模拟简单的 spring component scan

/**
* specified characters provider
*/
package org.vic.demo.utils;

public class CommonCharacters {
	
	public static final String _DOT = ".";
	
	public static final String _BLANK = "";
	
	public static final String _SLASH_0 = "/";
	
	public static final String _SLASH_1 = "\\";
}

 简单的工具

package org.vic.demo.utils;

public class VStringUtils {
	
	
	
	public static boolean isNotEmpty (String string) {
		if (string != null && (!CommonCharacters._BLANK.equals(string.trim()))) {
			return true;
		}
		return false;
	}
	
}

package org.vic.demo.utils;

import java.util.Arrays;
import java.util.Collection;

public class VCollectionUtils {
	
	public static boolean isNotEmpty (Collection<?> c) {
		if (c != null && c.size() > 0) {
			return true;
		}
		return false;
	}
	
	public static<T> boolean isNotEmpty(T[] array) {
		if (array != null) {
			return isNotEmpty(Arrays.asList(array));
		} else {
			return false;
		}
	}
	
}

   mimic scanner

  只是一个简单的模拟，只扫描给定包路径下的类，不支持多层扫描。如果需要可以在这个基础上改一下。

  可以加一个解析传入package路径的类或者方法，把不同的配置转换成多个单独的package，这样就不用修改    这里的解析代码了。

   

package org.vic.demo.Annotation.scanner;

import java.io.File;
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.net.URL;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

import org.vic.demo.utils.CommonCharacters;
import org.vic.demo.utils.VCollectionUtils;
import org.vic.demo.utils.VStringUtils;

public class PackageScanner {
	
	private static Map<Class<?>, Set<Annotation>> map = new HashMap<>(); 
	
	private static final String _PROTOCOL_FILE = "file";
	
	private static final String _CLASS_SYMBO = ".class";
	
	private static String[] package_paths = null;
	
	private static class PackageScannerHolder {
		public static PackageScanner instance = new PackageScanner(package_paths);
	}
	
	public static PackageScanner getInstance (String... packagePaths) {
		package_paths = packagePaths;
		return PackageScannerHolder.instance;
	}
	
	private PackageScanner (String... packageNames) {
		if (VCollectionUtils.isNotEmpty(packageNames)) {
			try {
				ClassScanner(packageNames);
			} catch (ClassNotFoundException | IOException e) {
				e.printStackTrace();
			}
		}
		
	}
	
	private void ClassScanner (String... packagePaths) throws IOException, ClassNotFoundException {
		for (String packagePath : packagePaths) {
			if (VStringUtils.isNotEmpty(packagePath)) {
				String path = convertPackagePath2FilePath(packagePath);
				Enumeration<URL> urls = Thread.currentThread().getContextClassLoader().getResources(path);
				while (urls.hasMoreElements()) {
					URL url = urls.nextElement();
					if (url.getProtocol().equalsIgnoreCase(_PROTOCOL_FILE)) {
						String fileAbsolutePath = url.getFile();
						processor(fileAbsolutePath, packagePath);
					}
				}
			}
		}
	}
	
	private void processor (String absolutePath, String currentPackagePath) throws ClassNotFoundException {
		File dir = new File(absolutePath);
		File[] files = dir.listFiles();
		if (VCollectionUtils.isNotEmpty(files)) {
			for (File file : files) {
				if (file.isFile()) {
					String fileName = file.getName();
					String className = currentPackagePath + CommonCharacters._DOT + (fileName.replace(_CLASS_SYMBO, CommonCharacters._BLANK));
					Class<?> clazz = Class.forName(className);
					fix(clazz);
				}
			}
		}
	}
	
	private void fix (Class<?> clazz) {
		Set<Annotation> existingAnnotations = map.get(clazz);
		if (VCollectionUtils.isNotEmpty(existingAnnotations)) {
			return;
		}
		Annotation[] annotations = clazz.getAnnotations();
		if (VCollectionUtils.isNotEmpty(annotations)) {
			Set<Annotation> set = new LinkedHashSet<Annotation>();
			set.addAll(Arrays.asList(annotations));
			System.out.println("put class =======" + clazz.getName() + "======= to map!");
			map.put(clazz, set);
		}
	}
	
	private String convertPackagePath2FilePath (String packagePath) {
		return packagePath.replace(CommonCharacters._DOT, CommonCharacters._SLASH_0);
	}
	
}