ServletResourceHandler.java

/*******************************************************************************
 * Copyright (c) 2010, 2014 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.orion.internal.server.servlets;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.core.filesystem.IFileStore;
import org.eclipse.core.runtime.IPath;
import org.eclipse.core.runtime.Path;
import org.eclipse.orion.internal.server.servlets.file.NewFileServlet;
import org.eclipse.orion.internal.server.sftpfile.AuthCoreException;
import org.eclipse.orion.server.core.ProtocolConstants;

/**
 * A servlet resource handler processes an HTTP request for a given resource.
 * The handler is given a resource object that has been constructed based on the
 * request URL and headers. The handler is responsible for filling in the response content type, headers,
 * and body as appropriate for a given result object.
 * 
 * @param <T> The type of resource this handler processes.
 */
public abstract class ServletResourceHandler<T> {
	/**
	 * An enumeration of the HTTP method types.
	 */
	public enum Method {
		GET, HEAD, OPTIONS, POST, PUT, DELETE;
		/**
		 * Convenience method to convert an HTTP method string into an
		 * enumerated type.
		 */
		public static Method fromString(String methodName) {
			if ("GET".equals(methodName)) //$NON-NLS-1$
				return GET;
			if ("PUT".equals(methodName)) //$NON-NLS-1$
				return PUT;
			if ("POST".equals(methodName)) //$NON-NLS-1$
				return POST;
			if ("HEAD".equals(methodName)) //$NON-NLS-1$
				return HEAD;
			if ("OPTIONS".equals(methodName)) //$NON-NLS-1$
				return OPTIONS;
			if ("DELETE".equals(methodName)) //$NON-NLS-1$
				return DELETE;
			return null;
		}
	}

	/**
	 * Convenience method to convert an HTTP method string into an
	 * enumerated type.
	 */
	public static Method getMethod(HttpServletRequest request) {
		return Method.fromString(request.getMethod());
	}

	/**
	 * Convenience method to obtain the URI of the request
	 */
	public static URI getURI(HttpServletRequest request) {
		String path = request.getServletPath();
		String pathInfo = request.getPathInfo();
		if (pathInfo != null) {
			path += request.getPathInfo();
		}
		try {
			// Note: no query string!
			return new URI("orion", null, path, null, null);
		} catch (URISyntaxException e) {
			//location not properly encoded
			return null;
		}
	}

	public static URI resovleOrionURI(HttpServletRequest request, URI uri) {
		if (!uri.getScheme().equals("orion"))
			return uri;

		try {
			return new URI(null, null, request.getContextPath() + uri.getPath(), uri.getQuery(), uri.getFragment());
		} catch (URISyntaxException e) {
			//location not properly encoded
			return null;
		}
	}

	public static String toOrionLocation(HttpServletRequest request, String location) {
		String contextPath = request.getContextPath();
		if (location != null && contextPath.length() != 0 && location.startsWith(contextPath)) {
			location = location.substring(contextPath.length());
		}
		return location;
	}

	/**
	 * Handles the given HTTP request for the provided resource.
	 * 
	 * @param request The HTTP request object
	 * @param response The servlet response object
	 * @param object The object that is the target resource for the request
	 */
	public abstract boolean handleRequest(HttpServletRequest request, HttpServletResponse response, T object) throws ServletException;

	/**
	 * Checks if the provided exception is an authentication failure. If so, it configures the appropriate
	 * response and returns <code>true</code>. If the exception is not an authentication
	 * failure this method takes no action and returns <code>false</code>.
	 */
	protected boolean handleAuthFailure(HttpServletRequest request, HttpServletResponse response, Exception e) {
		if (e instanceof AuthCoreException) {
			String realm = ((AuthCoreException) e).getRealm();
			response.setHeader(ProtocolConstants.HEADER_WWW_AUTHENTICATE, "Basic realm=\"" + realm + "\""); //$NON-NLS-1$ //$NON-NLS-2$
			try {
				response.sendError(HttpServletResponse.SC_UNAUTHORIZED);
				return true;
			} catch (IOException ioException) {
				//return false below and let caller handle as general error
			}
		}
		//not an authentication failure
		return false;
	}

	/**
	 * Maps the client-facing location URL of a file or directory back to the local
	 * file system path on the server. Returns <code>null</code> if the
	 * location could not be resolved to a local file system location.
	 */
	protected IFileStore resolveSourceLocation(HttpServletRequest request, String locationString) throws URISyntaxException {
		URI sourceLocation = new URI(locationString);
		//resolve relative URI against request URI
		String sourcePath = sourceLocation.getPath().substring(request.getContextPath().length());
		//first segment is the servlet path
		IPath path = new Path(sourcePath).removeFirstSegments(1);
		return NewFileServlet.getFileStore(request, path);
	}
}