使用javadom解析器解析xml

我不熟悉Java和XML，需要从XML文件中获取一些数据

这是我的xml

<?xml version="1.0" encoding="UTF-8"?>
<course name="BSc (Hons) Software Engineering" version="5.0" type="FT" lowerbound="2012" upperbound="2014" >
   <year id="1">
      <semester id="1">
         <module>
            <code>HCA1105C</code>
            <name>Computer Architecture</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>PROG1115C</code>
            <name>Object Oriented Software Development I</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>MATH1103C</code>
            <name>Decision Mathematics</name>
            <credits>3</credits>
            <hrs_per_wk>2+1</hrs_per_wk>
         </module>
         <module>
            <code>ITE1107C</code>
            <name>Language and Communication Seminar</name>
            <credits>3</credits>
            <hrs_per_wk>2+1</hrs_per_wk>
         </module>
         <module>
            <code>MGMT1101C</code>
            <name>Management Seminar</name>
            <credits>3</credits>
            <hrs_per_wk>2+1</hrs_per_wk>
         </module>
      </semester>
      <semester id="2">
         <module>
            <code>PROG1116C</code>
            <name>Object Oriented Software Development II</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>WAT1116C</code>
            <name>Internet Programming I</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>MATH1101C</code>
            <name>Analytic Methods for Computing</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>DBT1111C</code>
            <name>Database Design</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
      </semester>
   </year>
   <year id="2">
      <semester id="1">
         <module>
            <code>CAN2112C</code>
            <name>Network Design &amp; Programming</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>WAT2117C</code>
            <name>Internet Programming II</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>OSS2109C</code>
            <name>Operating Systems</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>PROG2117C</code>
            <name>Desktop Application Development</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
      </semester>
      <semester id="2">
         <module>
            <code>SDT2114C</code>
            <name>Requirements Engineering</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>MATH2323C</code>
            <name>Numerical Methods</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>MCT2104C</code>
            <name>Mobile Application Development</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>MCT2104C</code>
            <name>Mobile Application Development</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>WAT2124C</code>
            <name>Web Services</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>MGMT2104C</code>
            <name>Research &amp; Development Seminar</name>
            <credits>3</credits>
            <hrs_per_wk>2+1</hrs_per_wk>
         </module>
      </semester>
   </year>
   <year id="3">
      <semester id="1">
         <module>
            <code>SECU3119C</code>
            <name>Secure Software Development</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>MULT3114C</code>
            <name>Game Development</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>SEM3112C</code>
            <name>Project Management Seminar</name>
            <credits>3</credits>
            <hrs_per_wk>2+1</hrs_per_wk>
         </module>
      </semester>
      <semester id="2">
         <module>
            <code>SDT3104C</code>
            <name>Enterprise Software Development</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>WAT3125C</code>
            <name>Emerging Web Technologies</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>SEM3113C</code>
            <name>Software Quality Management</name>
            <credits>4</credits>
            <hrs_per_wk>2+2</hrs_per_wk>
         </module>
         <module>
            <code>MGMT3105C</code>
            <name>Entrepreneurship Seminar</name>
            <credits>3</credits>
            <hrs_per_wk>2+1</hrs_per_wk>
         </module>
         <module>
            <code>PROJ3105C</code>
            <name>Systems Development Project</name>
            <credits>9</credits>
            <hrs_per_wk />
         </module>
      </semester>
   </year>
</course>

假设我想得到第一学期第一年的所有模块代码

HCA1105C
PROG1115C
MATH1103C
ITE1107C
MGMT1101C

这是到目前为止我的代码

try {   
    File inputFile = new File(System.getProperty("user.dir") + "/courses/bse.xml");
        DocumentBuilderFactory dbFactory
                = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(inputFile);
        doc.getDocumentElement().normalize();
        NodeList nList = doc.getElementsByTagName("year");
        for (int i = 0; i < nList.getLength(); i++) {
            Node nNode = nList.item(i);
            if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                Element eElement = (Element) nNode;
               //if (Integer.parseInt(eElement.getAttribute("id")) == 1 ) {
                   System.out.println(eElement.getElementsByTagName("code").item(0).getTextContent());
               //}
            }
        }
    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, e.getMessage(), "Fatal Error", JOptionPane.ERROR_MESSAGE);
        System.exit(1);
    }

