如何使用用户输入将另一个XML元素添加到预先存在的文件中？

Question

I have a program that creates a XML file for a music library, with different elements such as artist, album etc. I have hard coded one entry:

        //Root elements
        Document doc = docBuilder.newDocument();
        Element rootElement = doc.createElement("Albums");
        doc.appendChild(rootElement);

        //Album elements
        Element album = doc.createElement("Album");
        rootElement.appendChild(album);

        //Set attribute to album element
        Attr attr = doc.createAttribute("ID");
        attr.setValue("1");
        album.setAttributeNode(attr);

        //Title elements
        Element title = doc.createElement("Title");
        title.appendChild(doc.createTextNode("A Weekend in the City"));
        album.appendChild(title);

        //Artist elements
        Element artist = doc.createElement("Artist");
        artist.appendChild(doc.createTextNode("Bloc Party"));
        album.appendChild(artist);

        //Year elements
        Element year = doc.createElement("Year");
        year.appendChild(doc.createTextNode("2007"));
        album.appendChild(year);

But I want the program to ask the user if they want to add more records to the XML file, this is what I have so far:

        if ((input.equals("Y")) || (input.equals("y")))
        {
            System.out.println("How many records would you like to add?");
            String userInput = scanner.next();
            int numRecords=Integer.parseInt(userInput);

            for (int i=0; i<numRecords; i++)
            {
                System.out.println("Enter the name of the album");
                String getTitle = scanner.nextLine();
                album.appendChild(doc.createTextNode(getTitle));
                album.appendChild(title);
                System.out.println("Enter the name of the artist");
                String getArtist = scanner.nextLine();
                artist.appendChild(doc.createTextNode(getArtist));
                album.appendChild(artist);
                System.out.println("Enter the year the album was released");
                String getYear = scanner.nextLine();
                artist.appendChild(doc.createTextNode(getYear));
                album.appendChild(year);

            } //End for loop

However, this only appends the user input to the existing records rather than creating a new record. Is what I am asking possible?

Sorry if this kind of question has already been answered, couldn't find a similar question anywhere! Thanks in advance.

Answer 1

It sounds like you want to have multiple <Album> elements but your program only creates the 1 <Album> element you hard coded and then appends the title, artist, year elements from user input inside the single <Album> element?

The problem is you are appending to <Album> rather than <Albums> with this line in your for loop:

album.appendChild(doc.createTextNode(getTitle));

Instead of calling appendChild on your existing album variable, you'll need to create a new album variable and append it to rootElement.

Since you'll be using the exact same code to append an <Album> as you did with your hard coded elements, I would suggest creating a method to avoid writing duplicate code, such as:

private void appendAlbum(Element rootElement, String titleStr, String id, String artistStr, String yearStr) {
    Element album = doc.createElement("Album");
    rootElement.appendChild(album);

    //Set attribute to album element
    Attr attr = doc.createAttribute("ID");
    attr.setValue(id);
    album.setAttributeNode(attr);

    //Title elements
    Element title = doc.createElement("Title");
    title.appendChild(doc.createTextNode(titleStr));
    album.appendChild(title);

    //Artist elements
    Element artist = doc.createElement("Artist");
    artist.appendChild(doc.createTextNode(artistStr));
    album.appendChild(artist);

    //Year elements
    Element year = doc.createElement("Year");
    year.appendChild(doc.createTextNode(yearStr));
    album.appendChild(year);
}

The rootElement argument is the <Albums> element you created in your hard coded version.

You can call this method for your hard coded version as well:

appendAlbum(rootElement, "A Weekend in the City", "1", "Bloc Party", "2007")

As a side note you can simplify your program slight by using the equalsIgnoreCase() method to check the user input, instead of checking for upper and lower case Y.

input.equalsIgnoreCase("y")