Package org.apache.logging.log4j.util

Class LoaderUtil

java.lang.Object

org.apache.logging.log4j.util.LoaderUtil

public final class LoaderUtil
extends Object

Consider this class private. Utility class for ClassLoaders.

See Also:

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

Field Summary

Fields

Modifier and Type	Field	Description
static String	IGNORE_TCCL_PROPERTY	System property to set to ignore the thread context ClassLoader.

Method Summary

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

System property to set to ignore the thread context ClassLoader.

Since:

2.1

See Also:

Constant Field Values

Method Detail

getThreadContextClassLoader

public static 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.

getClassLoaders

public static ClassLoader[] getClassLoaders()

isClassAvailable

public static boolean isClassAvailable(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 Class<?> loadClass(String className)
                          throws 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:

ClassNotFoundException - if the specified class name could not be found

Since:

2.1

newInstanceOf

public static <T> T newInstanceOf(Class<T> clazz)
                           throws InstantiationException,
                                  IllegalAccessException,
                                  InvocationTargetException

Loads and instantiates a Class using the default constructor.

Type Parameters:

T - the type of the class modeled by the Class object.

Parameters:

clazz - The class.

Returns:

new instance of the class.

Throws:

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

InstantiationException - if there was an exception whilst instantiating the class

InvocationTargetException - if there was an exception whilst constructing the class

Since:

2.7

newInstanceOf

public static <T> T newInstanceOf(String className)
                           throws ClassNotFoundException,
                                  IllegalAccessException,
                                  InstantiationException,
                                  InvocationTargetException

Loads and instantiates a Class using the default constructor.

Parameters:

className - The class name.

Returns:

new instance of the class.

Throws:

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

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

InstantiationException - if there was an exception whilst instantiating the class

InvocationTargetException - if there was an exception whilst constructing the class

Since:

2.1

newCheckedInstanceOf

public static <T> T newCheckedInstanceOf(String className,
                                         Class<T> clazz)
                                  throws ClassNotFoundException,
                                         InvocationTargetException,
                                         InstantiationException,
                                         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:

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

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

InstantiationException - if there was an exception whilst instantiating the class

InvocationTargetException - if there was an exception whilst constructing the class

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

Since:

2.1

newCheckedInstanceOfProperty

public static <T> T newCheckedInstanceOfProperty(String propertyName,
                                                 Class<T> clazz)
                                          throws ClassNotFoundException,
                                                 InvocationTargetException,
                                                 InstantiationException,
                                                 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:

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

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

InstantiationException - if there was an exception whilst instantiating the class

InvocationTargetException - if there was an exception whilst constructing the class

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

Since:

2.5

findResources

public static Collection<URL> findResources(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