类加载工具类

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Properties;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * 用来加载类，classpath下的资源文件，属性文件等。
 * getExtendResource(StringrelativePath)方法，可以使用../符号来加载classpath外部的资源。
 */
public class ClassLoaderUtil {
	private static Log log = LogFactory.getLog(ClassLoaderUtil.class);

	/**
	 *Thread.currentThread().getContextClassLoader().getResource("")
	 */

	/**
	 * 加载Java类。 使用全限定类名
	 *
	 * @return
	 * @paramclassName
	 */
	public static Class loadClass(String className) {
		try {
			return getClassLoader().loadClass(className);
		} catch (ClassNotFoundException e) {
			throw new RuntimeException("class not found '" + className + "'", e);
		}
	}

	/**
	 * 得到类加载器
	 *
	 * @return
	 */
	public static ClassLoader getClassLoader() {
		return ClassLoaderUtil.class.getClassLoader();
	}

	/**
	 * 提供相对于classpath的资源路径，返回文件的输入流
	 *
	 * @param relativePath 必须传递资源的相对路径。是相对于classpath的路径。如果需要查找classpath外部的资源，需要使用../来查找
	 * @return 文件输入流
	 * @throws IOException
	 * @throws MalformedURLException
	 */
	public static InputStream getStream(String relativePath) throws MalformedURLException, IOException {
		if (!relativePath.contains("../")) {
			return getClassLoader().getResourceAsStream(relativePath);
		} else {
			return ClassLoaderUtil.getStreamByExtendResource(relativePath);
		}
	}

	/**
	 * @param url
	 * @return *@throwsIOException
	 */
	public static InputStream getStream(URL url) throws IOException {
		if (url != null) {
			return url.openStream();
		} else {
			return null;
		}
	}


	/**
	 * @param relativePath 必须传递资源的相对路径。是相对于classpath的路径。如果需要查找classpath外部的资源，需要使用../来查找
	 * @return
	 * @throws MalformedURLException
	 * @throws IOException
	 */
	public static InputStream getStreamByExtendResource(String relativePath) throws MalformedURLException, IOException {
		return ClassLoaderUtil.getStream(ClassLoaderUtil.getExtendResource(relativePath));
	}


	/**
	 * 提供相对于classpath的资源路径，返回属性对象，它是一个散列表
	 *
	 * @return
	 * @paramresource
	 */
	public static Properties getProperties(String resource) {
		Properties properties = new Properties();
		try {
			properties.load(getStream(resource));
		} catch (IOException e) {
			throw new RuntimeException("couldn't load properties file '" + resource + "'", e);
		}
		return properties;
	}


	/**
	 * 得到本Class所在的ClassLoader的Classpath的绝对路径。
	 * URL形式的
	 *
	 * @return
	 */
	public static String getAbsolutePathOfClassLoaderClassPath() {
		ClassLoaderUtil.log.info(ClassLoaderUtil.getClassLoader().getResource("").toString());
		return ClassLoaderUtil.getClassLoader().getResource("").toString();
	}

	/**
	 * @param relativePath 必须传递资源的相对路径。是相对于classpath的路径。如果需要查找classpath外部的资源，需要使用../来查找
	 * @return 资源的绝对URL
	 * @throws MalformedURLException
	 */
	public static URL getExtendResource(String relativePath) throws MalformedURLException {
		ClassLoaderUtil.log.info("传入的相对路径：" + relativePath);
		//ClassLoaderUtil.log.info(Integer.valueOf(relativePath.indexOf("../"))) ;
		if (!relativePath.contains("../")) {
			return ClassLoaderUtil.getResource(relativePath);
		}
		String classPathAbsolutePath = ClassLoaderUtil.getAbsolutePathOfClassLoaderClassPath();
		if (relativePath.substring(0, 1).equals("/")) {
			relativePath = relativePath.substring(1);
		}
		ClassLoaderUtil.log.info(Integer.valueOf(relativePath.lastIndexOf("../")));
		//类似于../../../../
		String wildcardString = relativePath.substring(0, relativePath.lastIndexOf("../") + 3);
		//相对于路径部分
		relativePath = relativePath.substring(relativePath.lastIndexOf("../") + 3);
		//总共向上几级
		int containSum = ClassLoaderUtil.containSum(wildcardString, "../");
		classPathAbsolutePath = ClassLoaderUtil.cutLastString(classPathAbsolutePath, "/", containSum);
		String resourceAbsolutePath = classPathAbsolutePath + relativePath;
		ClassLoaderUtil.log.info("绝对路径：" + resourceAbsolutePath);
		URL resourceAbsoluteURL = new URL(resourceAbsolutePath);
		return resourceAbsoluteURL;
	}

	/**
	 * @param source
	 * @param dest
	 * @return
	 */
	private static int containSum(String source, String dest) {
		int containSum = 0;
		int destLength = dest.length();
		while (source.contains(dest)) {
			containSum = containSum + 1;
			source = source.substring(destLength);
		}
		return containSum;
	}

	/**
	 * @param source
	 * @param dest
	 * @param num
	 * @return
	 */
	private static String cutLastString(String source, String dest, int num) {
		// String cutSource=null;
		for (int i = 0; i <= num; i++) {
			//source=source.substring(0, source.lastIndexOf(dest, source.length()-2)+1);
			source = source.substring(0, source.lastIndexOf(dest));
		}
		return source + File.separator;
	}

	/**
	 * @return
	 * @paramre source
	 */
	public static URL getResource(String resource) {
		ClassLoaderUtil.log.info("传入的相对于classpath的路径：" + resource);
		return ClassLoaderUtil.getClassLoader().getResource(resource);
	}

	/**
	 * @param args
	 * @throws MalformedURLException
	 */
	public static void main(String[] args) throws MalformedURLException {
		//ClassLoaderUtil.getExtendResource("../spring/dao.xml");
		//ClassLoaderUtil.getExtendResource("../../../src/log4j.properties");
		ClassLoaderUtil.getExtendResource("log4j.properties");
		System.out.println(ClassLoaderUtil.getClassLoader().getResource("log4j.properties").toString());
	}
}