Dom4j操作XML文件

1. 创建并写入XML

    public static void writeXML(String filename){
        try {
            Document document = DocumentHelper.createDocument();
            Element root = document.addElement("PortConfig");
            Element ePort;

            ePort = root.addElement("Port");
            ePort.addAttribute("Portname", "portBloodpress");
            ePort.addAttribute("Portnumber", "COM12");

            ePort = root.addElement("Port");
            ePort.addAttribute("Portname", "portWah");
            ePort.addAttribute("Portnumber", "COM14");

            ePort = root.addElement("Port");
            ePort.addAttribute("Portname", "portBloodsugar");
            ePort.addAttribute("Portnumber", "COM16");

            ePort = root.addElement("Port");
            ePort.addAttribute("Portname", "portBloodfat");
            ePort.addAttribute("Portnumber", "COM18");

            ePort = root.addElement("Port");
            ePort.addAttribute("Portname", "portUric");
            ePort.addAttribute("Portnumber", "COM20");

            OutputFormat format = new OutputFormat("    ", true);
            XMLWriter output = new XMLWriter(new FileWriter(new File(filename)), format);
            output.write(document);
            output.close();

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

首先用DocumentHelper创建一个Document对象，然后给Document添加一个Element，也就是根Element；然后可以在这个根Element下面添加若干个Element，每一个Element用addAttribute()添加了属性名称和属性值；最后，使用XMLWriter把Document写入文件。

2. 读取并解析XML

    public static void readXML(String filename){

        try {
            SAXReader saxReader = new SAXReader();
            Document document = saxReader.read(filename);
            // 获取根节点
            Element portConfig = document.getRootElement();
            for (Iterator i = portConfig.elementIterator(); i.hasNext();) {
                Element port = (Element) i.next();
                String aname = port.attributeValue("Portname");
                String avalue = port.attributeValue("Portnumber");
                if (aname.equals("portBloodpress")){
                    Constant.portBloodpress = avalue;
                }
                else if (aname.equals("portWah")){
                    Constant.portWah = avalue;
                }
                else if (aname.equals("portBloodsugar")){
                    Constant.portBloodsugar = avalue;
                }
                else if (aname.equals("portBloodfat")){
                    Constant.portBloodfat = avalue;
                }
                else if (aname.equals("portUric")){
                    Constant.portUric = avalue;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

首先创建一个SAXReader，用这个SAXReader读出一个Document；然后获得这个Document的根Element，迭代获得根Element下面的每一个Element，对每一个Element，使用attributeValue()获得它的属性值。

3. 更新XML

    public static void updateXML(String filename){
        try {
            File f = new File(filename);
            SAXReader saxReader = new SAXReader();
            Document document = saxReader.read(curDir + "\\port_config.xml");
            // 获取根节点
            Element portConfig = document.getRootElement();
            for (Iterator i = portConfig.elementIterator(); i.hasNext();) {
                Element port = (Element) i.next();
                String aname = port.attributeValue("Portname");
                if (aname.equals("portBloodpress")){
                    port.setAttributeValue("Portnumber", Constant.portBloodpress);
                }
                else if (aname.equals("portWah")){
                    port.setAttributeValue("Portnumber", Constant.portWah);
                }
                else if (aname.equals("portBloodsugar")){
                    port.setAttributeValue("Portnumber", Constant.portBloodsugar);
                }
                else if (aname.equals("portBloodfat")){
                    port.setAttributeValue("Portnumber", Constant.portBloodfat);
                }
                else if (aname.equals("portUric")){
                    port.setAttributeValue("Portnumber", Constant.portUric);
                }
            }
            XMLWriter output = new XMLWriter(new FileWriter(new File(curDir + "\\port_config.xml")));
            output.write(document);
            output.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

更新和读取的过程差不多，只是对需要更新的属性用setAttributeValue()方法更新，最后再用XMLWriter写入文件。

XML文件：

<?xml version="1.0" encoding="UTF-8"?>
<PortConfig>
    <Port Portname="portBloodpress" Portnumber="COM126"/>
    <Port Portname="portWah" Portnumber="COM146"/>
    <Port Portname="portBloodsugar" Portnumber="COM166"/>
    <Port Portname="portBloodfat" Portnumber="COM186"/>
    <Port Portname="portUric" Portnumber="COM206"/>
</PortConfig>