resourceloader.java

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package com.lyrisoft.util.io;

import java.io.InputStream;
import java.util.StringTokenizer;

/**
 * A class that loads resources from locations relative to the CLASSPATH
 *
 * $Id: ResourceLoader.java,v 1.3 2000/10/04 07:13:46 taso Exp $
 */
public class ResourceLoader {
    /**
    * Get a resource as an InputStream from within the CLASSPATH.
    *
    * Example:  If I am an instance of foo.bar.AnObject, and I call
    * <pre>
    * InputStream is = ResourceLoader.getResource(this, myfile.txt);
    * </pre>
    *
    * I will get an InputStream to the file, "myfile.txt", from the first
    * occurence of foo/bar/myfile.txt, relative to the classpath.
    *
    * @param caller the caller object -
    *               used to determine the package (directory)
    * @param filename the name of the resource
    * @exception ResourceException if the resource is not found
    */
    public static InputStream getResource(Object caller, String filename)
        throws ResourceException
    {
        Class c = null;
        if (caller instanceof Class) {
            c = (Class)caller;
        } else {
            c = caller.getClass();
        }

        // resolve pathname from the classname
        // (change dots to slashes and append the filename)
        StringTokenizer st = new StringTokenizer(c.getName(), ".");
        StringBuffer sb = new StringBuffer();
        int cnt = st.countTokens();
        for (int i=0; i < cnt-1; i++) {
            if (i > 0) {
                sb.append("/");
            }
                sb.append(st.nextToken());
        }
        sb.append("/");
        sb.append(filename);

        String pathname = sb.toString();
        return getResource(pathname);
    }

    /**
     * Load a resource from the CLASSPATH.  relativePath should use forward-slashes
     * and omit the first slash.
     *
     * e.g., getResource("path/to/my/resource");
     *
     * @param relativePath
     */
    public static InputStream getResource(String relativePath) throws ResourceException {
        // we use the actual ClassLoader rather than the simple,
        // Class.getResource() method, because we want the SYSTEM
        // ClassLoader, not a Servlet ClassLoader, or any other loader.
        InputStream is = ClassLoader.getSystemResourceAsStream(relativePath);
        if (is == null) {
            throw new ResourceException("Could not locate resource, " + relativePath);
        }
        return is;
    }
}