Package weka.core

Class WekaPackageLibIsolatingClassLoader

java.lang.Object
java.lang.ClassLoader
java.security.SecureClassLoader
java.net.URLClassLoader
weka.core.WekaPackageLibIsolatingClassLoader
All Implemented Interfaces:
Closeable, AutoCloseable
public class WekaPackageLibIsolatingClassLoader extends URLClassLoader

A ClassLoader that loads/finds classes from one Weka plugin package. This includes the top-level jar file(s) and third-party libraries in the package's lib directory. First checks the parent classloader (typically application classloader) - covers general stuff and weka core classes. Next tries the package jar files and third-party libs covered by this classloader/package. Next tries packages this one depends on and their third-party libs - this is transitive. Finally tries all top-level package jar files over all packages.

The basic assumption for Weka packages is that classes present in top-level jar package jar files contain Weka-related code (schemes, filters, GUI panels, tools, etc.), that is visible to all other packages via Weka's dynamic class discovery mechanism. A top-level jar file should not contain any third-party library code. If package A needs to compile against (and explicitly reference) classes provided by package B (either top-level jar or third-party library), then it should declare a dependency on package B.

Version:
$Revision: $
Author:
Mark Hall (mhall{[at]}pentaho{[dot]}com)

  • Constructor Details

    • WekaPackageLibIsolatingClassLoader

      public WekaPackageLibIsolatingClassLoader(WekaPackageClassLoaderManager repo, File packageDir) throws Exception
      Constructor
      Parameters:
      repo - a reference to the classloader manager
      packageDir - the package directory for the package covered by this classloader
      Throws:
      Exception - if a problem occurs

  • Method Details

    • getPackageClassLoadersForDependencies

      public List<WekaPackageLibIsolatingClassLoader> getPackageClassLoadersForDependencies()
      Gets a list of class loaders for the packages that this one depends on
      Returns:
      a list of class loaders for the packages that this one depends on

    • getResource

      public URL getResource(String name)
      Find a named resource. First checks parent classloader and stuff covered by this classloader. Next tries packages that this one depends on.
      Overrides:
      getResource in class ClassLoader
      Parameters:
      name - the name of the resource to look for
      Returns:
      the URL of the resource, or null if the resource is not found

    • getResources

      public Enumeration<URL> getResources(String name) throws IOException
      Find an enumeration of resources matching the supplied name. First checks parent classloader and stuff covered by this classloader. Next tries packages that this one depends on.
      Overrides:
      getResources in class ClassLoader
      Parameters:
      name - the name to look for
      Returns:
      an enumeration of URLs
      Throws:
      IOException - if a problem occurs

    • hasThirdPartyClass

      public boolean hasThirdPartyClass(String className)
      Returns true if this classloader is covering the named third-party class
      Parameters:
      className - the third-party classname to check for
      Returns:
      true if this classloader is covering the named third-party class

    • toString

      public String toString()
      String representation of this classloader
      Overrides:
      toString in class Object
      Returns:
      the string representation of this classloader

    • getPackageName

      public String getPackageName()
      Return the name of the package that this classloader loads classes for
      Returns:
      return the name of the package that this classloader loads classes for

    • getPackageJarEntries

      public Set<String> getPackageJarEntries()
      Get a Set of the names of all classes contained within top-level jar files in this package
      Returns:
      a Set of the names of classes contained in top-level jar files in this package

    • checkForMissingFiles

      public static boolean checkForMissingFiles(Package toLoad, File packageRoot, PrintStream... progress)
      Checks to see if there are any missing files/directories for a given package. If there are missing files, then the package can't be loaded. An example would be a connector package that, for whatever reason, can't include a necessary third-party jar file in its lib folder, and requires the user to download and install this jar file manually.
      Parameters:
      toLoad - the package to check
      packageRoot - the root directory of the package
      progress - for printing progress/error info
      Returns:
      true if good to go