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  package org.apache.cayenne.configuration.xml;
  
  import java.util.Arrays;
  import java.util.Objects;
  
  import org.apache.cayenne.CayenneRuntimeException;
  import org.apache.cayenne.util.LocalizedStringsHandler;
  import org.xml.sax.Attributes;
  import org.xml.sax.SAXException;
  
  /**
   * Handler that can validate root tag name, version and namespace.
   *
   * @since 4.1
   */
  public abstract class VersionAwareHandler extends NamespaceAwareNestedTagHandler {
  
      protected String rootTag;
  
      public VersionAwareHandler(LoaderContext loaderContext, String rootTag) {
          super(loaderContext);
          setAllowAllNamespaces(true);
          this.rootTag = Objects.requireNonNull(rootTag);
      }
  
      @Override
      protected boolean processElement(String namespaceURI, String localName, Attributes attributes) throws SAXException {
          if(rootTag.equals(localName)) {
              validateVersion(attributes, XMLDataChannelDescriptorLoader.SUPPORTED_PROJECT_VERSIONS);
              validateNamespace(namespaceURI);
          } else {
              throw new CayenneRuntimeException("Illegal XML root tag: %s, expected: %s", localName, rootTag);
          }
          return false;
      }
  
      protected void validateVersion(Attributes attributes, String[] supportedVersions) {
          String version = attributes.getValue("project-version");
          if(Arrays.binarySearch(supportedVersions, version) < 0) {
              throw new CayenneRuntimeException("Unsupported project version: %s, please upgrade project using Modeler or " +
                      "include cayenne-project-compatibility module v%s",
                      version, LocalizedStringsHandler.getString("cayenne.version"));
          }
      }
  
      protected void validateNamespace(String realNamespace) {
          if(!targetNamespace.equals(realNamespace)) {
              throw new CayenneRuntimeException("Unknown XML namespace %s, expected %s. Probably xml was modified.",
                      realNamespace, targetNamespace);
          }
      }
  }
  