DocumentBuilderFactory获取可用的功能？

Question

我正在尝试在DocumentBuilderFactory上设置功能。但是，它只是抛出一个javax.xml.parsers.ParserConfigurationException，并将特性名称作为消息：

public void execute() throws Exception
{
    // Get the factory.
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

    // Xerces 1 - http://xerces.apache.org/xerces-j/features.html#external-general-entities
    // Xerces 2 - http://xerces.apache.org/xerces2-j/features.html#external-general-entities
    setFeature(dbf, "http://xml.org/sax/features/external-general-entities", false);

    // Xerces 2 only - http://xerces.apache.org/xerces-j/features.html#external-general-entities
    setFeature(dbf, "http://apache.org/xml/features/disallow-doctype-decl", true);

    ...
}

private void setFeature(DocumentBuilderFactory dbf, String name, boolean value)
{
    try {
        dbf.setFeature(name, value);
    } catch (ParserConfigurationException e) {
        e.printStackTrace(); // <- see below
    }
}

该错误没有提供任何有用的信息：

javax.xml.parsers.ParserConfigurationException: http://xml.org/sax/features/external-general-entities
    at org.apache.harmony.xml.parsers.DocumentBuilderFactoryImpl.setFeature(DocumentBuilderFactoryImpl.java:101)
    at com.kounta.printing.epson.EpsonReceiptTranslator.setFeature(EpsonReceiptTranslator.java:76)
    at com.kounta.printing.epson.EpsonReceiptTranslator.execute(EpsonReceiptTranslator.java:49)
    at com.kounta.printing.epson.EpsonPrintJob$1.run(EpsonPrintJob.java:48)
    at com.kounta.util.TaskQueue.internalRun(TaskQueue.java:68)
    at com.kounta.util.TaskQueue.access$100(TaskQueue.java:11)
    at com.kounta.util.TaskQueue$InternalRunnable.run(TaskQueue.java:79)
    at java.lang.Thread.run(Thread.java:841)

有没有办法获得所有受支持的特性？还是我做错了什么？这两个功能都会抛出异常。

Answer 1

因此，事实证明，默认提供的XML解析器是垃圾和不完整的(这并不奇怪，因为这是android)，我最终发现了问题：

https://android.googlesource.com/platform/libcore/+/6bcf32ab404c39b85d25430f6df16503ef3526cf/xml/src/main/java/org/apache/harmony/xml/parsers/DocumentBuilderFactoryImpl.java#101

因此，尽管文档要求所有的XML解析器都支持FEATURE_SECURE_PROCESSING -http://developer.android.com/reference/javax/xml/parsers/SAXParserFactory.html#setFeature(java.lang.String,%20boolean)，但实际上并非如此。

解决方案是我必须使用一个不同的库来处理XML的解析。