在Java DOM文档中设置名称空间和前缀 [英] Setting namespaces and prefixes in a Java DOM document
问题描述
我正在尝试将ResultSet转换为XML文件。
我首先使用这个例子进行序列化。
I'm trying to convert a ResultSet to an XML file. I've first used this example for the serialization.
import org.w3c.dom.bootstrap.DOMImplementationRegistry;
import org.w3c.dom.Document;
import org.w3c.dom.ls.DOMImplementationLS;
import org.w3c.dom.ls.LSSerializer;
...
DOMImplementationRegistry registry = DOMImplementationRegistry.newInstance();
DOMImplementationLS impl =
(DOMImplementationLS)registry.getDOMImplementation("LS");
...
LSSerializer writer = impl.createLSSerializer();
String str = writer.writeToString(document);
在我完成这项工作后，我尝试验证我的XML文件，有几个警告。
一个关于没有doctype的问题。所以我尝试了另一种方法来实现它。我遇到了Transformer课程。这个类让我设置编码，doctype等。
After I made this work, I tried to validate my XML file, there were a couple of warnings. One about not having a doctype. So I tried another way to implement this. I came across the Transformer class. This class lets me set the encoding, doctype, etc.
前面的实现支持自动命名空间修复。以下不是。
The previous implementation supports automatic namespace fix-up. The following does not.
private static Document toDocument(ResultSet rs) throws Exception {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.newDocument();
URL namespaceURL = new URL("http://www.w3.org/2001/XMLSchema-instance");
String namespace = "xmlns:xsi="+namespaceURL.toString();
Element messages = doc.createElementNS(namespace, "messages");
doc.appendChild(messages);
ResultSetMetaData rsmd = rs.getMetaData();
int colCount = rsmd.getColumnCount();
String attributeValue = "true";
String attribute = "xsi:nil";
rs.beforeFirst();
while(rs.next()) {
amountOfRecords = 0;
Element message = doc.createElement("message");
messages.appendChild(message);
for(int i = 1; i <= colCount; i++) {
Object value = rs.getObject(i);
String columnName = rsmd.getColumnName(i);
Element messageNode = doc.createElement(columnName);
if(value != null) {
messageNode.appendChild(doc.createTextNode(value.toString()));
} else {
messageNode.setAttribute(attribute, attributeValue);
}
message.appendChild(messageNode);
}
amountOfRecords++;
}
logger.info("Amount of records archived: " + amountOfRecords);
TransformerFactory tff = TransformerFactory.newInstance();
Transformer tf = tff.newTransformer();
tf.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
tf.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
tf.setOutputProperty(OutputKeys.INDENT, "yes");
BufferedWriter bf = createFile();
StreamResult sr = new StreamResult(bf);
DOMSource source = new DOMSource(doc);
tf.transform(source, sr);
return doc;
}
当我测试之前的实现时，我得到了一个TransformationException：前缀的命名空间' xsi'尚未声明。正如您所看到的，我已尝试将带有xsi前缀的命名空间添加到文档的根元素中。经过测试，我仍然得到了例外。设置命名空间及其前缀的正确方法是什么？
While I was testing the previous implementation I got an TransformationException: Namespace for prefix 'xsi' has not been declared. As you can see I've tried to add a namespace with the xsi prefix to the root element of my document. After testing this I still got the Exception. What is the correct way to set namespaces and their prefixes?
编辑：我对第一个实现的另一个问题是XML文档中的最后一个元素没有最后三个结束标记。
Another problem I have with the first implementation is that the last element in the XML document doesn't have the last three closing tags.
推荐答案
您还没有在根节点中添加名称空间声明;你刚刚在命名空间中声明了根节点，两个完全不同的东西。构建DOM时，需要在每个相关节点上引用命名空间。换句话说，当你添加你的属性时，你需要定义它的命名空间（例如，setAttributeNS）。
You haven't added the namespace declaration in the root node; you just declared the root node in the namespace, two entirely different things. When building a DOM, you need to reference the namespace on every relevant Node. In other words, when you add your attribute, you need to define its namespace (e.g., setAttributeNS).
旁注：虽然XML命名空间看起来像URL，但它们真的不是T。这里不需要使用URL类。
Side note: Although XML namespaces look like URLs, they really aren't. There's no need to use the URL class here.
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