Java中的XML解析
2016-08-09 20:07
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XML解析
什么是XMl ?- XML 指可扩展标记语言（EXtensible Markup Language）
- XML 是一种标记语言，很类似 HTML
- XML 的设计宗旨是传输数据，而非显示数据
- XML 标签没有被预定义。您需要自行定义标签。
- XML 被设计为具有自我描述性。
- XML 是 W3C 的推荐标准
XML的解析和生成
接下来总结xml解析(生成)的三种方案:1. Android自带Pull解析
XML解析import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
/**
* Project: Day11_PullXml
* Created: Lulu
* Date: 2016/8/9
*/
public class TestPull {
public static void main(String[] args) {
/*
Pull的xml解析
parser: 转换
*/
try {
//工厂类, 生产对象
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
//XmlPullParser类对象解析xml的
XmlPullParser parser = factory.newPullParser();
//首先设置输入流(当前为文件输入流) 编码格式
parser.setInput(new FileInputStream("res/test.xml"), "UTF-8");
int type;
Note note = null;
while ((type = parser.next()) != XmlPullParser.END_DOCUMENT) {
switch (type) {
case XmlPullParser.START_DOCUMENT:
//开始文档没有用
break;
//这个字段下是最重要的
case XmlPullParser.START_TAG:
switch (parser.getName()) {
case "note":
note = new Note();
break;
case "to":
note.getToes().add(parser.nextText());
break;
case "from":
note.setFrom(parser.nextText());
break;
case "heading":
Heading heading = new Heading();
// 第一个值为命名空间, 第二个是属性名
heading.setFont(parser.getAttributeValue(null, "font"));
heading.setColor(parser.getAttributeValue(null, "color"));
heading.setText(parser.nextText());
note.setHeading(heading);
break;
case "body" :
note.getBodies().add(new Body());
break;
case "font":
note.getBodies().getLast().setFont(parser.nextText());
break;
case "color":
note.getBodies().getLast().setColor(parser.nextText());
break;
case "level":
note.getBodies().getLast().setLevel(Integer.parseInt(parser.nextText()));
break;
case "message":
note.getBodies().getLast().setMessage(parser.nextText());
break;
}
break;
}
}
System.out.println(note);
} catch (XmlPullParserException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}实体类对象不再贴出, 不过务必注意Note类中的getBodies方法, 在返回之前要检查对象是否为空, 为空则创建对戏
public LinkedList<Body> getBodies() {
if (bodies == null){
bodies = new LinkedList<>();
}
return bodies;
}XML生成
/**
* Project: Day11_PullXml
* Created: Lulu
* Date: 2016/8/9
* 使用pullxml生成xml
*/
public class TestPull01 {
public static void main(String[] args) {
try (FileOutputStream fos = new FileOutputStream("res/out.xml")){
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
//就是把对象让其可传递
XmlSerializer serializer = factory.newSerializer();
//设置输出流
serializer.setOutput(fos, "UTF-8");
serializer.startDocument("UTF-8", true);
serializer.startTag(null, "note");
serializer.startTag(null, "to");
serializer.text("你好");
serializer.endTag(null, "to") ;
serializer.startTag(null, "to");
serializer.text("4545644646");
serializer.endTag(null, "to") ;
serializer.endTag(null, "note");
serializer.endDocument();
} catch (XmlPullParserException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}2. SAX解析
MyHandler.javapackage org.lulu.learn;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
import java.util.Stack;
/**
* Project: Day11_SAXXml
* Created: Lulu
* Date: 2016/8/9
*/
public class MyHandler extends DefaultHandler {
private Note note;
//定义一个栈
private Stack<String> nameStack;
public MyHandler(Note note) {
this.note = note;
}
@Override
public void startDocument() throws SAXException {
super.startDocument();
//初始化实体类
nameStack = new Stack<>();
}
@Override
public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
super.startElement(uri, localName, qName, attributes);
nameStack.push(qName);
// System.out.println(qName);
switch (qName){
case "note":
note.setLevel(Integer.parseInt(attributes.getValue("level")));
break;
case "heading":
note.setHeading(new Heading());
break;
case "body":
note.setBody(new Body());
