com.ibm.aglets.tahiti
Class AgletClassLoader

java.lang.Object
  java.lang.ClassLoader
      com.ibm.aglets.tahiti.AgletClassLoader

All Implemented Interfaces:

ResourceManager

Direct Known Subclasses:

JarAgletClassLoader

class AgletClassLoader

extends java.lang.ClassLoader

implements ResourceManager

Class AgletClassLoader is responsible for loading classes for the aglets. This class has a class loader cache as a static member and store all class loader objects with keys which is the URL of the origin of classes managed by the loader. In aglets bytecodes of classes are transfered with objects. Therefore, there may be many version of classes whose names are same in an aglet server. In aglets classes are managed based on their origin. Classes which sources of their bytecodes are same are managed by a same aglet loader in an aglet server. Therefore, an object can access objects if sources of their class bytecodes are same, otherwise ClassCastException will occur.

An aglet loader caches classes and their bytecodes.

Version:

1.20 $Date: 2002/02/20 22:06:26 $

Author:

Danny B. Lange, Gaku Yamamoto, Mitsuru Oshima

Nested Class Summary

Nested classes inherited from class java.lang.ClassLoader

Field Summary

(package private) static AgentProfile	_agent_profile
protected static CacheManager	_cache Cache to store bytecodes of classes.
private java.net.URL	_codeBase
protected DigestTable	_digest_table Digest table for classes managed by this classloader.
private java.security.cert.Certificate	_ownerCert
private java.util.Hashtable	_resolvedClassCache Cache to store resolved classes.
private java.util.Vector	_resources
private static LogCategory	log

Fields inherited from class java.lang.ClassLoader

Constructor Summary

protected

AgletClassLoader(java.net.URL codebase, java.security.cert.Certificate owner) Constructs a new AgletClassLoader with codebase.

Method Summary

void	addResource(java.lang.Object o) Adds a feature to the Resource attribute of the AgletClassLoader object
void	cacheResolvedClass(java.lang.Class cls) Description of the Method
boolean	contains(java.lang.Class cls) Checks if the given class is managed by this manager.
void	disposeAllResources() Description of the Method
private static void	dumpBytes(byte[] bytes) Description of the Method
void	finalize() Shout when an AgletClassLoader object is caught by GC.
private byte[]	findByteCode(java.lang.String classname) Description of the Method
protected byte[]	findByteCodeInCache(java.lang.String filename) Description of the Method
private java.lang.Class	findClassInternal(java.lang.String name) Loads a class
private java.lang.Class	findResolvedClass(java.lang.String classname) Gets the class specified by the name from resolved cache.
Archive	getArchive(ClassName[] t) Gets the archive attribute of the AgletClassLoader object
ClassName[]	getClassNames(java.lang.Class[] classes) Computes Digest
java.net.URL	getCodeBase() Tells where the class was loaded from.
java.security.cert.Certificate	getOwnerCertificate() Gets certificate of the owner.
protected byte[]	getResourceAsByteArray(java.lang.String filename) Gets the resourceAsByteArray attribute of the AgletClassLoader object
java.io.InputStream	getResourceAsStream(java.lang.String filename) Gets the resourceAsStream attribute of the AgletClassLoader object
void	importArchive(Archive a) Description of method.
protected java.lang.Class	loadClass(java.lang.String name, boolean resolve) Loads a class specified by the param name.
private java.lang.Class	loadClassFromCodeBase(java.lang.String classname) Description of the Method
private byte[]	loadResourceFromCodeBase(java.lang.String name) The method for loading class data.
boolean	match(ClassName[] table) Description of the Method
boolean	matchAndImport(ClassName[] table) Description of the Method
AgletThread	newAgletThread(MessageManager mm) Description of the Method
private void	putResource(java.lang.String name, byte[] data) Description of the Method
private void	releaseCacheEntries() Description of the Method
void	resumeAllThreads() Description of the Method
void	setResourceManagerContext() Sets the resourceManagerContext attribute of the AgletClassLoader object
void	stopAllThreads() Description of the Method
void	stopThreadGroup() Description of the Method
void	suspendAllThreads() Description of the Method
java.lang.String	toString() Description of the Method
void	unsetResourceManagerContext() Description of the Method
private static void	verboseOut(java.lang.String msg) Description of the Method

