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<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Copyright 2000-2005 Sun Microsystems, Inc. All Rights Reserved.
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DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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This code is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License version 2 only, as
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published by the Free Software Foundation. Sun designates this
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particular file as subject to the "Classpath" exception as provided
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by Sun in the LICENSE file that accompanied this code.
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This code is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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version 2 for more details (a copy is included in the LICENSE file that
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accompanied this code).
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You should have received a copy of the GNU General Public License version
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2 along with this work; if not, write to the Free Software Foundation,
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Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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CA 95054 USA or visit www.sun.com if you need additional information or
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have any questions.
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-->
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>javax.xml.transform</title>
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<meta name="CVS"
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content="$Id: package.html,v 1.2 2005/06/10 03:50:39 jeffsuttor Exp $" />
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<meta name="AUTHOR"
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content="Jeff.Suttor@Sun.com" />
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</head>
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<body>
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<p>This package defines the generic APIs for processing transformation
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instructions, and performing a transformation from source to result. These
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interfaces have no dependencies on SAX or the DOM standard, and try to make as
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few assumptions as possible about the details of the source and result of a
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transformation. It achieves this by defining
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{@link javax.xml.transform.Source} and
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{@link javax.xml.transform.Result} interfaces.
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</p>
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<p>To define concrete classes for the user, the API defines specializations
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of the interfaces found at the root level. These interfaces are found in
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{@link javax.xml.transform.sax}, {@link javax.xml.transform.dom},
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and {@link javax.xml.transform.stream}.
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</p>
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<h3>Creating Objects</h3>
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<p>The API allows a concrete
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{@link javax.xml.transform.TransformerFactory} object to be created from
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the static function
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{@link javax.xml.transform.TransformerFactory#newInstance}.
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</p>
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<h3>Specification of Inputs and Outputs</h3>
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<p>This API defines two interface objects called
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{@link javax.xml.transform.Source} and
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{@link javax.xml.transform.Result}. In order to pass Source and Result
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objects to the interfaces, concrete classes must be used.
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Three concrete representations are defined for each of these
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objects:
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{@link javax.xml.transform.stream.StreamSource} and
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{@link javax.xml.transform.stream.StreamResult},
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{@link javax.xml.transform.sax.SAXSource} and
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{@link javax.xml.transform.sax.SAXResult}, and
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{@link javax.xml.transform.dom.DOMSource} and
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{@link javax.xml.transform.dom.DOMResult}. Each of these objects defines
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a FEATURE string (which is i the form of a URL), which can be passed into
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{@link javax.xml.transform.TransformerFactory#getFeature} to see if the
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given type of Source or Result object is supported. For instance, to test if a
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DOMSource and a StreamResult is supported, you can apply the following
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test.
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</p>
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<pre>
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<code>
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TransformerFactory tfactory = TransformerFactory.newInstance();
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if (tfactory.getFeature(DOMSource.FEATURE) && tfactory.getFeature(StreamResult.FEATURE)) {
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...
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}
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</code>
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</pre>
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<h3>
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<a name="qname-delimiter">Qualified Name Representation</a>
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</h3>
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<p><a href="http://www.w3.org/TR/REC-xml-names">Namespaces</a>
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present something of a problem area when dealing with XML objects. Qualified
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Names appear in XML markup as prefixed names. But the prefixes themselves do
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not hold identity. Rather, it is the URIs that they contextually map to that
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hold the identity. Therefore, when passing a Qualified Name like "xyz:foo"
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among Java programs, one must provide a means to map "xyz" to a namespace.
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</p>
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<p>One solution has been to create a "QName" object that holds the
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namespace URI, as well as the prefix and local name, but this is not always an
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optimal solution, as when, for example, you want to use unique strings as keys
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in a dictionary object. Not having a string representation also makes it
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difficult to specify a namespaced identity outside the context of an XML
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document.
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</p>
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<p>In order to pass namespaced values to transformations,
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for
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instance when setting a property or a parameter on a
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{@link javax.xml.transform.Transformer} object,
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this specification defines that a
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String "qname" object parameter be passed as two-part string, the namespace URI
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enclosed in curly braces ({}), followed by the local name. If the qname has a
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null URI, then the String object only contains the local name. An application
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can safely check for a non-null URI by testing to see if the first character of
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the name is a '{' character.
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</p>
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<p>For example, if a URI and local name were obtained from an element
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defined with <xyz:foo xmlns:xyz="http://xyz.foo.com/yada/baz.html"/>,
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then the Qualified Name would be "{http://xyz.foo.com/yada/baz.html}foo".
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Note that the prefix is lost.
