying this class loader.
Throws: SecurityException if the SecurityManager disallows the creation of a ClassLoader. SecurityException
See Also: SecureClassLoader
SecureClassLoader) is called first, which
can throw a SecurityException. Then the supplied URLs are added
in the order given to the URLClassLoader which uses these URLs to
load classes and resources (after using the supplied parent ClassLoader).
It will use the supplied URLStreamHandlerFactory to get the
protocol handlers of the supplied URLs.Parameters: urls Locations that should be searched by this ClassLoader when resolving Classes or Resources. parent The parent class loader used before trying this class loader. factory Used to get the protocol handler for the URLs.
Throws: SecurityException if the SecurityManager disallows the creation of a ClassLoader. SecurityException
See Also: SecureClassLoader
Parameters: newUrl the location to add
Parameters: name The name of the package manifest The manifest describing the specification, implementation and sealing details of the package url the code source url to seal the package
Returns: the defined Package
Throws: IllegalArgumentException If this package name already exists in this class loader
Parameters: className the classname to find
Returns: a Class object representing the found class
Throws: ClassNotFoundException when the class could not be found or loaded
Parameters: resourceName the resource name to look for
Returns: the URL if found, null otherwise
Parameters: resourceName the name of the resource to lookup
Returns: a (possible empty) enumeration of URLs where the resource can be found
Throws: IOException when an error occurs accessing one of the locations
SecureClassLoader.getPermissions() and the actual
permissions to access the objects referenced by the URL of the
code source. The extra permissions added depend on the protocol
and file portion of the URL in the code source. If the URL has
the "file" protocol ends with a '/' character then it must be a
directory and a file Permission to read everything in that
directory and all subdirectories is added. If the URL had the
"file" protocol and doesn't end with a '/' character then it must
be a normal file and a file permission to read that file is
added. If the URL has any other protocol then a
socket permission to connect and accept connections from the host
portion of the URL is added.
Parameters: source The codesource that needs the permissions to be accessed
Returns: the collection of permissions needed to access the code resource
See Also: getPermissions
Returns: All the currently used URLs
URLClassLoader that gets
classes from the supplied URLs. This class loader
will have as parent the standard system class loader.
Parameters: urls the initial URLs used to resolve classes and resources
Returns: the class loader
Throws: SecurityException when the calling code does not have
permission to access the given URLs
URLClassLoader that gets
classes from the supplied URLs and with the supplied
loader as parent class loader.
Parameters: urls the initial URLs used to resolve classes and resources parent the parent class loader
Returns: the class loader
Throws: SecurityException when the calling code does not have
permission to access the given URLs