Java : Transformer (XML) con ejemplos

Transformer (Java SE 22 & JDK 22) en Java con ejemplos.
Encontrará ejemplos de código en la mayoría de los métodos de Transformer.

Nota :

Este artículo puede utilizar software de traducción para su comodidad. Consulte también la versión original en inglés.

Summary

Una instancia de esta clase abstracta puede transformar un árbol de origen en un árbol de resultados. (Traducción automática)

Class diagram

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.newDocument();

final var root = document.createElement("root");
document.appendChild(root);

final var text = document.createTextNode("abcd");
root.appendChild(text);

final var factory = TransformerFactory.newInstance();
final var transformer = factory.newTransformer();

final var source = new DOMSource(document);
final var result = new StreamResult(new StringWriter());
transformer.transform(source, result);

//<?xml version="1.0" encoding="UTF-8" standalone="no"?><root>abcd</root>
System.out.println(result.getWriter());

Constructors

Transformer ()

El constructor predeterminado está protegido a propósito. (Traducción automática)

protected. I think it's rare to create a subclass of this class. Therefore, the code example is omitted.

Methods

abstract void clearParameters ()

Borre todos los parámetros establecidos con setParameter. (Traducción automática)

final var xml = """
        <root/>
        """;

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

final var xsl = """
        <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
          <xsl:output omit-xml-declaration="yes" />
          <xsl:param name="param">aaaa</xsl:param>

          <xsl:template match="root">
            <xsl:copy-of select="$param" />
          </xsl:template>

        </xsl:stylesheet>
        """;

final var factory = TransformerFactory.newInstance();
final var transformer = factory.newTransformer(
        new StreamSource(new ByteArrayInputStream(xsl.getBytes())));

System.out.println(transformer.getParameter("param")); // null
transformer.setParameter("param", "bbbb");

{
    System.out.println(transformer.getParameter("param")); // bbbb

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //bbbb
    System.out.println(result.getWriter());
}

transformer.clearParameters();

{
    System.out.println(transformer.getParameter("param")); // null

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //aaaa
    System.out.println(result.getWriter());
}

abstract ErrorListener getErrorListener ()

Obtener el controlador de eventos de error en efecto para la transformación. (Traducción automática)

// An XML text with incorrect syntax.
final var xml = """
        <root>
            <<<child>aaa</child>
        </root>
        """;

final var factory = TransformerFactory.newInstance();
final var transformer = factory.newTransformer();

final var listener = new ErrorListener() {
    @Override
    public void warning(TransformerException exception) {
        System.out.println("-- ErrorListener warning --");
        System.out.println(exception);
    }

    @Override
    public void error(TransformerException exception) {
        System.out.println("-- ErrorListener error --");
        System.out.println(exception);
    }

    @Override
    public void fatalError(TransformerException exception) {
        System.out.println("-- ErrorListener fatalError --");
        System.out.println(exception);
    }
};

transformer.setErrorListener(listener);
System.out.println(listener == transformer.getErrorListener()); // true

final var source = new StreamSource(new ByteArrayInputStream(xml.getBytes()));
final var result = new StreamResult(new StringWriter());

try {
    transformer.transform(source, result);
} catch (TransformerException e) {
    System.out.println("-- TransformerException --");
    System.out.println(e);
}

// Result
// ↓
//-- ErrorListener error --
//javax.xml.transform.TransformerException:
// The content of elements must consist of well-formed character data or markup.
//-- TransformerException --
//javax.xml.transform.TransformerException:
// org.xml.sax.SAXParseException; lineNumber: 2; columnNumber: 6;
// The content of elements must consist of well-formed character data or markup.

abstract Properties getOutputProperties ()

Obtenga una copia de las propiedades de salida para la transformación. (Traducción automática)

final var xml = """
        <root><child>aaa</child></root>
        """;

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

final var transformer = TransformerFactory.newInstance().newTransformer();

{
    final var ret = transformer.getOutputProperties();
    System.out.println(ret.size()); // 0

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<?xml version="1.0" encoding="UTF-8" standalone="no"?><root><child>aaa</child></root>
    System.out.println(result.getWriter());
}

final var properties = new Properties();
properties.setProperty(OutputKeys.INDENT, "yes");
properties.setProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

transformer.setOutputProperties(properties);

{
    final var ret = transformer.getOutputProperties();
    System.out.println(ret); // {indent=yes, omit-xml-declaration=yes}

