Iterates through all resources in current thread's ClassLoader and searches for .class files, then attempts to parse the class name from file name, and find the Class object.

Description

Demo Code


//package com.java2s;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.Modifier;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLDecoder;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

public class Main {

    /**//ww w. j a v a  2 s  .  c  o m
     * Iterates through all resources in current thread's <code>ClassLoader</code> and searches for
     * <i>.class</i> files, then attempts to parse the class name from file name, and find the 
     * <code>Class</code> object. <br>
     * Searches only through <i>.jar</i> files and extracted <i>.class</i> files, so, for example, 
     * it can't search the java.* package.
     * 
     * @param packageName search in this package
     * @return <code>Set</code> of found <code>Class</code> objects
     * @throws IOException
     */
    public static Set<Class<?>> getAllClasses(String packageName)
            throws IOException {
        Set<Class<?>> classes = new HashSet<Class<?>>();

        if (packageName == null || packageName.length() == 0) {
            return classes;
        }

        for (URL resource : Collections.list(getClassLoader().getResources(
                packageName.replace('.', '/')))) {
            if (resource.getProtocol().equalsIgnoreCase("jar")) {
                classes.addAll(getClassesInJarResource(resource,
                        packageName));
            } else if (resource.getProtocol().equalsIgnoreCase("file")) {
                classes.addAll(getClassesInFileResource(
                        new File(URLDecoder.decode(resource.getPath(),
                                "UTF-8")), packageName));
            }
        }

        return classes;
    }

    private static ClassLoader getClassLoader() {
        return Thread.currentThread().getContextClassLoader();
    }

    private static Set<Class<?>> getClassesInJarResource(URL resource,
            String packageName) throws IOException {
        Set<Class<?>> classes = new HashSet<Class<?>>();

        JarURLConnection conn = (JarURLConnection) resource
                .openConnection();
        JarFile jar = conn.getJarFile();

        for (JarEntry entry : Collections.list(jar.entries())) {
            String n = entry.getName();
            if (n.startsWith(packageName.replace('.', '/'))
                    && n.endsWith(".class")) {
                if (n.contains("$")) {
                    if (isAnonymous(n)) {
                        return classes;
                    }
                }
                String className = n.replace("/", ".").substring(0,
                        n.length() - 6);
                try {
                    Class<?> klass = getClassForName(className);
                    if (!Modifier.isPrivate(klass.getModifiers())) {
                        classes.add(klass);
                    }
                } catch (ClassNotFoundException e) {
                    //
                }
            }
        }

        return classes;
    }

    private static Set<Class<?>> getClassesInFileResource(File file,
            String packageName) throws IOException {
        Set<Class<?>> classes = new HashSet<Class<?>>();

        if (file.exists()) {
            if (file.isDirectory()) {
                for (File f : file.listFiles()) {
                    classes.addAll(getClassesInFileResource(f, packageName));
                }
            } else {
                String fileName = file.getAbsolutePath();
                if (fileName.endsWith(".class")) {
                    if (fileName.contains("$")) {
                        String innerName = fileName.substring(
                                fileName.lastIndexOf("$") + 1,
                                fileName.lastIndexOf("."));
                        if (isAnonymous(innerName)) {
                            // Ignore anonymous inner classes
                            return classes;
                        }
                    }
                    // removes the .class extension
                    fileName = fileName.substring(0, fileName.length() - 6);
                    fileName = fileName.replace(getSystemFileSeperator(),
                            ".");
                    fileName = fileName.substring(fileName
                            .indexOf(packageName));

                    try {
                        Class<?> klass = getClassForName(fileName);
                        if (!Modifier.isPrivate(klass.getModifiers())) {
                            classes.add(klass);
                        }
                    } catch (ClassNotFoundException e) {
                        //
                    }
                }
            }
        }

        return classes;
    }

    private static boolean isAnonymous(String className) {
        return className.matches("\\d*");
    }

    private static Class<?> getClassForName(String className)
            throws ClassNotFoundException {
        try {
            Class<?> c = Class.forName(className);
            return c;
        } catch (Exception exception) {
            throw new ClassNotFoundException(
                    "Exception getting class for name: " + className
                            + " - " + exception.getMessage());
        } catch (Error error) {
            throw new ClassNotFoundException(
                    "Error getting class for name: " + className + " - "
                            + error.getMessage());
        }
    }

    private static String getSystemFileSeperator() {
        String p = System.getProperty("file.separator");
        if (p == null) {
            p = "/";
        }
        return p;
    }
}
Iterates through all resources in current thread's ClassLoader and searches for .class files, then attempts to parse the class name from file name, and find the Class object. - Java Reflection

Description

Demo Code

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