Java之旅--XML/JSON

XML和JSON是两种常用的数据交换格式。虽然对于XML和JSON的各种操作，仅仅是常用的工具jar包的使用，没有什么技术含量，但鉴于这两种数据格式的普遍使用，还是拿出一点时间，进行一下简单总结。

XML

XML官网：http://www.xml.com/

XML保留字符有5个：&、>、<、'、""。

对于XML的解析方式，有两种：DOM方式和SAX方式。DOM是读入内存之后进行各种操作，SAX是流式操作、一次性的。其他的一些工具jar包，比如JDOM、DOM4J，都是对于这两种方式的高层次封装。

参考网址：

http://wenku.baidu.com/link?url=7VjI_4xMpWdV2O82WrNI2KO2UNuhefJYeGYe17QUmH89Nlc9NH20oVr8ZMJ2w1RSvphm5UE88L4FhB4fJgCcV4HldRlJsP9n_o1n1r7gunG

http://inotgaoshou.iteye.com/blog/1012188

DOM图示：

SAX图示：

演示代码：

import java.io.File;import java.util.Stack;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.SAXParser;import javax.xml.parsers.SAXParserFactory;import org.w3c.dom.Attr;import org.w3c.dom.Comment;import org.w3c.dom.Document;import org.w3c.dom.Element;import org.w3c.dom.NamedNodeMap;import org.w3c.dom.Node;import org.w3c.dom.NodeList;import org.xml.sax.Attributes;import org.xml.sax.SAXException;import org.xml.sax.helpers.DefaultHandler;/** * 演示两种XML的解析方式：DOM和SAX *  * 至于JDOM和DOM4J，只是在这两种方式之上的更高层次的封装 * */public class XmlDemo {public static void main(String[] args) throws Exception {XmlDemo xmlDemo = new XmlDemo();// DOM方式DomDemo domDemo = xmlDemo.new DomDemo("src/main/java/com/cl/roadshow/java/xml/people.xml");domDemo.iterateByName("PERSON");domDemo.recursiveElement();// SAX方式SaxDemo saxDemo = xmlDemo.new SaxDemo("src/main/java/com/cl/roadshow/java/xml/people.xml");saxDemo.showEvents();saxDemo.parseDocument();}/** * DOM方式解析XML *  */class DomDemo {private String path;public DomDemo(String path) {this.path = path;}/** * 查询所有符合给到名称的Node，大小写敏感 *  * @param tagName * @throws Exception */public void iterateByName(String tagName) throws Exception {// 获得DOM解析器工厂DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();// 获得具体的DOM解析器DocumentBuilder db = dbf.newDocumentBuilder();// 解析XML文档，获得Document对象（根结点）Document doc = db.parse(new File(path));NodeList nodeList = doc.getElementsByTagName(tagName);for (int i = 0; i < nodeList.getLength(); i++) {Element element = (Element) nodeList.item(i);String content = element.getElementsByTagName("NAME").item(0).getFirstChild().getNodeValue();System.out.println("name:" + content);content = element.getElementsByTagName("ADDRESS").item(0).getFirstChild().getNodeValue();System.out.println("address:" + content);content = element.getElementsByTagName("TEL").item(0).getFirstChild().getNodeValue();System.out.println("tel:" + content);content = element.getElementsByTagName("FAX").item(0).getFirstChild().getNodeValue();System.out.println("fax:" + content);content = element.getElementsByTagName("EMAIL").item(0).getFirstChild().getNodeValue();System.out.println("email:" + content);System.out.println("--------------------------------------");}}/** * 从根节点开始，遍历XML的所有元素 *  * @throws Exception */public void recursiveElement() throws Exception {DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();DocumentBuilder db = dbf.newDocumentBuilder();Document doc = db.parse(new File(path));// 获得根元素结点Element root = doc.getDocumentElement();parseElement(root);}/** * 递归方法 *  * @param element */private void parseElement(Element element) {String tagName = element.getNodeName();NodeList children = element.getChildNodes();System.out.print("<" + tagName);// element元素的所有属性所构成的NamedNodeMap对象，需要对其进行判断NamedNodeMap map = element.getAttributes();// 如果该元素存在属性if (null != map) {for (int i = 0; i < map.getLength(); i++) {// 获得该元素的每一个属性Attr attr = (Attr) map.item(i);String attrName = attr.getName();String attrValue = attr.getValue();System.out.print(" " + attrName + "=\"" + attrValue + "\"");}}System.out.print(">");for (int i = 0; i < children.getLength(); i++) {Node node = children.item(i);// 获得结点的类型short nodeType = node.getNodeType();if (nodeType == Node.ELEMENT_NODE) {// 是元素，继续递归parseElement((Element) node);} else if (nodeType == Node.TEXT_NODE) {// 递归出口System.out.print(node.getNodeValue());} else if (nodeType == Node.COMMENT_NODE) {System.out.print("<!--");Comment comment = (Comment) node;// 注释内容String data = comment.getData();System.out.print(data);System.out.print("-->");}}System.out.print("</" + tagName + ">");}}/** * SAX方式解析XML * */class SaxDemo {private String path;public SaxDemo(String path) {this.path = path;}public void showEvents() throws Exception {// 获得SAX解析器工厂实例SAXParserFactory factory = SAXParserFactory.newInstance();// 获得SAX解析器实例SAXParser parser = factory.newSAXParser();// 开始进行解析parser.parse(new File(path), new EventHandler());}public void parseDocument() throws Exception {// 获得SAX解析器工厂实例SAXParserFactory factory = SAXParserFactory.newInstance();// 获得SAX解析器实例SAXParser parser = factory.newSAXParser();// 开始进行解析parser.parse(new File(path), new ParseHandler());}/** * 演示SAX解析方式的事件驱动过程 * */class EventHandler extends DefaultHandler {@Overridepublic void startDocument() throws SAXException {System.out.println("\n--------------------------------------");System.out.println("start document");}@Overridepublic void endDocument() throws SAXException {System.out.println("finish document");System.out.println("--------------------------------------");}@Overridepublic void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {System.out.println("start element");}@Overridepublic void endElement(String uri, String localName, String qName) throws SAXException {System.out.println("finish element");}}/** * 演示用SAX方式解析PERSON节点的过程 * */class ParseHandler extends DefaultHandler {private Stack<String> stack = new Stack<String>();private String name;private String tel;@Overridepublic void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {stack.push(qName);for (int i = 0; i < attributes.getLength(); i++) {String attrName = attributes.getQName(i);String attrValue = attributes.getValue(i);System.out.println(attrName + "=" + attrValue);}}@Overridepublic void characters(char[] ch, int start, int length) throws SAXException {String tag = stack.peek();if ("NAME".equals(tag)) {name = new String(ch, start, length);} else if ("TEL".equals(tag)) {tel = new String(ch, start, length);}}@Overridepublic void endElement(String uri, String localName, String qName) throws SAXException {stack.pop(); // 表示该元素已经解析完毕，需要从栈中弹出if ("PERSON".equals(qName)) {System.out.println("NAME：" + name);System.out.println("TEL：" + tel);System.out.println();}}}}}

