JAVA 解析 XML

XML文件时很多项目经常使用的配置或者其他用途的文件格式，解析xml文件格式的开发包也很多，本文主要使用java自带的DOM解析包。本文以一个实际例子来讲述解析xml文件的过程。

目标：解析这样一个XML文件

employees.xml

=======内容开始========

<?xml version="1.0" encoding="UTF-8"?>
<Personnel>
<Employee type="permanent">
<Name>Seagull</Name>
<Id>3674</Id>
<Age>34</Age>
</Employee>
<Employee type="contract">
<Name>Robin</Name>
<Id>3675</Id>
<Age>25</Age>
</Employee>
<Employee type="permanent">
<Name>Crow</Name>
<Id>3676</Id>
<Age>28</Age>
</Employee>
</Personnel>

=======内容结束========

目标是：输出如下内容

Employee Details - Name:Seagull, Type:permanent, Id:3674, Age:34.

Employee Details - Name:Robin, Type:contract, Id:3675, Age:25.

Employee Details - Name:Crow, Type:permanent, Id:3676, Age:28.

主要步骤

1，

• Get a document builder using document builder factory and parse the xml file to create a DOM object
• Get a list of employee elements from the DOM
• For each employee element get the id, name, age and type. Create an employee value object and add it to the list.
• At the end iterate through the list and print the employees to verify we parsed it right.

a) 获取document builder

public void parseXmlFile(){ //get the factory DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); try { //Using factory get an instance of document builder DocumentBuilder db = dbf.newDocumentBuilder(); //parse using builder to get DOM representation of the XML file System.out.println("start to parse"); org.w3c.dom.Document dom = db.parse("employees.xml"); parseDocument(dom); }catch(ParserConfigurationException pce) { pce.printStackTrace(); }catch(SAXException se) { se.printStackTrace(); }catch(IOException ioe) { ioe.printStackTrace(); } }

b) 获取employee elements列表
Get the rootElement from the DOM object.From the root element get all employee elements. Iterate through each employee element to load the data.

private void parseDocument(Document dom){ //get the root element Element docEle = dom.getDocumentElement(); //get a nodelist of elements NodeList nl = docEle.getElementsByTagName("Employee"); if(nl != null && nl.getLength() > 0) { for(int i = 0 ; i < nl.getLength();i++) { //get the employee element Element el = (Element)nl.item(i); //get the Employee object Employee e = getEmployee(el); //add it to list myEmpls.add(e); } } }

c)读取每个员工的信息

/** * I take an employee element and read the values in, create * an Employee object and return it */ private Employee getEmployee(Element empEl) { //for each <employee> element get text or int values of //name ,id, age and name String name = getTextValue(empEl,"Name"); int id = getIntValue(empEl,"Id"); int age = getIntValue(empEl,"Age"); String type = empEl.getAttribute("type"); //Create a new Employee with the value read from the xml nodes Employee e = new Employee(name,id,age,type); return e; } /** * I take a xml element and the tag name, look for the tag and get * the text content * i.e for <employee><name>John</name></employee> xml snippet if * the Element points to employee node and tagName is 'name' I will return John */ private String getTextValue(Element ele, String tagName) { String textVal = null; NodeList nl = ele.getElementsByTagName(tagName); if(nl != null && nl.getLength() > 0) { Element el = (Element)nl.item(0); textVal = el.getFirstChild().getNodeValue(); } return textVal; } /** * Calls getTextValue and returns a int value */ private int getIntValue(Element ele, String tagName) { //in production application you would catch the exception return Integer.parseInt(getTextValue(ele,tagName)); }

d) I打印输出

public void printData(){ System.out.println("No of Employees '" + myEmpls.size() + "'."); for(Employee emp : myEmpls){ System.out.println("Employee Details -"+ "Name:"+emp.getName()+" ID:"+emp.getID()+" Age:" +emp.getAge()+" Type:"+emp.getType()); } }

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