Xalan 확장 함수 구현 내에서 XPath 식을 어떻게 평가합니까?

Xalan 2.7.1에 의해 확장 기능에 제공된 컨텍스트 내에서 XPath 식을 평가하려고합니다. 어떤 이유로 Xalan에서 내부 예외가 발생하면 항상 실패합니다.Xalan 확장 함수 구현 내에서 XPath 식을 어떻게 평가합니까?

참고 :이 작업을 실행하려면 classpath에 xalan-j이 필요합니다.

package org.example; 

import java.io.*; 
import java.util.*; 
import java.util.logging.*; 
import javax.xml.namespace.NamespaceContext; 
import javax.xml.transform.*; 
import javax.xml.transform.stream.*; 
import javax.xml.xpath.*; 
import org.w3c.dom.*; 
import org.w3c.dom.traversal.NodeIterator; 
import org.apache.xalan.extensions.ExpressionContext; 

public class XalanExtension { 

    public static final String NS = "org:example:foo"; 

    public static final String XSLT = "" + 
"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + 
"<xsl:stylesheet \n" + 
" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\"\n" + 
" xmlns:foo=\"org:example:foo\"\n" + 
" xmlns:fun=\"xalan://org.example.XalanExtension\"\n" + 
" version=\"1.0\"> \n" + 
" \n" + 
" <xsl:template match=\"*|@*\">\n" + 
"  <xsl:apply-templates select=\"*|@*\"/>\n" + 
" </xsl:template>\n" + 
" \n" + 
" <xsl:template match=\"foo:test\">\n" + 
"  <xsl:variable name=\"result\" select=\"fun:evaluate(.)\"/>\n" + 
"  <xsl:message>\n" + 
"   Test: <xsl:value-of select=\".\"/> Result: <xsl:value-of select=\"$result\"/>\n" + 
"  </xsl:message>\n" + 
" </xsl:template>\n" + 
" \n" + 
"</xsl:stylesheet>"; 

    public static final String XML = "" + 
"<?xml version=\"1.0\" encoding=\"utf-8\"?>\n" + 
"<tests xmlns=\"org:example:foo\">\n" + 
" <a>1</a>\n" + 
" <b>2</b>\n" + 
" <c>3</c>\n" + 
" <test>../foo:a &gt; 5</test>\n" + 
"</tests>"; 

    private TransformerFactory xalanTransFact; 

    public XalanExtension() { 
     xalanTransFact = new org.apache.xalan.processor.TransformerFactoryImpl(); 
    } 

    public void transform() { 
     try { 
      StringWriter writer; 

      writer = new StringWriter(); 

      System.out.println(org.apache.xalan.Version.getVersion()); 

      Transformer transformer = xalanTransFact.newTransformer(new StreamSource(new StringReader(XSLT))); 
      transformer.setOutputProperty(OutputKeys.INDENT, "yes"); 
      transformer.setOutputProperty(OutputKeys.METHOD, "text"); 
      transformer.setOutputProperty(OutputKeys.ENCODING, "utf-8"); 

      transformer.transform(
        new StreamSource(new StringReader(XML)), 
        new StreamResult(writer)); 

      System.out.println(writer.toString()); 
     } catch (TransformerConfigurationException ex) { 
      Logger.getLogger(XalanExtension.class.getName()).log(Level.SEVERE, null, ex); 
     } catch (TransformerException ex) { 
      Logger.getLogger(XalanExtension.class.getName()).log(Level.SEVERE, null, ex); 
     } 
    } 

    public static void main(String[] args) { 
     XalanExtension instance = new XalanExtension(); 
     instance.transform(); 
    } 

    public static final NodeList evaluate(ExpressionContext ctx, NodeIterator nodes) { 
     // first node in document order 
     Node node = nodes.nextNode(); 
     if (node != null && node.hasChildNodes()) { 
      try { 
       String xpathExpression = node.getFirstChild().getNodeValue(); 

       XPathFactory xpathFactory = XPathFactory.newInstance(); 
       XPath xpath = xpathFactory.newXPath(); 
       xpath.setNamespaceContext(new NamespaceContext() { 
        @Override 
        public String getNamespaceURI(String prefix) { 
         if ("foo".equals(prefix)) { 
          return NS; 
         } 
         return null; 
        } 

        @Override 
        public String getPrefix(String namespaceURI) { 
         if (NS.equals(namespaceURI)) { 
          return "foo"; 
         } 
         return null; 
        } 

