java.lang.ClassCastException, DeepNodeListImpl 不能被转换
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java.lang.ClassCastException, DeepNodeListImpl cannot be cast
提问by zeptyan
here is my code :
这是我的代码：
public void Login() {
try{
DocumentBuilderFactory builderfactory = DocumentBuilderFactory.newInstance();
DocumentBuilder db = builderfactory.newDocumentBuilder();
File path = new File("src/dataPengguna/dataPengguna.xml");
Document doc = db.parse(path);
Element pengguna = (Element) doc.getElementsByTagName("pengguna");
NodeList list = pengguna.getElementsByTagName("user");
for (int i = 0; i < list.getLength(); i++) {
Element user = (Element) list.item(i);
Node username = user.getElementsByTagName("username").item(i);
Node password = user.getElementsByTagName("password").item(i);
if(loginuser.getText().equals(username.getTextContent())
&& loginpass.getText().equals(password.getTextContent())){
JOptionPane.showMessageDialog(rootPane, "welcome");
}
}
}catch(Exception e){
e.printStackTrace();
}
}
here is my xml :
这是我的 xml：
<?xml version="1.0" encoding="UTF-8"?>
<pengguna>
<user>
<nama>septian</nama>
<username>septiansykes</username>
<password>1234</password>
<status>belumpinjam</status>
</user>
<user>
<nama>koko</nama>
<username>kokosan</username>
<password>12er</password>
<status>belumpinjam</status>
</user>
<user>
<nama>tamrin</nama>
<username>tamrincs</username>
<password>gt234</password>
<status>belumpinjam</status>
</user>
</pengguna>
and here is my error :
这是我的错误：
java.lang.ClassCastException:com.sun.org.apache.xerces.internal.dom.DeepNodeListImpl cannot be cast to org.w3c.dom.Element
i try to get the element at the xml file, i want to check the element username and password, but there is an error about the cast class, it's seem difficult for me,... thanks before
我尝试在 xml 文件中获取元素，我想检查元素用户名和密码，但是关于 cast 类有错误，这对我来说似乎很困难，...谢谢之前
回答by Jon Skeet
This is the problem:
这就是问题：
Element pengguna = (Element) doc.getElementsByTagName("pengguna");
getElementsByTagNamedoesn't return a single element - it returns multiple elements. You probably want something like:
getElementsByTagName不返回单个元素 - 它返回多个元素。你可能想要这样的东西：
NodeList penggunas = doc.getElementsByTagName("pengguna");
if (penggunas.getLength() != 1) {
// Handle this - e.g. throw an exception
}
Element pengguna = (Element) penggunas.item(0);
EDIT: Later, you've got a bug here:
编辑：后来，你在这里有一个错误：
Node username = user.getElementsByTagName("username").item(i);
Node password = user.getElementsByTagName("password").item(i);
This should be:
这应该是：
Node username = user.getElementsByTagName("username").item(0);
Node password = user.getElementsByTagName("password").item(0);
You're already within the userelement - so you alwayswant the first usernameand passwordelements within that element. Otherwise you're asking for the second usernameelement within the second userelement, the third usernameelement within the third userelement etc. The numbering is relevant to the element that you're in, not some global count.
您已经在user元素中 - 所以您总是想要该元素中的第一个username和password元素。否则，您将要求第二个username元素中的第二个user元素，第三个username元素中的第三个user元素等。编号与您所在的元素相关，而不是某些全局计数。
回答by eternay
getElementByTagName()returns a NodeListand you try to cast it to an Element. This line is incorrect and will give you the ClassCastException:
getElementByTagName()返回 a ，NodeList然后您尝试将其强制转换为Element。这一行是不正确的，会给你ClassCastException：
Element pengguna = (Element) doc.getElementsByTagName("pengguna");
