Class RootLoader

All Implemented Interfaces:, java.lang.AutoCloseable

public class RootLoader
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

    Constructor Description
    RootLoader​(java.lang.ClassLoader parent)
    Constructs a RootLoader without classpath.
    RootLoader​([] urls, java.lang.ClassLoader parent)
    Constructs a RootLoader with a parent loader and an array of URLs as its classpath.
    RootLoader​(LoaderConfiguration lc)
    Constructs a RootLoader with a LoaderConfiguration object which holds the classpath.
  • Method Summary

    Modifier and Type Method Description
    void addURL​( url)
    protected java.lang.Class<?> findClass​(java.lang.String name) getResource​(java.lang.String name)
    protected java.lang.Class<?> loadClass​(java.lang.String name, boolean resolve)

    Methods inherited from class

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

    Methods inherited from class

    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 RootLoader without classpath.
      parent - the parent Loader
    • RootLoader

      public RootLoader​([] urls, java.lang.ClassLoader parent)
      Constructs a RootLoader with a parent loader and an array of URLs as its classpath.
    • RootLoader

      public RootLoader​(LoaderConfiguration lc)
      Constructs a 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
      loadClass in class java.lang.ClassLoader
    • getResource

      public getResource​(java.lang.String name)
      getResource in class java.lang.ClassLoader
    • addURL

      public void addURL​( url)
      addURL in class
    • findClass

      protected java.lang.Class<?> findClass​(java.lang.String name) throws java.lang.ClassNotFoundException
      findClass in class