有人能帮我找出在评估以下XPath表达式时我所犯的错误吗？
我想通过XPath获取xml中"Model"节点下的所有"DataTable"节点。
这是我的XML文档:
<?xml version="1.0" encoding="UTF-8"?>
<Root>
<Application>
<Model>
<DataSet name="ds" primaryTable="Members" openRows="1">
<DataTable name="Members" openFor="write">
<DataColumn name="id" type="String" mandatory="true" primaryKey="true" valueBy="user"/>
<DataColumn name="name" type="String" mandatory="true" valueBy="user"/>
<DataColumn name="address" type="String" mandatory="false" valueBy="user"/>
<DataColumn name="city" type="String" mandatory="false" valueBy="user"/>
<DataColumn name="country" type="String" mandatory="false" valueBy="user"/>
</DataTable>
</DataSet>
</Model>
<View>
<Composite>
<Grid>
<Label value="ID:" row="0" column="0" />
<Label value="Name:" row="1" column="0" />
<Label value="Address:" row="2" column="0" />
<Label value="City:" row="3" column="0" />
<Label value="Country:" row="4" column="0" />
<TextField name="txtId" row="0" column="1" />
<TextField name="txtName" row="1" column="1" />
<TextField name="txtAddress" row="2" column="1" />
<TextField name="txtCity" row="3" column="1" />
<TextField name="txtCountry" row="4" column="1" />
</Grid>
</Composite>
</View>
</Application>
</Root>
以下是提取所需节点列表的Java代码：
try {
DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
domFactory.setNamespaceAware(true);
domFactory.setIgnoringComments(true);
domFactory.setIgnoringElementContentWhitespace(true);
DocumentBuilder builder = domFactory.newDocumentBuilder();
Document dDoc = builder.parse("D:\TEST\myFile.xml");
XPath xpath = XPathFactory.newInstance().newXPath();
NodeList nl = (NodeList) xpath.evaluate("//Model//DataTable", dDoc, XPathConstants.NODESET);
System.out.println(nl.getLength());
}catch (Exception ex) {
System.out.println(ex.getMessage());
}
加载和解析xml文件没有问题，我可以在dDoc中看到正确的节点。问题出在xpath上，在评估我的表达式时返回空值。为了测试目的，我尝试了许多其他表达式，但每次结果的NodeList "nl"都没有任何项。