com.goldencode.p2j.classloader

Class MultiClassLoader

java.lang.Object

java.lang.ClassLoader

com.goldencode.p2j.classloader.MultiClassLoader

public class MultiClassLoader
extends java.lang.ClassLoader

This class provides a container for managing class loaders for multiple jars. When determining the class loader for a file, first it searches for a managed jar which handles that file. If it was found, then it delegates the request to it; else, it delegates the request to this class loader's parent.

To use this class loader, set this property when starting the server: -Djava.system.class.loader=com.goldencode.p2j.classloader.MultiClassLoader

Field Summary

Fields

Modifier and Type	Field and Description
private static java.util.List<java.lang.String>	classpathJars A set containing all jars added to the classpath when the server was started.
private java.util.Map<java.lang.String,JarClassLoader>	jclByClasses Map each class to the classloader which handles it.
private java.util.Map<java.lang.String,JarClassLoader>	loaders Map containing as key the jar name and as value its associated class loader.
private static CentralLogger	LOG logger
private static java.lang.String	managedLibsDir Managed customer libraries directory path.

Constructor Summary

Constructors

Constructor and Description
MultiClassLoader(java.lang.ClassLoader parent) C'tor.

Method Summary

Modifier and Type	Method and Description
static ErrorCode	addJarLoader(java.lang.String jarName) Register the given jar to be handled by its own class loader.
private ErrorCode	addJarLoaderImpl(java.lang.String jarName, boolean fullPath) Register the given jar to be handled by its own class loader.
private void	appendToClassPathForInstrumentation(java.lang.String path) To support dynamic additions to the class path at runtime, the class loader needs to define this private method.
protected java.lang.Class<?>	findClass(java.lang.String name) Find and load the class with the given name.
protected java.net.URL	findResource(java.lang.String name) Finds the resource with the given name.
java.lang.Class<?>	getClass(java.lang.String name) Find and load the class with the given name.
static java.lang.ClassLoader	getClassLoader() Utility method to obtain the MultiClassLoader instance from the current thread's context class loader.
static boolean	handledByJar(java.lang.Class<?> clazz, java.lang.String jarName) Check if the given class is handled by a custom jar loader for the given jar.
static boolean	handledByJar(java.lang.String className, java.lang.String jarName) Check if the given class is handled by a custom jar loader for the given jar.
static ClassInfo[]	listClasses(java.lang.String jarName) List all classes in the given jar.
static java.lang.String[]	listRegisteredJars() List the jars handled by custom class loaders.
static java.lang.String[]	listUnregisteredJars() List the jars which may be handled by custom class loaders (they reside in the given path, are not yet handled by custom class loaders and are not in the classpath).
java.lang.Class<?>	loadClass(java.lang.String name) Find and load the class with the given name.
static java.lang.String	managedCustomerLibs() Get the managed customer libs folder.
static ErrorCode	removeJarLoader(java.lang.String jarName) Remove the classloader associated with the given jar.
private ErrorCode	removeJarLoaderImpl(java.lang.String jarName) Remove the classloader associated with the given jar.

Methods inherited from class java.lang.ClassLoader

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

Methods inherited from class java.lang.Object

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

Field Detail

LOG

private static final CentralLogger LOG

logger

loaders

private final java.util.Map<java.lang.String,JarClassLoader> loaders

Map containing as key the jar name and as value its associated class loader.

jclByClasses

private final java.util.Map<java.lang.String,JarClassLoader> jclByClasses

Map each class to the classloader which handles it.

managedLibsDir

private static volatile java.lang.String managedLibsDir

Managed customer libraries directory path. If null then it hasn't been read yet, otherwise it is contained in the zero element of the array.

classpathJars

private static final java.util.List<java.lang.String> classpathJars

A set containing all jars added to the classpath when the server was started.

Constructor Detail

MultiClassLoader

public MultiClassLoader(java.lang.ClassLoader parent)

C'tor. Instantiate the class loader by linking it with its parent.

Parameters:

parent - Parent class loader.

Method Detail

handledByJar

public static boolean handledByJar(java.lang.Class<?> clazz,
                                   java.lang.String jarName)

Check if the given class is handled by a custom jar loader for the given jar.

Parameters:

clazz - The class object.

jarName - The jar name.

Returns:

See above.

handledByJar

public static boolean handledByJar(java.lang.String className,
                                   java.lang.String jarName)

Check if the given class is handled by a custom jar loader for the given jar.

Parameters:

className - The name of the class to be checked.

jarName - The jar name.

