Package org.codehaus.groovy.tools

Class 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 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 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

      All Methods Instance Methods Concrete Methods 
      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 Detail

      • 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

    • Method Detail

      • 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