問題：

java使用NekoHTML解析HTML的時候發現NekoHTML總是把標籤名轉換成大寫，導致之前寫的XPath都用不了，雖然可以用指令碼把之前的歷史XPath都轉換一遍，但是如果新來的運營不知道的話，還是可能會出現不必要的麻煩。

分析：

在網上一頓搜尋，發現自己的blog裡也有寫，只是之前沒有注意，NekoHTML提供了一些配置項，可以精確的配置NekoHTML的行為。 與我們這個問題相關的配置是：

DOMParser parser = new DOMParser();
parser.setProperty("http://cyberneko.org/html/properties/names/elems", "match");
//解析HTML檔案
parser.parse("http://www.baidu.com");
 //獲取解析後的DOM樹
Document document = parser.getDocument();
 

設定以後發現竟然沒有用，關鍵是NekoHTML的官網也上不去，不知道是被牆了還是怎麼。後來幸好在github找到一份映象，找到了文件。 文件中這麼寫著：

Why are the DOM element names always uppercase?

The HTML DOM specification explicitly states that element and attribute names follow the semantics, including case-sensitivity, specified in the HTML 4specification. In addition, 

section 1.2.1 of the HTML 4.01 specification states:

Element names are written in uppercase letters (e.g., BODY). Attribute names are written in lowercase letters (e.g., lang, onsubmit).

The Xerces HTML DOM implementation (used by default in the NekoHTML DOMParser class) follows this convention. Therefore, even if the "http://cyberneko.org/html/properties/names/elems" property is set to "lower", the DOM will still uppercase the element names.

To get around this problem, instantiate a Xerces2 DOMParser object using the NekoHTML parser configuration. By default, the Xerces DOM parser class creates a standard XML DOM tree, not an HTML DOM tree. Therefore, the element and attribute names will follow the settings for the "http://cyberneko.org/html/properties/names/elems" and "http://cyberneko.org/html/properties/names/attrs" properties. However, realize that the application will not be able to cast the document nodes to the HTML DOM interfaces for accessing the document's information.

The following sample code shows how to instantiate a DOM parser using the NekoHTML parser configuration:

// import org.apache.xerces.parsers.DOMParser;
// import org.cyberneko.html.HTMLConfiguration;

DOMParser parser = new DOMParser(new HTMLConfiguration());

大意就是說為了符合HTML4.01標準，NekoHTML會將TagName轉換為大寫，無論是否設定剛才說的配置項。解決辦法就是使用

org.apache.xerces.parsers.DOMParser代替原來的DOMParser。具體程式碼看下面的解決方案吧

解決方案：

直接插程式碼了：

        HTMLConfiguration htmlConfiguration = new HTMLConfiguration();
        htmlConfiguration.setProperty("http://cyberneko.org/html/properties/names/elems", "match");
        org.apache.xerces.parsers.DOMParser parser = new org.apache.xerces.parsers.DOMParser(htmlConfiguration);
        InputSource inputSource = new InputSource("http://www.baidu.com");
        parser.parse(inputSource);
        System.out.println(parser.getXMLParserConfiguration().getProperty("http://cyberneko.org/html/properties/names/elems"));
        //獲取解析後的DOM樹
        Document document = parser.getDocument();
        String xml = new XMLDocument(document).toString();
        System.out.println(xml);

附上pom.xml的相關依賴

        <dependency>
            <groupId>net.sourceforge.nekohtml</groupId>
            <artifactId>nekohtml</artifactId>
            <version>1.9.22</version>
        </dependency>