Methods inherited from class java.lang.ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, definePackage, findClass, findLibrary, findLoadedClass, findResource, findResources, findSystemClass, getPackage, getPackages, getParent, getResource, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.ibm.aglets.ResourceManager

loadClass

Field Detail

_cache

protected static CacheManager _cache

Cache to store bytecodes of classes.

Since:

_agent_profile

static AgentProfile _agent_profile

log

private static final LogCategory log

_digest_table

protected DigestTable _digest_table

Digest table for classes managed by this classloader.

_codeBase

private java.net.URL _codeBase

_ownerCert

private java.security.cert.Certificate _ownerCert

_resolvedClassCache

private java.util.Hashtable _resolvedClassCache

Cache to store resolved classes.

_resources

private java.util.Vector _resources

Constructor Detail

AgletClassLoader

protected AgletClassLoader(java.net.URL codebase,
                           java.security.cert.Certificate owner)

Constructs a new AgletClassLoader with codebase.

Parameters:

codebase - the codebase in which the all classes are originated.

owner - Certificate of the owner

Method Detail

dumpBytes

private static void dumpBytes(byte[] bytes)

Description of the Method

Parameters:

bytes - Description of Parameter

Since:

verboseOut

private static void verboseOut(java.lang.String msg)

Description of the Method

Parameters:

msg - Description of Parameter

Since:

setResourceManagerContext

public void setResourceManagerContext()

Sets the resourceManagerContext attribute of the AgletClassLoader object

Specified by:

setResourceManagerContext in interface ResourceManager

Since:

getArchive

public Archive getArchive(ClassName[] t)

Gets the archive attribute of the AgletClassLoader object

Specified by:

getArchive in interface ResourceManager

Parameters:

t - Description of Parameter

Returns:

The archive value

Since:

getClassNames

public ClassName[] getClassNames(java.lang.Class[] classes)

Computes Digest

Specified by:

getClassNames in interface ResourceManager

Parameters:

classes - Description of Parameter

Returns:

The classNames value

Since:

getCodeBase

public java.net.URL getCodeBase()

Tells where the class was loaded from.

Returns:

The codeBase value

Since:

getOwnerCertificate

public java.security.cert.Certificate getOwnerCertificate()

Gets certificate of the owner. (replacement of getIdentity)

Returns:

Certificate of the owner

Since:

getResourceAsStream

public java.io.InputStream getResourceAsStream(java.lang.String filename)

Gets the resourceAsStream attribute of the AgletClassLoader object

Parameters:

filename - Description of Parameter

Returns:

The resourceAsStream value

Since:

addResource

public void addResource(java.lang.Object o)

Adds a feature to the Resource attribute of the AgletClassLoader object

Specified by:

addResource in interface ResourceManager

Parameters:

o - The feature to be added to the Resource attribute

Since:

cacheResolvedClass

public void cacheResolvedClass(java.lang.Class cls)

Description of the Method

Parameters:

cls - Description of Parameter

Since:

contains

public boolean contains(java.lang.Class cls)

Checks if the given class is managed by this manager.

Specified by:

contains in interface ResourceManager

Parameters:

cls - Description of Parameter

Returns:

Description of the Returned Value

Since:

disposeAllResources

public void disposeAllResources()

Description of the Method

Specified by:

disposeAllResources in interface ResourceManager

Since:

finalize

public void finalize()

Shout when an AgletClassLoader object is caught by GC. This method is for verifing whether a class loader becomes a target of GC or not.

Since:

importArchive

public void importArchive(Archive a)

Description of method.