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<root>
    //    <child>aaa</child>
    //</root>
    System.out.println(result.getWriter());
}

abstract String getOutputProperty (String name)

Obtenga una propiedad de salida que esté vigente para el transformador. (Traducción automática)

final var xml = """
        <root><child>aaa</child></root>
        """;

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

final var transformer = TransformerFactory.newInstance().newTransformer();

{
    final var ret1 = transformer.getOutputProperty(OutputKeys.INDENT);
    System.out.println(ret1); // "no"

    final var ret2 = transformer.getOutputProperty(OutputKeys.OMIT_XML_DECLARATION);
    System.out.println(ret2); // "no"

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<?xml version="1.0" encoding="UTF-8" standalone="no"?><root><child>aaa</child></root>
    System.out.println(result.getWriter());
}

transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

{
    final var ret1 = transformer.getOutputProperty(OutputKeys.INDENT);
    System.out.println(ret1); // "yes"

    final var ret2 = transformer.getOutputProperty(OutputKeys.OMIT_XML_DECLARATION);
    System.out.println(ret2); // "yes"

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<root>
    //    <child>aaa</child>
    //</root>
    System.out.println(result.getWriter());
}

abstract Object getParameter (String name)

Obtener un parámetro que se configuró explícitamente con setParameter. (Traducción automática)

final var xml = """
        <root/>
        """;

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

final var xsl = """
        <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
          <xsl:output omit-xml-declaration="yes" />
          <xsl:param name="param">aaaa</xsl:param>

          <xsl:template match="root">
            <xsl:copy-of select="$param" />
          </xsl:template>

        </xsl:stylesheet>
        """;

final var factory = TransformerFactory.newInstance();
final var transformer = factory.newTransformer(
        new StreamSource(new ByteArrayInputStream(xsl.getBytes())));

System.out.println(transformer.getParameter("param")); // null
transformer.setParameter("param", "bbbb");

{
    System.out.println(transformer.getParameter("param")); // bbbb

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //bbbb
    System.out.println(result.getWriter());
}

transformer.clearParameters();

{
    System.out.println(transformer.getParameter("param")); // null

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //aaaa
    System.out.println(result.getWriter());
}

abstract URIResolver getURIResolver ()

Obtenga un objeto que se utilizará para resolver las URI utilizadas en document(). (Traducción automática)

final var sampleA = Path.of("R:", "java-work", "sample-a.xml");
System.out.println(sampleA); // R:\java-work\sample-a.xml

Files.writeString(sampleA, """
        <root>aaa</root>
        """);

final var sampleB = Path.of("R:", "java-work", "sample-b.xml");
System.out.println(sampleB); // R:\java-work\sample-b.xml

Files.writeString(sampleB, """
        <root>bbb</root>
        """);

final var xml = """
        <root/>
        """;

final var xsl = """
        <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
          <xsl:output omit-xml-declaration="yes" />
          <xsl:variable name="doc" select="document('file:///R:/java-work/sample-a.xml')" />

          <xsl:template match="/">
            <xsl:copy-of select="$doc" />
          </xsl:template>

        </xsl:stylesheet>
        """;

final var factory = TransformerFactory.newInstance();
final var transformer = factory.newTransformer(
        new StreamSource(new ByteArrayInputStream(xsl.getBytes())));

{
    System.out.println(transformer.getURIResolver()); // null

    final var source = new StreamSource(new ByteArrayInputStream(xml.getBytes()));
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<root>aaa</root>
    System.out.println(result.getWriter());
}

final var urlResolver = new URIResolver() {
    @Override
    public Source resolve(String href, String base) {
        if ("file:///R:/java-work/sample-a.xml".equals(href)) {
            return new StreamSource("file:///R:/java-work/sample-b.xml");
        }

        return null;
    }
};

transformer.setURIResolver(urlResolver);

{
    System.out.println(transformer.getURIResolver() == urlResolver); // true

    final var source = new StreamSource(new ByteArrayInputStream(xml.getBytes()));
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<root>bbb</root>
    System.out.println(result.getWriter());
}

void reset ()

Restablezca este transformador a su configuración original. (Traducción automática)

final var transformer = TransformerFactory.newInstance().newTransformer();

transformer.setParameter("param", "bbbb");
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

System.out.println(transformer.getParameter("param")); // "bbbb"
System.out.println(transformer.getOutputProperty(OutputKeys.INDENT)); // "yes"
System.out.println(transformer.getOutputProperty(OutputKeys.OMIT_XML_DECLARATION)); // "yes"

transformer.reset();

