doc.getElementById(id); null
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doc.getElementById(id); null
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Open Declaration Element org.w3c.dom.Document.getElementById(String elementId) Returns the Element that has an ID attribute with the given value. If no such element exists, this returns null . If more than one element has an ID attribute with that value, what is returned is undefined. The DOM implementation is expected to use the attribute Attr.isId to determine if an attribute is of type ID. Note: Attributes with the name "ID" or "id" are not of type ID unless so defined. Parameters: elementId The unique id value for an element. Returns: The matching element or null if there is none. Since: DOM Level 2
demo:
<dependency>
<groupId>org.xmlunit</groupId>
<artifactId>xmlunit-matchers</artifactId>
<version>2.3.0</version>
</dependency>
import java.io.StringReader;
import javax.xml.transform.stream.StreamSource;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.xmlunit.transform.Transformation;
public class TT {
public static void main(String[] args) {
String xmlStr = "<table><tr id="aaa">這是一行</tr></table>";
// String xmlStr = "<!DOCTYPE table [<!ATTLIST tr id ID #REQUIRED>]><table><tr id="aaa">這是一行</tr></table>";
Transformation transformation = new Transformation(new StreamSource(new StringReader(xmlStr)));
Document doc = transformation.transformToDocument();
Element tr = doc.getElementById("aaa");
System.out.println(tr);
}
}
輸出結(jié)果是：null
原因見紅色字內(nèi)容
如何解決：
為該文檔聲明DTD
其中有一種內(nèi)部聲明方法如下：
<?xml version="1.0"?> <!DOCTYPE note [ <!ELEMENT note (to,from,heading,body)> <!ELEMENT to (#PCDATA)> <!ELEMENT from (#PCDATA)> <!ELEMENT heading (#PCDATA)> <!ELEMENT body (#PCDATA)> ]> <note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend</body> </note>
還有一種外部聲明方法：
<?xml version="1.0"?> <!DOCTYPE note SYSTEM "note.dtd"> <note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>
其中內(nèi)部聲明方法的解釋是：
https://www.w3schools.com/xml/xml_dtd_elements.asp
本例的解決方案：
<!DOCTYPE table [<!ATTLIST tr id ID #REQUIRED>]>
語法：
<!ATTLIST element-name attribute-name attribute-type attribute-value>
https://www.w3schools.com/xml/xml_dtd_intro.asp
https://www.w3schools.com/xml/xml_dtd_attributes.asp
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