weka.core

Class WekaPackageClassLoaderManager

java.lang.Object

weka.core.WekaPackageClassLoaderManager

public class WekaPackageClassLoaderManager
extends java.lang.Object

Class that manages classloaders from individual Weka plugin packages. Maintains a collection of WekaPackageLibIsolatingClassLoaders - one for each package. Utils.forName() and weka.Run use this classloader to find/instantiate schemes exposed in top-level package jar files. Client code in a package should do the same, unless directly referring to classes in other packages, in which case the other packages should be explicit dependencies. This classloader will not find classes in third-party libraries inside a package's lib directory.

Classes are searched for first in the parent classloader and then in the top-level package jar files.

See Also:

WekaPackageLibIsolatingClassLoader

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Map<java.lang.String,WekaPackageLibIsolatingClassLoader>	m_classBasedClassLoaderLookup Lookup for classloaders keyed by class names from top-level package jar files
protected java.util.Map<java.lang.String,WekaPackageLibIsolatingClassLoader>	m_packageJarClassLoaders Map of package classloaders keyed by package name
protected java.io.File	m_pathToWekaJarFile Path to the weka.jar file on the classpath
protected static WekaPackageClassLoaderManager	s_singletonLoader

Method Summary

Modifier and Type	Method and Description
java.lang.ClassLoader	addPackageToClassLoader(java.io.File packageDir) Create a class loader for the given package directory
protected static boolean	classExists(java.lang.String className) Check to see if the named class exists in this classloader
protected java.lang.Class<?>	findClass(java.lang.String name) Attempts to find the named class.
protected java.lang.Class<?>	findClass(java.lang.String packageName, java.lang.String className) Try to find a class from the classloader for the named package.
java.lang.ClassLoader	findClassloaderForResource(java.lang.String name) Get the classloader that covers the jar that contains the named resource.
java.net.URL	findResource(java.lang.String name) Find a named resource.
protected java.net.URL	findResource(java.lang.String packageName, java.lang.String name) Try to find a resource from the classloader for the named package.
java.util.Enumeration<java.net.URL>	findResources(java.lang.String name) Find a named resource.
protected java.util.Enumeration<java.net.URL>	findResources(java.lang.String packageName, java.lang.String name) Try to find a resource from the classloader for the named package.
static java.lang.Class<?>	forName(java.lang.String className) Return the class object for the supplied class name.
static java.lang.Class<?>	forName(java.lang.String className, boolean initialize) Return the class object for the supplied class name.
java.lang.ClassLoader	getLoaderForClass(java.lang.String className) Attempts to locate a classloader for the named class.
WekaPackageLibIsolatingClassLoader	getPackageClassLoader(java.lang.String packageName) Get the classloader for the named package
java.util.Set<java.lang.String>	getPackageJarFileClasses() Get a set of all classes contained in all top-level jar files from Weka packages.
java.io.File	getPathToWekaJarFile() Return the path to the weka.jar file (if found) on the classpath.
java.net.URL[]	getWekaClassloaderClasspathEntries() Get the entries in the Weka class loader (i.e. the class loader that loads the core weka classes) as an array of URLs.
static WekaPackageClassLoaderManager	getWekaPackageClassLoaderManager() Gets the singleton instance of the WekaPackageClassLoaderManager
protected static void	injectAllClassesInFromStream(java.io.InputStream inStream) Inject all classes from the supplied input stream into the root classloader.
protected static void	injectAllClassesInJar(java.io.File jarPath) Inject all classes in the supplied jar file into the root classloader
protected static void	injectAllClassesInJar(java.io.File jarPath, boolean injectToRootClassLoader) Inject all classes in the supplied jar file into the parent or root classloader
protected static void	injectClasses(java.io.File jarPath, java.util.List<java.lang.String> classJarPaths, java.util.List<java.lang.String> classes, boolean injectToRootClassLoader) Inject classes from the supplied jar file into the Weka or root classloader.
protected static void	injectClasses(java.io.InputStream jarStream, java.util.List<java.lang.String> classJarPaths, java.util.List<java.lang.String> classes, boolean injectToRootClassLoader) Inject classes from the supplied stream into the Weka or root classloader.
protected void	injectMTJCoreClasses() Injects the MTJ core classes into the root classloader.
static java.lang.Object	objectForName(java.lang.String className) Return an instantiated instance of the supplied class name.
protected void	performIntegrityCheck() Checks each classloader to make sure that their dependencies are available (i.e. a classloader for each dependency is present).
void	removeClassLoaderForPackage(java.lang.String packageName) Removes the named package classloader from those managed by this class.

