java - 通过使用 xpath 获取同级值来查找 xml 节点值

Question

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代码

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 字段，其中 dsrValue=Yes 和 enumMapping 属性 dsrName= yesno 使用 xpath。如果我使用

则会出现错误

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

Answer 1

这是一种可能的 XPath 表达式:

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

说明:

• /mappings :定位根元素mappings
• /enumMapping[@dsrName='yesno'] :从根元素中查找子元素 enumMapping，其中 dsrName 属性值等于“是的”
• /valueMap[dsrValue='Yes'] :从这样的 enumMapping 中，找到子元素 valueMap 其中 dsrValue 子元素等于"is"
• /emValue :从这样的 valueMap 返回子元素 emValue

我还建议使用单引号和 String.Format() 来清理一下代码:

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