XML节点和子节点

Question

header = new LinkedHashMap<String,Object>();
Element headerElement = (Element)doc.getElementsByTagName( "Header").item(0);
NodeList elementList = headerElement.getElementsByTagName( "*" );
for( int index =0; index < elementList.getLength(); index++ ){
    Node element = elementList.item(index);
    System.out.println( element.getChildNodes().item(0).getTextContent() ); // Statement A          
    System.out.println( element.getTextContent()); // Statement B

Both Statement A and Statement B are printing the same output.

What does it means, every node is a child node for itself??

And the input XML is

<Header>
    <tag1>1</tag1>
    <tag2>2</tag2>
    <tag3>3</tag3>
    <tag4>4</tag4>
</Header>

Answer 1

From the documentation of Node.getTextContent() , for a node type of ELEMENT_NODE :

concatenation of the textContent attribute value of every child node, excluding COMMENT_NODE and PROCESSING_INSTRUCTION_NODE nodes. This is the empty string if the node has no children.

Whereas for a text node, the return value of the method is just nodeValue , ie the text of the node.

So yes - calling this on an element with a single child node which is a text node will give you the same results as calling it directly on that text node. But in other cases you'd get different results. For example, if you had an element like this:

<tag>1<break />2</tag>

there would be two child text nodes and one child element node, and the result would be "1 2" (or possibly "12"; I'm not sure how spacing works in this concatenation off-hand, but you can check).

It's not a matter of a node "containing itself" - it's simply a matter of the definition of what this method does.

Answer 2

getTextContent() returns returns the text content of this node and its descendants .

Statement A executed at tag1 returns the text node below ( 1 )

Statement B executed at the same place gets the child nodes of tag1 (a list with one text node), selects the first (only) text node and displays its text value.

In this instance they are the same thing.