Methods inherited from class java.lang.Object

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

Field Detail

s_singletonLoader

protected static final WekaPackageClassLoaderManager s_singletonLoader

m_packageJarClassLoaders

protected java.util.Map<java.lang.String,WekaPackageLibIsolatingClassLoader> m_packageJarClassLoaders

Map of package classloaders keyed by package name

m_classBasedClassLoaderLookup

protected java.util.Map<java.lang.String,WekaPackageLibIsolatingClassLoader> m_classBasedClassLoaderLookup

Lookup for classloaders keyed by class names from top-level package jar files

m_pathToWekaJarFile

protected java.io.File m_pathToWekaJarFile

Path to the weka.jar file on the classpath

Method Detail

injectMTJCoreClasses

protected void injectMTJCoreClasses()

Injects the MTJ core classes into the root classloader. This is so that they are visible to the MTJ native library loader (if a MTJ native package is installed).

getWekaPackageClassLoaderManager

public static WekaPackageClassLoaderManager getWekaPackageClassLoaderManager()

Gets the singleton instance of the WekaPackageClassLoaderManager

Returns:

the singleton instance of hte WekaPackageClassLoaderManager

objectForName

public static java.lang.Object objectForName(java.lang.String className)
                                      throws java.lang.Exception

Return an instantiated instance of the supplied class name. This method will attempt to find a package that owns the named class first, before falling back on the current and then parent class loader. Use this method instead of Class.forName().newInstance().

Parameters:

className - the name of the class to get an instance of

Returns:

an instantiated object

Throws:

java.lang.Exception - if the class cannot be found, or a problem occurs during instantiation

forName

public static java.lang.Class<?> forName(java.lang.String className)
                                  throws java.lang.ClassNotFoundException

Return the class object for the supplied class name. This method will attempt to find a package that owns the named class first, before falling back on the current, and then parent, class loader. Use this method instead of Class.forName().

Parameters:

className - the name of hte class to get an instance of

Returns:

a class object

Throws:

java.lang.ClassNotFoundException - if the named class cannot be found.

forName

public static java.lang.Class<?> forName(java.lang.String className,
                                         boolean initialize)
                                  throws java.lang.ClassNotFoundException

Return the class object for the supplied class name. This method will attempt to find a package that owns the named class first, before falling back on the current, and then parent, class loader. Use this method instead of Class.forName().

Parameters:

className - the name of hte class to get an instance of

initialize - true if the class should be initialized

Returns:

a class object

Throws:

java.lang.ClassNotFoundException - if the named class cannot be found.

getPathToWekaJarFile

public java.io.File getPathToWekaJarFile()

Return the path to the weka.jar file (if found) on the classpath.

Returns:

the path to the weka.jar file on the classpath, or null if no weka.jar file was found.

getWekaClassloaderClasspathEntries

public java.net.URL[] getWekaClassloaderClasspathEntries()

Get the entries in the Weka class loader (i.e. the class loader that loads the core weka classes) as an array of URLs. This is primarily used by Weka's dynamic class discovery mechanism, so that all Weka schemes on the classpath can be discovered. If the Weka class loader is an instance of URLClassLoader then the URLs encapsulated within are returned. Otherwise, if the system class loader is the classloader that loads Weka then the entries from java.class.path are returned. Failing that, we assume that Weka and any other supporting classes (not including packages) can be found in the WEKA_CLASSPATH environment variable. This latter case can be used to handle the situation where the weka.jar is loaded by a custom (non-URLClassLoader) withn an app server (for example).

