UploadHandlerAbstract.java

package com.gwt.ui.client.gwtupld;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.google.gwt.core.client.GWT;
import com.google.gwt.http.client.URL;

public abstract class UploadHandlerAbstract {
  protected Options options;
  private List<String> queue;
  protected Map<String, Map<String, String>> params;
  protected UploadProgressHandlers progressHandlers;

  /**
   * Adds file or file input to the queue
   *
   * @param o Object to add (InputElement or File)
   * @return id
   **/
  protected abstract String add(Object o);

  /**
   * Sends the file identified by id and additional query params to the server
   * @param id
   * @param params
   */
  public void upload(String id, Map<String, String> params) {
    this.queue.add(id);
    this.params.put(id, params);
    final int size = queue.size();
    if (size <= this.options.getMaxConnections()) {
      _upload(id, params);
    }
  }

  /**
   * Cancels file upload by id
   * @param id file id
   */
  public void cancel(String id) {
    _cancel(id);
    _dequeue(id);
  }

  public void cancelAll(String id) {
    for (String s : queue) {
      _cancel(s);
    }
  }

  /**
   * Returns name of the file identified by id
   *
   * @param id file id
   * @return file name
   */
  protected abstract String getName(String id);

  /**
   * Returns size of the file identified by id
   *
   * @param id file id
   * @return file size
   */
  protected abstract int getSize(String id);

  @Deprecated
  protected List<String> getQueue() {
    return queue;
  }

  /**
   * Actual upload method
   * @param id file id
   * @param params parameters to pass with request
   */
  protected abstract String _upload(String id, Map<String, String> params);

  /**
   * Actual cancel method
   * @param id file id
   */
  protected abstract void _cancel(String id);

  /**
   * Removes element from queue, starts upload of next
   */
  protected void _dequeue(String id) {
    final int i = queue.indexOf(id);
    queue.remove(i);

    final int max = options.getMaxConnections();
    if (queue.size() >= max && i < max) {
      String nextId = queue.get(max - 1);
      this._upload(nextId, params.get(nextId));
    }
  }

  protected UploadHandlerAbstract(UploadProgressHandlers progressHandlers,
                                  Options options) {
    this.progressHandlers = progressHandlers;
    this.options = options;
    this.queue = new ArrayList<String>();
    this.params = new HashMap<String, Map<String, String>>();
  }

  protected void log(String s) {
    if (options.debug) {
      GWT.log("[uploader] " + s);
    }
  }

  // TODO: are there any standard methods to do this?
  /**
   * Appends parameters to URL
   * @param url
   * @param params
   * @return
   */
  protected String appendParamsToAction(String url, Map<String, String> params) {
    StringBuilder sb = new StringBuilder(url);
    if (params != null) {
      int i = 0;
      for (String key : params.keySet()) {
        sb.append(i == 0 && !url.contains("?") ? "?" : "&");
        sb.append(key).append("=").append(URL.encodeQueryString(params.get(key)));
        i++;
      }
    }
    return sb.toString();
  }
}