具有使用XPath

Question

其兄弟值查找XML節點值我有以下XML文件

<?xml version="1.0"?> 
<mappings> 
    <enumMapping id="1" dsrName="yesno" emName="yesno_t"> 
     <valueMap> 
      <dsrValue>Yes</dsrValue> 
      <emValue>1</emValue> 
     </valueMap> 
     <valueMap> 
      <dsrValue>No</dsrValue> 
      <emValue>2</emValue> 
     </valueMap> 

    </enumMapping> 
    <enumMapping id="2" dsrName="altRoutingOnConFailure" emName="Alternate_Routing_On_Connection_Failure_t"> 
     <valueMap> 
      <dsrValue>Same Peer</dsrValue> 
      <emValue>1</emValue> 
     </valueMap> 
     <valueMap> 
      <dsrValue>Different Peer</dsrValue> 
      <emValue>2</emValue> 
     </valueMap> 
     <valueMap> 
      <dsrValue>Same Connection</dsrValue> 
      <emValue>3</emValue> 
     </valueMap> 
    </enumMapping> 
</mappings> 

和Java代碼

public class Parser { 
    Document doc; 
    public Parser(String filename) 
    { 
     try{ 
      File inputFile = new File(filename); 
      DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance(); 
      DocumentBuilder dBuilder = dbFactory.newDocumentBuilder(); 
      doc = dBuilder.parse(inputFile); 
      doc.getDocumentElement().normalize(); 
      }catch(Exception e) 
      { 
       e.printStackTrace(); 
      } 

    } 

    public void searchDsrEnum(String dsrName,String dsrValue) 
    { 

      XPathFactory xPathfactory = XPathFactory.newInstance(); 
      XPath xpath = xPathfactory.newXPath(); 
      try { 
      XPathExpression expr = xpath.compile("mappings/enumMapping[@dsrName=\""+dsrName+"\"]/valueMap/dsrValue"); 
      NodeList n1=(NodeList)expr.evaluate(doc,XPathConstants.NODESET); 
      System.out.println(n1.getLength()); 


      //System.out.println(n1.); 

     } catch (XPathExpressionException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 
    } 


} 

我需要找到emValue領域，隨着dsrValue = Yes和enumMapping屬性dsrName=yesno使用xpath。如果我使用 我發現了一個錯誤

XPathExpression expr = xpath.compile("mappings/enumMapping[@dsrName=\""+dsrName+"\"]/valueMap//[dsrValue/text()=\""+dsrValue+"\"]/emValue"); 

Answer 1

這是一種可能的XPath表達式：

/mappings/enumMapping[@dsrName='yesno']/valueMap[dsrValue='Yes']/emValue 

解釋：

• /mappings：定位根元素mappings
• /enumMapping[@dsrName='yesno']：從r OOT元素，找到子元素enumMapping其中dsrName屬性值等於"yesno"
• /valueMap[dsrValue='Yes']：從這樣enumMapping，找到子元素valueMap其中dsrValue子元素等於"Yes"
• /emValue：從這樣valueMap返回子元素emValue

我還建議使用單引號和String.Format()來清理代碼：

String query = "/mappings/enumMapping[@dsrName='%s']/valueMap[dsrValue='%s']/emValue"; 
XPathExpression expr = xpath.compile(String.Format(query, dsrName, dsrValue));