Returns:

an array of URLs containing the entries available to the classloader that loads the core weka classes

getPackageJarFileClasses

public java.util.Set<java.lang.String> getPackageJarFileClasses()

Get a set of all classes contained in all top-level jar files from Weka packages. These classes are globally visible across all packages.

Returns:

a set of all classes in all top-level package jar files

removeClassLoaderForPackage

public void removeClassLoaderForPackage(java.lang.String packageName)

Removes the named package classloader from those managed by this class. Attempts to close the classloader and remove any file locks (under Windows) that it might be holding

Parameters:

packageName - the name of the package to remove the classloader for

addPackageToClassLoader

public java.lang.ClassLoader addPackageToClassLoader(java.io.File packageDir)
                                              throws java.lang.Exception

Create a class loader for the given package directory

Parameters:

packageDir - the directory of a Weka package to create a class loader for

Throws:

java.lang.Exception - if a problem occurs

getLoaderForClass

public java.lang.ClassLoader getLoaderForClass(java.lang.String className)

Attempts to locate a classloader for the named class. Tries the Weka classloader and globally visible package classes first. Note that this also finds classes that are contained in a package's lib directory. General code should not be looking directly for such third-party classes. Instead, if they require third-party classes they should reference them directly (and compile against the libraries in question), and then either include the third party libraries in their own lib directory or declare a dependency on the package that contains them. This method is used by Weka's deserialization routines (in SerializationHelper and SerializedObject) that need to locate classes (including third-party library ones) that might have been serialized when saving a learning scheme.

Parameters:

className - the name of the class to locate a classloader for

Returns:

a classloader

getPackageClassLoader

public WekaPackageLibIsolatingClassLoader getPackageClassLoader(java.lang.String packageName)

Get the classloader for the named package

Parameters:

packageName - the name of the package to get the classloader for

Returns:

the package's classloader, or null if the package is not known (or perhaps was not loaded for some reason)

findClass

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

Attempts to find the named class. Tries the Weka classloader first (for core Weka classes and general Java classes) and then tries package classloaders (with respect to the globally visible classes contained in their top-level jar files). Note that this method will not find classes contained in third-party libraries that reside in lib directories).

Parameters:

name - the name of the class to find

Returns:

the class object

Throws:

java.lang.ClassNotFoundException - if the named class cannot be found

findResource

public java.net.URL findResource(java.lang.String name)

Find a named resource. This searches the Weka classloader and all package classloaders. Note that it will only find resources contained in a package's top-level jar file(s).

Parameters:

name - the name of the resource to find

Returns:

a URL to the resource, or null if the resource could not be located

findClassloaderForResource

public java.lang.ClassLoader findClassloaderForResource(java.lang.String name)

Get the classloader that covers the jar that contains the named resource. Note that this considers the Weka classloader and package classloaders (with respect to resources contained in their top-level jar file(s))

Parameters:

name - the name of the resource to get the owning classloader for

Returns:

the classloader that "owns" the resource

findResources

public java.util.Enumeration<java.net.URL> findResources(java.lang.String name)
                                                  throws java.io.IOException

Find a named resource. This searches the Weka classloader and all package classloaders. Note that it will only find resources contained in a package's top-level jar file(s).

