ClassRelativeResourceLoader.java

package com.firefly.utils.io;

import com.firefly.utils.Assert;
import com.firefly.utils.StringUtils;

/**
 * {@link ResourceLoader} implementation that interprets plain resource paths
 * as relative to a given {@code java.lang.Class}.
 * 
 * @see Class#getResource(String)
 * @see ClassPathResource#ClassPathResource(String, Class)
 */
public class ClassRelativeResourceLoader extends DefaultResourceLoader {

	private final Class<?> clazz;


	/**
	 * Create a new ClassRelativeResourceLoader for the given class.
	 * @param clazz the class to load resources through
	 */
	public ClassRelativeResourceLoader(Class<?> clazz) {
		Assert.notNull(clazz, "Class must not be null");
		this.clazz = clazz;
		setClassLoader(clazz.getClassLoader());
	}

	@Override
	protected Resource getResourceByPath(String path) {
		return new ClassRelativeContextResource(path, this.clazz);
	}


	/**
	 * ClassPathResource that explicitly expresses a context-relative path
	 * through implementing the ContextResource interface.
	 */
	private static class ClassRelativeContextResource extends ClassPathResource implements ContextResource {

		private final Class<?> clazz;

		public ClassRelativeContextResource(String path, Class<?> clazz) {
			super(path, clazz);
			this.clazz = clazz;
		}

		@Override
		public String getPathWithinContext() {
			return getPath();
		}

		@Override
		public Resource createRelative(String relativePath) {
			String pathToUse = StringUtils.applyRelativePath(getPath(), relativePath);
			return new ClassRelativeContextResource(pathToUse, this.clazz);
		}
	}

}