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rnrneverdies
Asked: 2020-04-02 10:23:05 +0800 CST 2020-04-02 10:23:05 +0800 CST

如何从 XML 中获取同名元素？

  • 772

我需要获取与此类似的 XMLurl的所有元素的属性。<media:content/>

<rss version='2.0' xmlns:media='http://search.yahoo.com/mrss/'>
    <channel>
        <item>
            <media:group>
                <media:content url='https://valor'/>
            </media:group>
        </item>
        <item>
            <media:group>
                <media:content url='https://valor'/>
            </media:group>
        </item>    
    </channel>
</rss>

这是我尝试过的一种方法，但它contents.getLength()返回零。

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();

Document doc = builder.parse(inputStream);
NodeList contents = doc.getElementsByTagNameNS("http://search.yahoo.com/mrss/", "content");

我尝试过使用 XPath... 再次contents.getLength()返回零。

XPathFactory factory2 = XPathFactory.newInstance();
XPath xpath = factory2.newXPath();
// XPathExpression expr = xpath.compile("//content"); 
XPathExpression expr = xpath.compile("//*[name()='content']");
NodeList contents = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);

我从来没有得到所需的节点，有什么建议吗？

java

3 Answers

  1. Best Answer

    要使用方法..NS，当您创建 DOM 时，您必须调用方法factory.setNamespaceAware(true);

    • 2

  2. 要获取属性的值（在本例中为 url），具有以下.rss形式之一：

    <rss version='2.0' xmlns:media='http://search.yahoo.com/mrss/'>
    <channel>
        <item>
            <media:group>
                <media:content url='https://www.stackoverflow.com'/>
            </media:group>
        </item>
        <item>
            <media:group>
                <media:content url='https://www.cnn.com'/>
            </media:group>
        </item>
    </channel>
</rss>

    可以通过获取节点列表并访问它们的值来访问元素：

    import java.net.URL;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import java.io.IOException;
import java.io.InputStream;
import org.xml.sax.SAXException;
    ...
    ...

      InputStream inputStream =  url.openStream();
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document doc = builder.parse(inputStream);

        NodeList contents = doc.getElementsByTagName("item");

            for (int i = 0; i < contents.getLength(); ++i)
            {
                Element elemA = (Element) contents.item(i);
                NodeList valueListB = elemA.getElementsByTagName("media:group");
                for (int j = 0; j < valueListB.getLength(); ++j) {
                    Element elemB = (Element) valueListB.item(j);
                    NodeList valueListC = elemB.getElementsByTagName("media:content");
                    for (int k = 0; k < valueListC.getLength(); ++k)
                    {
                        Element elemC = (Element) valueListC.item(k);
                       System.out.println("url: " + elemC.getAttribute("url"));
                    }
                }
            }

    或者您可以直接进入元素，在本例中为 " media:content" 并获取其 " " 属性的值url：

     try {
    URL   url = new URL(feedUrl);
    InputStream inputStream =  url.openStream();
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    DocumentBuilder builder = factory.newDocumentBuilder();
    Document doc = builder.parse(inputStream);

        NodeList contents = doc.getElementsByTagName("media:content");
        for (int i = 0; i < contents.getLength(); ++i) {
            Element elemA = (Element) contents.item(i);
            System.out.println("url: " + elemA.getAttribute("url"));
        }

    } catch (IOException e) {
       System.out.println(e.getMessage());
    } catch (ParserConfigurationException e) {
        System.out.println(e.getMessage());
    }catch (SAXException e) {
        System.out.println(e.getMessage());
    }

    将获得价值：

    url: https://www.stackoverflow.com
url: https://www.cnn.com

    在此处输入图像描述

    • 0

  3. XML:

    0OK30-1-0000013-66271741VisaGoldBs50007000-200011/01/201511/01/2020ASCACamacho30-1-0000013-6111122222VisaGold$us40002000200011/03/2014jar19/01/20ASCAEl

    JAVA：您阅读 XML： DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = null; 字符串消息错误=空；整数 RespCod = -1; 字符串 msgResp = ""; 尝试 { db = dbf.newDocumentBuilder(); InputSource is = new InputSource(); is.setCharacterStream(new StringReader(xmlresponse)); 尝试 { 文档文档 = db.parse(is); NodeList responseCode = document .getElementsByTagName("ResponseCode"); NodeList responseMessage = document .getElementsByTagName("ResponseMessage");

                for (int i = 0; i < codigoRespuesta.getLength(); i++) {
                String codRespuesta = codigoRespuesta.item(i)
                        .getTextContent();
                codResp = Integer.parseInt(codRespuesta);
                msjResp = mensajeRespuesta.item(i).getTextContent();
            }
        } catch (SAXException e) {
            e.printStackTrace();
            if (logger.isDebugEnabled())
                logger.logDebug(messageError);
            return null;
        } catch (IOException e) {
            e.printStackTrace();
            if (logger.isDebugEnabled())
                logger.logDebug(messageError);
            return null;
        }
    } catch (ParserConfigurationException e1) {
        // handle ParserConfigurationException
        e1.printStackTrace();
        if (logger.isDebugEnabled())
            logger.logDebug(messageError);
        return null;
    }

    你得到数据：try { db = dbf.newDocumentBuilder(); InputSource is = new InputSource(); is.setCharacterStream(new StringReader(xmlresponse)); 尝试 { 文档文档 = db.parse(is);

                // NodeList listDatos =
            // doc.getElementsByTagName("DatosTarjeta");
            // for (int i = 0; i < listDatos.getLength(); i++) {
            //
            // NodeList hijos = listDatos.item(i).getChildNodes();
            // for (int j = 0; j < hijos.getLength(); j++) {
            // logger.logDebug("Datos " + i + " : "
            // + hijos.item(j).getNodeName() + ": "
            // + hijos.item(j).getTextContent());
            // }
            //
            // }

            NodeList list = document.getElementsByTagName("DatosTarjeta");
            for (int i = 0; i < list.getLength(); i++) {

                NodeList elements = list.item(i).getChildNodes();

                logger.logDebug("Datos " + i + " : "
                        + list.item(i).getTextContent());

    //ALL 在这里迭代你想输出的地方 } } catch (SAXException e) { e.printStackTrace(); if (logger.isDebugEnabled()) logger.logDebug(messageError); 返回空值；} catch (IOException e) { e.printStackTrace(); if (logger.isDebugEnabled()) logger.logDebug(messageError); 返回空值；} } 捕捉（ParserConfigurationException e1）{ e1.printStackTrace(); if (logger.isDebugEnabled()) logger.logDebug(messageError); 返回空值；}

    希望对你有帮助...

    • -2