        @Override 
        public Iterator getPrefixes(String namespaceURI) { 
         return null; 
        } 
       }); 

       return (NodeList) xpath.evaluate(xpathExpression, ctx.getContextNode(), XPathConstants.NODESET); 
      } catch (XPathExpressionException ex) { 
       Logger.getLogger(XalanExtension.class.getName()).log(Level.SEVERE, "xpath evaluation failed", ex); 
      } 
     } 
     return null; 
    } 
}

확장 기능은 org.example.XalanExtension.evaluate(ExpressionContext, NodeIterator)에 구현됩니다. Xalan에 의해 호출되지만, 사용중인 XPath 평가 코드가 작동하지 않습니다. 이 프로그램은 실제로 잘 알려진 값을 가진 특정 요소를 찾습니다.이 요소는 실제로 나타나는 컨텍스트에서 평가할 XPath 식입니다.

I 얻는 프로그램에서 다음과 같은 출력 :

Xalan Java 2.7.1 
jan. 31, 2017 3:09:10 PM org.example.XalanExtension evaluate 
SEVERE: xpath evaluation failed 

javax.xml.transform.TransformerException: Unknown error in XPath. 
    at org.apache.xpath.XPath.execute(XPath.java:365) 
    at org.apache.xpath.XPath.execute(XPath.java:303) 
    at org.apache.xpath.jaxp.XPathImpl.eval(XPathImpl.java:216) 
    at org.apache.xpath.jaxp.XPathImpl.evaluate(XPathImpl.java:281) 
    at org.example.XalanExtension.evaluate(XalanExtension.java:116) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:498) 
    at org.apache.xalan.extensions.ExtensionHandlerJavaClass.callFunction(ExtensionHandlerJavaClass.java:367) 
    at org.apache.xalan.extensions.ExtensionHandlerJavaClass.callFunction(ExtensionHandlerJavaClass.java:440) 
    at org.apache.xalan.extensions.ExtensionsTable.extFunction(ExtensionsTable.java:222) 
    at org.apache.xalan.transformer.TransformerImpl.extFunction(TransformerImpl.java:473) 
    at org.apache.xpath.functions.FuncExtFunction.execute(FuncExtFunction.java:208) 
    at org.apache.xpath.XPath.execute(XPath.java:337) 
    at org.apache.xalan.templates.ElemVariable.getValue(ElemVariable.java:280) 
    at org.apache.xalan.templates.ElemVariable.execute(ElemVariable.java:248) 
    at org.apache.xalan.templates.ElemApplyTemplates.transformSelectedNodes(ElemApplyTemplates.java:395) 
    at org.apache.xalan.templates.ElemApplyTemplates.execute(ElemApplyTemplates.java:178) 
    at org.apache.xalan.templates.ElemApplyTemplates.transformSelectedNodes(ElemApplyTemplates.java:395) 
    at org.apache.xalan.templates.ElemApplyTemplates.execute(ElemApplyTemplates.java:178) 
    at org.apache.xalan.transformer.TransformerImpl.executeChildTemplates(TransformerImpl.java:2400) 
    at org.apache.xalan.transformer.TransformerImpl.applyTemplateToNode(TransformerImpl.java:2270) 
    at org.apache.xalan.transformer.TransformerImpl.transformNode(TransformerImpl.java:1356) 
    at org.apache.xalan.transformer.TransformerImpl.transform(TransformerImpl.java:709) 
    at org.apache.xalan.transformer.TransformerImpl.transform(TransformerImpl.java:1273) 
    at org.apache.xalan.transformer.TransformerImpl.transform(TransformerImpl.java:1251) 
    at org.example.XalanExtension.transform(XalanExtension.java:67) 
    at org.example.XalanExtension.main(XalanExtension.java:81) 
Caused by: java.lang.NullPointerException 
    at org.apache.xpath.axes.AxesWalker.setRoot(AxesWalker.java:221) 
    at org.apache.xpath.axes.ReverseAxesWalker.setRoot(ReverseAxesWalker.java:53) 
    at org.apache.xpath.axes.WalkingIterator.setRoot(WalkingIterator.java:157) 
    at org.apache.xpath.axes.NodeSequence.setRoot(NodeSequence.java:265) 
    at org.apache.xpath.axes.LocPathIterator.execute(LocPathIterator.java:212) 
    at org.apache.xpath.Expression.execute(Expression.java:155) 
    at org.apache.xpath.operations.Operation.execute(Operation.java:109) 
    at org.apache.xpath.XPath.execute(XPath.java:337) 
    ... 28 more 
--------- 
java.lang.NullPointerException 
    at org.apache.xpath.axes.AxesWalker.setRoot(AxesWalker.java:221) 
    at org.apache.xpath.axes.ReverseAxesWalker.setRoot(ReverseAxesWalker.java:53) 
    at org.apache.xpath.axes.WalkingIterator.setRoot(WalkingIterator.java:157) 
    at org.apache.xpath.axes.NodeSequence.setRoot(NodeSequence.java:265) 
    at org.apache.xpath.axes.LocPathIterator.execute(LocPathIterator.java:212) 
    at org.apache.xpath.Expression.execute(Expression.java:155) 
    at org.apache.xpath.operations.Operation.execute(Operation.java:109) 
    at org.apache.xpath.XPath.execute(XPath.java:337) 
    at org.apache.xpath.XPath.execute(XPath.java:303) 
    at org.apache.xpath.jaxp.XPathImpl.eval(XPathImpl.java:216) 
    at org.apache.xpath.jaxp.XPathImpl.evaluate(XPathImpl.java:281) 
    at org.example.XalanExtension.evaluate(XalanExtension.java:116) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:498) 
    at org.apache.xalan.extensions.ExtensionHandlerJavaClass.callFunction(ExtensionHandlerJavaClass.java:367) 
    at org.apache.xalan.extensions.ExtensionHandlerJavaClass.callFunction(ExtensionHandlerJavaClass.java:440) 
    at org.apache.xalan.extensions.ExtensionsTable.extFunction(ExtensionsTable.java:222) 
    at org.apache.xalan.transformer.TransformerImpl.extFunction(TransformerImpl.java:473) 
    at org.apache.xpath.functions.FuncExtFunction.execute(FuncExtFunction.java:208) 
    at org.apache.xpath.XPath.execute(XPath.java:337) 
    at org.apache.xalan.templates.ElemVariable.getValue(ElemVariable.java:280) 
    at org.apache.xalan.templates.ElemVariable.execute(ElemVariable.java:248) 
    at org.apache.xalan.templates.ElemApplyTemplates.transformSelectedNodes(ElemApplyTemplates.java:395) 
    at org.apache.xalan.templates.ElemApplyTemplates.execute(ElemApplyTemplates.java:178) 
    at org.apache.xalan.templates.ElemApplyTemplates.transformSelectedNodes(ElemApplyTemplates.java:395) 
    at org.apache.xalan.templates.ElemApplyTemplates.execute(ElemApplyTemplates.java:178) 
    at org.apache.xalan.transformer.TransformerImpl.executeChildTemplates(TransformerImpl.java:2400) 
    at org.apache.xalan.transformer.TransformerImpl.applyTemplateToNode(TransformerImpl.java:2270) 
    at org.apache.xalan.transformer.TransformerImpl.transformNode(TransformerImpl.java:1356) 
    at org.apache.xalan.transformer.TransformerImpl.transform(TransformerImpl.java:709) 
    at org.apache.xalan.transformer.TransformerImpl.transform(TransformerImpl.java:1273) 
    at org.apache.xalan.transformer.TransformerImpl.transform(TransformerImpl.java:1251) 
    at org.example.XalanExtension.transform(XalanExtension.java:67) 
    at org.example.XalanExtension.main(XalanExtension.java:81) 
--------------- linked to ------------------ 
javax.xml.xpath.XPathExpressionException: javax.xml.transform.TransformerException: Unknown error in XPath. 

