DOM解析XML遇到的子节点个数问题
xml文件如下：
<?xml version="1.0" encoding="UTF-8"?>
<books>
<book>book text</book>
</books>
个人以为books的子节点只有1个。
测试如下：
try {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(new File("test.xml"));
Element root = document.getDocumentElement();
//System.out.println(root.getNodeName());
NodeList nodeList = root.getChildNodes();
System.out.println("length =" + nodeList.getLength());
} catch (Exception e) {
// TODO: handleexception
e.printStackTrace();
}
结果如下：
length =3；
百思不得其解，后来终于测试出来子节点是1个Element节点和2个Text节点。
修改xml文件并打印测试如下：
<?xml version="1.0" encoding="UTF-8"?>
<books>
before
<book>book text</book>
after
</books>
try {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(new File("test.xml"));
Element root = document.getDocumentElement();
//System.out.println(root.getNodeName());
NodeList nodeList = root.getChildNodes();
System.out.println("length =" + nodeList.getLength());
for(int i = 0; i <nodeList.getLength(); ++i)
{
Node node = nodeList.item(i);
if(node.getNodeType() == Node.TEXT_NODE)
System.out.println(node.getNodeValue());
else if(node.getNodeType() == Node.ELEMENT_NODE)
System.out.println(node.getNodeName());
//System.out.println(node.getNodeType());
}
} catch (Exception e) {
// TODO: handleexception
e.printStackTrace();
}
结果如下：
length = 3；
before
book
after
原来每个子节点与父节点之间都有默认的Text节点，如果没有赋值的话，节点内容为空，但仍然作为一个空节点存在着。这就是为什么子节点个数为3而不是1