Is it possible to find all classes or interfaces in a given package? (Quickly looking at e.g. Package, it would seem like no.)
I've been trying to use the Reflections library, but had some problems using it, and there were too many jars I should include just to simply obtain the classes on a package.
I'll post a solution I've found in this duplicate question: How to get all classes names in a package?
The answer was written by sp00m; I've added some corrections to make it work:
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.Enumeration;
import java.util.LinkedList;
import java.util.List;
public final class ClassFinder {
private final static char DOT = '.';
private final static char SLASH = '/';
private final static String CLASS_SUFFIX = ".class";
private final static String BAD_PACKAGE_ERROR = "Unable to get resources from path '%s'. Are you sure the given '%s' package exists?";
public final static List> find(final String scannedPackage) {
final ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
final String scannedPath = scannedPackage.replace(DOT, SLASH);
final Enumeration resources;
try {
resources = classLoader.getResources(scannedPath);
} catch (IOException e) {
throw new IllegalArgumentException(String.format(BAD_PACKAGE_ERROR, scannedPath, scannedPackage), e);
}
final List> classes = new LinkedList>();
while (resources.hasMoreElements()) {
final File file = new File(resources.nextElement().getFile());
classes.addAll(find(file, scannedPackage));
}
return classes;
}
private final static List> find(final File file, final String scannedPackage) {
final List> classes = new LinkedList>();
if (file.isDirectory()) {
for (File nestedFile : file.listFiles()) {
classes.addAll(find(nestedFile, scannedPackage));
}
//File names with the $1, $2 holds the anonymous inner classes, we are not interested on them.
} else if (file.getName().endsWith(CLASS_SUFFIX) && !file.getName().contains("$")) {
final int beginIndex = 0;
final int endIndex = file.getName().length() - CLASS_SUFFIX.length();
final String className = file.getName().substring(beginIndex, endIndex);
try {
final String resource = scannedPackage + DOT + className;
classes.add(Class.forName(resource));
} catch (ClassNotFoundException ignore) {
}
}
return classes;
}
}
To use it just call the find method as sp00n mentioned in this example: I've added the creation of instances of the classes if needed.
List> classes = ClassFinder.find("com.package");
ExcelReporting excelReporting;
for (Class> aClass : classes) {
Constructor constructor = aClass.getConstructor();
//Create an object of the class type
constructor.newInstance();
//...
}