Java XML解析問題

Question

我正面臨着訪問XML值的困難，任何人都可以讓我知道我在想什麼。

String xml = "<Standard p1:oid=\"00000000-0000-0000-0000-000000f674c1\"\n" + 
       "        xmlns:p1=\"com.iMelt.metaCore.DataObjects.Core\" xmlns=\"com.iMelt.Car.Model.Core\"\n" + 
       "        reasonCode=\"0\">\n" + 
       " <p1:__info p1:eid=\"00000000-0000-0000-0000-000000000000\">\n" + 
       "  <p1:creationDate>2016-05-28T20:33:45.337+00:00</p1:creationDate>\n" + 
       "  <p1:lastEditorRef>Administrator</p1:lastEditorRef>\n" + 
       "  <p1:version>5</p1:version>\n" + 
       " </p1:__info>\n" + 
       " <ChangeState>Approved</ChangeState></Standard>"; 

byte[] byteArray = xml.getBytes(); 
ByteArrayInputStream inputStream = new ByteArrayInputStream(byteArray); 
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); 
factory.setNamespaceAware(true); 
DocumentBuilder builder = factory.newDocumentBuilder(); 
Document doc = builder.parse(inputStream); 
XPathFactory xpathfactory = XPathFactory.newInstance(); 
XPath xpath = xpathfactory.newXPath(); 
XPathExpression expr = xpath.compile("/Standard/ChangeState"); 
Object result = expr.evaluate(doc, XPathConstants.NODESET); 

Answer 1

的問題是，是，你不必節點被稱爲「標準」和「改變狀態」，你已經命名空間標準和改變狀態的版本節點。

因此，您需要使用XPath.setNamespace（）方法將前綴與命名空間相關聯，然後在xpath表達式中使用該前綴。注意：因爲你只使用在查詢默認的命名空間，這就是你必須指定，像

String xml = "<Standard p1:oid=\"00000000-0000-0000-0000-000000f674c1\"\n" 
      + "        xmlns:p1=\"com.iMelt.metaCore.DataObjects.Core\" xmlns=\"com.iMelt.Car.Model.Core\"\n" 
      + "        reasonCode=\"0\">\n" + " <p1:__info p1:eid=\"00000000-0000-0000-0000-000000000000\">\n" 
      + "  <p1:creationDate>2016-05-28T20:33:45.337+00:00</p1:creationDate>\n" + "  <p1:lastEditorRef>Administrator</p1:lastEditorRef>\n" 
      + "  <p1:version>5</p1:version>\n" + " </p1:__info>\n" + " <ChangeState>Approved</ChangeState></Standard>"; 

    byte[] byteArray = xml.getBytes(); 
    ByteArrayInputStream inputStream = new ByteArrayInputStream(byteArray); 
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); 
    factory.setNamespaceAware(true); 
    DocumentBuilder builder = factory.newDocumentBuilder(); 
    Document doc = builder.parse(inputStream); 
    XPathFactory xpathfactory = XPathFactory.newInstance(); 
    XPath xpath = xpathfactory.newXPath(); 
    xpath.setNamespaceContext(new NamespaceContext() { 

     @Override 
     public String getNamespaceURI(String prefix) { 
      return "com.iMelt.Car.Model.Core"; 
     } 

     @Override 
     public String getPrefix(String namespaceURI) { 

      return "x"; 
     } 

     @Override 
     public Iterator getPrefixes(String namespaceURI) { 
      return null; 
     } 

    }); 
    XPathExpression expr = xpath.compile("/x:Standard/x:ChangeState"); 
    NodeList result = (NodeList) expr.evaluate(doc, XPathConstants.NODESET); 

的其他不太有效的選項是去除聲明

factory.setNamespaceAware(true); 

Answer 2

下面的代碼輸出「批准」。我已經刪除了factory.setNamespaceAware(true);，以便您不需要指定默認名稱空間並在末尾添加代碼以輸出文本值。

import java.util.*; 
import java.lang.*; 
import java.io.*; 
import javax.xml.parsers.*; 
import org.w3c.dom.*; 
import javax.xml.xpath.*; 

// ... 

String xml = "<Standard p1:oid=\"00000000-0000-0000-0000-000000f674c1\"\n" + 
       "        xmlns:p1=\"com.iMelt.metaCore.DataObjects.Core\" xmlns=\"com.iMelt.Car.Model.Core\"\n" + 
       "        reasonCode=\"0\">\n" + 
       " <p1:__info p1:eid=\"00000000-0000-0000-0000-000000000000\">\n" + 
       "  <p1:creationDate>2016-05-28T20:33:45.337+00:00</p1:creationDate>\n" + 
       "  <p1:lastEditorRef>Administrator</p1:lastEditorRef>\n" + 
       "  <p1:version>5</p1:version>\n" + 
       " </p1:__info>\n" + 
       " <ChangeState>Approved</ChangeState></Standard>"; 

byte[] byteArray = xml.getBytes(); 
ByteArrayInputStream inputStream = new ByteArrayInputStream(byteArray); 
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); 
DocumentBuilder builder = factory.newDocumentBuilder(); 
Document doc = builder.parse(inputStream); 
XPathFactory xpathfactory = XPathFactory.newInstance(); 
XPath xpath = xpathfactory.newXPath(); 
XPathExpression expr = xpath.compile("/Standard/ChangeState"); 
NodeList result = (NodeList)expr.evaluate(doc, XPathConstants.NODESET); 
Node node = result.item(0); 
System.out.println(node.getTextContent());