0%

Java解析XML

前言

XML语法详解

定义一个xml文档

1
2
3
4
5
<?xml version="1.0" encoding="UTF-8"?>
<store>
<book id="01">第一本书</book>
<book id="02">第二本书</book>
</store>

原生解析

DOM解析

  • 优点:容易实现增删改操作
  • 缺点:xml过大时容易造成内存溢出

Document API文档js中的类似

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
public static void main(String[] args) throws Exception{
String filePath = "./src/main/resources/1.xml";

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(filePath);
NodeList books = doc.getElementsByTagName("book"); // 根据标签名获取标签
for (int i = 0; i < books.getLength(); i++) {
Node book = books.item(i);
NamedNodeMap attr= book.getAttributes();
System.out.println(i+"i:"+book.getTextContent()); // 输出book标签的文本内容
for(int j = 0; j < attr.getLength(); j++){
System.out.println(j+"j:"+attr.item(j)); // 输出book标签的所有属性值
}
}
// 添加一个标签
Element newBook = doc.createElement("book");
newBook.setAttribute("id", books.getLength()+1+""); // 设置属性
doc.getElementsByTagName("store").item(0).appendChild(newBook); // 添加到内存document中,此时未写入磁盘
TransformerFactory tffactory = TransformerFactory.newInstance();
Transformer tf = tffactory.newTransformer();
tf.transform(new DOMSource(doc), new StreamResult(filePath)); // 将document通过流的形式写入磁盘
}

SAX解析

  • 优点:不会造成内存溢出,适合查询
  • 缺点:不能进行增删改操作
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
@Test
public void testSAX() throws ParserConfigurationException, SAXException, IOException {
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();
parser.parse(new File(filePath), new DefaultHandler(){
@Override
public void startElement(String uri, String localName,String qName,Attributes attributes)
throws SAXException{
System.out.print("<"+qName+">"); // 开始标签
}

@Override
public void characters(char[] ch, int start, int length) throws SAXException {
System.out.print(new String(ch, start, length)); // 标签内容
}

@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
System.out.println("</"+qName+">"); // 结束标签
}
});
}

dom4j解析

导入

maven项目

1
2
3
4
5
<dependency>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
<version>1.6.1</version>
</dependency>

使用方法

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
@Test
public void testDOM4J() throws DocumentException, IOException {
SAXReader reader = new SAXReader();
Document doc = reader.read(new File(filePath));
Element root = doc.getRootElement();
List<Element> books = root.elements("book");
for(Element book : books){
List<Element> names = book.elements("name");
System.out.print("bookID:"+book.attributeValue("id"));
for(Element name : names){
System.out.println(name.getText());
}
}

//写入操作
Element newBook = root.addElement("book");
newBook.addAttribute("id", books.size()+1+""); // 添加属性
newBook.addElement("name").setText("第"+(books.size()+1)+"本书"); // 添加元素
XMLWriter writer = new XMLWriter(new FileOutputStream(new File(filePath)), // 流
OutputFormat.createPrettyPrint()); // 格式化写入
writer.write(doc);
writer.close();
}

支持xpath

导入maven项目

1
2
3
4
5
<dependency>
<groupId>jaxen</groupId>
<artifactId>jaxen</artifactId>
<version>1.1.6</version>
</dependency>

使用

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
/*
//book 所有book标签
/store/book/name 所有store标签下的book标签下的name标签
/* 所有标签,通配符
/store/book[1]/name[last()] store标签下的第一个book标签下的最后一个name标签
//book[@id] 所有有id属性的book标签
//book[@id='01'] 所有id属性值为01的book标签
*/
@Test
public void testXPath() throws DocumentException {
SAXReader reader = new SAXReader();
Document doc = reader.read(new File(filePath));
XPath xPath = new DefaultXPath("//name");
List<Element> names = xPath.selectNodes(doc);
for (Element name : names) {
System.out.println(name.getTextTrim());
}
}
点击进入云乞讨模式!