归一化DOM没有归一化的相同效果 [英] Normalization DOM same effect without normalize

问题描述

在此处阅读答案：
用Java进行DOM解析时的规范化-它是如何工作的？

我了解规范化将删除空的相邻文本节点，因此尝试了以下xml： / p>

I understand that the normalization will remove empty adjacent text nodes, I tried the following xml :

<company>hello
wor
ld
</company>

具有以下代码：

    try {
        DocumentBuilder dBuilder = DocumentBuilderFactory.newInstance()
                .newDocumentBuilder();


        Document doc = dBuilder.parse(file);
        doc.getDocumentElement().normalize();

        System.out.println("Root element :" + doc.getDocumentElement().getNodeName());
        System.out.println(doc.getDocumentElement().getChildNodes().getLength());
        System.out.println(doc.getDocumentElement().getChildNodes().item(0).getTextContent());

    } catch (Exception e) {
        e.printStackTrace();
    }

即使没有规范化，我也总是为元素 company获得1个子节点。结果是：

I always get 1 child node for the element "company" even without normalize. the result is :

Root element :company
1
hello
wor
ld

那么这是怎么了？有人可以解释吗？

so what is wrong here ? can anyone explain ? shouldn't I get hello world in one line.

推荐答案

解析器已经在创建标准化的DOM树。

The parser is already creating a normalized DOM tree.

normalize（）方法对于构建/修改DOM很有用，因为它可能不会导致树标准化，在这种情况下，该方法将为您将其标准化。

The normalize() method is useful for when you're building/modifying the DOM, which might not result in a normalized tree, in which case the method will normalize it for you.

通用助手

private static void printDom(String indent, Node node) {
    System.out.println(indent + node);
    for (Node child = node.getFirstChild(); child != null; child = child.getNextSibling())
        printDom(indent + "  ", child);
}

示例1

public static void main(String[] args) throws Exception {
    String xml = "<Root>text 1<!-- test -->text 2</Root>";
    DocumentBuilder domBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
    Document doc = domBuilder.parse(new InputSource(new StringReader(xml)));
    printDom("", doc);
    deleteComments(doc);
    printDom("", doc);
    doc.normalizeDocument();
    printDom("", doc);
}
private static void deleteComments(Node node) {
    if (node.getNodeType() == Node.COMMENT_NODE)
        node.getParentNode().removeChild(node);
    else {
        NodeList children = node.getChildNodes();
        for (int i = 0; i < children.getLength(); i++)
            deleteComments(children.item(i));
    }
}

输出

[#document: null]
  [Root: null]
    [#text: text 1]
    [#comment:  test ]
    [#text: text 2]

[#document: null]
  [Root: null]
    [#text: text 1]
    [#text: text 2]

[#document: null]
  [Root: null]
    [#text: text 1text 2]

示例2

public static void main(String[] args) throws Exception {
    DocumentBuilder domBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
    Document doc = domBuilder.newDocument();
    Element root = doc.createElement("Root");
    doc.appendChild(root);
    root.appendChild(doc.createTextNode("Hello"));
    root.appendChild(doc.createTextNode(" "));
    root.appendChild(doc.createTextNode("World"));
    printDom("", doc);
    doc.normalizeDocument();
    printDom("", doc);
}

输出

[#document: null]
  [Root: null]
    [#text: Hello]
    [#text:  ]
    [#text: World]

[#document: null]
  [Root: null]
    [#text: Hello World]

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