System.out.println(transformer.getParameter("param")); // null
System.out.println(transformer.getOutputProperty(OutputKeys.INDENT)); // "no"
System.out.println(transformer.getOutputProperty(OutputKeys.OMIT_XML_DECLARATION)); // "no"

abstract void setErrorListener (ErrorListener listener)

Establezca el detector de eventos de error en efecto para la transformación. (Traducción automática)

// An XML text with incorrect syntax.
final var xml = """
        <root>
            <<<child>aaa</child>
        </root>
        """;

final var factory = TransformerFactory.newInstance();
final var transformer = factory.newTransformer();

final var listener = new ErrorListener() {
    @Override
    public void warning(TransformerException exception) {
        System.out.println("-- ErrorListener warning --");
        System.out.println(exception);
    }

    @Override
    public void error(TransformerException exception) {
        System.out.println("-- ErrorListener error --");
        System.out.println(exception);
    }

    @Override
    public void fatalError(TransformerException exception) {
        System.out.println("-- ErrorListener fatalError --");
        System.out.println(exception);
    }
};

transformer.setErrorListener(listener);
System.out.println(listener == transformer.getErrorListener()); // true

final var source = new StreamSource(new ByteArrayInputStream(xml.getBytes()));
final var result = new StreamResult(new StringWriter());

try {
    transformer.transform(source, result);
} catch (TransformerException e) {
    System.out.println("-- TransformerException --");
    System.out.println(e);
}

// Result
// ↓
//-- ErrorListener error --
//javax.xml.transform.TransformerException:
// The content of elements must consist of well-formed character data or markup.
//-- TransformerException --
//javax.xml.transform.TransformerException:
// org.xml.sax.SAXParseException; lineNumber: 2; columnNumber: 6;
// The content of elements must consist of well-formed character data or markup.

abstract void setOutputProperties (Properties oformat)

Establecer las propiedades de salida para la transformación. (Traducción automática)

final var xml = """
        <root><child>aaa</child></root>
        """;

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

final var transformer = TransformerFactory.newInstance().newTransformer();

{
    final var ret = transformer.getOutputProperties();
    System.out.println(ret.size()); // 0

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<?xml version="1.0" encoding="UTF-8" standalone="no"?><root><child>aaa</child></root>
    System.out.println(result.getWriter());
}

final var properties = new Properties();
properties.setProperty(OutputKeys.INDENT, "yes");
properties.setProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

transformer.setOutputProperties(properties);

{
    final var ret = transformer.getOutputProperties();
    System.out.println(ret); // {indent=yes, omit-xml-declaration=yes}

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<root>
    //    <child>aaa</child>
    //</root>
    System.out.println(result.getWriter());
}

abstract void setOutputProperty (String name, String value)

Establezca una propiedad de salida que tendrá efecto para la transformación. (Traducción automática)

final var xml = """
        <root><child>aaa</child></root>
        """;

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

final var transformer = TransformerFactory.newInstance().newTransformer();

{
    final var ret1 = transformer.getOutputProperty(OutputKeys.INDENT);
    System.out.println(ret1); // "no"

    final var ret2 = transformer.getOutputProperty(OutputKeys.OMIT_XML_DECLARATION);
    System.out.println(ret2); // "no"

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<?xml version="1.0" encoding="UTF-8" standalone="no"?><root><child>aaa</child></root>
    System.out.println(result.getWriter());
}

transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

{
    final var ret1 = transformer.getOutputProperty(OutputKeys.INDENT);
    System.out.println(ret1); // "yes"

    final var ret2 = transformer.getOutputProperty(OutputKeys.OMIT_XML_DECLARATION);
    System.out.println(ret2); // "yes"

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<root>
    //    <child>aaa</child>
    //</root>
    System.out.println(result.getWriter());
}

abstract void setParameter (String name, Object value)

Añade un parámetro para la transformación. (Traducción automática)

final var xml = """
        <root/>
        """;

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

final var xsl = """
        <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
          <xsl:output omit-xml-declaration="yes" />
          <xsl:param name="param">aaaa</xsl:param>

          <xsl:template match="root">
            <xsl:copy-of select="$param" />
          </xsl:template>

        </xsl:stylesheet>
        """;

final var factory = TransformerFactory.newInstance();
final var transformer = factory.newTransformer(
        new StreamSource(new ByteArrayInputStream(xsl.getBytes())));