Parameters:

name - the name of the resource to find

Returns:

an enumeration of URLs to the resource, or null if the resource could not be located

Throws:

java.io.IOException

findClass

protected java.lang.Class<?> findClass(java.lang.String packageName,
                                       java.lang.String className)

Try to find a class from the classloader for the named package. Note that this will traverse transitive package dependencies

Parameters:

packageName - the name of the package to check for the class

className - the name of the class to search for

Returns:

the named class or null if the class could not be found

findResource

protected java.net.URL findResource(java.lang.String packageName,
                                    java.lang.String name)

Try to find a resource from the classloader for the named package. Note that this will traverse transitive package dependencies

Parameters:

packageName - the name of the package to check for the resource

name - the name of the resource to search for

Returns:

a URL to the resource, or null if the resource could not be found

findResources

protected java.util.Enumeration<java.net.URL> findResources(java.lang.String packageName,
                                                            java.lang.String name)

Try to find a resource from the classloader for the named package. Note that this will traverse transitive package dependencies

Parameters:

packageName - the name of the package to check for the resource

name - the name of the resource to search for

Returns:

an enumeration of URLs to the resource, or null if the resource could not be found

classExists

protected static boolean classExists(java.lang.String className)

Check to see if the named class exists in this classloader

Parameters:

className - the name of the class to check for

Returns:

true if the class exists in this classloader

injectAllClassesInJar

protected static void injectAllClassesInJar(java.io.File jarPath,
                                            boolean injectToRootClassLoader)
                                     throws java.lang.Exception

Inject all classes in the supplied jar file into the parent or root classloader

Parameters:

jarPath - the path to the jar in question

injectToRootClassLoader - true to inject right up to the root

Throws:

java.lang.Exception - if a problem occurs

injectAllClassesInJar

protected static void injectAllClassesInJar(java.io.File jarPath)
                                     throws java.lang.Exception

Inject all classes in the supplied jar file into the root classloader

Parameters:

jarPath - the path to the jar in question

Throws:

java.lang.Exception - if a problem occurs

injectAllClassesInFromStream

protected static void injectAllClassesInFromStream(java.io.InputStream inStream)
                                            throws java.lang.Exception

Inject all classes from the supplied input stream into the root classloader. Assumes that the zip entries can be read from the input stream (i.e. a jar/zip file is the target)

Parameters:

inStream - the input stream to process

Throws:

java.lang.Exception - if a problem occurs

injectClasses

protected static void injectClasses(java.io.File jarPath,
                                    java.util.List<java.lang.String> classJarPaths,
                                    java.util.List<java.lang.String> classes,
                                    boolean injectToRootClassLoader)
                             throws java.lang.Exception

Inject classes from the supplied jar file into the Weka or root classloader.

Parameters:

jarPath - the path to the jar file to process

classJarPaths - an optional list of paths to classes in the jar file to inject (if null then all classes in the jar file are injected)

classes - an optional list of fully qualified class names. This should correspond to the paths in classJarPaths, but contain just the class name along with slashes replaced by "." and the .class extension removed.

injectToRootClassLoader - true if the classes are to be injected into the root classloader rather than the Weka classloader

Throws:

java.lang.Exception - if a problem occurs

injectClasses

protected static void injectClasses(java.io.InputStream jarStream,
                                    java.util.List<java.lang.String> classJarPaths,
                                    java.util.List<java.lang.String> classes,
                                    boolean injectToRootClassLoader)
                             throws java.lang.Exception

Inject classes from the supplied stream into the Weka or root classloader.

Parameters:

jarStream - input stream to process. Is expected that jar/zip entries can be read from the stream

classJarPaths - an optional list of paths to classes in the jar file to inject (if null then all classes in the jar file are injected)

classes - an optional list of fully qualified class names. This should correspond to the paths in classJarPaths, but contain just the class name along with slashes replaced by "." and the .class extension removed.

injectToRootClassLoader - true if the classes are to be injected into the root classloader rather than the Weka classloader

Throws:

java.lang.Exception - if a problem occurs

performIntegrityCheck

protected void performIntegrityCheck()

Checks each classloader to make sure that their dependencies are available (i.e. a classloader for each dependency is present). This method is called by WekaPackageManager after loading all packages, but before dynamic class discovery is invoked. This takes care of any issues that might arise from the user toggling the load status of a package, or perhaps manually installing packages that preclude one another, which might make one or more dependencies unavailable