Package jmri.util.xml

Class XMLUtil

java.lang.Object
jmri.util.xml.XMLUtil
public final class XMLUtil extends Object
Utility class collecting library methods related to XML processing. org.openide.xml.XMLUtil adapted to work in JMRI. This should maintain strict API conformance to the OpenIDE implementation.

  • Method Details

    • createXMLReader

      public static XMLReader createXMLReader() throws SAXException
      Create a simple parser.
      Returns:
      createXMLReader(false, false)
      Throws:
      SAXException - if a parser fulfilling given parameters can not be created

    • createXMLReader

      public static XMLReader createXMLReader(boolean validate) throws SAXException
      Create a simple parser, possibly validating.
      Parameters:
      validate - if true, a validating parser is returned
      Returns:
      createXMLReader(validate, false)
      Throws:
      SAXException - if a parser fulfilling given parameters can not be created

    • createXMLReader

      public static XMLReader createXMLReader(boolean validate, boolean namespaceAware) throws SAXException
      Creates a SAX parser.

      See parse(org.xml.sax.InputSource, boolean, boolean, org.xml.sax.ErrorHandler, org.xml.sax.EntityResolver) for hints on setting an entity resolver.

      Parameters:
      validate - if true, a validating parser is returned
      namespaceAware - if true, a namespace aware parser is returned
      Returns:
      XMLReader configured according to passed parameters
      Throws:
      FactoryConfigurationError - Application developers should never need to directly catch errors of this type.
      SAXException - if a parser fulfilling given parameters can not be created

    • createDocument

      public static Document createDocument(String rootQName, String namespaceURI, String doctypePublicID, String doctypeSystemID) throws DOMException
      Creates an empty DOM document. E.g.: 
       Document doc = createDocument("book", null, null, null);
      creates new DOM of a well-formed document with root element named book.
      Parameters:
      rootQName - qualified name of root element, for example myroot or ns:myroot
      namespaceURI - URI of root element namespace or null
      doctypePublicID - public ID of DOCTYPE or null
      doctypeSystemID - system ID of DOCTYPE or null if no DOCTYPE required and doctypePublicID is also null
      Returns:
      new DOM Document
      Throws:
      DOMException - if new DOM with passed parameters can not be created
      FactoryConfigurationError - Application developers should never need to directly catch errors of this type.

    • parse

      public static Document parse(InputSource input, boolean validate, boolean namespaceAware, ErrorHandler errorHandler, EntityResolver entityResolver) throws IOException, SAXException
      Parses an XML document into a DOM tree.

      Remember that when parsing XML files you often want to set an explicit entity resolver. For example, consider a file such as this: 

       <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE root PUBLIC "-//NetBeans//DTD Foo 1.0//EN" "http://www.netbeans.org/dtds/foo-1_0.dtd">
 <root/>

      If you parse this with a null entity resolver, or you use the default resolver (EntityCatalog.getDefault) but do not do anything special with this DTD, you will probably find the parse blocking to make a network connection even when you are not validating. That is because DTDs can be used to define entities and other XML oddities, and are not a pure constraint language like Schema or RELAX-NG.

      There are three basic ways to avoid the network connection.

      1. Register the DTD. This is generally the best thing to do. See EntityCatalog's documentation for details, but for example in your layer use: 
         <filesystem>
   <folder name="xml">
     <folder name="entities">
       <folder name="NetBeans">
         <file name="DTD_Foo_1_0"
               url="resources/foo-1_0.dtd">
           <attr name="hint.originalPublicID"
                 stringvalue="-//NetBeans//DTD Foo 1.0//EN"/>
         </file>
       </folder>
     </folder>
   </folder>
 </filesystem>

        Now the default system entity catalog will resolve the public ID to the local copy in your module, not the network copy. Additionally, anyone who mounts the "NetBeans Catalog" in the XML Entity Catalogs node in the Runtime tab will be able to use your local copy of the DTD automatically, for validation, code completion, etc. (The network URL should really exist, though, for the benefit of other tools!)

      2. You can also set an explicit entity resolver which maps that particular public ID to some local copy of the DTD, if you do not want to register it globally in the system for some reason. If handed other public IDs, just return null to indicate that the system ID should be loaded.
      3. In some cases where XML parsing is very performance-sensitive, and you know that you do not need validation and furthermore that the DTD defines no infoset (there are no entity or character definitions, etc.), you can speed up the parse. Turn off validation, but also supply a custom entity resolver that does not even bother to load the DTD at all:
         public InputSource resolveEntity(String pubid, String sysid)
     throws SAXException, IOException {
   if (pubid.equals("-//NetBeans//DTD Foo 1.0//EN")) {
     return new InputSource(new ByteArrayInputStream(new byte[0]));
   } else {
     return EntityCatalog.getDefault().resolveEntity(pubid, sysid);
   }
 }
      Parameters:
      input - a parser input (for URL users use: new InputSource(url.toString())
      validate - if true validating parser is used
      namespaceAware - if true DOM is created by namespace aware parser
      errorHandler - a error handler to notify about exception (such as defaultErrorHandler()) or null
      entityResolver - SAX entity resolver (such as EntityCatalog#getDefault) or null
      Returns:
      document representing given input
      Throws:
      IOException - if an I/O problem during parsing occurs
      SAXException - is thrown if a parser error occurs
      FactoryConfigurationError - Application developers should never need to directly catch errors of this type.

