Question

想获取文件并使用它的xml内容，然后更新其中一个标签，但更明显错误ffstream = session（flowfile），后来关闭ffstream.close（）实际上没有关闭并抛出异常，这里我的代码应该改变什么？

flowFile = session.putAttribute(flowFile,"filename",file.getName() + ".xml");
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = builderFactory.newDocumentBuilder();
Document xmlDocument = builder.parse(ffStream);
ffStream.close();
XPath xPath = XPathFactory.newInstance().newXPath();
NodeList myNodeList = (NodeList) xPath.compile("//runAs/text()")
    .evaluate(flowFile, XPathConstants.NODESET);myNodeList.item(0).setNodeValue("false");
FlowFile flowFile2=session.create();
flowFile = session.putAttribute(flowFile2,"filename","config" + ".xml");
session.write(flowFile2, new OutputStreamCallback() {
    @Override
    public void process(final OutputStream out) throws IOException {
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = null;
        try {
            transformer = transformerFactory.newTransformer();
        } catch (TransformerConfigurationException e) {
            e.printStackTrace();
        }
        DOMSource source = new DOMSource(xmlDocument);
        ByteArrayOutputStream bos=new ByteArrayOutputStream();
        StreamResult result=new StreamResult(bos);
        try {
            transformer.transform(source, result);
        } catch (TransformerException e) {
            e.printStackTrace();
        }
        byte []array=bos.toByteArray();
        out.write(array);
    }
});

Answer 1

您的代码未显示ffStream的创建或初始化，您使用的是ffStream = session.read（flowFile）吗？如果是这样，一旦调用putAttribute（），您为之前版本的流文件打开的输入流就不再有效，因为您已经通过调用putAttribute（）创建了一个较新的版本。

之后你也遇到了一些问题。例如，您最终创建了一个新的流文件，但在session.write（）之后使用原始流文件的指针/变量来引用它。这肯定会引起问题。如果要覆盖传入的流文件，请将session.write（）与StreamCallback而不是OutputStreamCallback一起使用。如果要保留传入的流文件并创建一个新文件，我建议为每个流文件（flowFile和flowFile2）维护一个变量，并在每次更新该文件时更新该变量（通过session.write，session.putAttribute，等）

Answer 2

我已经删除了.putAttribute（），并且在session.write（）函数中读取xml文档后关闭了ffstream会话，并且工作得很好。

InputStream ffStream=session.read(flowFile);
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = builderFactory.newDocumentBuilder();
Document xmlDocument = builder.parse(ffStream);

XPath xPath = XPathFactory.newInstance().newXPath();
XPathExpression myNodeList = (XPathExpression) xPath.compile("/localAttributes");

Node nodeGettingChanged = (Node) myNodeList.evaluate(xmlDocument, XPathConstants.NODE);
NodeList childNodes = nodeGettingChanged.getChildNodes();
for (int i = 0; i != childNodes.getLength(); ++i)
{
    Node child = childNodes.item(i);
    if (!(child instanceof Element))
        continue;

    if (child.getNodeName().equals("runAs"))
        child.getFirstChild().setNodeValue("false") ;
}

session.write(flowFile, new StreamCallback() {
    @Override
    public void process(InputStream inputStream, OutputStream outputStream) throws IOException {
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = null;
        try {
            transformer = transformerFactory.newTransformer();
        } catch (TransformerConfigurationException e) {
            e.printStackTrace();
        }
        DOMSource source = new DOMSource(xmlDocument);
        ffStream.close();
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        StreamResult result = new StreamResult(bos);
        try {
            transformer.transform(source, result);
        } catch (TransformerException e) {
            e.printStackTrace();
        }
        byte[] array = bos.toByteArray();
        outputStream.write(array);
    }
});

会话未在nifi自定义处理器内关闭异常

2 个答案: