Source
and Result
interfaces. To provide concrete classes for the user, the API defines specializations of the interfaces found at the root level. These interfaces are found in javax.xml.transform.sax
, javax.xml.transform.dom
, javax.xml.transform.stax
, and javax.xml.transform.stream
.
The API allows a concrete TransformerFactory
object to be created from the static function TransformerFactory.newInstance()
.
This API defines two interface objects called Source
and Result
. In order to pass Source and Result objects to the interfaces, concrete classes must be used. The following concrete representations are defined for each of these objects: StreamSource
and StreamResult
, StAXSource
and StAXResult
, and SAXSource
and SAXResult
, and DOMSource
and DOMResult
. Each of these objects defines a FEATURE string (which is in the form of a URL), which can be passed into TransformerFactory.getFeature(java.lang.String)
to see if the given type of Source or Result object is supported. For instance, to test if a DOMSource and a StreamResult is supported, you can apply the following test.
TransformerFactory tfactory = TransformerFactory.newInstance();
if (tfactory.getFeature(DOMSource.FEATURE) &&
tfactory.getFeature(StreamResult.FEATURE)) {
...
}
Namespaces present something of a problem area when dealing with XML objects. Qualified Names appear in XML markup as prefixed names. But the prefixes themselves do not hold identity. Rather, it is the URIs that they contextually map to that hold the identity. Therefore, when passing a Qualified Name like "xyz:foo" among Java programs, one must provide a means to map "xyz" to a namespace.
One solution has been to create a "QName" object that holds the namespace URI, as well as the prefix and local name, but this is not always an optimal solution, as when, for example, you want to use unique strings as keys in a dictionary object. Not having a string representation also makes it difficult to specify a namespaced identity outside the context of an XML document.
In order to pass namespaced values to transformations, for instance when setting a property or a parameter on a Transformer
object, this specification defines that a String "qname" object parameter be passed as two-part string, the namespace URI enclosed in curly braces ({}), followed by the local name. If the qname has a null URI, then the String object only contains the local name. An application can safely check for a non-null URI by testing to see if the first character of the name is a '{' character.
For example, if a URI and local name were obtained from an element defined with <xyz:foo xmlns:xyz="http://xyz.foo.com/yada/baz.html"/>, then the Qualified Name would be "{http://xyz.foo.com/yada/baz.html}foo". Note that the prefix is lost.
Serialization of the result tree to a stream can be controlled with the Transformer.setOutputProperties(java.util.Properties)
and the Transformer.setOutputProperty(java.lang.String, java.lang.String)
methods. These properties only apply to stream results, they have no effect when the result is a DOM tree or SAX event stream.
Strings that match the XSLT specification for xsl:output attributes can be referenced from the OutputKeys
class. Other strings can be specified as well. If the transformer does not recognize an output key, a IllegalArgumentException
is thrown, unless the key name is namespace qualified. Output key names that are namespace qualified are always allowed, although they may be ignored by some implementations.
If all that is desired is the simple identity transformation of a source to a result, then TransformerFactory
provides a TransformerFactory.newTransformer()
method with no arguments. This method creates a Transformer that effectively copies the source to the result. This method may be used to create a DOM from SAX events or to create an XML or HTML stream from a DOM or SAX events.
The transformation API throw three types of specialized exceptions. A TransformerFactoryConfigurationError
is parallel to the FactoryConfigurationError
, and is thrown when a configuration problem with the TransformerFactory exists. This error will typically be thrown when the transformation factory class specified with the "javax.xml.transform.TransformerFactory" system property cannot be found or instantiated.
A TransformerConfigurationException
may be thrown if for any reason a Transformer can not be created. A TransformerConfigurationException may be thrown if there is a syntax error in the transformation instructions, for example when TransformerFactory.newTransformer(javax.xml.transform.Source)
is called.
TransformerException
is a general exception that occurs during the course of a transformation. A transformer exception may wrap another exception, and if any of the TransformerException.printStackTrace()
methods are called on it, it will produce a list of stack dumps, starting from the most recent. The transformer exception also provides a SourceLocator
object which indicates where in the source tree or transformation instructions the error occurred. TransformerException.getMessageAndLocation()
may be called to get an error message with location info, and TransformerException.getLocationAsString()
may be called to get just the location string.
Transformation warnings and errors are sent to an ErrorListener
, at which point the application may decide to report the error or warning, and may decide to throw an Exception
for a non-fatal error. The ErrorListener
may be set via TransformerFactory.setErrorListener(javax.xml.transform.ErrorListener)
for reporting errors that have to do with syntax errors in the transformation instructions, or via Transformer.setErrorListener(javax.xml.transform.ErrorListener)
to report errors that occur during the transformation. The ErrorListener
on both objects will always be valid and non-null
, whether set by the application or a default implementation provided by the processor.
The API provides a way for URIs referenced from within the stylesheet instructions or within the transformation to be resolved by the calling application. This can be done by creating a class that implements the URIResolver
interface, with its one method, URIResolver.resolve(java.lang.String, java.lang.String)
, and use this class to set the URI resolution for the transformation instructions or transformation with TransformerFactory.setURIResolver(javax.xml.transform.URIResolver)
or Transformer.setURIResolver(javax.xml.transform.URIResolver)
. The URIResolver.resolve
method takes two String arguments, the URI found in the stylesheet instructions or built as part of the transformation process, and the base URI against which the first argument will be made absolute if the absolute URI is required. The returned Source
object must be usable by the transformer, as specified in its implemented features.
Class | Description |
---|---|
ErrorListener | The listener interface used by a TransformerFactory or Transformer to notify callers of error messages that occur during a transformation process. |
OutputKeys | Provides string constants that can be used to set output properties for a Transformer, or to retrieve output properties from a Transformer or Templates object. |
Result | An object that implements this interface contains the information needed to build a transformation result tree. |
Source | An object that implements this interface contains the information needed to act as source input (XML source or transformation instructions). |
SourceLocator | This interface is primarily for the purposes of reporting where an error occurred in the XML source or transformation instructions. |
Templates | An object that implements this interface is the runtime representation of processed transformation instructions. |
Transformer | An instance of this abstract class can transform a source tree into a result tree. |
TransformerConfigurationException | Indicates a serious configuration error. |
TransformerException | This class specifies an exceptional condition that occurred during the transformation process. |
TransformerFactory | A TransformerFactory instance can be used to create Transformer and Templates objects. |
TransformerFactoryConfigurationError | Thrown when a problem with configuration with the Transformer Factories exists. |
URIResolver | An object that implements this interface that can be called by the processor to turn a URI used in document(), xsl:import, or xsl:include into a Source object. |
© 1993, 2023, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.xml/javax/xml/transform/package-summary.html