System.out.println(transformer.getParameter("param")); // null
transformer.setParameter("param", "bbbb");

{
    System.out.println(transformer.getParameter("param")); // bbbb

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //bbbb
    System.out.println(result.getWriter());
}

transformer.clearParameters();

{
    System.out.println(transformer.getParameter("param")); // null

    final var source = new DOMSource(document);
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //aaaa
    System.out.println(result.getWriter());
}

abstract void setURIResolver (URIResolver resolver)

Establezca un objeto que se utilizará para resolver las URI utilizadas en document(). (Traducción automática)

final var sampleA = Path.of("R:", "java-work", "sample-a.xml");
System.out.println(sampleA); // R:\java-work\sample-a.xml

Files.writeString(sampleA, """
        <root>aaa</root>
        """);

final var sampleB = Path.of("R:", "java-work", "sample-b.xml");
System.out.println(sampleB); // R:\java-work\sample-b.xml

Files.writeString(sampleB, """
        <root>bbb</root>
        """);

final var xml = """
        <root/>
        """;

final var xsl = """
        <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
          <xsl:output omit-xml-declaration="yes" />
          <xsl:variable name="doc" select="document('file:///R:/java-work/sample-a.xml')" />

          <xsl:template match="/">
            <xsl:copy-of select="$doc" />
          </xsl:template>

        </xsl:stylesheet>
        """;

final var factory = TransformerFactory.newInstance();
final var transformer = factory.newTransformer(
        new StreamSource(new ByteArrayInputStream(xsl.getBytes())));

{
    System.out.println(transformer.getURIResolver()); // null

    final var source = new StreamSource(new ByteArrayInputStream(xml.getBytes()));
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<root>aaa</root>
    System.out.println(result.getWriter());
}

final var urlResolver = new URIResolver() {
    @Override
    public Source resolve(String href, String base) {
        if ("file:///R:/java-work/sample-a.xml".equals(href)) {
            return new StreamSource("file:///R:/java-work/sample-b.xml");
        }

        return null;
    }
};

transformer.setURIResolver(urlResolver);

{
    System.out.println(transformer.getURIResolver() == urlResolver); // true

    final var source = new StreamSource(new ByteArrayInputStream(xml.getBytes()));
    final var result = new StreamResult(new StringWriter());
    transformer.transform(source, result);

    //<root>bbb</root>
    System.out.println(result.getWriter());
}

abstract void transform (Source xmlSource, Result outputTarget)

Transformar la fuente XML en un resultado. (Traducción automática)

// DOM -> XML text

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.newDocument();

final var root = document.createElement("root");
document.appendChild(root);

final var text = document.createTextNode("abcd");
root.appendChild(text);

final var transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

final var source = new DOMSource(document);
final var result = new StreamResult(new StringWriter());
transformer.transform(source, result);

//<root>abcd</root>
System.out.println(result.getWriter());

// Transforms an XML text with XSL.

final var xml = """
        <root>abcd</root>
        """;

final var xsl = """
        <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
          <xsl:output omit-xml-declaration="yes" />

          <xsl:template match="/">012<xsl:value-of select="." />XYZ</xsl:template>

        </xsl:stylesheet>
        """;

final var transformer = TransformerFactory.newInstance().newTransformer(
        new StreamSource(new ByteArrayInputStream(xsl.getBytes())));

final var source = new StreamSource(new ByteArrayInputStream(xml.getBytes()));
final var result = new StreamResult(new StringWriter());
transformer.transform(source, result);

//012abcdXYZ
System.out.println(result.getWriter());

// DOM → SAX

final var builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
final var document = builder.newDocument();

final var root = document.createElement("root");
document.appendChild(root);

final var text = document.createTextNode("abcd");
root.appendChild(text);

final var transformer = TransformerFactory.newInstance().newTransformer();

final var handler = new DefaultHandler() {

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) {
        System.out.println("startElement : " + qName);
    }

    @Override
    public void endElement(String uri, String localName, String qName) {
        System.out.println("endElement : " + qName);
    }

    @Override
    public void characters(char[] ch, int start, int length) {
        System.out.println("text : " + new String(ch, start, length));
    }
};

final var source = new DOMSource(document);
final var result = new SAXResult(handler);

//startElement : root
//text : abcd
//endElement : root
transformer.transform(source, result);

Ejemplos de API