如何通过属性值获取XML字符串

huangapple
go评论108阅读模式
英文:

How to get an XML string by attribute value

问题

我正在尝试解析一个 XML 文件，以获取“流程图”中步骤的按步骤 ID 排列的内容，该 ID 是 steps 的子元素：

  1. <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  2. <CATALOG>
  3.   <FLOWCHART>
  4.     <PRIMARYCODE>FC1</PRIMARYCODE>
  5.     <NAME>Flowchart 1</NAME>
  6.     <STEPS>
  7.       <STEP id="1">was powered on.</STEP>
  8.       <STEP id="2">was not connected with a connection plate.</STEP>
  9.     </STEPS>
  10.   </FLOWCHART>
  11.   <FLOWCHART>
  12.     <PRIMARYCODE>FC2</PRIMARYCODE>
  13.     <NAME>Flowchart2</NAME>
  14.     <STEPS>
  15.       <STEP id="1">was not powered on.</STEP>
  16.       <STEP id="2">was connected with a connection plate.</STEP>
  17.     </STEPS>
  18.   </FLOWCHART>
  19. </CATALOG>

我目前拥有的 Java 代码将打印出所有步骤、流程图代码和流程图描述，但是如何通过整数值请求特定的步骤？

  1. import javax.xml.parsers.DocumentBuilderFactory;
  2. import javax.xml.parsers.DocumentBuilder;
  3. import org.w3c.dom.Document;
  4. import org.w3c.dom.NodeList;
  5. import org.w3c.dom.Node;
  6. import org.w3c.dom.Element;
  7. import java.io.File;
  9. public class Flowchart
  10. {
  11.     public static void main(String argv[])
  12.     {
  13.         try
  14.         {
  15.             // 创建文件类的构造函数并解析 XML 文件
  16.             File file = new File("src/flowchart.xml");
  17.             // 获取文档构建器的实例的工厂
  18.             DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
  19.             // 创建一个解析指定 XML 文件的构建器的实例
  20.             DocumentBuilder db = dbf.newDocumentBuilder();
  21.             Document doc = db.parse(file);
  22.             doc.getDocumentElement().normalize();
  23.             System.out.println("Root element: " + doc.getDocumentElement().getNodeName());
  24.             NodeList nodeList = doc.getElementsByTagName("FLOWCHART");
  25.             // nodeList 不能迭代，因此我们使用 for 循环
  26.             for (int itr = 0; itr < nodeList.getLength(); itr++)
  27.             {
  28.                 Node node = nodeList.item(itr);
  29.                 System.out.println("\nNode Name: " + node.getNodeName());
  30.                 if (node.getNodeType() == Node.ELEMENT_NODE)
  31.                 {
  32.                     Element eElement = (Element) node;
  33.                     System.out.println("Flowchart ID: "+ eElement.getElementsByTagName("PRIMARYCODE").item(0).getTextContent());
  34.                     for (int i = 0; i < (eElement.getElementsByTagName("STEPS").getLength() + 1) ; i++)
  35.                     {
  36.                         System.out.println("Steps: "+ eElement.getElementsByTagName("STEP").item(i).getTextContent());
  37.                     }
  38.                 }
  39.             }
  40.         }
  41.         catch (Exception e)
  42.         {
  43.             e.printStackTrace();
  44.         }
  45.     }
  46. }
英文:

I am trying to parse an XML file to get a "flowchart" step by the step id which is a child element of steps:

  1. &lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot; standalone=&quot;yes&quot;?&gt;
  2. &lt;CATALOG&gt;
  3. &lt;FLOWCHART&gt;
  4. &lt;PRIMARYCODE&gt;FC1&lt;/PRIMARYCODE&gt;
  5. &lt;NAME&gt;Flowchart 1&lt;/NAME&gt;
  6. &lt;STEPS&gt;
  7. &lt;STEP id=&quot;1&quot;&gt;was powered on.&lt;/STEP&gt;
  8. &lt;STEP id=&quot;2&quot;&gt;was not connected with a connection plate.&lt;/STEP&gt;
  9. &lt;/STEPS&gt;
  10. &lt;/FLOWCHART&gt;
  11. &lt;FLOWCHART&gt;
  12. &lt;PRIMARYCODE&gt;FC2&lt;/PRIMARYCODE&gt;
  13. &lt;NAME&gt;Flowchart2&lt;/NAME&gt;
  14. &lt;STEPS&gt;
  15. &lt;STEP id=&quot;1&quot;&gt;was not powered on.&lt;/STEP&gt;
  16. &lt;STEP id=&quot;2&quot;&gt;was connected with a connection plate.&lt;/STEP&gt;
  17. &lt;/STEPS&gt;
  18. &lt;/FLOWCHART&gt;
  19. &lt;/CATALOG&gt;

The Java Code that I have thus far will print all the steps and the flowchart code, and flowchart description but how to I request a specific step by an integer value?

