Package 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:
java.io.Closeable, java.lang.AutoCloseable
public class RootLoader
extends java.net.URLClassLoader
This ClassLoader should be used as root of class loaders. Any RootLoader does have its 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 its 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 Description
    RootLoader​(java.lang.ClassLoader parent)
    constructs a new RootLoader without classpath
    RootLoader​(java.net.URL[] urls, java.lang.ClassLoader parent)
    constructs a new RootLoader with a parent loader and an array of URLs as classpath
    RootLoader​(LoaderConfiguration lc)
    constructs a new RootLoader with a LoaderConfiguration object which holds the classpath

  • Method Summary

    Modifier and Type Method Description
    void addURL​(java.net.URL url)
    adds an url to the classpath of this classloader
    protected java.lang.Class findClass​(java.lang.String name)  
    java.net.URL getResource​(java.lang.String name)
    returns the URL of a resource, or null if it is not found
    protected java.lang.Class loadClass​(java.lang.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, findClass, findLibrary, findLoadedClass, findResource, findSystemClass, getClassLoadingLock, getDefinedPackage, getDefinedPackages, getName, getPackage, getPackages, getParent, getPlatformClassLoader, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, getUnnamedModule, isRegisteredAsParallelCapable, loadClass, registerAsParallelCapable, resolveClass, resources, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • RootLoader

      public RootLoader​(java.lang.ClassLoader parent)
      constructs a new RootLoader without classpath
      Parameters:
      parent - the parent Loader

    • RootLoader

      public RootLoader​(java.net.URL[] urls, java.lang.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 Details

    • loadClass

      protected java.lang.Class loadClass​(java.lang.String name, boolean resolve) throws java.lang.ClassNotFoundException
      loads a class using the name of the class
      Overrides:
      loadClass in class java.lang.ClassLoader
      Throws:
      java.lang.ClassNotFoundException

    • getResource

      public java.net.URL getResource​(java.lang.String name)
      returns the URL of a resource, or null if it is not found
      Overrides:
      getResource in class java.lang.ClassLoader

    • addURL

      public void addURL​(java.net.URL url)
      adds an url to the classpath of this classloader
      Overrides:
      addURL in class java.net.URLClassLoader

    • findClass

      protected java.lang.Class findClass​(java.lang.String name) throws java.lang.ClassNotFoundException
      Overrides:
      findClass in class java.net.URLClassLoader
      Throws:
      java.lang.ClassNotFoundException