Java扫描classpath指定包路径下所有class

在写框架时 经常需要扫描classpath指定包路径下带有某个Annotation的类，自己整理了一下 封装成一个工具类了，供大家参考。

源代码

ClassPathResourceScanner.java 如下：

package com.bytebeats.jupiter.ioc;

import com.bytebeats.jupiter.util.ClassHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.IOException;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLDecoder;
import java.util.*;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.regex.Pattern;

/**
 * ${DESCRIPTION}
 *
 * @author Ricky Fung
 * @create 2016-12-11 16:02
 */
public class ClassPathCandidateComponentScanner {
    private final Logger logger = LoggerFactory.getLogger(getClass());

    public static final String CLASS_SUFFIX = ".class";

    private static final Pattern INNER_PATTERN = java.util.regex.Pattern.compile("\\$(\\d+).", java.util.regex.Pattern.CASE_INSENSITIVE);

    public Set<Class<?>> findCandidateComponents(String packageName) throws IOException {
        if (packageName.endsWith(".")) {
            packageName = packageName.substring(0, packageName.length()-1);
        }
        Map<String, String> classMap = new HashMap<>(32);
        String path = packageName.replace(".", "/");
        Enumeration<URL> urls = findAllClassPathResources(path);
        while (urls!=null && urls.hasMoreElements()) {
            URL url = urls.nextElement();
            String protocol = url.getProtocol();
            if ("file".equals(protocol)) {
                String file = URLDecoder.decode(url.getFile(), "UTF-8");
                File dir = new File(file);
                if(dir.isDirectory()){
                    parseClassFile(dir, packageName, classMap);
                }else {
                    throw new IllegalArgumentException("file must be directory");
                }
            } else if ("jar".equals(protocol)) {
                parseJarFile(url, classMap);
            }
        }

Set<Class<?>> set = new HashSet<>(classMap.size());
        for(String key : classMap.keySet()){
            String className = classMap.get(key);
            try {
set.add(ClassHelper.forName(className));
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        }
        return set;
    }

    protected void parseClassFile(File dir, String packageName, Map<String, String> classMap){
        if(dir.isDirectory()){
            File[] files = dir.listFiles();
            for (File file : files) {
                parseClassFile(file, packageName, classMap);
            }
        } else if(dir.getName().endsWith(CLASS_SUFFIX)) {
            String name = dir.getPath();
            name = name.substring(name.indexOf("classes")+8).replace("\\", ".");
            System.out.println("file:"+dir+"\t class:"+name);
            addToClassMap(name, classMap);
        }
    }

    protected void parseJarFile(URL url, Map<String, String> classMap) throws IOException {
        JarFile jar = ((JarURLConnection) url.openConnection()).getJarFile();
        Enumeration<JarEntry> entries = jar.entries();
        while (entries.hasMoreElements()) {
            JarEntry entry = entries.nextElement();
            if (entry.isDirectory()) {
                continue;
            }
            String name = entry.getName();
            if(name.endsWith(CLASS_SUFFIX)){
                addToClassMap(name.replace("/", "."), classMap);
            }
        }
    }

    private boolean addToClassMap(String name, Map<String, String> classMap){

        if(INNER_PATTERN.matcher(name).find()){ //过滤掉匿名内部类
            System.out.println("anonymous inner class:"+name);
            return false;
        }
        System.out.println("class:"+name);
        if(name.indexOf("$")>0){ //内部类
            System.out.println("inner class:"+name);
        }
        if(!classMap.containsKey(name)){
            classMap.put(name, name.substring(0, name.length()-6)); //去掉.class
        }
        return true;
    }

    protected Enumeration<URL> findAllClassPathResources(String path) throws IOException {
        if(path.startsWith("/")){
            path = path.substring(1);
        }
        Enumeration<URL> urls = ClassHelper.getClassLoader().getResources(path);

        return urls;
    }

}

使用方法

ClassPathCandidateComponentScanner scanner = new ClassPathCandidateComponentScanner();
//要扫描的包名
String packageName = "com.bytebeats";
//获取该包下所有的类名称
Set<Class<?>> set = scanner.findCandidateComponents(packageName);
System.out.println(set.size());
for (Class<?> cls : set){
    System.out.println(cls.getName());
}

这方面已经有一些不错的开源项目，例如：
reflections：https://github.com/ronmamo/reflections
Scannotation：http://scannotation.sourceforge.net/