Java: reading xml with many nested elements

Question

I have xml that looks somewhat similar to the following. I need to get values from attributes and tags and store them. But i cant understand how to get to level 2(3,4, etc) nested elements. I use following code that i found on the internet, it uses DOM but i cant get correct RegNumber and its attributes. Thanks in advance.

nodeList = xmldocument.getElementsByTagName("Header");      
        if (nodeList != null && nodeList.getLength() > 0) {
            for (int i = 0; i < nodeList.getLength(); i++) {
                //get the header element
                Element header = (Element) nodeList.item(i);
                System.out.println("Element: " + ((Element)nodeList.item(i)).getNodeName());
                System.out.println(header.getAttribute("time"));
            }
        }
        nodeList = xmldocument.getElementsByTagName("Document");      
        if (nodeList != null && nodeList.getLength() > 0) {
            for (int i = 0; i < nodeList.getLength(); i++) {

                //get the document element
                Element document = (Element) nodeList.item(i);
                System.out.println("Element: " + ((Element)nodeList.item(i)).getNodeName());
                System.out.println(document.getAttribute("Id"));

                nodeList = document.getElementsByTagName("RegNumber"); 
                for (int j = 0; j < nodeList.getLength(); j++) {

                    //get the RegNumber element
                    Element regNumber = (Element) nodeList.item(j);
                    System.out.println("Element: " + ((Element)nodeList.item(j)).getNodeName());
                    System.out.println(regNumber.getAttribute("regpoint"));

                }
            }

        }

xml:


            
            
                123/456
                
                
                    456/789
                    
                        
                            
                            
                            2001-12-17T09:30:47Z
                        
                        test@test.com.ua
                        
                    
                
                
    
            
                
                
                    
                    
                
            
            
                
                    
                        
                        
                        2011-12-17T09:30:47Z
                    
                    smirnov@test.com
                    
                
                
                    
                    
                    
                    
                    
                
            
            
                
                    
                    
                        kmu@test.com
                        
                    
                
                
                    kmu@test.com
                    
                    
                        
                        
                        2011-12-17T09:30:47Z
                    
                
                
                    
                    
                    
                    
                    
                
            
            
                
                    
                    
                
                
                    
                        
                        
                    
                    sofki@test.com



edit. As advised i try to figure out JAXB thingy. xjc tool generated 3 classes: ObjectFactory, package-info, XML. I found this code to create object from xml:

public static void main(String[] args) {
        try {

            File file = new File("F:\Untitled3.xml");
            JAXBContext jaxbContext = JAXBContext.newInstance(XML.class);

            Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
            XML xml = (XML) jaxbUnmarshaller.unmarshal(file);
            System.out.println(xml);

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


Is this the correct way, or i need to use ObjectFactory?:

ObjectFactory f =new ObjectFactory();
            XML xml1 = f.createXML();


How do i create object with all tags and attributes, and then create xml file from it? Im new to java and jaxb stuff, so please bear with me.

勿绮语 · Accepted Answer

It is usually not meaningful or commonly useful for method letting you access nodes at certain depth. This is not only about Java, but rather the DOM spec, and I believe that's the right decision.

People usually access nodes through one of many meaningful ways:

Through tag name, and tag name usually indicates the meaning of the node.
XPath - the meaning full structure of the document.
Binding, for example JAXB (basically you are not dealing with XML any more but java classes)
There is the old SAX (not DOM) and StAX (a mixture of DOM and SAX)

Look up xpath and that would be really helpful.

Java: reading xml with many nested elements

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