Java Class from Package getClassesInPackage(String packageName)

Description

Retrieves recursively all the classes belonging to a package.

License

Apache License

Parameter

Parameter	Description
packageName	a parameter

Exception

Parameter	Description
ClassNotFoundException	if any error occurs

Return

the list of Class found

Declaration

public static List<Class<?>> getClassesInPackage(String packageName) throws ClassNotFoundException 

Method Source Code

//package com.java2s;
//License from project: Apache License 

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

import java.net.URL;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.Enumeration;

import java.util.List;

import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;

public class Main {
    /**// w  w  w  .  j  ava  2s  .  co m
     * Retrieves recursively all the classes belonging to a package.
     * 
     * @param packageName
     * @return the list of Class found
     * @throws ClassNotFoundException if any error occurs
     */
    public static List<Class<?>> getClassesInPackage(String packageName) throws ClassNotFoundException {
        return getClassesInPackage(packageName, Thread.currentThread().getContextClassLoader());
    }

    /**
     * Retrieves recursively all the classes belonging to a package.
     * 
     * @param packageName
     * @param classLoader the class loader used to load the class in the given package
     * @return the list of Class found
     * @throws ClassNotFoundException if any error occurs
     */
    public static List<Class<?>> getClassesInPackage(String packageName, ClassLoader classLoader)
            throws ClassNotFoundException {
        try {
            if (classLoader == null) {
                throw new ClassNotFoundException("Can't get class loader.");
            }
            String path = packageName.replace('.', '/');
            // Ask for all resources for the path
            Enumeration<URL> resources = classLoader.getResources(path);
            List<Class<?>> classes = new ArrayList<Class<?>>();
            while (resources.hasMoreElements()) {
                URL resource = resources.nextElement();
                File directory = new File(URLDecoder.decode(resource.getPath(), "UTF-8"));
                if (directory.canRead()) {
                    classes.addAll(getClassesInDirectory(directory, packageName, classLoader));
                } else {
                    // it's a jar file
                    String jarName = directory.getPath().substring(5, directory.getPath().indexOf(".jar") + 4);
                    classes.addAll(getClassesInJarFile(jarName, packageName, classLoader));
                }
            }
            return classes;
        } catch (NullPointerException x) {
            throw new ClassNotFoundException(
                    packageName + " does not appear to be a valid package (Null pointer exception)", x);
        } catch (UnsupportedEncodingException encex) {
            throw new ClassNotFoundException(
                    packageName + " does not appear to be a valid package (Unsupported encoding)", encex);
        } catch (IOException ioex) {
            throw new ClassNotFoundException(
                    "IOException was thrown when trying to get all resources for " + packageName, ioex);
        }
    }

    private static List<Class<?>> getClassesInDirectory(File directory, String packageName, ClassLoader classLoader)
            throws UnsupportedEncodingException {
        List<Class<?>> classes = new ArrayList<Class<?>>();
        // Capture all the .class files in this directory
        // Get the list of the files contained in the package
        String[] files = directory.list();
        for (String currentFile : files) {
            // we are only interested in .class files
            if (currentFile.endsWith(".class")) {
                // removes the .class extension
                // CHECKSTYLE:OFF
                try {
                    String className = packageName + '.' + currentFile.substring(0, currentFile.length() - 6);
                    classes.add(loadClass(className, classLoader));
                } catch (Throwable e) {
                    // do nothing. this class hasn't been found by the loader, and we don't care.
                }
                // CHECKSTYLE:ON
            } else {
                // It's another package
                String subPackageName = packageName + '.' + currentFile;
                // Ask for all resources for the path
                URL resource = classLoader.getResource(subPackageName.replace('.', '/'));
                File subDirectory = new File(URLDecoder.decode(resource.getPath(), "UTF-8"));
                List<Class<?>> classesForSubPackage = getClassesInDirectory(subDirectory, subPackageName,
                        classLoader);
                classes.addAll(classesForSubPackage);
            }
        }
        return classes;
    }

    private static List<Class<?>> getClassesInJarFile(String jar, String packageName, ClassLoader classLoader)
            throws IOException {
        List<Class<?>> classes = new ArrayList<Class<?>>();
        JarInputStream jarFile = null;
        jarFile = new JarInputStream(new FileInputStream(jar));
        JarEntry jarEntry;
        while ((jarEntry = jarFile.getNextJarEntry()) != null) {
            if (jarEntry != null) {
                String className = jarEntry.getName();
                if (className.endsWith(".class")) {
                    className = className.substring(0, className.length() - ".class".length()).replace('/', '.');
                    if (className.startsWith(packageName)) {
                        // CHECKSTYLE:OFF
                        try {
                            classes.add(loadClass(className.replace('/', '.'), classLoader));
                        } catch (Throwable e) {
                            // do nothing. this class hasn't been found by the loader, and we don't care.
                        }
                        // CHECKSTYLE:ON
                    }
                }
            }
        }
        closeJarFile(jarFile);
        return classes;
    }

    private static Class<?> loadClass(String className, ClassLoader classLoader) throws ClassNotFoundException {
        return Class.forName(className, true, classLoader);
    }

    private static void closeJarFile(final JarInputStream jarFile) throws IOException {
        if (jarFile != null) {
            jarFile.close();
        }
    }
}

Related

1. getClassesForPackage(String packageName)
2. getClassesForPackage(String pckgname)
3. getClassesForPackage(String pckgname)
4. getClassesInPackage(String packageName)
5. getClassesInPackage(String packageName)
6. getClassesInPackage(String pckgname)
7. getClassesInPackage(String targetPackage)
8. getClassNameByPackage(String packageName)
9. getClassNamesByPkg(String pkg)