Java XML DOM 写入新信息而不覆盖以前的信息

Question

我正在尝试构建一个日历，我希望将所有约会存储在 XML 文件中，但是，我似乎找不到如何执行此操作。我一直在阅读有类似问题的人的答案，但似乎没有任何效果，这是我拥有的 DOM 类，“createDocument”方法的所有输入都来自文本框:

import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.*;


public class GeneradorDOM {
    private Document doc;


    public GeneradorDOM() throws ParserConfigurationException {
        DocumentBuilderFactory factoria = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factoria.newDocumentBuilder();
        doc = builder.newDocument();
    }


    public void createDocument(String hour, int day, int month, int year, String name,
                               String lastName, String title, String description,String row, String column) throws IOException{

        Element root = doc.getDocumentElement();
        Element appointment = doc.createElement("appointment");

/* Instead of root,  I have tried with the following code as well:
        Element appointments = doc.createElement("appointments");
        doc.appendChild(appointments);

        Element appointment = doc.createElement("appointment");
        appointments.appendChild(appointment);
*/

        Element nameElement = doc.createElement("name");
        Text nameText = doc.createTextNode(name);
        appointment.appendChild(nameElement);
        nameElement.appendChild(nameText);
        appointment.appendChild(nameElement);

        Element lastNameElement = doc.createElement("lastname");
        Text lastNameText = doc.createTextNode(lastName);
        appointment.appendChild(lastNameElement);
        lastNameElement.appendChild(lastNameText);
        appointment.appendChild(lastNameElement);

        Element dayElement = doc.createElement("day");
        Text dayText = doc.createTextNode(Integer.toString(day));
        appointment.appendChild(dayElement);
        dayElement.appendChild(dayText);


        Element monthElement = doc.createElement("month");
        Text monthText = doc.createTextNode(Integer.toString(month));
        appointment.appendChild(monthElement);
        monthElement.appendChild(monthText);

        Element yearElement = doc.createElement("year");
        Text yearText = doc.createTextNode(Integer.toString(year));
        appointment.appendChild(yearElement);
        yearElement.appendChild(yearText);

        Element hourElement = doc.createElement("hour");
        Text hourText = doc.createTextNode(hour);
        appointment.appendChild(hourElement);
        hourElement.appendChild(hourText);



        Element titleElement = doc.createElement("title");
        Text titleText = doc.createTextNode(title);
        appointment.appendChild(titleElement);
        titleElement.appendChild(titleText);

        Element descriptionElement = doc.createElement("description");
        Text descriptionText = doc.createTextNode(description);
        appointment.appendChild(descriptionElement);
        descriptionElement.appendChild(descriptionText);

        Element rowElement = doc.createElement("row");
        Text rowText = doc.createTextNode(row);
        appointment.appendChild(rowElement);
        rowElement.appendChild(rowText);

        Element columnElement = doc.createElement("column");
        Text columnText = doc.createTextNode(column);
        appointment.appendChild(columnElement);
        columnElement.appendChild(columnText);

        root.appendChild(appointment);

    }

    public void generateXML() throws TransformerConfigurationException, IOException, TransformerException{
        TransformerFactory factoria = TransformerFactory.newInstance();
        Transformer transformer = factoria.newTransformer();

        Source source = new DOMSource(doc);
        File file = new File("Appointments.xml");
        FileWriter fw = new FileWriter(file);
        PrintWriter pw = new PrintWriter(fw);

        StreamResult result = new StreamResult(new FileOutputStream("Appointments.xml", true));

        transformer.transform(source, result);

    }
}

Answer 1

这是一个很好的起点，基本上你不能创建一个空的 xml 并读取并解析为 DOM 对象，因为你会看到一个异常。

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Calendar;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Text;
import org.xml.sax.SAXException;

public class PersisterAppointment {

    private static String APPOINTMENT_FILE_NAME = "Appointments.xml"; 

    public static void main(String args[]){
        PersisterAppointment demo = new PersisterAppointment();
        try {
            demo.persistAppointment("Edgard","Rendón",Calendar.getInstance(),"Title field","Description field","row field","column field");
            demo.persistAppointment("Brandon","Ramirez",Calendar.getInstance(),"Title field","Description field","row field","column field");
        } catch (ParserConfigurationException | TransformerException | SAXException | IOException e) {
            e.printStackTrace();
        }
    }

    public boolean isAppointment(){
        File file = new File(APPOINTMENT_FILE_NAME);
        return file.exists();
    }

    public void persistAppointment(String iname, String ilastname, Calendar calendar, String ititle, String idescription, String irow, String icolumn) throws ParserConfigurationException, TransformerException, SAXException, IOException{
        DocumentBuilderFactory docfactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder docbuilder = docfactory.newDocumentBuilder();
        Document doc;

        if(isAppointment()){
            InputStream is = new FileInputStream(APPOINTMENT_FILE_NAME);
            doc = docbuilder.parse(is);
        }else{
            doc = docbuilder.newDocument();
        }

        TransformerFactory tfactory = TransformerFactory.newInstance();
        Transformer transformer = tfactory.newTransformer();


        Source source = new DOMSource(doc);
        File file = new File(APPOINTMENT_FILE_NAME);


        Element appointment = doc.createElement("appointment");
        doc.appendChild(appointment);


        Element ename = doc.createElement("name");
        Element elastname = doc.createElement("lastname");
        Element eday = doc.createElement("day");
        Element emonth = doc.createElement("month");
        Element eyear = doc.createElement("year");
        Element ehour = doc.createElement("hour");
        Element etitle = doc.createElement("title");
        Element edescription = doc.createElement("description");
        Element erow = doc.createElement("row");
        Element ecolumn = doc.createElement("column");

        Text tname = doc.createTextNode(iname);
        Text tlastname = doc.createTextNode(ilastname);
        Text tday = doc.createTextNode(String.valueOf(calendar.get(Calendar.DAY_OF_MONTH)));
        Text tmonth = doc.createTextNode(String.valueOf(calendar.get(Calendar.MONTH)));
        Text tyear = doc.createTextNode(String.valueOf(calendar.get(Calendar.YEAR)));
        Text thour = doc.createTextNode(String.valueOf(calendar.get(Calendar.HOUR_OF_DAY)));
        Text ttitle = doc.createTextNode(ititle);
        Text tdescription = doc.createTextNode(idescription);
        Text trow = doc.createTextNode(irow);
        Text tcolumn = doc.createTextNode(icolumn);


        ename.appendChild(tname);
        elastname.appendChild(tlastname);
        eday.appendChild(tday);
        emonth.appendChild(tmonth);
        eyear.appendChild(tyear);
        ehour.appendChild(thour);
        etitle.appendChild(ttitle);
        edescription.appendChild(tdescription);
        erow.appendChild(trow);
        ecolumn.appendChild(tcolumn);

        appointment.appendChild(ename);
        appointment.appendChild(elastname);
        appointment.appendChild(eday);
        appointment.appendChild(emonth);
        appointment.appendChild(eyear);
        appointment.appendChild(ehour);
        appointment.appendChild(etitle);
        appointment.appendChild(edescription);
        appointment.appendChild(erow);
        appointment.appendChild(ecolumn);

        StreamResult result = new StreamResult(file);

            transformer.transform(source, result);
        }
    }
}

您只需要修改代码即可在现有的xml文件中添加新节点