Configuration.java

package org.springframework.roo.project;

import org.apache.commons.lang3.Validate;
import org.springframework.roo.support.util.XmlUtils;
import org.w3c.dom.Element;

/**
 * Immutable representation of an configuration specification for a (Maven)
 * build plugin
 * 
 * @author Alan Stewart
 * @since 1.1
 */
public class Configuration implements Comparable<Configuration> {

  /**
   * Factory method
   * 
   * @param configurationElement the XML node from which to parse the instance
   *            (can be <code>null</code>)
   * @return <code>null</code> if a <code>null</code> element is given
   * @since 1.2.0
   */
  public static Configuration getInstance(final Element configurationElement) {
    if (configurationElement == null) {
      return null;
    }
    return new Configuration(configurationElement);
  }

  private final Element configuration;

  /**
   * Constructor from an XML element. Consider using
   * {@link #getInstance(Element)} instead for null-safety.
   * 
   * @param configuration the XML element specifying the configuration
   *            (required)
   */
  public Configuration(final Element configuration) {
    Validate.notNull(configuration, "configuration must be specified");
    this.configuration = configuration;
  }

  public int compareTo(final Configuration o) {
    if (o == null) {
      throw new NullPointerException();
    }
    return XmlUtils.compareNodes(configuration, o.configuration) ? 0 : 1;
  }

  @Override
  public boolean equals(final Object obj) {
    return obj instanceof Configuration && compareTo((Configuration) obj) == 0;
  }

  /**
   * Returns the XML element that defines this configuration
   * 
   * @return a non-<code>null</code> element
   */
  public Element getConfiguration() {
    return configuration;
  }

  @Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + (configuration == null ? 0 : configuration.hashCode());
    return result;
  }
}