1. Solve the problem: load all classes under the package through the package name in the form of com.xxx.yyy.zzz

2. Code:

package com.chuyutech.rssp.openservice.service.data;

import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.net.URL;
import java.net.URLDecoder;
import java.util.Enumeration;
import java.util.LinkedHashSet;
import java.util.Set;

/**
 * @description: Simple file operation class, including basic operation of some files
 * 
 * @author cwh
 *
 */
public class FileOpreation {

	/**
	 * Access disk files based on package name
	 * 
	 * @param packageName:Shaped like com.xxx.yyy.zzz, divided by dots
	 */
	public static Set<Class<?>> getClazz(String packageName) {
		// Recursion
		boolean isRecursion = true;
		// Define variables, save class file
		Set<Class<?>> clazz = new LinkedHashSet<Class<?>>();
		char dot = '.';
		char sprit = '/';
		try {
			// Get the ContextClassLoader class loader according to the current thread. Note: the conversion of separator
			// The resource defined by the getResources method is a '/' separator

			Enumeration<URL> resources = Thread.currentThread().getContextClassLoader()
					.getResources(packageName.replace(dot, sprit));
			// Ergodic enumeration
			while (resources.hasMoreElements()) {
				URL url = resources.nextElement();
// url:file:/E:/03.WorkSpaceToNew/soldier-openservice/target/classes/com/chuyutech/rssp/openservice/common/db/dao
				System.out.println("url:" + url.toString());
				// Get agreement name
				String protocol = url.getProtocol();
				// If it is a File type, the next step is the operation of the File class
				if (protocol.equals("file")) {
					//					Decoding URLs using a specific encoding scheme
					String packagePath = URLDecoder.decode(url.getFile(), "UTF-8");
//					Call method to get file recursively
					getClazzFromPath(packageName, packagePath, isRecursion, clazz);
				}
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		return clazz;
	}

	/**
	 * Get class file in file
	 * 
	 * @param packageName:Package name;
	 *            packagePath:File path; isRecursion: recursion or not
	 */
	public static void getClazzFromPath(String packageName, String packagePath, boolean isRecursion,
			Set<Class<?>> clazz) {
		char dot = '.';
		// Get File object based on pathname
		File file = new File(packagePath);

		if (!file.exists() || !file.isDirectory()) {
			return;
		}
		// List all files as an array of files
		File[] files = file.listFiles(new FileFilter() {
			// Anonymous inner class overrides FIleFilter
			@Override
			public boolean accept(File pathName) {
	// Custom filter rules if you can loop (including subdirectories) or end with. Class files (compiled java class files)
				return ((isRecursion && pathName.isDirectory()) || pathName.getName().endsWith(".class"));
			}
		});
		// Traversing files
		for (File destFile : files) {
			// Continue scanning if directory
			if (destFile.isDirectory()) {
				getClazzFromPath(packageName + dot + destFile.getName(), destFile.getAbsolutePath(), isRecursion,
						clazz);
			} else {
				// If the java class file is removed after compilation, only the class name will be left
				String fileName = destFile.getName().substring(0, destFile.getName().lastIndexOf(dot));
				// Add to collection to load class with full package name + ". + filename
				try {
					// Class<?> forName = Class.forName(packageName + dot +
					// Classname; this method initializes the static static code block of the loaded class
					Class<?> loadClass = Thread.currentThread().getContextClassLoader()
							.loadClass(packageName + dot + fileName);
					clazz.add(loadClass);
				} catch (ClassNotFoundException e) {
					e.printStackTrace();
				}
			}

		}
	}

	public static void main(String[] args) {
		String packageName = "com.chuyutech.rssp.openservice.common.db.dao";
		Set<Class<?>> clazz = getClazz(packageName);
		System.out.println(clazz.size());
		for (Class<?> class1 : clazz) {
			System.out.println(class1.getName());
		}
	}

}

3. summary:

3.1: general logic of implementation:

Get the ContextClassLoader class loader according to the current thread, and get the URL corresponding to the package name through the getResources(String name) method of the class loader

Get the absolute path through the URL, and use java.io.listFiles(FileFilter filter) of the File class to list all files or directories

Recursively call the file or directory obtained in the previous step, and finally use Thread.currentThread().getContextClassLoader()
. loadClass(className) gets the Class object and saves it to the set collection

3.2: Note:

Conversion of separator: the resource defined by getResources method is' / 'separator
4. Result printing:

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