如何通過java的

Question

這裏是我的XML代碼使用循環讀取XML子節點的值...

<flow> 
    <TaskID>100</TaskID> 
    <TaskID>101</TaskID> 
    <TaskID>102</TaskID> 
    <TaskID>103</TaskID>  
</flow> 

我想知道如何獲得任務id值在Java中循環。請幫我...

Answer 1

DOM解析器的解決方案，非常簡單，不需要額外的庫。

public static void main(String[] args) throws SAXException, IOException, 
     ParserConfigurationException { 

    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); 
    DocumentBuilder builder = factory.newDocumentBuilder(); 

    String input = "<outer>"; 
    input += "<otherstuff><TaskID>123</TaskID></otherstuff>"; 
    input += "<flow>"; 
    input += "<TaskID>100</TaskID>"; 
    input += "<TaskID>101</TaskID>"; 
    input += "<TaskID>102</TaskID>"; 
    input += "<TaskID>103</TaskID>"; 
    input += "</flow>"; 
    input += "</outer>"; 
    Document document = builder.parse(new InputSource(new StringReader(
      input))); 

    NodeList flowList = document.getElementsByTagName("flow"); 
    for (int i = 0; i < flowList.getLength(); i++) { 
     NodeList childList = flowList.item(i).getChildNodes(); 
     for (int j = 0; j < childList.getLength(); j++) { 
      Node childNode = childList.item(j); 
      if ("TaskID".equals(childNode.getNodeName())) { 
       System.out.println(childList.item(j).getTextContent() 
         .trim()); 
      } 
     } 
    } 
} 

如果輸入來自文件，則需要使用FileReader。

Document document = builder.parse(new InputSource(new FileReader(
     new File("foo.xml")))); 

到的getElementsByTagName另一種（）是的XPath，對XML的查詢語言，這是非常有用的，如果你有複雜的條件相匹配集。

XPathFactory xPathfactory = XPathFactory.newInstance(); 
XPath xpath = xPathfactory.newXPath(); 
XPathExpression expr = xpath.compile("//flow/TaskID/text()"); 

Object result = expr.evaluate(document, XPathConstants.NODESET); 
NodeList nodes = (NodeList) result; 
for (int i = 0; i < nodes.getLength(); i++) { 
    System.out.println(nodes.item(i).getTextContent()); 
} 

如果您的XML文件較大，如MB/GB的100S或者你是一個低內存的平臺上再考慮SAX解析器。

String input = "<flow><TaskID>100</TaskID><TaskID>101</TaskID><TaskID>102</TaskID><TaskID>103</TaskID></flow>"; 
SAXParser sax = SAXParserFactory.newInstance().newSAXParser(); 
DefaultHandler handler = new DefaultHandler() { 
    private StringBuilder buffer = new StringBuilder(); 
    @Override 
    public void endElement(String uri, String localName, String qName) 
      throws SAXException { 
     if ("TaskID".equals(qName)) { 
      System.out.println(buffer); 
      buffer = new StringBuilder(); 
     } 
    } 
    @Override 
    public void characters(char[] ch, int start, int length) 
      throws SAXException { 
     buffer.append(ch, start, length); 
    } 
    @Override 
    public void startElement(String uri, String localName, 
      String qName, Attributes attributes) throws SAXException { 
     buffer = new StringBuilder(); 
    } 
}; 
sax.parse(new InputSource(new StringReader(input)), handler); 

Answer 2

使用XPath下面是詳細信息：

http://www.vogella.com/articles/JavaXML/article.html

Answer 3

下面是使用JDOM，它比現有的Java XML解析器提供了更舒適的API的例子：

import java.io.File; 
import org.jdom2.*; 
import org.jdom2.input.*; 

public class Test { 
    // TODO: More appropriate exception handling :) 
    public static void main (String[] args) throws Exception { 
     SAXBuilder builder = new SAXBuilder(); 
     Document doc = builder.build(new File("test.xml")); 
     Element root = doc.getRootElement(); 
     for (Element element : root.getChildren("TaskID")) { 
      System.out.println(element.getText()); 
     } 
    } 
} 

當然，這是假設XML文檔足夠小，可以加載到內存中。 （很明顯，你也可以使用內置的庫，如果你沒有在做很多 XML的工作，那麼這將是很好 - 我只是發現它們有點原始，如果你做任何大量的工作）。

Answer 4

我個人使用JDOM庫來處理我所有的XML操作。下面是我該怎麼做;

String xml = "<flow> " + 
        "<TaskID>100</TaskID>" + 
        "<TaskID>101</TaskID>" + 
        "<TaskID>102</TaskID>" + 
        "<TaskID>103</TaskID>" + 
       "</flow>"; 

org.jdom.Document doc = new SAXBuilder().build(new StringReader(xml)); 

org.jdom.Element rootElement = doc.getRootElement(); 

List<Element> eles = rootElement.getChildren("TaskID"); 

for(Element el : eles) 
    System.out.println(el.getName()+" : "+el.getValue()); 

你可以得到它的文檔在這裏：http://www.jdom.org/

Answer 5

讀取XML兒童SAX

<?xml version="1.0"?> 
<Patriarch> 
    <name>Bill</name> 
    <wife> 
     <name>Vi</name> 
    </wife> 
    <son> 
     <name>Bill</name> 
    </son> 
    <daughter> 
     <name>Jeri</name> 
     <husband> 
     <name>Mark</name> 
     </husband> 
     <son> 
     <name>Greg</name> 
     </son> 
     <son> 
     <name>Tim</name> 
     </son> 
     <son> 
     <name>Mark</name> 
     </son> 
     <son> 
     <name>Josh</name> 
     <wife> 
      <name>Kristine</name> 
     </wife> 
     <son> 
      <name>Blake</name> 
     </son> 
     <daughter> 
      <name>Liah</name> 
     </daughter> 
     </son> 
    </daughter> 
</Patriarch> 

和Java代碼：

public class ParseXmlSAX { 

    public static void main(String[] args) { 
     new ParseXmlSAX("file.xml"); 
    } 

    public ParseXmlSAX(final String file) { 
     try { 

      SAXParserFactory factory = SAXParserFactory.newInstance(); 
      SAXParser saxParser = factory.newSAXParser(); 

      DefaultHandler handler = new DefaultHandler() { 
       String key = null; 

       public void startElement(String uri, String localName, String qName, Attributes attributes) 
         throws SAXException { 

        if (key == null) 
         key = "|"; 
        else 
         key += qName + "|"; 

       } 

       public void endElement(String uri, String localName, String qName) throws SAXException { 

        if (!key.equals("|")) 
         key = key.substring(0, key.lastIndexOf(qName)); 

       } 

       public void characters(char ch[], int start, int length) throws SAXException { 
        String conteudo = new String(ch, start, length).trim(); 

        if (!conteudo.isEmpty()) { 
         System.out.println(key + " = " + conteudo); 
        } 

       } 

      }; 

      saxParser.parse(this.getClass().getResourceAsStream(file), handler); 

     } catch (Exception e) { 
      e.printStackTrace(); 
     } 

    } 
}