xslt: Saxon 9.4与Saxon 9.6中的消息

Question

当使用Saxon时，我试图从java代码中抛出异常，它将包含来自xsl:message标记的消息。

使用以下xslt文件

<?xml version="1.0" encoding="UTF-8" ?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/">
        <xsl:message terminate="yes">exception message</xsl:message>
    </xsl:template>
</xsl:stylesheet>

在Saxon 9.4上使用以下代码

public static void main(String[] args) throws TransformerException {
    try {
        TransformerFactory fact = new net.sf.saxon.TransformerFactoryImpl();
        Transformer newTransformer = fact.newTransformer(new StreamSource(new File("throw.xslt")));
        ((net.sf.saxon.Controller)newTransformer).setRecoveryPolicy(Configuration.DO_NOT_RECOVER);
        ((net.sf.saxon.Controller)newTransformer).setMessageEmitter(new MessageWarner());
        newTransformer.transform(new StreamSource(new File("input.xml")), new StreamResult(new File("output.xml")));
    } catch (TransformerException e) {
        System.out.println("THIS IS EXCEPTION: " + e.getMessage() + " <<<");
        throw e;
    }
}   

它提供了THIS IS EXCEPTION: exception message <<<，这是我所期望的行为。

但在Saxon 9.6上，由于API的更改，代码做了一些调整

public static void main(String[] args) throws TransformerException {
    try {
        TransformerFactory fact = new net.sf.saxon.TransformerFactoryImpl();
        Transformer newTransformer = fact.newTransformer(new StreamSource(new File("throw.xslt")));
        ((net.sf.saxon.jaxp.TransformerImpl)newTransformer).getUnderlyingController().setRecoveryPolicy(Configuration.DO_NOT_RECOVER);
        ((net.sf.saxon.jaxp.TransformerImpl)newTransformer).getUnderlyingController().setMessageEmitter(new MessageWarner());
        newTransformer.transform(new StreamSource(new File("input.xml")), new StreamResult(new File("output.xml")));
    } catch (TransformerException e) {
        System.out.println("THIS IS EXCEPTION: " + e.getMessage() + " <<<");
        throw e;
    }
}

它提供THIS IS EXCEPTION: Processing terminated by xsl:message at line 4 in throw.xslt <<<，而xsl:message在某个地方丢失了。

如何在9.6上实现9.4行为？

Answer 1

这是由于MessageEmitter正在向其发送消息的消息侦听器。在saxon 9.6中，默认的侦听器实现了UnfailingErrorListener，它不能抛出异常(就像9.6中的所有其他侦听器一样)，但是在9.4中可以抛出来自侦听器的异常。

但是，您可以实现自己的消息发射器，它会在遇到xml:message时抛出异常，并将terminate设置为yes，如下所示：

final class ExceptionThrowingMessageEmitter extends XMLEmitter {
  boolean abort = false;

  public void startDocument(int properties) throws XPathException {
    setWriter(new StringWriter());
    abort = (properties & ReceiverOptions.TERMINATE) != 0;
    super.startDocument(properties);
  }

  public void endDocument() throws XPathException {
    XPathException de = new XPathException(getWriter().toString());
    de.setErrorCode("XTMM9000");
    if (abort) {
      throw de;
    } else {
      //terminate set to no, do something like writing to the log file
    }
  }

  public void close() {
    // do nothing
  }
}

然后，像这样注册它：

transformer.getUnderlyingController().setMessageEmitter(new ExceptionThrowingMessageEmitter());  

这样，当存在终止xml:message时，将抛出异常

Answer 2

不幸的是，新的Processing terminated...消息是用net.sf.saxon.expr.instruct.Message (9.6.0-7中的Message.java:253)硬编码的。以下是一个解决方法，它可能会满足您的需求：

public static void main(String[] args) throws TransformerException {
    final StringWriter messageOut = new StringWriter();
    try {
        TransformerFactory fact = new net.sf.saxon.TransformerFactoryImpl();
        Transformer newTransformer = fact.newTransformer(new StreamSource(new File("throw.xslt")));
        ((net.sf.saxon.jaxp.TransformerImpl)newTransformer).getUnderlyingController().setRecoveryPolicy(Configuration.DO_NOT_RECOVER);
        ((net.sf.saxon.jaxp.TransformerImpl)newTransformer).getUnderlyingController().setMessageEmitter(new MessageEmitter() {
                @Override
                public void open() throws XPathException {
                    setWriter(messageOut);
                    super.open();
                }
        });

        newTransformer.transform(new StreamSource(new File("input.xml")), new StreamResult(new File("output.xml")));
    } catch (TransformerException e) {
        System.out.println("THIS IS EXCEPTION: " + e.getMessage() + " <<<");
        String message = messageOut.toString(); // this is the "exception message\n" that you want
        // not sure why it has a \n on it
        System.out.println("THIS IS THE MESSAGE WE WANT: " + message);
        throw new TransformerException(message, e); // rethrow using the captured message, if you really want that "exception message" available to a caller in e.getMessage()
    }
}