Java中的XML之四种方式生成XML文档：DOM，SAX，JD

现有以下XML文档books.xml,下面的示例生成此文档部分内容

<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
    <book id="1">
        <name>冰与火之歌</name>
        <author>乔治马丁</author>
        <year>2014</year>
        <price>89</price>
    </book>
    <book id="2">
        <name>安徒生童话</name>
        <year>2004</year>
        <price>77</price>
        <language>English</language>
    </book>
</bookstore>

DOM

1、创建DocumentBuilder对象

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();

2、添加节点

document.setXmlStandalone(true);
Element bookstore = document.createElement("bookStore");
//向bookstore根节点中添加子节点book
Element book = document.createElement("book");
Element name = document.createElement("name");
name.setTextContent("???");

book.appendChild(name);
book.setAttribute("id", "1");
//将book节点添加到bookstore根节点中
bookstore.appendChild(book);
//将bookstore节点（已经包含了book）添加到dom树中
document.appendChild(bookstore);

3、生成xml文件

TransformerFactory tff = TransformerFactory.newInstance();
Transformer tf = tff.newTransformer();
//设置文件
tf.setOutputProperty(OutputKeys.INDENT, "yes");
tf.transform(new DOMSource(document),new StreamResult(new File("books1.xml")));

---

SAX

1、创建一个TransformerFactory类的对象

SAXTransformerFactory tff = (SAXTransformerFactory) SAXTransformerFactory.newsInstance();

2、通过SAXTransformerFactory对象创建一个TransformerHandler对象

TransformerHandler handler = tff.newTransformerHandler();

3、通过handler对象创建一个Transformer对象

Transformer tr = handler.getTransformer();

4、通过Transformer对象对生成的xml文件进行设置

// 设置xml的编码
tr.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
// 设置xml的“是否换行”
tr.setOutputProperty(OutputKeys.INDENT, "yes");
5、创建一个Result对象
```java
File f = new File("newbooks.xml");
if (!f.exists()) {
    f.createNewFile();
}

6、创建Result对象，并且使其与handler关联

Result result = new StreamResult(new FileOutputStream(f));
handler.setResult(result);

7、利用handler对象进行xml文件内容的编写O

// 打开document
handler.startDocument();

8、添加节点属性和节点值

AttributesImpl attr = new AttributesImpl();
handler.startElement("", "", "bookstore", attr);
for (Book book : bookList) {
    attr.clear();
    attr.addAttribute("", "", "id", "", book.getId());
    handler.startElement("", "", "book", attr);
    // 创建name节点
    if (book.getName() != null && !book.getName().trim().equals("")) {
        attr.clear();
        handler.startElement("", "", "name", attr);
        handler.characters(book.getName().toCharArray(), 0, book
                .getName().length());
        handler.endElement("", "", "name");
    }
    handler.endElement("", "", "book");
}
handler.endElement("", "", "bookstore");
// 关闭document
handler.endDocument();

---

JDOM

1.生成一个根节点

Element rss = new Element("rss");

2.为节点添加属性

rss.setAttribute("version", "2.0");

3.生成一个document对象

Document document = new Document(rss);
Element channel = new Element("channel");
rss.addContent(channel);
Element title = new Element("title");
title.setText("<![CDATA[上海移动互联网产业促进中心正式揭牌 ]]>");
channel.addContent(title);
//设置文件编码和换行
Format format = Format.getCompactFormat();
format.setIndent("");
format.setEncoding("GBK");

4.创建XMLOutputter的对象

XMLOutputter outputer = new XMLOutputter(format);

5.利用outputer将document对象转换成xml文档

outputer.output(document, new FileOutputStream(new File("rssnews.xml")));

---

DOM4J

使用DOM4J生成RSS文件

1.创建document对象，代表整个xml文档

Document document = DocumentHelper.createDocument();

2.创建根节点rss

Element rss = document.addElement("rss");

3.向rss节点中添加version属性

rss.addAttribute("version", "2.0");

4.生成子节点及节点内容

Element channel = rss.addElement("channel");
Element title = channel.addElement("title");
title.setText("<![CDATA[上海移动互联网产业促进中心正式揭牌 ]]>");

5.设置生成xml的格式

OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("GBK");

6.生成xml文件

File file = new File("rssnews.xml");
XMLWriter writer;
writer = new XMLWriter(new FileOutputStream(file), format);
//设置是否转义，默认值是true，代表转义
writer.setEscapeText(false);
writer.write(document);
writer.close();

参阅：
慕课网：Java眼中的XML---文件读取
java核心技术 卷II：高级特性