用Java-Dom Parser解析多级XML文件

Question

我有一个xml文件，它包含3个类别：employee_list、position_details和employee_info。

<?xml version="1.0" encoding="UTF-8"?>
<employee>
<employee_list>
<employee ID="1">
<firstname>Andrei</firstname>
<lastname>Rus</lastname>
<age>23</age>
<position-skill ref="Java"/>
<detail-ref ref="AndreiR"/>
</employee>
<employee ID="2">
<firstname>Ion</firstname>
<lastname>Popescu</lastname>
<age>25</age>
<position-skill ref="Python"/>
<detail-ref ref="IonP"/>
</employee>
<employee ID="3">
<firstname>Georgiana</firstname>
<lastname>Domide</lastname>
<age>33</age>
<position-skill ref="C"/>
<detail-ref ref="GeorgianaD"/>
</employee>
</employee_list>
<position_details>
<position ID="Java">
<role>Junior Developer</role>
<skill_name>Java</skill_name>
<experience>1</experience><!-- years of experience -->
</position>
<position ID="Python">
<role>Developer</role>
<skill_name>Python</skill_name>
<experience>3</experience> 
</position>
<position ID="C">
<role>Senior Developer</role>
<skill_name>C</skill_name>
<experience>5</experience>
</position>
</position_details>
<employee_info>
<detail ID="AndreiR">
<username>AndreiR</username>
<residence>Timisoara</residence>
<yearOfBirth>1999</yearOfBirth>
<phone>0</phone>
</detail>
<detail ID="IonP">
<username>IonP</username>
<residence>Timisoara</residence>
<yearOfBirth>1997</yearOfBirth>
<phone>0</phone>
</detail>
<detail ID="GeorgianaD">
<username>GeorgianaD</username>
<residence>Arad</residence>
<yearOfBirth>1989</yearOfBirth>
<phone>0</phone>
</detail>
</employee_info>
</employee>

我想为所有三个类别编写java代码，但到目前为止，我只成功地通过了第一个类别(employee_list)。当我试图从position_list或employee_info类别中检索信息时，程序无法根据每个类别找到信息。

我为这三个类别编写了Java代码，结果如下：

package Dom;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
public class main {
public static void main(String[] args) {
try {
File xmlDoc = new File("employees.xml");
DocumentBuilderFactory dbFact = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuild = dbFact.newDocumentBuilder(); 
Document doc = dBuild.parse(xmlDoc);

//Citim radacina
//                                    doc localizeaza radacina   da numele ei
System.out.println("Root element: " + doc.getDocumentElement().getNodeName());
System.out.println("-----------------------------------------------------------------------------");

//citim un array de studenti pe care il denumim NodeList
NodeList nList = doc.getElementsByTagName("employee");
System.out.println("Total Category inside = " + nList.getLength());
System.out.println("-----------------------------------------------------");


for(int i = 0 ; i<nList.getLength();i++) {
Node nNode = nList.item(i);
//System.out.println("Node name: " + nNode.getNodeName()+" " + (i+1));
if(nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Person id#: " + eElement.getAttribute("id"));
System.out.println("Person Last Name: " + eElement.getElementsByTagName("lastname").item(0).getTextContent());
System.out.println("Person First name: " + eElement.getElementsByTagName("firstname").item(0).getTextContent());
System.out.println("Person Age: " + eElement.getElementsByTagName("age").item(0).getTextContent());
System.out.println("--------------------------------------------------------------------------");
}
}

System.out.println("=============================================================================================");

nList = doc.getElementsByTagName("position");
System.out.println("Total Category inside = " + nList.getLength());
System.out.println("-----------------------------------------------------");
for(int i = 0 ; i<nList.getLength();i++) {
Node nNode = nList.item(i);
//System.out.println("Node name: " + nNode.getNodeName()+" " + (i+1));
if(nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Role: " + eElement.getElementsByTagName("role").item(0).getTextContent());
System.out.println("Skill: "+ eElement.getElementsByTagName("skill_name").item(0).getTextContent());
System.out.println("Experience: "+ eElement.getElementsByTagName("experience").item(0).getTextContent());
System.out.println("--------------------------------------------------------------------------");
}
}