---

您的代码正在读取每年的第一个模块。这是因为，对于您指定的标准，节点列表将有3个节点：year=1、year=2、year=3

如果您想阅读第1年的所有模块，那么您需要以year=1递归到文档的子部分。然后你就可以拿到学期结单了。您需要进一步递归到学期=1的孩子

您可以尝试使用带有xpath的查询，在这里您可以直接获得year=1和term=1的模块

使用XPath修改代码进行编辑：

try {   
    File inputFile = new File("courses.xml");
        DocumentBuilderFactory dbFactory
                = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(inputFile);
        doc.getDocumentElement().normalize();

        XPath xPath =  XPathFactory.newInstance().newXPath();
        String expression = "/course/year[@id=1]/semester[@id=1]/module/code";
        NodeList nodeList = (NodeList) xPath.compile(expression).evaluate(doc, XPathConstants.NODESET);
        System.out.println(expression);
        for (int i = 0; i < nodeList.getLength(); i++) {
            System.out.println(nodeList.item(i).getTextContent()); 
        }
    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, e.getMessage(), "Fatal Error", JOptionPane.ERROR_MESSAGE);
        System.exit(1);
    }

---

检查子节点并深入查看模块将给出如下预期结果

public static void main(String[] args) {
        try {
            File inputFile = new File("Snippet.xml");
            DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
            Document doc = dBuilder.parse(inputFile);
            doc.getDocumentElement().normalize();
            NodeList nList = doc.getElementsByTagName("year");
            for (int i = 0; i < nList.getLength(); i++) {
                Node nNode = nList.item(i);
                if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                    Element eElement = (Element) nNode;
                    if (Integer.parseInt(eElement.getAttribute("id")) == 1) { // Found year 1
                        NodeList semeterList = nNode.getChildNodes();
                        for (int j = 0; j < semeterList.getLength(); j++) {
                            nNode = semeterList.item(j);
                            if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                                Element semesterNode = (Element) nNode;
                                if (Integer.parseInt(semesterNode.getAttribute("id")) == 1) { //Found semester 1
                                    NodeList moduleList = semesterNode.getChildNodes();
                                    for (int k = 0; k < moduleList.getLength(); k++) {
                                        nNode = moduleList.item(k);
                                        if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                                            Element modeluNode = (Element) nNode;
                                            System.out.println(modeluNode.getElementsByTagName("code").item(0).getTextContent());
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
            JOptionPane.showMessageDialog(null, e.getMessage(), "Fatal Error", JOptionPane.ERROR_MESSAGE);
            System.exit(1);
        }
    }

---

我们可以使用以下代码通过DOM获取所有代码：

try {   
        File inputFile = new File("src/resources/res.xml");
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(inputFile);
        doc.getDocumentElement().normalize();
        NodeList nList = doc.getElementsByTagName("module");
        for (int i = 0; i < nList.getLength(); i++) {
             Node nNode = nList.item(i);
             if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                 Element eElement = (Element) nNode;
                 System.out.println(eElement.getElementsByTagName("code").item(0).getTextContent());
             }
        }
     } catch (Exception e) {
            JOptionPane.showMessageDialog(null, e.getMessage(), "Fatal Error", JOptionPane.ERROR_MESSAGE);
            System.exit(1);
      }

我们还可以通过每年->学期->模块循环获取代码，然后获取属性代码。上述代码给出了以下结果：

HCA1105C PROG1115C MATH1103C ITE1107C MGMT1101C PROG1116C 瓦特1116C 数学1101C DBT1111C CAN2112C WAT2117C OSS2109C PROG2117C SDT2114C 数学2323C MCT2104C MCT2104C WAT2124C MGMT2104C SECU3119C MULT3114C SEM3112C SDT3104C 瓦特3125C SEM3113C MGMT3105C

---

PROJ3105C

稍微修改一下，获取模块节点，然后从那里获取代码。取决于您是否需要任何额外信息。但这应该是首选答案。

try {   
        File inputFile = new File("src/resources/res.xml");
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(inputFile);
        doc.getDocumentElement().normalize();
        NodeList nList = doc.getElementsByTagName("module");
        for (int i = 0; i < nList.getLength(); i++) {
             Node nNode = nList.item(i);
             if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                 Element eElement = (Element) nNode;
                 System.out.println(eElement.getElementsByTagName("code").item(0).getTextContent());
             }
        }
     } catch (Exception e) {
            JOptionPane.showMessageDialog(null, e.getMessage(), "Fatal Error", JOptionPane.ERROR_MESSAGE);
            System.exit(1);
      }