    • write

      public static void write(Document doc, OutputStream out, String enc) throws IOException
      Writes a DOM document to a stream. The precise output format is not guaranteed but this method will attempt to indent it sensibly.

      Important: There might be some problems with <![CDATA[ ]]> sections in the DOM tree you pass into this method. Specifically, some CDATA sections my not be written as CDATA section or may be merged with other CDATA section at the same level. Also if plain text nodes are mixed with CDATA sections at the same level all text is likely to end up in one big CDATA section.
      For nodes that only have one CDATA section this method should work fine.

      Parameters:
      doc - DOM document to be written
      out - data sink
      enc - XML-defined encoding name (for example, "UTF-8")
      Throws:
      IOException - if JAXP fails or the stream cannot be written to

    • validate

      public static void validate(Element data, Schema schema) throws SAXException
      Check whether a DOM tree is valid according to a schema. Example of usage: 
       Element fragment = ...;
 SchemaFactory f = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
 Schema s = f.newSchema(This.class.getResource("something.xsd"));
 try {
     XMLUtil.validate(fragment, s);
     // valid
 } catch (SAXException x) {
     // invalid
 }
      Parameters:
      data - a DOM tree
      schema - a parsed schema
      Throws:
      SAXException - if validation failed
      Since:
      org.openide.util 7.17

    • toAttributeValue

      public static String toAttributeValue(String val) throws CharConversionException
      Escape passed string as XML attibute value (<, &, ' and " will be escaped. Note: An XML processor returns normalized value that can be different.
      Parameters:
      val - a string to be escaped
      Returns:
      escaped value
      Throws:
      CharConversionException - if val contains an improper XML character
      Since:
      1.40

    • toElementContent

      public static String toElementContent(String val) throws CharConversionException
      Escape passed string as XML element content (<, & and > in ]]> sequences).
      Parameters:
      val - a string to be escaped
      Returns:
      escaped value
      Throws:
      CharConversionException - if val contains an improper XML character
      Since:
      1.40

    • toHex

      public static String toHex(byte[] val, int start, int len)
      Can be used to encode values that contain invalid XML characters. At SAX parser end must be used pair method to get original value.
      Parameters:
      val - data to be converted
      start - offset
      len - count
      Returns:
      the converted data
      Since:
      1.29

    • fromHex

      public static byte[] fromHex(char[] hex, int start, int len) throws IOException
      Decodes data encoded using toHex.
      Parameters:
      hex - data to be converted
      start - offset
      len - count
      Returns:
      the converted data
      Throws:
      IOException - if input does not represent hex encoded value
      Since:
      1.29

    • appendChildElement

      public static void appendChildElement(Element parent, Element el, String[] order) throws IllegalArgumentException
      Append a child element to the parent at the specified location. Starting with a valid document, append an element according to the schema sequence represented by the order. All existing child elements must be include as well as the new element. The existing child element following the new child is important, as the element will be 'inserted before', not 'inserted after'.
      Parameters:
      parent - parent to which the child will be appended
      el - element to be added
      order - order of the elements which must be followed
      Throws:
      IllegalArgumentException - if the order cannot be followed, either a missing existing or new child element is not specified in order
      Since:
      8.4

    • findSubElements

      public static List<Element> findSubElements(Element parent) throws IllegalArgumentException
      Find all direct child elements of an element. Children which are all-whitespace text nodes or comments are ignored; others cause an exception to be thrown.
      Parameters:
      parent - a parent element in a DOM tree
      Returns:
      a list of direct child elements (may be empty)
      Throws:
      IllegalArgumentException - if there are non-element children besides whitespace
      Since:
      8.4

    • findElement

      public static Element findElement(Element parent, String name, String namespace) throws IllegalArgumentException
      Search for an XML element in the direct children of parent only. This compares localName (nodeName if localName is null) to name, and checks the tags namespace with the provided namespace. A null namespace will match any namespace.

      This is differs from the DOM version by:

      • not searching recursively
      • returns a single result
      Parameters:
      parent - a parent element
      name - the intended local name
      namespace - the intended namespace (or null)
      Returns:
      the one child element with that name, or null if none
      Throws:
      IllegalArgumentException - if there is multiple elements of the same name
      Since:
      8.4

    • findText

      public static String findText(Node parent)
      Extract nested text from a node. Currently does not handle coalescing text nodes, CDATA sections, etc.
      Parameters:
      parent - a parent element
      Returns:
      the nested text, or null if none was found
      Since:
      8.4

    • translateXML

      public static Element translateXML(Element from, String namespace)
      Convert an XML fragment from one namespace to another.
      Parameters:
      from - element to translate
      namespace - namespace to be translated to
      Returns:
      the element in the new namespace
      Since:
      8.4

    • copyDocument

      public static void copyDocument(Element from, Element to, String newNamespace)
      Copy elements from one document to another attaching at the specified element and translating the namespace.
      Parameters:
      from - copy the children of this element (exclusive)
      to - where to attach the copied elements
      newNamespace - destination namespace
      Since:
      8.4

    • defaultErrorHandler

      public static ErrorHandler defaultErrorHandler()
      Create an XML error handler that rethrows errors and fatal errors and logs warnings.
      Returns:
      a standard error handler
      Since:
      8.4