Returns:

See above.

addJarLoader

public static ErrorCode addJarLoader(java.lang.String jarName)
                              throws RestrictedUseException

Register the given jar to be handled by its own class loader.

Parameters:

jarName - The jar name.

Returns:

ErrorCode.SUCCESS if the loading was done. Else, it returns an error code.

Throws:

RestrictedUseException - if called improperly.

removeJarLoader

public static ErrorCode removeJarLoader(java.lang.String jarName)
                                 throws RestrictedUseException

Remove the classloader associated with the given jar.

Parameters:

jarName - The jar name.

Returns:

ErrorCode.SUCCESS if the deregistration was done. Else, it returns an error code.

Throws:

RestrictedUseException - if called improperly.

managedCustomerLibs

public static java.lang.String managedCustomerLibs()

Get the managed customer libs folder. First, it checks managed.libs.dir system property, then, as a fallback, it checks the configuration directory (path is /server/default/managed-libs-dir or /server/<serverID>/managed-libs-dir).

Returns:

managed customer libs folder or null if it is not specified.

listClasses

public static ClassInfo[] listClasses(java.lang.String jarName)

List all classes in the given jar. The classes will not be initialized.

Parameters:

jarName - The jar name.

Returns:

The list of classes in this jar or null in case of error.

listRegisteredJars

public static java.lang.String[] listRegisteredJars()

List the jars handled by custom class loaders.

Returns:

See above.

listUnregisteredJars

public static java.lang.String[] listUnregisteredJars()

List the jars which may be handled by custom class loaders (they reside in the given path, are not yet handled by custom class loaders and are not in the classpath).

The unregistered jars are searched in the customer_libs property specified at server startup. If it was not specified, then it will return an empty list.

Returns:

See above.

findResource

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

Finds the resource with the given name. First it searches the loaded jars; if not found, delegates the search to the parent class loader.

Overrides:

findResource in class java.lang.ClassLoader

Parameters:

name - The resource name

Returns:

A URL object for reading the resource, or null if the resource could not be found

findClass

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

Find and load the class with the given name. If this is in one of the registered Jar class loaders, it will delegate the loading to it. Else, the search is delegated to the parent class loader.

Overrides:

findClass in class java.lang.ClassLoader

Returns:

The Class object.

Throws:

java.lang.ClassNotFoundException - If the class can not be found or class linkage has error occurred.

loadClass

public java.lang.Class<?> loadClass(java.lang.String name)
                             throws java.lang.ClassNotFoundException

Find and load the class with the given name. If this is in one of the registered Jar class loaders, it will delegate the loading to it. Else, the search is delegated to the parent class loader.

Overrides:

loadClass in class java.lang.ClassLoader

Returns:

The Class object.

Throws:

java.lang.ClassNotFoundException - If the class can not be found or class linkage has error occurred.

getClass

public java.lang.Class<?> getClass(java.lang.String name)
                            throws java.lang.ClassNotFoundException

Find and load the class with the given name. If this is in one of the registered Jar class loaders, it will delegate the loading to it. Else, the search is delegated to the parent class loader.

Parameters:

name - The class name

Returns:

The Class object, or null if this class does not belong to any of the registered jars.

Throws:

java.lang.ClassNotFoundException - If the class belongs must be handled by a JarClassLoader but can not be loaded.

appendToClassPathForInstrumentation

private void appendToClassPathForInstrumentation(java.lang.String path)

To support dynamic additions to the class path at runtime, the class loader needs to define this private method. This will be invoked from the native VM code, to load a jar.

This method does not have to be public.

Parameters:

path - The full path of the jar to be appended.

addJarLoaderImpl

private ErrorCode addJarLoaderImpl(java.lang.String jarName,
                                   boolean fullPath)

Register the given jar to be handled by its own class loader.

Parameters:

jarName - The jar name.

fullPath - true if the jarName contains also the jar's path. When false, it is assumed that the path is the one specified in the "customer_libs" system property.

Returns:

ErrorCode.SUCCESS if the loading was done. Else, it returns an error code.

removeJarLoaderImpl

private ErrorCode removeJarLoaderImpl(java.lang.String jarName)

Remove the classloader associated with the given jar.

Parameters:

jarName - The jar name.

Returns:

ErrorCode.SUCCESS if the deregistration was done. Else, it returns an error code.

getClassLoader

public static java.lang.ClassLoader getClassLoader()

Utility method to obtain the MultiClassLoader instance from the current thread's context class loader. If no MultiClassLoader is found in the thread hierarchy, it returns the system class loader.

Returns:

The MultiClassLoader instance if found, otherwise the system class loader.