DynamicClassLoader 动态加载/重新(动态)加载 class，,运行期重新加载一个已经加

DynamicClassLoader 动态加载/重新(动态)加载 class，,运行期重新加载一个已经加

运行期重新加载一个已经加载过的class,必须重新new一个DynamicClassLoader对象进行加载,java规范中规定,同一个ClassLoader对象中只能加载一次相同的class

DynamicClassLoader.java

package libra.law.util;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import java.net.MalformedURLException;import java.net.URL;import java.net.URLConnection;public class DynamicClassLoader extends ClassLoader {public DynamicClassLoader(ClassLoader parent) {   super(parent);}@SuppressWarnings("unchecked")public Class loadClass(String classPath, String className)    throws ClassNotFoundException {   try {    String url = classPathParser(classPath)      + classNameParser(className);    System.out.println(url);    URL myUrl = new URL(url);    URLConnection connection = myUrl.openConnection();    InputStream input = connection.getInputStream();    ByteArrayOutputStream buffer = new ByteArrayOutputStream();    int data = input.read();    while (data != -1) {     buffer.write(data);     data = input.read();    }    input.close();    byte[] classData = buffer.toByteArray();    return defineClass(noSuffix(className), classData, 0,      classData.length);   } catch (MalformedURLException e) {    e.printStackTrace();   } catch (IOException e) {    e.printStackTrace();   }   return null;}private String pathParser(String path) {   return path.replaceAll("\\\\", "/");}private String classPathParser(String path) {   String classPath = pathParser(path);   if (!classPath.startsWith("file:")) {    classPath = "file:" + classPath;   }   if (!classPath.endsWith("/")) {    classPath = classPath + "/";   }   return classPath;}private String classNameParser(String className) {   return className.substring(0, className.lastIndexOf(".")).replaceAll(     "\\.", "/")     + className.substring(className.lastIndexOf("."));}private String noSuffix(String className) {   return className.substring(0, className.lastIndexOf("."));}public static void main(String[] arguments) throws Exception {   String classPath = "C:\\Documents and Settings\\Administrator\\Workspaces\\MyEclipse7.5\\lhsp\\web\\WEB-INF\\classes";   String className = "libra.law.util.Test.class";   new DynamicClassLoader(DynamicClassLoader.class.getClassLoader())     .loadClass(classPath, className).newInstance();}}