    at org.apache.xpath.jaxp.XPathImpl.evaluate(XPathImpl.java:295) 
    at org.example.XalanExtension.evaluate(XalanExtension.java:116) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:498) 
    at org.apache.xalan.extensions.ExtensionHandlerJavaClass.callFunction(ExtensionHandlerJavaClass.java:367) 
    at org.apache.xalan.extensions.ExtensionHandlerJavaClass.callFunction(ExtensionHandlerJavaClass.java:440) 
    at org.apache.xalan.extensions.ExtensionsTable.extFunction(ExtensionsTable.java:222) 
    at org.apache.xalan.transformer.TransformerImpl.extFunction(TransformerImpl.java:473) 
    at org.apache.xpath.functions.FuncExtFunction.execute(FuncExtFunction.java:208) 
    at org.apache.xpath.XPath.execute(XPath.java:337) 
    at org.apache.xalan.templates.ElemVariable.getValue(ElemVariable.java:280) 
    at org.apache.xalan.templates.ElemVariable.execute(ElemVariable.java:248) 
    at org.apache.xalan.templates.ElemApplyTemplates.transformSelectedNodes(ElemApplyTemplates.java:395) 
    at org.apache.xalan.templates.ElemApplyTemplates.execute(ElemApplyTemplates.java:178) 
    at org.apache.xalan.templates.ElemApplyTemplates.transformSelectedNodes(ElemApplyTemplates.java:395) 
    at org.apache.xalan.templates.ElemApplyTemplates.execute(ElemApplyTemplates.java:178) 
    at org.apache.xalan.transformer.TransformerImpl.executeChildTemplates(TransformerImpl.java:2400) 
    at org.apache.xalan.transformer.TransformerImpl.applyTemplateToNode(TransformerImpl.java:2270) 
    at org.apache.xalan.transformer.TransformerImpl.transformNode(TransformerImpl.java:1356) 
    at org.apache.xalan.transformer.TransformerImpl.transform(TransformerImpl.java:709) 
    at org.apache.xalan.transformer.TransformerImpl.transform(TransformerImpl.java:1273) 
    at org.apache.xalan.transformer.TransformerImpl.transform(TransformerImpl.java:1251) 
    at org.example.XalanExtension.transform(XalanExtension.java:67) 
    at org.example.XalanExtension.main(XalanExtension.java:81) 
Caused by: javax.xml.transform.TransformerException: Unknown error in XPath. 
    at org.apache.xpath.XPath.execute(XPath.java:365) 
    at org.apache.xpath.XPath.execute(XPath.java:303) 
    at org.apache.xpath.jaxp.XPathImpl.eval(XPathImpl.java:216) 
    at org.apache.xpath.jaxp.XPathImpl.evaluate(XPathImpl.java:281) 
    ... 25 more 
Caused by: java.lang.NullPointerException 
    at org.apache.xpath.axes.AxesWalker.setRoot(AxesWalker.java:221) 
    at org.apache.xpath.axes.ReverseAxesWalker.setRoot(ReverseAxesWalker.java:53) 
    at org.apache.xpath.axes.WalkingIterator.setRoot(WalkingIterator.java:157) 
    at org.apache.xpath.axes.NodeSequence.setRoot(NodeSequence.java:265) 
    at org.apache.xpath.axes.LocPathIterator.execute(LocPathIterator.java:212) 
    at org.apache.xpath.Expression.execute(Expression.java:155) 
    at org.apache.xpath.operations.Operation.execute(Operation.java:109) 
    at org.apache.xpath.XPath.execute(XPath.java:337) 
    ... 28 more 