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</p>
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<h3>Result Tree Serialization</h3>
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<p>Serialization of the result tree to a stream can be controlled with
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the {@link javax.xml.transform.Transformer#setOutputProperties} and the
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{@link javax.xml.transform.Transformer#setOutputProperty} methods.
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These properties only apply to stream results, they have no effect when
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the result is a DOM tree or SAX event stream.</p>
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<p>Strings that match the <a href="http://www.w3.org/TR/xslt#output">XSLT
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specification for xsl:output attributes</a> can be referenced from the
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{@link javax.xml.transform.OutputKeys} class. Other strings can be
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specified as well.
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If the transformer does not recognize an output key, a
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{@link java.lang.IllegalArgumentException} is thrown, unless the
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key name is <a href="#qname-delimiter">namespace qualified</a>. Output key names
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that are namespace qualified are always allowed, although they may be
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ignored by some implementations.</p>
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<p>If all that is desired is the simple identity transformation of a
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source to a result, then {@link javax.xml.transform.TransformerFactory}
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provides a
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{@link javax.xml.transform.TransformerFactory#newTransformer()} method
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with no arguments. This method creates a Transformer that effectively copies
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the source to the result. This method may be used to create a DOM from SAX
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events or to create an XML or HTML stream from a DOM or SAX events. </p>
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<h3>Exceptions and Error Reporting</h3>
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<p>The transformation API throw three types of specialized exceptions. A
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{@link javax.xml.transform.TransformerFactoryConfigurationError} is parallel to
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the {@link javax.xml.parsers.FactoryConfigurationError}, and is thrown
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when a configuration problem with the TransformerFactory exists. This error
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will typically be thrown when the transformation factory class specified with
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the "javax.xml.transform.TransformerFactory" system property cannot be found or
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instantiated.</p>
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<p>A {@link javax.xml.transform.TransformerConfigurationException}
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may be thrown if for any reason a Transformer can not be created. A
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TransformerConfigurationException may be thrown if there is a syntax error in
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the transformation instructions, for example when
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{@link javax.xml.transform.TransformerFactory#newTransformer} is
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called.</p>
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<p>{@link javax.xml.transform.TransformerException} is a general
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exception that occurs during the course of a transformation. A transformer
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exception may wrap another exception, and if any of the
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{@link javax.xml.transform.TransformerException#printStackTrace()}
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methods are called on it, it will produce a list of stack dumps, starting from
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the most recent. The transformer exception also provides a
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{@link javax.xml.transform.SourceLocator} object which indicates where
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in the source tree or transformation instructions the error occurred.
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{@link javax.xml.transform.TransformerException#getMessageAndLocation()}
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may be called to get an error message with location info, and
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{@link javax.xml.transform.TransformerException#getLocationAsString()}
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may be called to get just the location string.</p>
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<p>Transformation warnings and errors are sent to an
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{@link javax.xml.transform.ErrorListener}, at which point the
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application may decide to report the error or warning, and may decide to throw
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an <code>Exception</code> for a non-fatal error. The <code>ErrorListener</code> may be set via
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{@link javax.xml.transform.TransformerFactory#setErrorListener} for
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reporting errors that have to do with syntax errors in the transformation
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instructions, or via
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{@link javax.xml.transform.Transformer#setErrorListener} to report
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errors that occur during the transformation. The <code>ErrorListener</code> on both objects
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will always be valid and non-<code>null</code>, whether set by the application or a default
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implementation provided by the processor.
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The default implementation provided by the processor will report all warnings and errors to <code>System.err</code>
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and does not throw any <code>Exception</code>s.
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Applications are <em>strongly</em> encouraged to register and use
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<code>ErrorListener</code>s that insure proper behavior for warnings and
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errors.
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</p>
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<h3>Resolution of URIs within a transformation</h3>
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<p>The API provides a way for URIs referenced from within the stylesheet
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instructions or within the transformation to be resolved by the calling
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application. This can be done by creating a class that implements the
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{@link javax.xml.transform.URIResolver} interface, with its one method,
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{@link javax.xml.transform.URIResolver#resolve}, and use this class to
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set the URI resolution for the transformation instructions or transformation
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with {@link javax.xml.transform.TransformerFactory#setURIResolver} or
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{@link javax.xml.transform.Transformer#setURIResolver}. The
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<code>URIResolver.resolve</code> method takes two String arguments, the URI found in the
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stylesheet instructions or built as part of the transformation process, and the
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base URI
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against which the first argument will be made absolute if the
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absolute URI is required.
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The returned {@link javax.xml.transform.Source} object must be usable by
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the transformer, as specified in its implemented features.</p>
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</body>
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</html>
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