Specified by:

importArchive in interface ResourceManager

Parameters:

a - Description of Parameter

Since:

match

public boolean match(ClassName[] table)

Description of the Method

Parameters:

table - Description of Parameter

Returns:

Description of the Returned Value

Since:

matchAndImport

public boolean matchAndImport(ClassName[] table)

Description of the Method

Parameters:

table - Description of Parameter

Returns:

Description of the Returned Value

Since:

newAgletThread

public AgletThread newAgletThread(MessageManager mm)

Description of the Method

Specified by:

newAgletThread in interface ResourceManager

Parameters:

mm - Description of Parameter

Returns:

Description of the Returned Value

Since:

resumeAllThreads

public void resumeAllThreads()

Description of the Method

Specified by:

resumeAllThreads in interface ResourceManager

Since:

stopAllThreads

public void stopAllThreads()

Description of the Method

Specified by:

stopAllThreads in interface ResourceManager

Since:

stopThreadGroup

public void stopThreadGroup()

Description of the Method

Specified by:

stopThreadGroup in interface ResourceManager

Since:

suspendAllThreads

public void suspendAllThreads()

Description of the Method

Specified by:

suspendAllThreads in interface ResourceManager

Since:

toString

public java.lang.String toString()

Description of the Method

Returns:

Description of the Returned Value

Since:

unsetResourceManagerContext

public void unsetResourceManagerContext()

Description of the Method

Specified by:

unsetResourceManagerContext in interface ResourceManager

Since:

getResourceAsByteArray

protected byte[] getResourceAsByteArray(java.lang.String filename)

Gets the resourceAsByteArray attribute of the AgletClassLoader object

Parameters:

filename - Description of Parameter

Returns:

The resourceAsByteArray value

Since:

findByteCodeInCache

protected byte[] findByteCodeInCache(java.lang.String filename)

Description of the Method

Parameters:

filename - Description of Parameter

Returns:

Description of the Returned Value

Since:

loadClass

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

Loads a class specified by the param name. If a bytecode of the class has not been loaded, an AgletClassLoader object will load the bytecode form the codebase and define the class. The loaded bytecode and class will be stored into the class data cache and the class cache respectively.

Parameters:

name - the name of the desired class.

resolve - true if the class must be resolved.

Returns:

a loaded class

Throws:

java.lang.ClassNotFoundException - if the class is not found.

Since:

findByteCode

private byte[] findByteCode(java.lang.String classname)

Description of the Method

Parameters:

classname - Description of Parameter

Returns:

Description of the Returned Value

Since:

findClassInternal

private java.lang.Class findClassInternal(java.lang.String name)
                                   throws java.lang.ClassNotFoundException

Loads a class

Parameters:

name - Description of Parameter

Returns:

Description of the Returned Value

Throws:

java.lang.ClassNotFoundException - Description of Exception

Since:

See Also:

loadClass(java.lang.String, boolean), AgletClassLoader#instantiageAglet

findResolvedClass

private java.lang.Class findResolvedClass(java.lang.String classname)

Gets the class specified by the name from resolved cache.

Parameters:

classname - Description of Parameter

Returns:

the class of the name, null if the class is not in the cache.

Since:

loadClassFromCodeBase

private java.lang.Class loadClassFromCodeBase(java.lang.String classname)
                                       throws java.lang.ClassNotFoundException

Description of the Method

Parameters:

classname - Description of Parameter

Returns:

Description of the Returned Value

Throws:

java.lang.ClassNotFoundException - Description of Exception

Since:

loadResourceFromCodeBase

private byte[] loadResourceFromCodeBase(java.lang.String name)

The method for loading class data. This loads the bytecode from codebase of this loader.

Parameters:

name - the class name.

Returns:

the bytecode for the class.

Since:

putResource

private void putResource(java.lang.String name,
                         byte[] data)

Description of the Method

Parameters:

name - Description of Parameter

data - Description of Parameter

Since:

releaseCacheEntries

private void releaseCacheEntries()

Description of the Method

Since: