XML文件--使用DOM示例

Posted 2020-08-26 Penney_

•     其他依赖字段/方法
  

// 书籍列表
	private List<Book> bookList = new LinkedList<Book>();
	/**
	 * 根据xml文件，得到书籍列表
	 * 
	 * @param file
	 * @return
	 */
	public List<Book> getBookList(String file) {
		parseXML(file);
		return bookList;
	}

• 获取DocumentBuilder(文件解析器)
  

/**
	* 获取DocumentBuilder对象
	*@return 
	*/
	private DocumentBuilder getDocumentBuilder() {
		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
		DocumentBuilder builder = null;
		try {
			builder = factory.newDocumentBuilder();
		} catch (ParserConfigurationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return builder;
	}

• 解析XML文件
  

	/**
	 * 读取XML，并将book对象存入书籍列表
	 * 
	 * @param file
	 */
	private void parseXML(String file) {
		// 1.临时书籍变量
		Book book;
		try {
			// 2.获取DocumentBuilder对象
			DocumentBuilder documentBuilder = getDocumentBuilder();
			// 3.加载XML文件到当前项目下，获取Document‘文档’对象
			Document document = documentBuilder.parse(file);
			// 4.获取节点名称是book的集合
			NodeList books = document.getElementsByTagName("book");
			// 5.遍历book节点集合
			for (int i = 0; i < books.getLength(); i++) {
				// 重置book变量
				book = new Book();
				// 5.1声明book节点变量
				Node bookNode = books.item(i);
				// 5.2获取book节点的属性集合
				NamedNodeMap nodeMap = bookNode.getAttributes();
				// 5.3遍历属性集合，判断并为book对象的属性赋值
				for (int j = 0; j < nodeMap.getLength(); j++) {
					// 5.4声明book的属性
					Node attrNode = nodeMap.item(j);
					// 5.5如果属性Name为id
					if (attrNode.getNodeName().equals("id")) {
						book.setId(Integer.valueOf(attrNode.getNodeValue()));
					}
				}
				// 5.6获取book节点的子节点
				NodeList childList = bookNode.getChildNodes();
				// 5.7遍历子节点
				for (int j = 0; j < childList.getLength(); j++) {
					// 5.8 声明book子节点
					Node child = childList.item(j);
					// 判断是否是节点。NodeType有三种：
					// Element(节点)：1，Attribute(属性)：2，#Text(文本)：3。
					if (Node.ELEMENT_NODE == child.getNodeType()) {
						// 5.9使用switch case判断，并为book对象属性赋值
						switch (child.getNodeName()) {
						case "title":
							book.setTitle(child.getTextContent());
							break;
						case "author":
							book.setAuthor(child.getTextContent());
							break;
						case "price":
							book.setPrice(Double.valueOf(child.getTextContent()));
							break;
						case "year":
							book.setYear(child.getTextContent());
							break;
						case "language":
							book.setLanguage(child.getTextContent());
							break;
						default:
							System.out.println("未知属性！");
						}
					}
				}
				// 6 将book对象放入集合
				bookList.add(book);
			}
		} catch (SAXException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

• 生成XML文件
  

/**
	 * 生成XML文件，写入book列表
	 * 
	 * @param file
	 */
	private void createXML(List<Book> bookList, String file, String encoding) {
		DocumentBuilder builder = getDocumentBuilder();
		//创建document文件
		Document document = builder.newDocument();
		// 在document中，创建根节点
		Element eBookstore = document.createElement("bookstore");
		for (Book book : bookList) {
			// 创建book节点
			Element eBook = document.createElement("book");
			// 为book节点添加id属性
			eBook.setAttribute("id", String.valueOf(book.getId()));
			// 创建book的子节点
			Element eTitle = document.createElement("title");
			// 创建CDATA元素
			CDATASection titleByCDATA = document.createCDATASection(book.getTitle());
			// 将CDATA元素加入title
			eTitle.appendChild(titleByCDATA);
			eTitle.setTextContent(book.getTitle());
			Element eAuthor = document.createElement("author");
			eAuthor.setTextContent(book.getAuthor());
			Element eYear = document.createElement("year");
			eYear.setTextContent(book.getYear());
			Element ePrice = document.createElement("price");
			ePrice.setTextContent(String.valueOf(book.getPrice()));
			Element eLanguage = document.createElement("language");
			eLanguage.setTextContent(book.getLanguage());
			// 将子节点添加到book中
			eBook.appendChild(eTitle);
			eBook.appendChild(eAuthor);
			eBook.appendChild(eYear);
			eBook.appendChild(ePrice);
			eBook.appendChild(eLanguage);
			// 将book节点添加到bookstore根节点中
			eBookstore.appendChild(eBook);
		}
		// 将bookstore节点添加到document中，目前文件只存在与内存中
		document.appendChild(eBookstore);
		// 创建TransformerFactory 对象
		Transformer former = getTransformer(encoding);
		try {
			// 创建输出流
			OutputStream output = new FileOutputStream(file);
			// 输出XML文件到硬盘
			former.transform(new DOMSource(document), new StreamResult(output));
		} catch (TransformerConfigurationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (TransformerException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

• 保存Tranformer对象，用于保存XML文件，设置自动换行和编码
  

/**
	 * 获取Tranformer对象
	 * 
	 * @param encoding
	 *            指定编码
	 * @return Tranformer
	 */
	private Transformer getTransformer(String encoding) {
		// 创建TransformerFactory 对象
		TransformerFactory factory = TransformerFactory.newInstance();
		Transformer former = null;
		try {
			former = factory.newTransformer();
			// 换行
			former.setOutputProperty(OutputKeys.INDENT, "yes");
			// 指定编码
			former.setOutputProperty(OutputKeys.ENCODING, encoding);
		} catch (TransformerConfigurationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace(); 
		}
		return former;
	}