java - 获取 XML 文件中的特定 child 姓名

Question

我有一个这样的 xml 文件:

<?xml version="1.0" encoding="UTF-8"?>
<ClOrdIDS><ClOrdID id="1"><Account>1005390</Account><Symbol>SAP</Symbol><SecurityID>4663789</SecurityID><SecurityExchange>XETR</SecurityExchange><Price>23.0</Price><Order_Type>Limit</Order_Type><Side>SELL</Side><Order_Quantity>0.001</Order_Quantity></ClOrdID><ClOrdID id="2"><Account>1005390</Account><Symbol>SAP</Symbol><SecurityID>4663789</SecurityID><SecurityExchange>XETR</SecurityExchange><Price>13.0</Price><Order_Type>Limit</Order_Type><Side>SELL</Side><Order_Quantity>0.001</Order_Quantity></ClOrdID><ClOrdID id="3"><Account>1005390</Account><Symbol>SAP</Symbol><SecurityID>4663789</SecurityID><SecurityExchange>XETR</SecurityExchange><Price>13.0</Price><Order_Type>Limit</Order_Type><Side>BUY</Side><Order_Quantity>0.001</Order_Quantity></ClOrdID><ClOrdID id="4"><Account>1005390</Account><Symbol>SAP</Symbol><SecurityID>4663789</SecurityID><SecurityExchange>XETR</SecurityExchange><Price>13.0</Price><Order_Type>Limit</Order_Type><Side>BUY</Side><Order_Quantity>0.001</Order_Quantity></ClOrdID><ClOrdID id="5"><Account>1005390</Account><Symbol>SAP</Symbol><SecurityID>4663789</SecurityID><SecurityExchange>XETR</SecurityExchange><Price>13.0</Price><Order_Type>Limit</Order_Type><Side>BUY</Side><Order_Quantity>0.001</Order_Quantity></ClOrdID><ClOrdID id="6"><Account>1005390</Account><Symbol>SAP</Symbol><SecurityID>4663789</SecurityID><SecurityExchange>XETR</SecurityExchange><Price>13.0</Price><Order_Type>Limit</Order_Type><Side>BUY</Side><Order_Quantity>0.001</Order_Quantity></ClOrdID><ClOrdID id="7"><Account>1005390</Account><Symbol>SAP</Symbol><SecurityID>4663789</SecurityID><SecurityExchange>XETR</SecurityExchange><Price>13.0</Price><Order_Type>Limit</Order_Type><Side>SELL</Side><Order_Quantity>0.001</Order_Quantity></ClOrdID></ClOrdIDS>

如何提取 clOrdID id="3"的子元素？

谢谢

Answer 1

你可以这样做

String xmlString = ... 
DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
Document doc = docBuilder.parse(xmlString);

XPathFactory xPathfactory = XPathFactory.newInstance();
XPath xpath = xPathfactory.newXPath();
String xpathExp = "/ClOrdIDS/ClOrdID[@id=\"3\"]";
NodeList childNodeList = (NodeList) xpath.evaluate(xpathExp, doc, XPathConstants.NODESET);