java里面如何扫描包

很多框架，比如springmvc，mybatis等使用注解，为了处理注解，必然要对包进行扫描，如果自己使用注解写通用代码，也要扫描包，下面代码给出扫描包的实现：

　package com.jjh.common;


import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLDecoder;
import java.nio.file.FileSystem;
import java.nio.file.FileVisitResult;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.nio.file.spi.FileSystemProvider;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Objects;

/**
 * @author Administrator
 *
 */
public final class Files {
    /**
     * 
     */
    private Files() {
        // TODO Auto-generated constructor stub
    }
    
    static public byte[] read(InputStream in) throws IOException
    {
        byte[] temp=new byte[4096];
        ByteArrayOutputStream buffer=new ByteArrayOutputStream();
        BufferedInputStream bin=new BufferedInputStream(in);
        for(;;)
        {
            int len=bin.read(temp);
            if(len>-1)
                buffer.write(temp, 0, len);
            else
                break;
        }
        return buffer.toByteArray();
    }


    static public String[] scanPackage(String packageName) throws Exception {
        packageName=packageName.replaceAll("\\.","/");
        URL url = Thread.currentThread().getContextClassLoader().getResource(packageName);
        url=new URL(URLDecoder.decode(url.toString(), "UTF-8"));
        FileSystemProvider provider =null;
        if(url.getProtocol().equals("jar"))
        {
               provider = getZipFSProvider();
                if (provider != null) {
                    try (FileSystem fs = provider.newFileSystem(Paths.get(url.getPath().replaceFirst("file:/", "").replaceFirst("!.*", "")),new HashMap<>())) {
                        return walkFileTree(fs.getPath(packageName),null).toArray(new String[0]);
                    } catch (Exception e) {
                        throw e;
                    }
                }
        }
        else if(url.getProtocol().equals("file"))
        {
            int end=url.getPath().lastIndexOf(packageName);
            String basePath=url.getPath().substring(1, end);
            return walkFileTree(Paths.get(url.getPath().replaceFirst("/","")),Paths.get(basePath)).toArray(new String[0]);
        }
        return null;
    }

    private static List<String> walkFileTree(Path path,Path basePath) throws IOException{
        // TODO Auto-generated method stub
        final List<String> result=new ArrayList<>();
        java.nio.file.Files.walkFileTree(path, new SimpleFileVisitor<Path>(){
            private String packageName=Objects.isNull(basePath)?"":basePath.toString();
            /* (non-Javadoc)
             * @see java.nio.file.SimpleFileVisitor#visitFile(java.lang.Object, java.nio.file.attribute.BasicFileAttributes)
             */
            @Override
            public FileVisitResult visitFile(Path arg0, BasicFileAttributes arg1) throws IOException {
                // TODO Auto-generated method stub
                if(arg0.toString().endsWith(".class"))
                {
                    result.add(arg0.toString().replace(packageName, "").substring(1).replace("\\", "/").replace(".class", "").replace("/", "."));
                }
                return FileVisitResult.CONTINUE;
            }

            /* (non-Javadoc)
             * @see java.nio.file.SimpleFileVisitor#preVisitDirectory(java.lang.Object, java.nio.file.attribute.BasicFileAttributes)
             */
            @Override
            public FileVisitResult preVisitDirectory(Path arg0, BasicFileAttributes arg1) throws IOException {
                // TODO Auto-generated method stub
                //packageName=basePath==null?arg0.toString().substring(1, arg0.toString().length()-1).replace("/", "."):basePath.relativize(arg0).toString().replace("\\", ".");
                return FileVisitResult.CONTINUE;
            }
                
        });
        return result;
    }

    static public FileSystemProvider getZipFSProvider() {
        for (FileSystemProvider provider : FileSystemProvider.installedProviders()) {
            if ("jar".equals(provider.getScheme()))
                return provider;
        }
        return null;
    }

    public static void main(String[] args) throws Exception {
        //C:\Program Files\Apache Software Foundation\Tomcat 8.0\wtpwebapps\j2ee\WEB-INF\hawk.xml
        // System.out.println(new
        // URL("jar:file:/home/whf/foo.jar!/cn/fh").getPath());
        for(String c:scanPackage("com.mysql.jdbc"))
            System.out.println(c);
        //System.out.println(Paths.get("file://C:/Users/Administrator/Desktop/pecker/build/classes/com/jjh/common"));
        
    }

}