org.apache.logging.log4j.util

Class LoaderUtil

java.lang.Object

org.apache.logging.log4j.util.LoaderUtil

public final class LoaderUtil
extends java.lang.Object

Consider this class private. Utility class for ClassLoaders.

See Also:

ClassLoader, RuntimePermission, Thread.getContextClassLoader(), ClassLoader.getSystemClassLoader()

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	LoaderUtil.ThreadContextClassLoaderGetter
(package private) static class	LoaderUtil.UrlResource URL and ClassLoader pair.

Field Summary

Fields

Modifier and Type	Field and Description
private static boolean	GET_CLASS_LOADER_DISABLED
static java.lang.String	IGNORE_TCCL_PROPERTY System property to set to ignore the thread context ClassLoader.
private static java.lang.Boolean	ignoreTCCL
private static java.lang.SecurityManager	SECURITY_MANAGER
private static java.security.PrivilegedAction<java.lang.ClassLoader>	TCCL_GETTER

Constructor Summary

Constructors

Modifier	Constructor and Description
private	LoaderUtil()

Method Summary

Modifier and Type	Method and Description
static java.util.Collection<java.net.URL>	findResources(java.lang.String resource) Finds classpath resources.
(package private) static java.util.Collection<LoaderUtil.UrlResource>	findUrlResources(java.lang.String resource)
static java.lang.ClassLoader	getThreadContextClassLoader() Gets the current Thread ClassLoader.
static boolean	isClassAvailable(java.lang.String className) Determines if a named Class can be loaded or not.
private static boolean	isIgnoreTccl()
static java.lang.Class<?>	loadClass(java.lang.String className) Loads a class by name.
static <T> T	newCheckedInstanceOf(java.lang.String className, java.lang.Class<T> clazz) Loads and instantiates a derived class using its default constructor.
static <T> T	newCheckedInstanceOfProperty(java.lang.String propertyName, java.lang.Class<T> clazz) Loads and instantiates a class given by a property name.
static <T> T	newInstanceOf(java.lang.Class<T> clazz) Loads and instantiates a Class using the default constructor.
static <T> T	newInstanceOf(java.lang.String className) Loads and instantiates a Class using the default constructor.

Methods inherited from class java.lang.Object

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

Field Detail

IGNORE_TCCL_PROPERTY

public static final java.lang.String IGNORE_TCCL_PROPERTY

System property to set to ignore the thread context ClassLoader.

Since:

2.1

See Also:

Constant Field Values

SECURITY_MANAGER

private static final java.lang.SecurityManager SECURITY_MANAGER

ignoreTCCL

private static java.lang.Boolean ignoreTCCL

GET_CLASS_LOADER_DISABLED

private static final boolean GET_CLASS_LOADER_DISABLED

TCCL_GETTER

private static final java.security.PrivilegedAction<java.lang.ClassLoader> TCCL_GETTER

Constructor Detail

LoaderUtil

private LoaderUtil()

Method Detail

getThreadContextClassLoader

public static java.lang.ClassLoader getThreadContextClassLoader()

Gets the current Thread ClassLoader. Returns the system ClassLoader if the TCCL is null. If the system ClassLoader is null as well, then the ClassLoader for this class is returned. If running with a SecurityManager that does not allow access to the Thread ClassLoader or system ClassLoader, then the ClassLoader for this class is returned.

Returns:

the current ThreadContextClassLoader.

isClassAvailable

public static boolean isClassAvailable(java.lang.String className)

Determines if a named Class can be loaded or not.

Parameters:

className - The class name.

Returns:

true if the class could be found or false otherwise.

Since:

2.7

loadClass

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

Loads a class by name. This method respects the IGNORE_TCCL_PROPERTY Log4j property. If this property is specified and set to anything besides false, then the default ClassLoader will be used.

Parameters:

className - The class name.

Returns:

the Class for the given name.

Throws:

java.lang.ClassNotFoundException - if the specified class name could not be found

Since:

2.1

newInstanceOf

public static <T> T newInstanceOf(java.lang.Class<T> clazz)
                           throws java.lang.InstantiationException,
                                  java.lang.IllegalAccessException,
                                  java.lang.reflect.InvocationTargetException

Loads and instantiates a Class using the default constructor.