SystemId Unknown; Line #14; Column #22; 
      Test: ../foo:a > 5 Result:

어떻게 내가 (그것을 제공과 관련하여)을 Xalan에 확장 기능 implmentation 내에서 XPath 식을 평가합니까? XPathFactory/XPath instance을 올바르게 초기화하지 않았습니까? 여기

는 위의 코드에서 두 개의 문서입니다 :

<?xml version="1.0" encoding="UTF-8"?> 
<xsl:stylesheet 
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
    xmlns:foo="org:example:foo" 
    xmlns:fun="xalan://org.example.XalanExtension" 
    version="1.0"> 

    <xsl:template match="*|@*"> 
     <xsl:apply-templates select="*|@*"/> 
    </xsl:template> 

    <xsl:template match="foo:test"> 
     <xsl:variable name="result" select="fun:evaluate(.)"/> 
     <xsl:message> 
      Test: <xsl:value-of select="."/> Result: <xsl:value-of select="$result"/> 
     </xsl:message> 
    </xsl:template> 

</xsl:stylesheet>

<?xml version="1.0" encoding="utf-8"?> 
<tests xmlns="org:example:foo"> 
    <a>1</a> 
    <b>2</b> 
    <c>3</c> 
    <test>../foo:a &gt; 5</test> 
</tests>

참고 : 나는 dyn:evaluate 기능을 잘 알고 있어요. 이 질문은 그것과 관련이 없습니다.