System.out.println("=============================================================================================");

nList = doc.getElementsByTagName("detail");
System.out.println("Total Category inside = " + nList.getLength());
System.out.println("-----------------------------------------------------");
for(int i = 0 ; i<nList.getLength();i++) {
Node nNode = nList.item(i);
//System.out.println("Node name: " + nNode.getNodeName()+" " + (i+1));
if(nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Person with username: " +  eElement.getElementsByTagName("username").item(0).getTextContent());
System.out.println("Username: " + eElement.getElementsByTagName("username").item(0).getTextContent());
System.out.println("Residence: "+ eElement.getElementsByTagName("residence").item(0).getTextContent());
System.out.println("Year of birth: "+ eElement.getElementsByTagName("yearOfBirth").item(0).getTextContent());
System.out.println("Phone: "+ eElement.getElementsByTagName("phone").item(0).getTextContent());
System.out.println("--------------------------------------------------------------------------");
}
}


}catch(Exception e) {

}

}
}

输出：

Root element: employee
-----------------------------------------------------------------------------
Total Category inside = 4
-----------------------------------------------------
Person id#: 
Person Last Name: Rus
Person First name: Andrei
Person Age: 23
--------------------------------------------------------------------------
Person id#: 
Person Last Name: Rus
Person First name: Andrei
Person Age: 23
--------------------------------------------------------------------------
Person id#: 
Person Last Name: Popescu
Person First name: Ion
Person Age: 25
--------------------------------------------------------------------------
Person id#: 
Person Last Name: Domide
Person First name: Georgiana
Person Age: 33
--------------------------------------------------------------------------
=============================================================================================
Total Category inside = 3
-----------------------------------------------------
Role: Junior Developer
Skill: Java
Experience: 1
--------------------------------------------------------------------------
Role: Developer
Skill: Python
Experience: 3
--------------------------------------------------------------------------
Role: Senior Developer
Skill: C
Experience: 5
--------------------------------------------------------------------------
=============================================================================================
Total Category inside = 3
-----------------------------------------------------
Person with username: AndreiR
Username: AndreiR
Residence: Timisoara
Year of birth: 1999
Phone: 0
--------------------------------------------------------------------------
Person with username: IonP
Username: IonP
Residence: Timisoara
Year of birth: 1997
Phone: 0
--------------------------------------------------------------------------
Person with username: GeorgianaD
Username: GeorgianaD
Residence: Arad
Year of birth: 1989
Phone: 0
--------------------------------------------------------------------------

是否有可能对输出进行稍微更多的分组，每个人采用以下形式：

PersonId
firstname
lastname
age
role
skill_name
experience
username
residence
yearOfBirth
phone

Answer 1

但您基本上已经完成了，您为这三个类别编写了代码"未能根据每个类别找到信息"；可能意味着输出不是期望的输出。原因可能是Document.getElementsByTagName()全局搜索所有将名称作为参数传递的元素。由于您的根元素也被命名为employee，因此它作为附加的Node包含在doc.getElementsByTagName("employee")上的NodeList中，顺便说一句，它没有自己的ID属性(注意：这些是区分大小写的)。因此；内部总类别＝4〃；。如果你在第一个Node/Element上做getElementsByTagName("lastname")，那就是根，果不其然，它下面有一个<lastname/>元素，只是不是直接的子元素，而是向下两级，第一个"；实际的"/期望的CCD_ 10。

因此，您可能想做的不是全局搜索元素名称，而是在类别的本地上下文中搜索，就像您已经在循环中的其他地方成功地搜索到的那样。也许只是改变

NodeList nList = doc.getElementsByTagName("employee");

至

NodeList nList = doc.getElementsByTagName("employee_list");
nList = ((Element)nList.item(0)).getElementsByTagName("employee");

employee_list类别，其他类别也是如此。

为了更好地对记录进行分组，您不需要立即输出/打印它们。您可以将从DOM获得的值复制/存储在您可以定义的类的对象的成员中，或者创建一个更通用的类，将字段值存储在包含Map的List中，或者类似的类。这样，您就可以对创建的对象或列表进行迭代/循环，并按您喜欢的顺序输出/打印字段值。