org.codehaus.groovy.tools

Class RootLoader

java.lang.Object

java.lang.ClassLoader

java.security.SecureClassLoader

java.net.URLClassLoader

org.codehaus.groovy.tools.RootLoader

All Implemented Interfaces:

Closeable, AutoCloseable

public class RootLoader
extends URLClassLoader

This ClassLoader should be used as root of class loaders. Any RootLoader does have it's own classpath. When searching for a class or resource this classpath will be used. Parent Classloaders are ignored first. If a class or resource can't be found in the classpath of the RootLoader, then parent is checked.

Note: this is very against the normal behavior of classloaders. Normal is to first check parent and then look in the resources you gave this classloader.

It's possible to add urls to the classpath at runtime through addURL(URL).

Why using RootLoader? If you have to load classes with multiple classloaders and a classloader does know a class which depends on a class only a child of this loader does know, then you won't be able to load the class. To load the class the child is not allowed to redirect it's search for the class to the parent first. That way the child can load the class. If the child does not have all classes to do this, this fails of course.

For example:

       parentLoader   (has classpath: a.jar;c.jar)
           |
           |
       childLoader    (has classpath: a.jar;b.jar;c.jar)
 

class C (from c.jar) extends B (from b.jar) childLoader.find("C")

 --> parentLoader does know C.class, try to load it
 --> to load C.class it has to load B.class
 --> parentLoader is unable to find B.class in a.jar or c.jar
 --> NoClassDefFoundException!
 

if childLoader had tried to load the class by itself, there would be no problem. Changing childLoader to be a RootLoader instance will solve that problem.

Constructor Summary

Constructors

Constructor and Description
RootLoader(LoaderConfiguration lc) constructs a new RootLoader with a LoaderConfiguration object which holds the classpath
RootLoader(URL[] urls, ClassLoader parent) constructs a new RootLoader with a parent loader and an array of URLs as classpath

Method Summary

Modifier and Type	Method and Description
void	addURL(URL url) adds an url to the classpath of this classloader
protected Class	findClass(String name)
URL	getResource(String name) returns the URL of a resource, or null if it is not found
protected Class	loadClass(String name, boolean resolve) loads a class using the name of the class

Methods inherited from class java.net.URLClassLoader

close, definePackage, findResource, findResources, getPermissions, getResourceAsStream, getURLs, newInstance, newInstance

Methods inherited from class java.security.SecureClassLoader

defineClass, defineClass

Methods inherited from class java.lang.ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findLibrary, findLoadedClass, findSystemClass, getClassLoadingLock, getPackage, getPackages, getParent, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, registerAsParallelCapable, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RootLoader

public RootLoader(URL[] urls,
                  ClassLoader parent)

constructs a new RootLoader with a parent loader and an array of URLs as classpath

RootLoader

public RootLoader(LoaderConfiguration lc)

constructs a new RootLoader with a LoaderConfiguration object which holds the classpath

Method Detail

loadClass

protected Class loadClass(String name,
                          boolean resolve)
                   throws ClassNotFoundException

loads a class using the name of the class

Overrides:

loadClass in class ClassLoader

Throws:

ClassNotFoundException

getResource

public URL getResource(String name)

returns the URL of a resource, or null if it is not found

Overrides:

getResource in class ClassLoader

addURL

public void addURL(URL url)

adds an url to the classpath of this classloader

Overrides:

addURL in class URLClassLoader

findClass

protected Class findClass(String name)
                   throws ClassNotFoundException

Overrides:

findClass in class URLClassLoader

Throws:

ClassNotFoundException