출처

2017-01-31 predi

그러면 부울 표현식'../foo:a > 5'을 평가하려고하지만 node-set/NodeList를 반환하겠습니까? 확장 기능 컨텍스트 외부에서 작동합니까? –

@MartinHonnen, 예. 그것은 어떤 객체라도 돌려 주어야한다. 그 miss-cast는 문제가 아니 었습니다. – predi

나는 너무 빨리 질문을했다. Xalan 확장 기능이 구현 된 방법을 살펴본 후 XPath 평가를 구현하는 Xalan 전용 코드 (예, dyn:evaluate)를 발견했습니다.

package org.example; 

import java.io.*; 
import java.util.logging.*; 
import javax.xml.transform.*; 
import javax.xml.transform.stream.*; 
import org.w3c.dom.*; 
import org.w3c.dom.traversal.NodeIterator; 
import org.apache.xalan.extensions.ExpressionContext; 
import org.apache.xpath.XPathContext; 
import org.apache.xpath.objects.XNodeSet; 

public class XalanExtension { 

    public static final String NS = "org:example:foo"; 

    public static final String XSLT = "" + 
"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + 
"<xsl:stylesheet \n" + 
" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\"\n" + 
" xmlns:foo=\"org:example:foo\"\n" + 
" xmlns:fun=\"xalan://org.example.XalanExtension\"\n" + 
" version=\"1.0\"> \n" + 
" \n" + 
" <xsl:template match=\"*|@*\">\n" + 
"  <xsl:apply-templates select=\"*|@*\"/>\n" + 
" </xsl:template>\n" + 
" \n" + 
" <xsl:template match=\"foo:test\">\n" + 
"  <xsl:variable name=\"result\" select=\"fun:evaluate(.)\"/>\n" + 
"  <xsl:message>\n" + 
"   Test: <xsl:value-of select=\".\"/> Result: <xsl:value-of select=\"$result\"/>\n" + 
"  </xsl:message>\n" + 
" </xsl:template>\n" + 
" \n" + 
"</xsl:stylesheet>"; 

    public static final String XML = "" + 
"<?xml version=\"1.0\" encoding=\"utf-8\"?>\n" + 
"<tests xmlns=\"org:example:foo\">\n" + 
" <a>1</a>\n" + 
" <b>2</b>\n" + 
" <c>3</c>\n" + 
" <test>../foo:a &gt; 5</test>\n" + 
"</tests>"; 

    private TransformerFactory xalanTransFact; 

    public XalanExtension() { 
     xalanTransFact = new org.apache.xalan.processor.TransformerFactoryImpl(); 
    } 

    public void transform() { 
     try { 
      StringWriter writer; 

      writer = new StringWriter(); 

      System.out.println(org.apache.xalan.Version.getVersion()); 

      Transformer transformer = xalanTransFact.newTransformer(new StreamSource(new StringReader(XSLT))); 
      transformer.setOutputProperty(OutputKeys.INDENT, "yes"); 
      transformer.setOutputProperty(OutputKeys.METHOD, "text"); 
      transformer.setOutputProperty(OutputKeys.ENCODING, "utf-8"); 

      transformer.transform(
        new StreamSource(new StringReader(XML)), 
        new StreamResult(writer)); 

      System.out.println(writer.toString()); 
     } catch (TransformerConfigurationException ex) { 
      Logger.getLogger(XalanExtension.class.getName()).log(Level.SEVERE, null, ex); 
     } catch (TransformerException ex) { 
      Logger.getLogger(XalanExtension.class.getName()).log(Level.SEVERE, null, ex); 
     } 
    } 

    public static void main(String[] args) { 
     XalanExtension instance = new XalanExtension(); 
     instance.transform(); 
    } 

    public static final Object evaluate(ExpressionContext myContext, NodeIterator nodes) { 
     if (myContext instanceof XPathContext.XPathExpressionContext) { 
      XPathContext xctxt = null; 
      Node node = nodes.nextNode(); 
      if (node != null && node.hasChildNodes()) { 
       String xpathExpr = node.getFirstChild().getNodeValue(); 
       try { 
        xctxt = ((XPathContext.XPathExpressionContext) myContext).getXPathContext(); 
        org.apache.xpath.XPath dynamicXPath = new org.apache.xpath.XPath(xpathExpr, xctxt.getSAXLocator(), 
          xctxt.getNamespaceContext(), 
          org.apache.xpath.XPath.SELECT); 

        return dynamicXPath.execute(xctxt, myContext.getContextNode(), xctxt.getNamespaceContext()); 
       } catch (TransformerException e) { 
        return new XNodeSet(xctxt.getDTMManager()); 
       } 
      } 
     } 
     return null; 
    } 
}

코드는 org.apache.xalan 및 org.apache.xpath 패키지에서 여러 클래스에 의존합니다. 원래의 시도와 같이 표준 JAXP 솔루션을 사용하여 동일한 결과를 얻지 못할 수도 있습니다.

출처

2017-01-31 15:11:42 predi

Xalan 확장 함수 구현 내에서 XPath 식을 어떻게 평가합니까?

답변

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