org.key_project.util.reflection

Class ClassLoaderUtil

java.lang.Object

org.key_project.util.reflection.ClassLoaderUtil

public class ClassLoaderUtil
extends java.lang.Object

This class provides utility methods to load classes at runtime which works in all supported application types:

• Java Application
• OSGI (Eclipse)

The Java reflection framework allows to load classes at runtime for instance via Class.forName(String). In a configuration-file configured classes can also be instantiated via the ServiceLoader. But both approaches work only, if the Class to work with is known by the current ClassLoader. This is no problem in a normal Java Application since all classes are managed by the same ClassLoader. But in an OSGI setup like Eclipse, each component (plug-in) has its own ClassLoader. The consequence is that the reflection framework can only work with classes in the same component as they are only known by the current ClassLoader.

To achieve the same behavior in all supported types provides this class utility methods which should be used instead:

• getClassforName(String) instead of Class.forName(String)
• #loadServices(Class, Class) instead of {@link ServiceLoader#load(Class)}

The application specific behavior is implemented in {@link IClassLoader} instances. The used instance is accessible via {@link #getClassLoader()} which is by default the {@link JavaApplicationClassLoader}. In an OSGI (Eclipse) setup the instance is replaced via {@link #setClassLoader(IClassLoader)} with an {@code OSGIClassLoader} instance.

Author:

Martin Hentschel

See Also:

IClassLoader, JavaApplicationClassLoader

Field Summary

Fields

Modifier and Type	Field and Description
private static IClassLoader	classLoader The IClassLoader instance to use.

Constructor Summary

Constructors

Constructor and Description
ClassLoaderUtil()

Method Summary

Modifier and Type	Method and Description
static java.lang.Class<?>	getClassforName(java.lang.String className) Returns the Class for the given class name similar to Class.forName(String) but with same behavior in all supported application types.
static IClassLoader	getClassLoader() Returns the used IClassLoader.
static <S> java.lang.Iterable<S>	loadServices(java.lang.Class<?> contextClass, java.lang.Class<S> service) Loads all configured services similar to ServiceLoader.load(Class) but with same behavior in all supported application types.
static <S> java.lang.Iterable<S>	loadServices(java.lang.Class<S> service) Loads all configured services similar to ServiceLoader.load(Class) but with same behavior in all supported application types.
static void	setClassLoader(IClassLoader classLoader) Sets the IClassLoader instance to use.

Methods inherited from class java.lang.Object

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

Field Detail

classLoader

private static IClassLoader classLoader

The IClassLoader instance to use.

Constructor Detail

ClassLoaderUtil

public ClassLoaderUtil()

Method Detail

getClassLoader

public static IClassLoader getClassLoader()

Returns the used IClassLoader.

Returns:

The used IClassLoader.

setClassLoader

public static void setClassLoader(IClassLoader classLoader)

Sets the IClassLoader instance to use.

Parameters:

classLoader - The IClassLoader instance to use.

getClassforName

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

Returns the Class for the given class name similar to Class.forName(String) but with same behavior in all supported application types.

Parameters:

className - The name of the class.

Returns:

The Class instance.

Throws:

java.lang.ClassNotFoundException - Occurred Exception if Class is not available.

loadServices

public static <S> java.lang.Iterable<S> loadServices(java.lang.Class<S> service)

Loads all configured services similar to ServiceLoader.load(Class) but with same behavior in all supported application types.

Parameters:

service - The requested service.

Returns:

An Iterable with the created service instances.

loadServices

public static <S> java.lang.Iterable<S> loadServices(java.lang.Class<?> contextClass,
                                                     java.lang.Class<S> service)

Loads all configured services similar to ServiceLoader.load(Class) but with same behavior in all supported application types.

Parameters:

contextClass - The calling Class which ClassLoader knows the configuration-file.

service - The requested service.

Returns:

An Iterable with the created service instances.