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 Summary

Constructors

Constructor and Description
WekaPackageLibIsolatingClassLoader(WekaPackageClassLoaderManager repo, File packageDir) Constructor

Method Summary

Modifier and Type	Method and Description
static boolean	checkForMissingFiles(Package toLoad, File packageRoot, PrintStream... progress) Checks to see if there are any missing files/directories for a given package.
List<WekaPackageLibIsolatingClassLoader>	getPackageClassLoadersForDependencies() Gets a list of class loaders for the packages that this one depends on
Set<String>	getPackageJarEntries() Get a Set of the names of all classes contained within top-level jar files in this package
String	getPackageName() Return the name of the package that this classloader loads classes for
URL	getResource(String name) Find a named resource.
Enumeration<URL>	getResources(String name) Find an enumeration of resources matching the supplied name.
boolean	hasThirdPartyClass(String className) Returns true if this classloader is covering the named third-party class
String	toString() String representation of this classloader

Methods inherited from class java.net.URLClassLoader

close, findResource, findResources, getResourceAsStream, getURLs, newInstance, newInstance

Methods inherited from class java.lang.ClassLoader

clearAssertionStatus, getParent, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

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 Detail

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