DOM4J source:

[DOM4J Open Source Package Directory]

How to learn DOM4J?

Detailed illustration::

dom4j-1.6.1/docs/index.html:

Quick start:

★★From here on, we can learn about dom4j★★:

Parsing XML,

Using Iterators,

Powerful Navigation with XPath,

Fast Looping,

Creating a new XML document,

Writing a document to a file,

Converting to and from Strings,

Styling a Document with XSLT

Javadoc:

Start parsing xml documents with dom4j:

The xml document to parse:

<?xml version="1.0" encoding="UTF-8"?>
<users> 
  <user id="A001"> 
    <name>Jack</name>  
    <age>22</age> 
  </user>  
  <user id="A002"> 
    <name>Zhang San</name>  
    <age>24</age> 
  </user>  
  <user id="B001"> 
    <name>petty thief</name>  
    <age>20</age> 
  </user>  
  <user id="B002"> 
    <name>Xiao Zhang</name>  
    <age>28</age> 
  </user>  
  <user id="0777"> 
    <name>Hunan City University</name>  
    <age>1200</age> 
  </user>  


</users>

(1) How to obtain DOM objects through dom4j?

SAXReader sax = new SAXReader();
Document dom = sax.read("./xml/users.xml");

With packages, here we derive the class hierarchy of DOM4J::

(2) How to obtain sub-elements?

(1) To obtain a single sub-element, the following methods are used:

element(String name),

(2) Obtain all the elements by the following methods:

elements(): List
elements(String name): List

(3) Individual elements or all elements can also be obtained by iterators:

elementIterator(): Iterator
elementIterator(String name): Iterator

Code demo:

public void helloDom4j() throws DocumentException {
    // Getting DOM objects
    SAXReader sax = new SAXReader();
    Document dom = sax.read("./xml/users.xml");

    // Get the root element
    Element root = dom.getRootElement();
    // Get the name of the root element
    String rootName = root.getName();
    System.out.println(rootName);
    /*
     * Some ways to get the child elements under the root element: root.elements()// Get all the child elements java.util.List
     * root.element(qName)//Gets the first element of the specified name, root.elements(qName)// Gets all the child elements of the specified name
     * root.elementIterator()//Get all the elements -- iterators
     * root.elementIterator(qName)//Gets all child elements of the specified name
     */

    // Requirements: Extract the first <user> information
    Element eUser = root.element("user");
    String id = eUser.attributeValue("id");
    String name = eUser.element("name").getTextTrim();
    String age = eUser.elementText("age");
    System.out.println(id + "," + name + "," + age);// Results: A001,Jack,22
}

Operation results:

Use DOM4J to add, delete and modify XML documents:

(1) Increase - Increase the last element

// increase---stay root Add one below<hncu>node
@Test
public void add() throws DocumentException, Exception {
    SAXReader sax = new SAXReader();
    Document dom = sax.read("./xml/users.xml");
    Element root = dom.getRootElement();
    // Add node
    Element eHncu = root.addElement("hncu");
    eHncu.addAttribute("id", "0737");
    Element eName = eHncu.addElement("name");
    eName.addText("hunan city university");
    Element eAge = eHncu.addElement("age");
    eAge.addText("15");

    // ////////////////////The following demo saves//////////////////////////////
    // Preservation----Persistence----Character stream to be brushed
    // method1: Simple way-----Pass directly Document One of them writer(writer w)To achieve
    /*
     * FileWriter fw=new FileWriter("./xml/users.xml/"); dom.write(fw);
     * fw.close();
     */
    // method2: Ordinary way-----adopt XMLwriter One of them writer(dom)
    /*
     * 2.1Constructing XMLWriter(OutputStream) XMLWriter xw =new XMLWriter(new
     * FileOutputStream("./xml/users.xml")); xw.write(dom); xw.close();
     */
    /*
     * 2.2Constructing XMLWriter(Writer writer) XMLWriter xw =new XMLWriter(new
     * FileWriter("./xml/users.xml/")); xw.write(dom); xw.close();
     */
    /*
     * 2.3Constructing XML Writer (Writer w, Output Format)
     * format)----Output Format, which can solve the problem of Chinese random code, can be output in a format.
     * format=OutputFormat.createPrettyPrint(); XMLWriter xw=new
     * XMLWriter(new FileOutputStream("./xml/users.xml/"), format);
     * xw.write(dom); xw.close();
     */
    OutputFormat format = OutputFormat.createPrettyPrint();
    XMLWriter xw = new XMLWriter(new FileOutputStream("./xml/users.xml/"),
            format);
    xw.write(dom);
    xw.close();
}

(2) Delete - Delete the last element

// Delete - Delete the last element
@Test
public void del() throws DocumentException, IOException {
    SAXReader sax = new SAXReader();
    Document dom = sax.read("./xml/users.xml");
    Element root = dom.getRootElement();
    List<Element> list = root.elements();
    Element e = list.get(list.size() - 1);
    e.getParent().remove(e);
    // Preservation
    XMLWriter xw = new XMLWriter(new FileOutputStream("./xml/users.xml"));
    xw.write(dom);
    xw.close();
}

(3) Change - modify the last element

// Change - modify the last element
@Test
public void update() throws Exception {
    SAXReader sax = new SAXReader();
    Document dom = sax.read("./xml/users.xml");
    Element root=dom.getRootElement();
    List<Element> list=root.elements();
    Element eLast =list.get(list.size()-1);
    eLast.addAttribute("id", "0777");
    eLast.element("name").setText("Hunan City University");
    eLast.element("age").setText("1200");
    XMLWriter xw=new XMLWriter(new FileOutputStream("./xml/users.xml"));
    xw.write(dom);
    xw.close();

}

(4) Check - traverse all

// Check - traverse all < user >
@Test
public void queryAll() throws DocumentException {
    SAXReader sax = new SAXReader();
    Document dom = sax.read("./xml/users.xml/");
    Element root = dom.getRootElement();
    Iterator<Element> it = root.elementIterator();
    while (it.hasNext()) {
        Element eUser = it.next();
        String id = eUser.attributeValue("id");
        String name = eUser.elementText("name");
        String age = eUser.elementText("age");
        System.out.println(id + "," + name + "," + age);
    }
}