dom4j

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SAXReader

feature属性，禁止校验dtd文件

使用 dom4j 解析 xml

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import com.sun.org.apache.xerces.internal.impl.Constants;

/**
 * 在读取文件时，去掉dtd的验证，可以缩短运行时间
 */
public static SAXReader getSAXReader(){
    SAXReader saxReader = new SAXReader(DOMDocumentFactory.getInstance(),false);
     try {
         saxReader.setFeature(Constants.XERCES_FEATURE_PREFIX + Constants.LOAD_EXTERNAL_DTD_FEATURE, false);  //设置不需要校验头文件
     } catch (Exception e) {
         e.printStackTrace();
     }
     return saxReader;
 }

读取String为DOMDocument

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String xml = "...xml...";
DOMDocument document = (DOMDocument) getSAXReader().read(new StringReader(xml));

DOMElement

顺序读取文本内容和子元素

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DOMElement root = doc.getRootElement();
for(Object element : root.content()){
    if( o instanceof DOMElement){
        System.out.println(((DOMElement)o).asXML())
    }
    if( o instanceof DOMText){
        System.out.println(((DOMText)o).getText().trim())
    }
}

XPATH

dom4j直接获取值

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doc.selectObject("substring(/root/name/text(),2)");

//选择所有有id属性元素(List<DOMAttribute>)
doc.selectObject("/root/@id")
//获取第一个匹配标签的id属性的值
doc.selectObject("string(/root/@id)")

//搜索当前dom的子节点
dom.selectNodes("child/name/text()")

获取tomcat运行端口

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//通过classpath定位tomcat配置文件conf/server.xml，使用xpath去解析
File serverXml = new File("/Users/li/java/apache-tomcat-7.0.70/conf/server.xml");
DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
domFactory.setNamespaceAware(true); // never forget this!
DocumentBuilder builder = domFactory.newDocumentBuilder();
Document doc = builder.parse(serverXml);
XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXPath();
XPathExpression expr = xpath.compile("/Server/Service[@name='Catalina']/Connector[starts-with(@protocol,'HTTP')]/@port[1]");
String result = (String) expr.evaluate(doc, XPathConstants.STRING);
port = result != null && result.length() > 0 ? Integer.valueOf(result) : null;