GmlPoint.java

/* Copyright (c) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package com.google.gdata.data.geo.impl;

import com.google.gdata.util.common.xml.XmlWriter;
import com.google.gdata.data.ExtensionDescription;
import com.google.gdata.data.ExtensionPoint;
import com.google.gdata.data.ExtensionProfile;
import com.google.gdata.data.geo.Namespaces;
import com.google.gdata.data.geo.Point;

import java.io.IOException;

/**
 * Extension for a GML gml:Point element.
 *
 * 
 */
@ExtensionDescription.Default(
    nsAlias=Namespaces.GML_ALIAS,
    nsUri=Namespaces.GML,
    localName=GmlPoint.NAME)
public class GmlPoint extends ExtensionPoint implements Point {

  static final String NAME = "Point";

  /**
   * Constructs an empty gml:Point element.
   */
  public GmlPoint() {}

  /**
   * Constructs a gml:Point element out of the given lat and lon values.
   * This will construct a gml:pos element to hold the actual values.  If the
   * values are null then an empty gml:pos element will be created.
   */
  public GmlPoint(Double lat, Double lon) {
    this(new GmlPos(lat, lon));
  }

  /**
   * Constructs a gml:Point element using the given Point coordinates for the
   * nested gml:pos element.  If the point is already a gml:pos, then it will
   * be used directly as the extension, otherwise a gml:pos element will be
   * created as a copy of the given point.
   */
  public GmlPoint(Point point) {
    if (point != null) {
      if (!(point instanceof GmlPos)) {
        point = new GmlPos(point);
      }
      setExtension(point);
    }
  }

  /**
   * Returns the suggested extension description with configurable
   * repeatability.
   */
  public static ExtensionDescription getDefaultDescription(boolean repeatable) {
    ExtensionDescription desc = new ExtensionDescription();
    desc.setExtensionClass(GmlPoint.class);
    desc.setNamespace(Namespaces.GML_NAMESPACE);
    desc.setLocalName(NAME);
    desc.setRepeatable(repeatable);
    return desc;
  }

  /**
   * Returns the suggested extension description and is repeatable.
   */
  public static ExtensionDescription getDefaultDescription() {
    return getDefaultDescription(true);
  }

  /*
   * Declare the extensions for gml point.  This contains a single element with
   * the coordinate which is the actual point.  This is for extensibility I
   * believe, but it ends up just being an extra level of wrapping.
   */
  @Override
  public void declareExtensions(ExtensionProfile extProfile) {
    // Declare the gml:pos extension.
    extProfile.declare(GmlPoint.class,
        GmlPos.getDefaultDescription(false));
    super.declareExtensions(extProfile);
  }

  /**
   * @return the value of the gml:pos element within this Point.
   */
  public Double getLatitude() {
    GmlPos coord = getExtension(GmlPos.class);
    return coord != null ? coord.getLatitude() : null;
  }

  /**
   * @return the value of the gml:pos element's longitude within this Point.
   */
  public Double getLongitude() {
    GmlPos coord = getExtension(GmlPos.class);
    return coord != null ? coord.getLongitude() : null;
  }

  /**
   * Sets the latitude and longitude of the gml:pos element of this Point to the
   * latitude and longitude coordinates specified.
   *
   * @param lat The latitude coordinate of this point.
   * @param lon the longitude coordinate of this point.
   */
  public void setGeoLocation(Double lat, Double lon) {
    GmlPos point = getExtension(GmlPos.class);
    if (point != null) {
      if (lat == null && lon == null) {
        removeExtension(point);
      } else {
        point.setGeoLocation(lat, lon);
      }
    } else if (lat != null || lon != null) {
      point = new GmlPos();
      setExtension(point);
      point.setGeoLocation(lat, lon);
    }
  }

  /**
   * Generates the XML corresponding to this gml point.
   */
  @Override
  public void generate(XmlWriter w, ExtensionProfile extProfile)
      throws IOException {

    generateStartElement(w, Namespaces.GML_NAMESPACE, NAME, null, null);

    // Generate the inner extensions (gml:pos).
    generateExtensions(w, extProfile);

    w.endElement(Namespaces.GML_NAMESPACE, NAME);
  }
}