break;
}
}
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
super.characters(ch, start, length);
String s = new String(ch, start, length).trim();
if (!s.isEmpty()) {
// System.out.println(s);
switch (nameStack.peek()) {
case "to" :
note.getTo().add(s);
break;
case "from" :
note.setFrom(s);
break;
case "font" :
switch (nameStack.get(nameStack.size() - 2)) {
case "heading":
note.getHeading().setFont(s);
break;
case "body":
note.getBody().setFont(s);
break;
}
break;
case "title" :
note.getHeading().setTitle(s);
break;
case "message" :
note.getBody().setMessage(s);
break;
}
}
}
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
super.endElement(uri, localName, qName);
nameStack.pop();
}
@Override
public void endDocument() throws SAXException {
super.endDocument();
}
}Test.java
package org.lulu.learn;
import org.xml.sax.SAXException;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.sax.SAXTransformerFactory;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
/**
*
* SAX只能解析不能序列化
*
* 1. 基本解析
* 2. 带嵌套的解析
* 3. 属性名重名解析
* 4.
*
* Project: Day11_SAXXml
* Created: Lulu
* Date: 2016/8/9
*/
public class Test {
public static void main(String[] args) {
try {
//1. 生成SAX工厂类
SAXParserFactory factory = SAXParserFactory.newInstance();
//2. 通过工厂类生成SAXParser对象
SAXParser parser = factory.newSAXParser();
Note note = new Note();
parser.parse(new FileInputStream("res/test.xml"), new MyHandler(note));
System.out.println(note.toString());
System.out.println(note.getLevel());
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}SAX生成xml过于麻烦, 这里我们只说到解析
3. Dom解析
Dom解析虽方便, 但是需要大量内存空间所以并不是特别实用XML解析
import org.w3c.dom.*;
import org.xml.sax.SAXException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.io.File;
import java.io.IOException;
/**
* Project: Day11_DomXml
* 创建过多的对象, 对内存有过大压力
* Created: Lulu
* Date: 2016/8/9
*/
public class Test {
public static void main(String[] args) {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(new File("res/test.xml"));
Element root = document.getDocumentElement();
Note note = new Note();
note.setTo(
root.getElementsByTagName("to").
item(0).
getTextContent());
note.setFrom(
root.getElementsByTagName("from").
item(0).getTextContent());
note.setHeading(
root.getElementsByTagName("heading").
item(0).getTextContent());
Body body = new Body();
Element body1 = (Element) root.getElementsByTagName("body").item(0);
body.setLevel(Integer.parseInt(body1.getAttribute("level")));
body.setFont(body1.getElementsByTagName("font").item(0).getTextContent());
body.setMessage(body1.getElementsByTagName("message").item(0).getTextContent());
System.out.println(body);
System.out.println(note.toString());
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ParserConfigurationException e) {
e.printStackTrace();
}
}
}XML生成
/**
* Project: Day11_DomXml
* Created: Lulu
* Date: 2016/8/9
*/
public class Test01 {
public static void main(String[] args) {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.newDocument();
Element note = document.createElement("note");
Element to = document.createElement("to");
to.setTextContent("电动车");
note.appendChild(to);
Element from = document.createElement("from");
from.setTextContent("电动车");
note.appendChild(from);
Element heading = document.createElement("heading");
heading.setTextContent("动车");
note.appendChild(heading);
Element body = document.createElement("body");
body.setTextContent("骑动车");
note.appendChild(body);
DOMSource domSource = new DOMSource();
domSource.setNode(note);
StreamResult result = new StreamResult();
result.setOutputStream(new FileOutputStream("res/out.xml"));
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}
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