如何使用带有 Java 对象作为参数的 XML 转换器? [英] How to use XML transformer with Java object as parameter?

问题描述

我正在编写一个 Java 应用程序，其目标是进行 XML 转换以生成 PDF 文档.我使用一个 XML 文件作为输入，它首先被解析为一个 java 对象.解析后我想在 XML 转换中使用该对象，因此我将其设置为转换器的参数:

I'm writing a Java application, where the goal is to do XML transformation to generate a PDF document. I'm using an XML file as input, which is first parsed to a java object. After parsing I want to use that object in the XML transformation, so I set it as a parameter for the transformer:

TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer(new StreamSource(stylesheet));
transformer.setParameter("foo", javaObject);

在 xsl 样式表中调用该对象的实例方法，如下所示:

An instance method of that object is called in the xsl stylesheet like this:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"
                xmlns:fo="http://www.w3.org/1999/XSL/Format"
                xmlns:pdf="http://xmlgraphics.apache.org/fop/extensions/pdf"
                xmlns:MyClass="foo.bar.MyClass"
>
...
<xsl:param name="foo"/>
<xsl:param name="seller" select="MyClass:myMethod($foo)"/>

我的问题是:这是一种正确的方法吗?哪种 XSLT 处理器适合以这种方式使用参数?还有其他方法吗?

My question is: is this a proper way to do this? Which XSLT processor is suitable for using parameters this way? Is there another way to do it?

我尝试了 Xalan (org.apache.xalan.xsltc.trax.TransformerFactoryImpl)，但我得到一个无法找到该方法的异常:

I tried out Xalan (org.apache.xalan.xsltc.trax.TransformerFactoryImpl) but I get an Exception that the method cannot be found:

ERROR:  'Cannot find external method 'foo.bar.MyClass.myMethod' (must be public).'
FATAL ERROR:  'Could not compile stylesheet'

该方法是公共的，没有参数.

The method is public and has no arguments.

推荐答案

对于 Saxon:可以在 http://www.saxonica.com/documentation/index.html#!extensibility/functions

For Saxon: Information on "reflexive" calls to external Java objects can be found at http://www.saxonica.com/documentation/index.html#!extensibility/functions

首先要注意的是它需要 Saxon-PE 或 -EE.

The first thing to note is that it requires Saxon-PE or -EE.

如果是没有参数的实例级(非静态)方法，那么最简单的方法是:

If it's an instance-level (non-static) method with no parameters, then the simplest approach is:

(a) 声明一个与类名对应的命名空间，例如

(a) declare a namespace corresponding to the class name, for example

xmlns:date="java:java.util.Date"

(b) 以外部对象作为第一个参数调用方法:

(b) call the method with the external object as the first argument:

date:getTime($date)

撒克逊人和夏兰人的机制并不相同，但有许多相似之处.

The Saxon and Xalan mechanisms are not identical, though there are many similarities.

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