在运行期动态加载jar包/class目录，jarclass,在运行期动态加载jar包

在运行期动态加载jar包/class目录，jarclass,在运行期动态加载jar包

在运行期动态加载jar包/class目录，提供比java -cp ??更灵活的类加载机制，例如运行期加载jdbc包、扩展插件包等等。

import java.io.*;import java.net.MalformedURLException;import java.net.URL;import java.util.ArrayList;import java.util.Arrays;import java.util.List;import java.util.zip.ZipEntry;import java.util.zip.ZipException;import java.util.zip.ZipFile;/** * 从指定目录、jar文件加载类</p> *  * 使用：通过下面的方式扩展当前加载器 *      ClassLoader cld=new DynaClassLoader(Thread.currentThread().getContextClassLoader()); *      cld.addEtries(****); *      Thread.currentThread().setContextClassLoader(); */public class DynaClassLoader extends ClassLoader {    //类资源,目录或者是jar    private List<File> entries = new ArrayList<File>();    /**     * @param parent     * @param entries     */    public DynaClassLoader(ClassLoader parent, File[] entries) {        super(parent);        this.entries.addAll(Arrays.asList(entries));    }    /**     * @param parent     */    public DynaClassLoader(ClassLoader parent) {        super(parent);    }    /**     * @param fs     */    public void addEtries(File[] fs) {        this.entries.addAll(Arrays.asList(fs));    }    public void clear() {        this.entries.clear();    }    /**     * @param fs     */    public void addEtry(File fs) {        this.entries.add(fs);    }    public String toString() {        String buf = "";        for (File file : entries) {            buf += file.getAbsolutePath() + ";";        }        return buf;    }    /**     * 加载class     * <p/>     * todo 是否需做缓存、仔细仿照父loadClass的过程、使用参数b     */    protected Class loadClass(String name, boolean b)            throws ClassNotFoundException {        //优先从父加载器获取        Class clazz = null;        try {            clazz = super.loadClass(name, b);            if (clazz != null) {                return clazz;            }        } catch (ClassNotFoundException e) {        }        //System.out.println("DynaClassLoader:load class->" + name);        int dotIndex = name.indexOf(".");        String separator = File.separator;        if (separator.equals("\\\\")) {            separator = "\\\\\\\\";        }        String fileName;        if (dotIndex != -1) {            fileName = new StringBuilder().append(name.replaceAll("\\\\.", separator)).append(".class").toString();        } else {            fileName = new StringBuilder().append(name).append(".class").toString();        }        InputStream is = getLocalResourceAsStream(fileName);        if (is == null) {            throw new ClassNotFoundException(name);        }        try {            Class loadedClass = readClass(name, is);            is.close();            if (loadedClass != null) {                return loadedClass;            } else {                throw new ClassNotFoundException(name);            }        } catch (Exception e) {            throw new ClassNotFoundException(name);        } finally {            try {                is.close();            } catch (IOException e) {            }        }    }    private Class readClass(String className, InputStream is) throws IOException {        BufferedInputStream bis = new BufferedInputStream(is);        ByteArrayOutputStream os = new ByteArrayOutputStream();        byte[] bytes = new byte[1024 * 10];        int readBytes;        while ((readBytes = bis.read(bytes)) != -1) {            os.write(bytes, 0, readBytes);        }        byte[] b = os.toByteArray();        return defineClass(className, b, 0, b.length);    }    /**     *     * @param name     * @return     */    private URL getLocalResource(String name) {        for (int i = 0; i < entries.size(); i++) {            File entry = entries.get(i);            if (entry.isDirectory() && entry.exists()) {                File f = new File(entry, name);                if (f.exists()) {                    URL url;                    try {                        url = f.toURI().toURL();                    } catch (MalformedURLException ex) {                        continue;                    }                    return url;                }            } else if (entry.isFile() && entry.exists()) {                URL url = null;                try {                    ZipFile zf = new ZipFile(entry);                    name = name.replaceAll("\\\\\\\\", "/");                    ZipEntry zipEntry = zf.getEntry(name);                    if (zipEntry == null) {                        continue;                    }                    String url_0_ = entry.getAbsolutePath().replaceAll("\\\\\\\\", "/");                    if (!url_0_.startsWith("/")) {                        url_0_ = new StringBuilder().append("/").append(url_0_).toString();                    }                    url = new URL(new StringBuilder().append("jar:<a href="file://">file://").append(url_0_).append("!/").append(name).toString());                } catch (ZipException zipexception) {                    zipexception.printStackTrace();                } catch (IOException ioexception) {                    ioexception.printStackTrace();                }                return url;            }        }        return null;    }    private InputStream getLocalResourceAsStream(String name) {        URL res = getLocalResource(name);        if (res == null) {            return null;        }        InputStream inputstream = null;        try {            inputstream = res.openStream();        } catch (IOException ex) {            ex.printStackTrace();        }        return inputstream;    }    /**     * 加载数据流     */    public InputStream getResourceAsStream(String name) {        InputStream _super = super.getResourceAsStream(name);        return _super != null ? _super : getLocalResourceAsStream(name);    }    /**     * 加载资源     */    public URL getResource(String name) {        URL resource = super.getResource(name);        return resource != null ? resource : getLocalResource(name);    }}//该片段来自于http://byrx.net