alma.acs.classloading

Class AcsComponentClassLoader

java.lang.Object

java.lang.ClassLoader

java.security.SecureClassLoader

java.net.URLClassLoader

alma.acs.classloading.AcsComponentClassLoader

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public class AcsComponentClassLoader
extends java.net.URLClassLoader

The component-specific class loader. Attempts to load classes directly, and only delegates to parent class loader after it failed. This bottom-up direction of classloading in the classloader hierarchy follows the J2EE convention, and thus violates the normal J2SE top-down direction.

This class requires the directories that contain component impl jars to be specified in the acs.components.classpath.jardirs property. The startup scripts must set this property. Other jar files (e.g. ACS jars) must be in different directories than those given by this property.

It is important to call the close() method when done with the classloader. Since ACS 12.3 (JDK 1.7) this method is provided by the base class. After changes in this area, make sure to manually run AcsComponentClassLoaderEnduranceTest to verify that there are no memory problems (non-heap OutOfMemoryError) as were seen in the past (http://jira.alma.cl/browse/COMP-4929).

TODO-: this class has a few things in common with AcsSystemClassLoader, so perhaps during some future refactoring a common base class could be extracted (between URLClassLoader and these).

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	PROPERTY_CLASSLOADERVERBOSE Name of the property that flags verbose mode of the component classloader.
static java.lang.String	PROPERTY_JARDIRS Name of the property that defines the directories for component implementation jar files.

Constructor Summary

Constructors

Constructor and Description
AcsComponentClassLoader(java.lang.ClassLoader parent, java.util.logging.Logger logger, java.lang.String componentName)

Method Summary

Modifier and Type	Method and Description
protected void	finalize()
protected java.lang.Class<?>	findClass(java.lang.String name) Calls super.findClass(name) and provides some System.out logging if in verbose mode.
java.lang.String	getProcessName() Taken from ClientLogManager.stripKnownLoggerNamespacePrefix().
java.lang.String	getSourceObject()
protected java.lang.Class<?>	loadClass(java.lang.String name, boolean resolve) Attempts to load the given class, and only delegates to parent class loader if it failed.

Methods inherited from class java.net.URLClassLoader

addURL, 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, findLibrary, findLoadedClass, findSystemClass, getClassLoadingLock, getPackage, getPackages, getParent, getResource, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, registerAsParallelCapable, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners

Methods inherited from class java.lang.Object

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

Field Detail

PROPERTY_JARDIRS

public static final java.lang.String PROPERTY_JARDIRS

Name of the property that defines the directories for component implementation jar files. Example value: ../lib/ACScomponents:/alma/ACS-5.0/ACSSW/lib/ACScomponents:".

See Also:

Constant Field Values

PROPERTY_CLASSLOADERVERBOSE

public static final java.lang.String PROPERTY_CLASSLOADERVERBOSE

Name of the property that flags verbose mode of the component classloader. Verbose mode is a debugging tool, only to be enabled locally by defining this property.

If enabled to be verbose, a component classloader will log the jar files it works with, the classes it loads or fails to load, and also prints a message when it is getting finalized. The latter is useful to monitor component class unloading.

See Also:

Constant Field Values

Constructor Detail

AcsComponentClassLoader

public AcsComponentClassLoader(java.lang.ClassLoader parent,
                               java.util.logging.Logger logger,
                               java.lang.String componentName)

Parameters:

parent - parent class loader (currently the container class loader)

logger - the container logger, for debug output (see PROPERTY_CLASSLOADERVERBOSE). This is also used to derive the processName when logging exceptions.

componentName - used for log messages in verbose mode

Method Detail

loadClass

protected java.lang.Class<?> loadClass(java.lang.String name,
                                       boolean resolve)
                                throws java.lang.ClassNotFoundException

Attempts to load the given class, and only delegates to parent class loader if it failed. This bottom-up direction of classloading in the classloader hierarchy resembles the J2EE convention, and thus violates the normal J2SE top-down direction.

TODO-: check if certain system or ACS classes should be skipped and delegated upward right away. This may improve performance, assuming a bunch of name.startsWith("java.") etc are faster than findLoadedClass and findClass.

Overrides:

loadClass in class java.lang.ClassLoader

Throws:

java.lang.ClassNotFoundException

See Also:

ClassLoader.loadClass(java.lang.String, boolean)

findClass

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

Calls super.findClass(name) and provides some System.out logging if in verbose mode.

Overrides:

findClass in class java.net.URLClassLoader

Throws:

java.lang.ClassNotFoundException

See Also:

ClassLoader.findClass(java.lang.String)

finalize

protected void finalize()
                 throws java.lang.Throwable

Overrides:

finalize in class java.lang.Object

Throws:

java.lang.Throwable

getSourceObject

public java.lang.String getSourceObject()

See Also:

ContextFinder

getProcessName

public java.lang.String getProcessName()

Taken from ClientLogManager.stripKnownLoggerNamespacePrefix(). Maybe it should be nice to generalize it and put it somewhere else. Strips the prepended constants #NS_CORBA, #NS_CONTAINER, #NS_COMPONENT etc from the logger namespace. This allows for a short, but possibly not unique display of the logger name.

TODO: This method is probably broken and must be checked. We may just pass contextName in the ctor.

See Also:

ContextFinder