Class Loader
- java.lang.Object
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- org.apache.logging.log4j.core.util.Loader
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public final class Loader extends Object
Load resources (or images) from various sources.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static ClassLoader
getClassLoader()
Returns the ClassLoader to use.static ClassLoader
getClassLoader(Class<?> class1, Class<?> class2)
static URL
getResource(String resource, ClassLoader defaultLoader)
This method will search forresource
in different places.static InputStream
getResourceAsStream(String resource, ClassLoader defaultLoader)
This method will search forresource
in different places.static ClassLoader
getThreadContextClassLoader()
Returns the ClassLoader of current thread if possible, or falls back to the system ClassLoader if none is available.static Class<?>
initializeClass(String className, ClassLoader loader)
Loads and initializes a named Class using a given ClassLoader.static boolean
isClassAvailable(String className)
Determines if a named Class can be loaded or not.static boolean
isJansiAvailable()
static Class<?>
loadClass(String className)
Loads a class by name.static Class<?>
loadClass(String className, ClassLoader loader)
Loads a named Class using a given ClassLoader.static Class<?>
loadSystemClass(String className)
Load a Class in thejava.*
namespace by name.static <T> T
newCheckedInstanceOf(String className, Class<T> clazz)
Loads, instantiates, and casts a Class using the 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(String className)
Loads and instantiates a Class using the default constructor.
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Method Detail
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getClassLoader
public static ClassLoader getClassLoader()
Returns the ClassLoader to use.- Returns:
- the ClassLoader.
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getThreadContextClassLoader
public static ClassLoader getThreadContextClassLoader()
Returns the ClassLoader of current thread if possible, or falls back to the system ClassLoader if none is available.- Returns:
- the TCCL.
- See Also:
LoaderUtil.getThreadContextClassLoader()
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getClassLoader
public static ClassLoader getClassLoader(Class<?> class1, Class<?> class2)
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getResource
public static URL getResource(String resource, ClassLoader defaultLoader)
This method will search forresource
in different places. The search order is as follows:- Search for
resource
using the thread context class loader under Java2. If that fails, search forresource
using the class loader that loaded this class (Loader
). Under JDK 1.1, only the the class loader that loaded this class (Loader
) is used. - Try one last time with
ClassLoader.getSystemResource(resource)
, that is is using the system class loader in JDK 1.2 and virtual machine's built-in class loader in JDK 1.1.
- Parameters:
resource
- The resource to load.defaultLoader
- The default ClassLoader.- Returns:
- A URL to the resource.
- Search for
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getResourceAsStream
public static InputStream getResourceAsStream(String resource, ClassLoader defaultLoader)
This method will search forresource
in different places. The search order is as follows:- Search for
resource
using the thread context class loader under Java2. If that fails, search forresource
using the class loader that loaded this class (Loader
). Under JDK 1.1, only the the class loader that loaded this class (Loader
) is used. - Try one last time with
ClassLoader.getSystemResource(resource)
, that is is using the system class loader in JDK 1.2 and virtual machine's built-in class loader in JDK 1.1.
- Parameters:
resource
- The resource to load.defaultLoader
- The default ClassLoader.- Returns:
- An InputStream to read the resouce.
- Search for
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initializeClass
public static Class<?> initializeClass(String className, ClassLoader loader) throws ClassNotFoundException
Loads and initializes a named Class using a given ClassLoader.- Parameters:
className
- The class name.loader
- The class loader.- Returns:
- The class.
- Throws:
ClassNotFoundException
- if the class could not be found.
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loadClass
public static Class<?> loadClass(String className, ClassLoader loader) throws ClassNotFoundException
Loads a named Class using a given ClassLoader.- Parameters:
className
- The class name.loader
- The class loader.- Returns:
- The class, or null if loader is null.
- Throws:
ClassNotFoundException
- if the class could not be found.
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loadSystemClass
public static Class<?> loadSystemClass(String className) throws ClassNotFoundException
Load a Class in thejava.*
namespace by name. Useful for peculiar scenarios typically involving Google App Engine.- Parameters:
className
- The class name.- Returns:
- The Class.
- Throws:
ClassNotFoundException
- if the Class could not be found.
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newInstanceOf
public static <T> T newInstanceOf(String className) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, 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 ClassLoadersIllegalAccessException
- if the class can't be instantiated through a public constructorInstantiationException
- if there was an exception whilst instantiating the classNoSuchMethodException
- if there isn't a no-args constructor on the classInvocationTargetException
- if there was an exception whilst constructing the class
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newCheckedInstanceOf
public static <T> T newCheckedInstanceOf(String className, Class<T> clazz) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException
Loads, instantiates, and casts a Class using the default constructor.- Type Parameters:
T
- The type to cast it to.- 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 ClassLoadersIllegalAccessException
- if the class can't be instantiated through a public constructorInstantiationException
- if there was an exception whilst instantiating the classNoSuchMethodException
- if there isn't a no-args constructor on the classInvocationTargetException
- if there was an exception whilst constructing the classClassCastException
- if the constructed object isn't type compatible withT
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newCheckedInstanceOfProperty
public static <T> T newCheckedInstanceOfProperty(String propertyName, Class<T> clazz) throws ClassNotFoundException, NoSuchMethodException, 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 ClassLoadersIllegalAccessException
- if the class can't be instantiated through a public constructorInstantiationException
- if there was an exception whilst instantiating the classNoSuchMethodException
- if there isn't a no-args constructor on the classInvocationTargetException
- if there was an exception whilst constructing the classClassCastException
- if the constructed object isn't type compatible withT
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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 orfalse
otherwise.
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isJansiAvailable
public static boolean isJansiAvailable()
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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 besidesfalse
, 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
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