DOM解析XML

DOM解析xml时在内存中生成DOM文档树，可以随机访问/增加/修改/删除其中的节点，十分方便，缺点是xml十分庞大时，解析会消耗较多内存

Node对象代表着DOM的基本类型，代表文档树中的一个节点（包括空格回车等），Element(元素),Attr（属性）,Text（文本）,Document(文档)都继承于Node

1.解析xml文档：

books.xml

<?xml version="1.0" encoding="UTF-8"?><books>   <book no="01">       <name>JAVA编程思想</name>       <price>100</price>   </book>   <book no="02">       <name>EFFECTIVE JAVA</name>       <price>100</price>   </book></books>

先使用解析器生成Document对象：

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder builder = factory.newDocumentBuilder();//得到document对象Document document = builder.parse(new File("D:/books.xml"));

解析过程：

static void readXml (Document document){//得到文档的根元素Element rootNode = document.getDocumentElement();//或者//Node rootNode = document.getElementsByTagName("books").item(0);//遍历books元素内的子元素NodeList bookList = rootNode.getChildNodes();//或者//NodeList bookList = document.getElementsByTagName("book");for (int i = 0; i < bookList.getLength(); i++) {Node bookNode = bookList.item(i);//去空格if (bookNode instanceof Element) {print("--------");print("元素：");print(bookNode.getNodeName());print("属性：");//获得属性print(((Element) bookNode).getAttribute("no"));//获得book节点下的所有元素for (int j = 0; j < bookNode.getChildNodes().getLength(); j++) {Node node = bookNode.getChildNodes().item(j);if (node instanceof Element) {print(bookNode.getNodeName()+"的子元素:");print(node.getNodeName());print(bookNode.getNodeName() +"的子元素值：");print(node.getTextContent());}}//作用和上面循环相同//Node child = bookNode.getFirstChild();//while (child != null) {//if (child instanceof Element) {//print(bookNode.getNodeName()+"的子元素:");//print(child.getNodeName());//print(bookNode.getNodeName() +"的子元素值：");//print(child.getTextContent());//}//child = child.getNextSibling();//}}}}public static void print(Object obj) {System.out.println(obj.toString());}

结果：

--------
元素：
book
属性：
01
book的子元素:
name
book的子元素值：
JAVA编程思想
book的子元素:
price
book的子元素值：
100
--------
元素：
book
属性：
02
book的子元素:
name
book的子元素值：
EFFECTIVE JAVA
book的子元素:
price
book的子元素值：
100

2.生成xml文档：

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder builder = factory.newDocumentBuilder();Document document = builder.newDocument();//------------添加节点------------Element books = document.createElement("books");document.appendChild(books);//属性Attr attr = document.createAttribute("no");attr.setValue("03");books.setAttributeNode(attr);Element book = document.createElement("book");books.appendChild(book);Element name = document.createElement("name");Element price = document.createElement("price");//文本值Text nameText = document.createTextNode("Servlet");Text priceText = document.createTextNode("200");name.appendChild(nameText);price.appendChild(priceText);book.appendChild(name);book.appendChild(price);//利用生成的dom创建dom输入源DOMSource source = new DOMSource(document);//保存转换后结果到books.xml文件中StreamResult result = new StreamResult(new File("books.xml"));//转换工厂类TransformerFactory tff = TransformerFactory.newInstance();Transformer tf = tff.newTransformer();tf.transform(source, result);

结果：

<?xml version="1.0" encoding="UTF-8" standalone="no"?><books no="03"><book><name>Servlet</name><price>200</price></book></books>