Parameters:

clazz - The class.

Returns:

new instance of the class.

Throws:

java.lang.IllegalAccessException - if the class can't be instantiated through a public constructor

java.lang.InstantiationException - if there was an exception whilst instantiating the class

java.lang.reflect.InvocationTargetException - if there was an exception whilst constructing the class

Since:

2.7

newInstanceOf

public static <T> T newInstanceOf(java.lang.String className)
                           throws java.lang.ClassNotFoundException,
                                  java.lang.IllegalAccessException,
                                  java.lang.InstantiationException,
                                  java.lang.NoSuchMethodException,
                                  java.lang.reflect.InvocationTargetException

Loads and instantiates a Class using the default constructor.

Parameters:

className - The class name.

Returns:

new instance of the class.

Throws:

java.lang.ClassNotFoundException - if the class isn't available to the usual ClassLoaders

java.lang.IllegalAccessException - if the class can't be instantiated through a public constructor

java.lang.InstantiationException - if there was an exception whilst instantiating the class

java.lang.NoSuchMethodException - if there isn't a no-args constructor on the class

java.lang.reflect.InvocationTargetException - if there was an exception whilst constructing the class

Since:

2.1

newCheckedInstanceOf

public static <T> T newCheckedInstanceOf(java.lang.String className,
                                         java.lang.Class<T> clazz)
                                  throws java.lang.ClassNotFoundException,
                                         java.lang.NoSuchMethodException,
                                         java.lang.reflect.InvocationTargetException,
                                         java.lang.InstantiationException,
                                         java.lang.IllegalAccessException

Loads and instantiates a derived class using its default constructor.

Type Parameters:

T - The type of the class to check.

Parameters:

className - The class name.

clazz - The class to cast it to.

Returns:

new instance of the class cast to T

Throws:

java.lang.ClassNotFoundException - if the class isn't available to the usual ClassLoaders

java.lang.IllegalAccessException - if the class can't be instantiated through a public constructor

java.lang.InstantiationException - if there was an exception whilst instantiating the class

java.lang.NoSuchMethodException - if there isn't a no-args constructor on the class

java.lang.reflect.InvocationTargetException - if there was an exception whilst constructing the class

java.lang.ClassCastException - if the constructed object isn't type compatible with T

Since:

2.1

newCheckedInstanceOfProperty

public static <T> T newCheckedInstanceOfProperty(java.lang.String propertyName,
                                                 java.lang.Class<T> clazz)
                                          throws java.lang.ClassNotFoundException,
                                                 java.lang.NoSuchMethodException,
                                                 java.lang.reflect.InvocationTargetException,
                                                 java.lang.InstantiationException,
                                                 java.lang.IllegalAccessException

Loads and instantiates a class given by a property name.

Type Parameters:

T - The type to cast it to.

Parameters:

propertyName - The property name to look up a class name for.

clazz - The class to cast it to.

Returns:

new instance of the class given in the property or null if the property was unset.

Throws:

java.lang.ClassNotFoundException - if the class isn't available to the usual ClassLoaders

java.lang.IllegalAccessException - if the class can't be instantiated through a public constructor

java.lang.InstantiationException - if there was an exception whilst instantiating the class

java.lang.NoSuchMethodException - if there isn't a no-args constructor on the class

java.lang.reflect.InvocationTargetException - if there was an exception whilst constructing the class

java.lang.ClassCastException - if the constructed object isn't type compatible with T

Since:

2.5

isIgnoreTccl

private static boolean isIgnoreTccl()

findResources

public static java.util.Collection<java.net.URL> findResources(java.lang.String resource)

Finds classpath resources.

Parameters:

resource - the name of the resource to find.

Returns:

a Collection of URLs matching the resource name. If no resources could be found, then this will be empty.

Since:

2.1

findUrlResources

static java.util.Collection<LoaderUtil.UrlResource> findUrlResources(java.lang.String resource)