JSON

JSON官网：http://www.json.org/json-zh.html

对于JSON的解析，各种语言下都有 很多可用客户端，在Java下，fastjson是推荐使用的一种，快、强大、无依赖。

代码演示：

import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import com.alibaba.fastjson.JSON;import com.alibaba.fastjson.TypeReference;/** * fastjson 是一个性能很好的 Java 语言实现的 JSON 解析器和生成器，来自阿里巴巴的工程师开发 *  *  * 主要特点：比其它任何基于Java的解析器和生成器更快，包括jackson；强大；零依赖 * */public class FastjsonDemo {public static void main(String[] args) {// 将JSON和JavaBean对象互相转换Person person = new Person(1, "张三", null);String jsonString = JSON.toJSONString(person);System.out.println(jsonString);person = JSON.parseObject(jsonString, Person.class);System.out.println(person.getName());System.out.println("--------------------------------------");// 将JSON字符串转化成List<JavaBean>对象Person person1 = new Person(1, "fastjson1", 11);Person person2 = new Person(2, "fastjson2", 22);List<Person> persons = new ArrayList<Person>();persons.add(person1);persons.add(person2);jsonString = JSON.toJSONString(persons);System.out.println("json字符串:" + jsonString);persons = JSON.parseArray(jsonString, Person.class);System.out.println(persons.toString());System.out.println("--------------------------------------");// 将JSON字符串转化成List<String>对象List<String> list1 = new ArrayList<String>();list1.add("fastjson1");list1.add("fastjson2");list1.add("fastjson3");jsonString = JSON.toJSONString(list1);System.out.println(jsonString);List<String> list2 = JSON.parseObject(jsonString, new TypeReference<List<String>>() {});System.out.println("list2：" + list2.toString());System.out.println("--------------------------------------");// JSON<Map<String,Object>>对象Map<String, Object> map = new HashMap<String, Object>();map.put("key1", "value1");map.put("key2", "value2");Map<String, Object> map2 = new HashMap<String, Object>();map2.put("key1", 1);map2.put("key2", 2);List<Map<String, Object>> list3 = new ArrayList<Map<String, Object>>();list3.add(map);list3.add(map2);jsonString = JSON.toJSONString(list3);System.out.println("json字符串:" + jsonString);List<Map<String, Object>> list4 = JSON.parseObject(jsonString, new TypeReference<List<Map<String, Object>>>() {});System.out.println("list4：" + list4.toString());}}class Person {private Integer id;private String name;private Integer age;public Person() {}public Person(Integer id, String name, Integer age) {super();this.id = id;this.name = name;this.age = age;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}@Overridepublic String toString() {StringBuilder sb = new StringBuilder();sb.append("ID:").append(id);sb.append("-Name:").append(name);sb.append("-Age:").append(age);return sb.toString();}}