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 java.lang.Object
Load resources (or images) from various sources.
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Constructor Summary
Constructors Modifier Constructor Description private
Loader()
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static java.lang.ClassLoader
getClassLoader()
Returns the ClassLoader to use.static java.lang.ClassLoader
getClassLoader(java.lang.Class<?> class1, java.lang.Class<?> class2)
static java.net.URL
getResource(java.lang.String resource, java.lang.ClassLoader defaultLoader)
This method will search forresource
in different places.static java.io.InputStream
getResourceAsStream(java.lang.String resource, java.lang.ClassLoader defaultLoader)
This method will search forresource
in different places.static java.lang.ClassLoader
getThreadContextClassLoader()
Returns the ClassLoader of current thread if possible, or falls back to the system ClassLoader if none is available.static java.lang.Class<?>
initializeClass(java.lang.String className, java.lang.ClassLoader loader)
Loads and initializes a named Class using a given ClassLoader.private static boolean
isChild(java.lang.ClassLoader loader1, java.lang.ClassLoader loader2)
Determines if one ClassLoader is a child of another ClassLoader.static boolean
isClassAvailable(java.lang.String className)
Determines if a named Class can be loaded or not.static boolean
isJansiAvailable()
static java.lang.Class<?>
loadClass(java.lang.String className)
Loads a class by name.static java.lang.Class<?>
loadClass(java.lang.String className, java.lang.ClassLoader loader)
Loads a named Class using a given ClassLoader.static java.lang.Class<?>
loadSystemClass(java.lang.String className)
Load a Class in thejava.*
namespace by name.static <T> T
newCheckedInstanceOf(java.lang.String className, java.lang.Class<T> clazz)
Loads, instantiates, and casts a Class using the 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.String className)
Loads and instantiates a Class using the default constructor.
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Field Detail
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LOGGER
private static final Logger LOGGER
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TSTR
private static final java.lang.String TSTR
- See Also:
- Constant Field Values
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Method Detail
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getClassLoader
public static java.lang.ClassLoader getClassLoader()
Returns the ClassLoader to use.- Returns:
- the ClassLoader.
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getThreadContextClassLoader
public static java.lang.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 java.lang.ClassLoader getClassLoader(java.lang.Class<?> class1, java.lang.Class<?> class2)
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getResource
public static java.net.URL getResource(java.lang.String resource, java.lang.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 java.io.InputStream getResourceAsStream(java.lang.String resource, java.lang.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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isChild
private static boolean isChild(java.lang.ClassLoader loader1, java.lang.ClassLoader loader2)
Determines if one ClassLoader is a child of another ClassLoader. Note that anull
ClassLoader is interpreted as the system ClassLoader as per convention.- Parameters:
loader1
- the ClassLoader to check for childhood.loader2
- the ClassLoader to check for parenthood.- Returns:
true
if the first ClassLoader is a strict descendant of the second ClassLoader.
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initializeClass
public static java.lang.Class<?> initializeClass(java.lang.String className, java.lang.ClassLoader loader) throws java.lang.ClassNotFoundException
Loads and initializes a named Class using a given ClassLoader.- Parameters:
className
- The class name.loader
- The class loader.- Returns:
- The class.
- Throws:
java.lang.ClassNotFoundException
- if the class could not be found.
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loadClass
public static java.lang.Class<?> loadClass(java.lang.String className, java.lang.ClassLoader loader) throws java.lang.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:
java.lang.ClassNotFoundException
- if the class could not be found.
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loadSystemClass
public static java.lang.Class<?> loadSystemClass(java.lang.String className) throws java.lang.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:
java.lang.ClassNotFoundException
- if the Class could not be found.
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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 ClassLoadersjava.lang.IllegalAccessException
- if the class can't be instantiated through a public constructorjava.lang.InstantiationException
- if there was an exception whilst instantiating the classjava.lang.NoSuchMethodException
- if there isn't a no-args constructor on the classjava.lang.reflect.InvocationTargetException
- if there was an exception whilst constructing the class
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newCheckedInstanceOf
public static <T> T newCheckedInstanceOf(java.lang.String className, java.lang.Class<T> clazz) throws java.lang.ClassNotFoundException, java.lang.NoSuchMethodException, java.lang.IllegalAccessException, java.lang.reflect.InvocationTargetException, java.lang.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:
java.lang.ClassNotFoundException
- if the class isn't available to the usual ClassLoadersjava.lang.IllegalAccessException
- if the class can't be instantiated through a public constructorjava.lang.InstantiationException
- if there was an exception whilst instantiating the classjava.lang.NoSuchMethodException
- if there isn't a no-args constructor on the classjava.lang.reflect.InvocationTargetException
- if there was an exception whilst constructing the classjava.lang.ClassCastException
- if the constructed object isn't type compatible withT
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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 ClassLoadersjava.lang.IllegalAccessException
- if the class can't be instantiated through a public constructorjava.lang.InstantiationException
- if there was an exception whilst instantiating the classjava.lang.NoSuchMethodException
- if there isn't a no-args constructor on the classjava.lang.reflect.InvocationTargetException
- if there was an exception whilst constructing the classjava.lang.ClassCastException
- if the constructed object isn't type compatible withT
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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 orfalse
otherwise.
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isJansiAvailable
public static boolean isJansiAvailable()
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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 besidesfalse
, 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
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