org.pageseeder.diffx.xml.Namespace Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of pso-diffx Show documentation
Diff-X
The newest version!
/*
 * Copyright (c) 2010-2021 Allette Systems (Australia)
 *    http://www.allette.com.au
 *
 * 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 org.pageseeder.diffx.xml;

import org.jetbrains.annotations.NotNull;

import javax.xml.XMLConstants;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.Properties;

/**
 * A namespace.
 *
 * This class also provides built XML namespaces as constants.
 *
 * @author Christophe Lauret
 * @version 0.9.0
 * @see Namespaces in XML 1.0
 * @since 0.6.0
 */
public final class Namespace {

  /**
   * Namespace instance to use to represent that there is no Namespace.
   * 
   * Defined by the Namespace specification to be "".
   */
  public static final Namespace NO_NAMESPACE = new Namespace(XMLConstants.NULL_NS_URI, XMLConstants.DEFAULT_NS_PREFIX);

  /**
   * Namespace instance for the built-in XML namespace.
   */
  public static final Namespace XML_NAMESPACE = new Namespace(XMLConstants.XML_NS_URI, XMLConstants.XML_NS_PREFIX);

  /**
   * Pseudo-namespace instance for XML namespace declarations.
   */
  public static final Namespace XMLNS_ATTRIBUTE = new Namespace(XMLConstants.XMLNS_ATTRIBUTE_NS_URI, XMLConstants.XMLNS_ATTRIBUTE);

  /**
   * The namespace URI.
   */
  private final String uri;

  /**
   * The namespace prefix
   */
  private final String prefix;

  private static final Map COMMON_NAMESPACES = new HashMap<>();

  public Namespace(String uri, String prefix) {
    this.uri = Objects.requireNonNull(uri);
    this.prefix = Objects.requireNonNull(prefix);
  }

  public @NotNull String getUri() {
    return this.uri;
  }

  public @NotNull String getPrefix() {
    return this.prefix;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    Namespace namespace = (Namespace) o;
    return getUri().equals(namespace.getUri()) && getPrefix().equals(namespace.getPrefix());
  }

  @Override
  public int hashCode() {
    return Objects.hash(getUri(), getPrefix());
  }

  @Override
  public String toString() {
    return "{" + this.uri + "}=" + this.prefix;
  }

  /**
   * @param namespace namespace to check.
   *
   * @return true if the namespace should be declared; false if it matches no namespace of built-in XML namespaces.
   */
  public static boolean isDeclarable(Namespace namespace) {
    return !(XML_NAMESPACE.equals(namespace) || XMLNS_ATTRIBUTE.equals(namespace) || NO_NAMESPACE.equals(namespace));
  }

  public static Namespace getCommon(String uri) {
    if (COMMON_NAMESPACES.isEmpty()) loadCommonNamespaces();
    return COMMON_NAMESPACES.get(uri);
  }

  private synchronized static void loadCommonNamespaces() {
    try {
      String resourceName = "namespaces.properties";
      Properties props = new Properties();
      try (InputStream resourceStream = Namespace.class.getResourceAsStream(resourceName)) {
        props.load(resourceStream);
      }
      props.forEach((prefix, uri) -> COMMON_NAMESPACES.put(uri.toString(), new Namespace(uri.toString(), prefix.toString())));
    } catch (Exception ex) {
      ex.printStackTrace();
    }
  }

}