  1. import javax.xml.parsers.DocumentBuilderFactory;
  2. import javax.xml.parsers.DocumentBuilder;
  3. import org.w3c.dom.Document;
  4. import org.w3c.dom.NodeList;
  5. import org.w3c.dom.Node;
  6. import org.w3c.dom.Element;
  7. import java.io.File;
  8. public class Flowchart
  9. {
  10. public static void main(String argv[])
  11. {
  12. try
  13. {
  14. //creating a constructor of file class and parsing an XML file
  15. File file = new File(&quot;src/flowchart.xml&quot;);
  16. //an instance of factory that gives a document builder
  17. DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
  18. //an instance of builder to parse the specified xml file
  19. DocumentBuilder db = dbf.newDocumentBuilder();
  20. Document doc = db.parse(file);
  21. doc.getDocumentElement().normalize();
  22. System.out.println(&quot;Root element: &quot; + doc.getDocumentElement().getNodeName());
  23. NodeList nodeList = doc.getElementsByTagName(&quot;FLOWCHART&quot;);
  24. // nodeList is not iterable, so we are using for loop
  25. for (int itr = 0; itr &lt; nodeList.getLength(); itr++)
  26. {
  27. Node node = nodeList.item(itr);
  28. System.out.println(&quot;\nNode Name: &quot; + node.getNodeName());
  29. if (node.getNodeType() == Node.ELEMENT_NODE)
  30. {
  31. Element eElement = (Element) node;
  32. System.out.println(&quot;Flowchart ID: &quot;+ eElement.getElementsByTagName(&quot;PRIMARYCODE&quot;).item(0).getTextContent());
  33. for (int i = 0; i &lt; (eElement.getElementsByTagName(&quot;STEPS&quot;).getLength() + 1) ; i++)
  34. {
  35. System.out.println(&quot;Steps: &quot;+ eElement.getElementsByTagName(&quot;STEP&quot;).item(i).getTextContent());
  36. }
  37. }
  38. }
  39. }
  40. catch (Exception e)
  41. {
  42. e.printStackTrace();
  43. }
  44. }
  45. }

答案1

得分: 1

为了实现这一目的，使用XPath API会更加方便：

  1. import javax.xml.xpath.XPathExpression;
  2. import javax.xml.xpath.XPathExpressionException;
  3. import javax.xml.xpath.XPathFactory;
  5. public static String getStep(Document doc, String flowchartName, int stepId) throws XPathExpressionException {
  6.     XPathFactory xpf = XPathFactory.newInstance();
  7.     XPathExpression xpath = xpf.newXPath().compile("/CATALOG/FLOWCHART[NAME='" 
  8.             + flowchartName 
  9.             + "']/STEPS/STEP[@id='" 
  10.             + stepId 
  11.             + "']");
  12.     return xpath.evaluate(doc);
  13. }
英文:

For this purpose much more convenient would be usage of XPath API:

  1. import javax.xml.xpath.XPathExpression;
  2. import javax.xml.xpath.XPathExpressionException;
  3. import javax.xml.xpath.XPathFactory;
  4. public static String getStep(Document doc, String flowchartName, int stepId) throws XPathExpressionException {
  5. XPathFactory xpf = XPathFactory.newInstance();
  6. XPathExpression xpath = xpf.newXPath().compile(&quot;/CATALOG/FLOWCHART[NAME=&#39;&quot; 
  7. + flowchartName 
  8. + &quot;&#39;]/STEPS/STEP[@id=&#39;&quot; 
  9. + stepId 
  10. + &quot;&#39;]&quot;);
  11. return xpath.evaluate(doc);
  12. }

huangapple
  • 本文由 发表于 2020年10月1日 09:24:51
  • 转载请务必保留本文链接：https://go.coder-hub.com/64147874.html
  • java
  • parsing
  • xml
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定