如何通過XPath讀取XML

Question

我有從我的XML文件中讀取XML的方法，我使用xpath從XML文件中獲取元素，但始終使我的對象為null。 我想獲取所有值元素，但請給我null。

那我的方法：

public ArrayList<Object> GetAnyEntity(String PathXPath) throws JAXBException {
        ArrayList<Object> list = new ArrayList<Object>();
        DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
        try {
            DocumentBuilder builder = domFactory.newDocumentBuilder();
            Document dDoc = builder.parse("Projects//asdad//ProjectDataBase.xml");
            XPath xPath = XPathFactory.newInstance().newXPath();
            NodeList nl = (NodeList)xPath.evaluate("//Project/Layer[@idLayer=2]", dDoc, XPathConstants.NODESET);
            for (int i = 0; i < nl.getLength(); i++) {
                list.add(nl.item(i));
            }
        } catch (Exception e) { 
            e.printStackTrace();
        }
        return list;
    } 

XML檔案：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Project xmlns="http://www.example.org/ProjectDataBase" name="name1" >
    <Layer idLayer="2">
        <LayerName>a</LayerName>
        <Order>2</Order>
        <Visible>false</Visible>
    </Layer>
</Project>

Answer 1

您正在2周圍誤認為''

//Project/Layer[@idLayer='2']