net.sourceforge.jfacets.util
Class ResolverUtil<T>

java.lang.Object
  net.sourceforge.jfacets.util.ResolverUtil<T>

public class ResolverUtil<T>
extends java.lang.Object

Utility for finding classes in the classpath. Borrowed from the Stripes Framework : http://www.stripesframework.org ! Thanks to Tim for that very useful piece of code :-)

Author:

Tim Fennell

Nested Class Summary

static class	ResolverUtil.AnnotatedWith A Test that checks to see if each class is annotated with a specific annotation.
static class	ResolverUtil.IsA A Test that checks to see if each class is assignable to the provided class.
static interface	ResolverUtil.Test A simple interface that specifies how to test classes to determine if they are to be included in the results produced by the ResolverUtil.

Field Summary

private java.lang.ClassLoader	classloader The ClassLoader to use when looking for classes.
private static JFacetsLogger	log An instance of Log to use for logging in this class.
private java.util.Set<java.lang.Class<? extends T>>	matches The set of matches being accumulated.

Constructor Summary

ResolverUtil()

Method Summary

protected void	addIfMatching(ResolverUtil.Test test, java.lang.String fqn) Add the class designated by the fully qualified class name provided to the set of resolved classes if and only if it is approved by the Test supplied.
void	find(ResolverUtil.Test test, java.lang.String packageName) Scans for classes starting at the package provided and descending into subpackages.
void	findAnnotated(java.lang.Class<? extends java.lang.annotation.Annotation> annotation, java.lang.String... packageNames) Attempts to discover classes that are annotated with to the annotation.
void	findImplementations(java.lang.Class parent, java.lang.String... packageNames) Attempts to discover classes that are assignable to the type provided.
java.util.Set<java.lang.Class<? extends T>>	getClasses() Provides access to the classes discovered so far.
java.lang.ClassLoader	getClassLoader() Returns the classloader that will be used for scanning for classes.
private void	loadImplementationsInDirectory(ResolverUtil.Test test, java.lang.String parent, java.io.File location) Finds matches in a physical directory on a filesystem.
private void	loadImplementationsInJar(ResolverUtil.Test test, java.lang.String parent, java.io.File jarfile) Finds matching classes within a jar files that contains a folder structure matching the package structure.
void	setClassLoader(java.lang.ClassLoader classloader) Sets an explicit ClassLoader that should be used when scanning for classes.

Methods inherited from class java.lang.Object

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

Field Detail

log

private static final JFacetsLogger log

An instance of Log to use for logging in this class.

matches

private java.util.Set<java.lang.Class<? extends T>> matches

The set of matches being accumulated.

classloader

private java.lang.ClassLoader classloader

The ClassLoader to use when looking for classes. If null then the ClassLoader returned by Thread.currentThread().getContextClassLoader() will be used.

Constructor Detail

ResolverUtil

public ResolverUtil()

Method Detail

getClasses

public java.util.Set<java.lang.Class<? extends T>> getClasses()

Provides access to the classes discovered so far. If no calls have been made to any of the find() methods, this set will be empty.

Returns:

the set of classes that have been discovered.

getClassLoader

public java.lang.ClassLoader getClassLoader()

Returns the classloader that will be used for scanning for classes. If no explicit ClassLoader has been set by the calling, the context class loader will be used.

Returns:

the ClassLoader that will be used to scan for classes

setClassLoader

public void setClassLoader(java.lang.ClassLoader classloader)

Sets an explicit ClassLoader that should be used when scanning for classes. If none is set then the context classloader will be used.

Parameters:

classloader - a ClassLoader to use when scanning for classes

findImplementations

public void findImplementations(java.lang.Class parent,
                                java.lang.String... packageNames)

Attempts to discover classes that are assignable to the type provided. In the case that an interface is provided this method will collect implementations. In the case of a non-interface class, subclasses will be collected. Accumulated classes can be accessed by calling getClasses().

Parameters:

parent - the class of interface to find subclasses or implementations of

packageNames - one or more package names to scan (including subpackages) for classes

findAnnotated

public void findAnnotated(java.lang.Class<? extends java.lang.annotation.Annotation> annotation,
                          java.lang.String... packageNames)

Attempts to discover classes that are annotated with to the annotation. Accumulated classes can be accessed by calling getClasses().

Parameters:

annotation - the annotation that should be present on matching classes

packageNames - one or more package names to scan (including subpackages) for classes

find

public void find(ResolverUtil.Test test,
                 java.lang.String packageName)

Scans for classes starting at the package provided and descending into subpackages. Each class is offered up to the Test as it is discovered, and if the Test returns true the class is retained. Accumulated classes can be fetched by calling getClasses().

Parameters:

test - an instance of ResolverUtil.Test that will be used to filter classes

packageName - the name of the package from which to start scanning for classes, e.g. net.sourceforge.stripes

loadImplementationsInDirectory

private void loadImplementationsInDirectory(ResolverUtil.Test test,
                                            java.lang.String parent,
                                            java.io.File location)

Finds matches in a physical directory on a filesystem. Examines all files within a directory - if the File object is not a directory, and ends with .class the file is loaded and tested to see if it is acceptable according to the Test. Operates recursively to find classes within a folder structure matching the package structure.

Parameters:

test - a Test used to filter the classes that are discovered

parent - the package name up to this directory in the package hierarchy. E.g. if /classes is in the classpath and we wish to examine files in /classes/org/apache then the values of parent would be org/apache

location - a File object representing a directory

loadImplementationsInJar

private void loadImplementationsInJar(ResolverUtil.Test test,
                                      java.lang.String parent,
                                      java.io.File jarfile)

Finds matching classes within a jar files that contains a folder structure matching the package structure. If the File is not a JarFile or does not exist a warning will be logged, but no error will be raised.

Parameters:

test - a Test used to filter the classes that are discovered

parent - the parent package under which classes must be in order to be considered

jarfile - the jar file to be examined for classes

addIfMatching

protected void addIfMatching(ResolverUtil.Test test,
                             java.lang.String fqn)

Add the class designated by the fully qualified class name provided to the set of resolved classes if and only if it is approved by the Test supplied.

Parameters:

test - the test used to determine if the class matches

fqn - the fully qualified name of a class