Java Class from Package getClassesForPackage(String pckgname)

Description

Attempts to list all the classes in the specified package as determined by the context class loader

License

Open Source License

Parameter

Parameter	Description
pckgname	the package name to search

Exception

Parameter	Description
ClassNotFoundException	if something went wrong

Return

a list of classes that exist within that package

Declaration

public static ArrayList<Class<?>> getClassesForPackage(String pckgname) throws ClassNotFoundException

Method Source Code


//package com.java2s;
//License from project: Open Source License 

import java.io.File;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import sun.net.www.protocol.file.FileURLConnection;

public class Main {
    /**/* w  w w .  j  a  v a2 s.c o m*/
     * Attempts to list all the classes in the specified package as determined
     * by the context class loader
     *
     * @param pckgname the package name to search
     * @return a list of classes that exist within that package
     * @throws ClassNotFoundException if something went wrong
     */
    public static ArrayList<Class<?>> getClassesForPackage(String pckgname) throws ClassNotFoundException {
        final ArrayList<Class<?>> classes = new ArrayList<>();

        try {
            final ClassLoader cld = Thread.currentThread().getContextClassLoader();

            if (cld == null) {
                throw new ClassNotFoundException("Can't get class loader.");
            }

            final Enumeration<URL> resources = cld.getResources(pckgname.replace('.', '/'));
            URLConnection connection;

            for (URL url = null; resources.hasMoreElements() && ((url = resources.nextElement()) != null);) {
                try {
                    connection = url.openConnection();

                    if (connection instanceof JarURLConnection) {
                        checkJarFile((JarURLConnection) connection, pckgname, classes);
                    } else if (connection instanceof FileURLConnection) {
                        try {
                            checkDirectory(new File(URLDecoder.decode(url.getPath(), "UTF-8")), pckgname, classes);
                        } catch (final UnsupportedEncodingException ex) {
                            throw new ClassNotFoundException(
                                    pckgname + " does not appear to be a valid package (Unsupported encoding)", ex);
                        }
                    } else {
                        throw new ClassNotFoundException(
                                pckgname + " (" + url.getPath() + ") does not appear to be a valid package");
                    }
                } catch (final IOException ioex) {
                    throw new ClassNotFoundException(
                            "IOException was thrown when trying to get all resources for " + pckgname, ioex);
                }
            }
        } catch (final NullPointerException ex) {
            throw new ClassNotFoundException(
                    pckgname + " does not appear to be a valid package (Null pointer exception)", ex);
        } catch (final IOException ioex) {
            throw new ClassNotFoundException(
                    "IOException was thrown when trying to get all resources for " + pckgname, ioex);
        }

        return classes;
    }

    /**
     * Private helper method.
     *
     * @param connection the connection to the jar
     * @param pckgname the package name to search for
     * @param classes the current ArrayList of all classes. This method will
     * simply add new classes.
     * @throws ClassNotFoundException if a file isn't loaded but still is in the
     * jar file
     * @throws IOException if it can't correctly read from the jar file.
     */
    private static void checkJarFile(JarURLConnection connection, String pckgname, ArrayList<Class<?>> classes)
            throws ClassNotFoundException, IOException {
        final JarFile jarFile = connection.getJarFile();
        final Enumeration<JarEntry> entries = jarFile.entries();
        String name;

        for (JarEntry jarEntry = null; entries.hasMoreElements() && ((jarEntry = entries.nextElement()) != null);) {
            name = jarEntry.getName();

            if (name.contains(".class")) {
                name = name.substring(0, name.length() - 6).replace('/', '.');

                if (name.contains(pckgname)) {
                    classes.add(Class.forName(name));
                }
            }
        }
    }

    /**
     * Private helper method
     *
     * @param directory The directory to start with
     * @param pckgname The package name to search for. Will be needed for
     * getting the Class object.
     * @param classes if a file isn't loaded but still is in the directory
     * @throws ClassNotFoundException
     */
    private static void checkDirectory(File directory, String pckgname, ArrayList<Class<?>> classes)
            throws ClassNotFoundException {
        File tmpDirectory;

        if (directory.exists() && directory.isDirectory()) {
            final String[] files = directory.list();

            for (final String file : files) {
                if (file.endsWith(".class")) {
                    try {
                        classes.add(Class.forName(pckgname + '.' + file.substring(0, file.length() - 6)));
                    } catch (final NoClassDefFoundError e) {
                        // do nothing. this class hasn't been found by the
                        // loader, and we don't care.
                    }
                } else if ((tmpDirectory = new File(directory, file)).isDirectory()) {
                    checkDirectory(tmpDirectory, pckgname + "." + file, classes);
                }
            }
        }
    }
}

Java Class from Package getClassesForPackage(String pckgname)

Description

License

Parameter

Exception

Return

Declaration

Method Source Code

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