de.jstacs.utils
Class SubclassFinder

java.lang.Object
  de.jstacs.utils.SubclassFinder

public class SubclassFinder
extends Object

Utility-class with static methods to

• find all sub-classes of a certain class (or interface) within the scope of the current class-loader
• find all sub-classes of a certain class (or interface) within the scope of the current class-loader that can be instantiated, i.e. that are neither interfaces nor abstract
• filter a set of classes by inheritance from a super-class
• obtain the class of an InstanceParameterSet that can be used to instantiate a sub-class of InstantiableFromParameterSet.
• obtain a CollectionParameter using all possible InstanceParameterSets (for classes that are a subclass of a specified superclass) as elements

The methods may fail to find a certain sub-class, if

• it was loaded by another ClassLoader than the caller
• it was loaded from a physically other place than the super-class, e.g. another jar-file.

Author:

Jan Grau, Jens Keilwagen

Constructor Summary

SubclassFinder()

Method Summary

static <S,T> LinkedList<Class<? extends S>>	filterBySuperclass(Class<S> superclass, LinkedList<Class<? extends T>> listToFilter) Returns a LinkedList of the Class objects for all classes in listToFilter that are sub-classes of superClass.
static <T> LinkedList<Class<? extends T>>	findInstantiableSubclasses(Class<T> clazz, String startPackage) Returns all sub-classes of T that can be instantiated, i.e.
static <T> LinkedList<Class<? extends T>>	findSubclasses(Class<T> clazz, String startPackage) Returns all sub-classes of T including interfaces and abstract classes that are located in a package below startPackage.
static <T> CollectionParameter	getCollection(Class<T> clazz, String startPackage, String name, String comment, boolean required) This method creates an CollectionParameter that contains InstanceParameterSet for each possible class.
static <T> LinkedList<InstanceParameterSet>	getInstanceParameterSets(Class<T> clazz, String startPackage) This method returns a list of InstanceParameterSets that can be used to create a subclass of clazz.
static LinkedList<Class<? extends InstanceParameterSet>>	getParameterSetFor(Class<? extends InstantiableFromParameterSet> clazz) Returns a LinkedList of the classes of the InstanceParameterSets that can be used to instantiate the sub-class of InstantiableFromParameterSet that is given by clazz

Methods inherited from class java.lang.Object

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

Constructor Detail

SubclassFinder

public SubclassFinder()

Method Detail

findInstantiableSubclasses

public static <T> LinkedList<Class<? extends T>> findInstantiableSubclasses(Class<T> clazz,
                                                                            String startPackage)
                                                                 throws ClassNotFoundException,
                                                                        IOException

Returns all sub-classes of T that can be instantiated, i.e. are neither an interface nor abstract, and that are located in a package below startPackage.

Type Parameters:

T - The class to obtain the sub-classes for

Parameters:

clazz - the Class object for T

startPackage - the package under which to search

Returns:

the Class objects for the sub-classes

Throws:

ClassNotFoundException - if one of the classes is present in the file system or jar but cannot be loaded by the class loader

IOException - is thrown if the classes are searched for in a jar file, but that file could not be accessed or read

filterBySuperclass

public static <S,T> LinkedList<Class<? extends S>> filterBySuperclass(Class<S> superclass,
                                                                      LinkedList<Class<? extends T>> listToFilter)

Returns a LinkedList of the Class objects for all classes in listToFilter that are sub-classes of superClass.

Type Parameters:

S - the class that is used as filter

T - a common super-class of all classes in listToFilter

Parameters:

superclass - the additional class to use as a filter criterion

listToFilter - the list of classes

Returns:

the filtered list

getParameterSetFor

public static LinkedList<Class<? extends InstanceParameterSet>> getParameterSetFor(Class<? extends InstantiableFromParameterSet> clazz)

Returns a LinkedList of the classes of the InstanceParameterSets that can be used to instantiate the sub-class of InstantiableFromParameterSet that is given by clazz

Parameters:

clazz - the Class object of the sub-class of InstantiableFromParameterSet

Returns:

a LinkedList of Classes of the corresponding InstanceParameterSets

findSubclasses

public static <T> LinkedList<Class<? extends T>> findSubclasses(Class<T> clazz,
                                                                String startPackage)
                                                     throws ClassNotFoundException,
                                                            IOException

Returns all sub-classes of T including interfaces and abstract classes that are located in a package below startPackage.

Type Parameters:

T - The class to obtain the sub-classes for

Parameters:

clazz - the Class object for T

startPackage - the package under which to search

Returns:

the Class objects for the sub-classes

Throws:

ClassNotFoundException - if one of the classes is present in the file system or jar but cannot be loaded by the class loader

IOException - is thrown if the classes are searched for in a jar file, but that file could not be accessed or read

getCollection

public static <T> CollectionParameter getCollection(Class<T> clazz,
                                                    String startPackage,
                                                    String name,
                                                    String comment,
                                                    boolean required)
                                         throws InstantiationException,
                                                IllegalAccessException,
                                                ClassNotFoundException,
                                                IOException

This method creates an CollectionParameter that contains InstanceParameterSet for each possible class. The classes are specified by findInstantiableSubclasses(Class, String) and filterBySuperclass(Class, LinkedList).

Type Parameters:

T - The class to use the sub-classes in the CollectionParameter

Parameters:

clazz - the Class object for T

startPackage - the package under which to start the search

name - the name of the CollectionParameter

comment - the comment for the CollectionParameter

required - whether the CollectionParameter is required

Returns:

a CollectionParameter that contains InstanceParameterSet for each possible class.

Throws:

InstantiationException - if any InstanceParameterSet has no nullary constructor; or if the instantiation fails for some other reason

IllegalAccessException - if any InstanceParameterSet or its nullary constructor is not accessible

ClassNotFoundException - if one of the classes is present in the file system or jar but cannot be loaded by the class loader

IOException - if the classes are searched for in a jar file, but that file could not be accessed or read

See Also:

findInstantiableSubclasses(Class, String), filterBySuperclass(Class, LinkedList), getInstanceParameterSets(Class, String)

getInstanceParameterSets

public static <T> LinkedList<InstanceParameterSet> getInstanceParameterSets(Class<T> clazz,
                                                                            String startPackage)
                                                                 throws ClassNotFoundException,
                                                                        IOException,
                                                                        InstantiationException,
                                                                        IllegalAccessException

This method returns a list of InstanceParameterSets that can be used to create a subclass of clazz. The classes are specified by findInstantiableSubclasses(Class, String) and filterBySuperclass(Class, LinkedList).

Type Parameters:

T - The class to use the sub-classes in the CollectionParameter

Parameters:

clazz - the Class object for T

startPackage - the package under which to start the search

Returns:

a LinkedList that contains InstanceParameterSet for each possible class.

Throws:

InstantiationException - if any InstanceParameterSet has no nullary constructor; or if the instantiation fails for some other reason

IllegalAccessException - if any InstanceParameterSet or its nullary constructor is not accessible

ClassNotFoundException - if one of the classes is present in the file system or jar but cannot be loaded by the class loader

IOException - if the classes are searched for in a jar file, but that file could not be accessed or read

See Also:

findInstantiableSubclasses(Class, String), filterBySuperclass(Class, LinkedList)