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/*
 * Beangle, Agile Development Scaffold and Toolkits.
 *
 * Copyright © 2005, The Beangle Software.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see .
 */
package org.beangle.inject.spring.web;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;

import javax.servlet.ServletContext;

import org.beangle.commons.lang.Assert;
import org.beangle.commons.web.util.RequestUtils;
import org.springframework.core.io.AbstractFileResolvingResource;
import org.springframework.core.io.ContextResource;
import org.springframework.core.io.Resource;
import org.springframework.util.StringUtils;

/**
 * @author chaostone
 * @version $Id: ServletContextResource.java Dec 21, 2011 4:53:53 PM chaostone $
 */

public class ServletContextResource extends AbstractFileResolvingResource implements ContextResource {

  private final ServletContext servletContext;

  private final String path;

  /**
   * Create a new ServletContextResource.
   * 
   * The Servlet spec requires that resource paths start with a slash, even if many containers
   * accept paths without leading slash too. Consequently, the given path will be prepended with a
   * slash if it doesn't already start with one.
   *
   * @param servletContext the ServletContext to load from
   * @param path the path of the resource
   */
  public ServletContextResource(ServletContext servletContext, String path) {
    // check ServletContext
    Assert.notNull(servletContext, "Cannot resolve ServletContextResource without ServletContext");
    this.servletContext = servletContext;

    // check path
    Assert.notNull(path, "Path is required");
    String pathToUse = StringUtils.cleanPath(path);
    if (!pathToUse.startsWith("/")) {
      pathToUse = "/" + pathToUse;
    }
    this.path = pathToUse;
  }

  /**
   * Return the ServletContext for this resource.
   */
  public final ServletContext getServletContext() {
    return this.servletContext;
  }

  /**
   * Return the path for this resource.
   */
  public final String getPath() {
    return this.path;
  }

  /**
   * This implementation checks ServletContext.getResource.
   *
   * @see javax.servlet.ServletContext#getResource(String)
   */
  @Override
  public boolean exists() {
    try {
      URL url = this.servletContext.getResource(this.path);
      return (url != null);
    } catch (MalformedURLException ex) {
      return false;
    }
  }

  /**
   * This implementation delegates to ServletContext.getResourceAsStream,
   * but throws a FileNotFoundException if no resource found.
   *
   * @see javax.servlet.ServletContext#getResourceAsStream(String)
   */
  public InputStream getInputStream() throws IOException {
    InputStream is = this.servletContext.getResourceAsStream(this.path);
    if (is == null) { throw new FileNotFoundException("Could not open " + getDescription()); }
    return is;
  }

  /**
   * This implementation delegates to ServletContext.getResource,
   * but throws a FileNotFoundException if no resource found.
   *
   * @see javax.servlet.ServletContext#getResource(String)
   */
  @Override
  public URL getURL() throws IOException {
    URL url = this.servletContext.getResource(this.path);
    if (url == null) { throw new FileNotFoundException(getDescription()
        + " cannot be resolved to URL because it does not exist"); }
    return url;
  }

  /**
   * This implementation delegates to ServletContext.getRealPath,
   * but throws a FileNotFoundException if not found or not resolvable.
   *
   * @see javax.servlet.ServletContext#getRealPath(String)
   */
  @Override
  public File getFile() throws IOException {
    String realPath = RequestUtils.getRealPath(this.servletContext, this.path);
    return new File(realPath);
  }

  /**
   * This implementation creates a ServletContextResource, applying the given path
   * relative to the path of the underlying file of this resource descriptor.
   */
  @Override
  public Resource createRelative(String relativePath) {
    String pathToUse = StringUtils.applyRelativePath(this.path, relativePath);
    return new ServletContextResource(this.servletContext, pathToUse);
  }

  /**
   * This implementation returns the name of the file that this ServletContext
   * resource refers to.
   */
  @Override
  public String getFilename() {
    return StringUtils.getFilename(this.path);
  }

  /**
   * This implementation returns a description that includes the ServletContext
   * resource location.
   */
  public String getDescription() {
    return "ServletContext resource [" + this.path + "]";
  }

  public String getPathWithinContext() {
    return this.path;
  }

  /**
   * This implementation compares the underlying ServletContext resource locations.
   */
  @Override
  public boolean equals(Object obj) {
    if (obj == this) { return true; }
    if (obj instanceof ServletContextResource) {
      ServletContextResource otherRes = (ServletContextResource) obj;
      return (this.servletContext.equals(otherRes.servletContext) && this.path.equals(otherRes.path));
    }
    return false;
  }

  /**
   * This implementation returns the hash code of the underlying
   * ServletContext resource location.
   */
  @Override
  public int hashCode() {
    return this.path.hashCode();
  }

}