java 使用 jdom 向现有 xml 添加内容
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adding content to existing xml with jdom
提问by Boyen
package xml.dierenshop.flaming.v1;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.output.XMLOutputter;
import org.jdom2.output.Format;
import java.io.FileWriter;
import java.io.IOException;
public class Writer {
public void Writer(String categorie, String code, String naamartikel, String beschrijvingartikel, double prijz, String imgurl, String imgurl2, String imgurl3, String imgurl4, String imgurl5) {
String prijs = String.valueOf(prijz);
Document document = new Document();
Element root = new Element("productlist");
String naamelement = "naam";
String categorieelement = "category";
String descriptionelement = "description";
Element child = new Element("product");
child.addContent(new Element(categorieelement).setText(categorie));
child.addContent(new Element("code").setText(code));
child.addContent(new Element(naamelement).setText(naamartikel));
child.addContent(new Element(descriptionelement).setText(beschrijvingartikel));
child.addContent(new Element("price").setText(prijs));
child.addContent(new Element("image").setText(imgurl));
child.addContent(new Element("image").setText(imgurl2));
child.addContent(new Element("image").setText(imgurl3));
child.addContent(new Element("image").setText(imgurl4));
child.addContent(new Element("image").setText(imgurl5));
root.addContent(child);
document.setContent(root);
try {
FileWriter writer = new FileWriter("products.xml");
XMLOutputter outputter = new XMLOutputter();
outputter.setFormat(Format.getPrettyFormat());
outputter.output(document, writer);
outputter.output(document, System.out);
} catch (IOException e) {
e.printStackTrace();
}
}
}
This is my class for writing an xml file with variables from my main class. The output here would be :
这是我的类，用于使用我的主类中的变量编写 xml 文件。这里的输出将是：
Now I have a problem, the next time I run this java application I want it to add a new product but keep the old one. However every time I try this, it replaces the old data with the new data.
现在我遇到了一个问题，下次我运行这个 java 应用程序时，我希望它添加一个新产品但保留旧产品。但是，每次我尝试这样做时，它都会用新数据替换旧数据。
回答by A4L
Basically, you need to load an existing xml file and make a Documentof it by parsing it and getting the root element from it. If the file does not exist then create a new document and a new root element. After that you can go on with the code you have shown.
基本上，您需要加载一个现有的 xml 文件并Document通过解析它并从中获取根元素来制作它。如果该文件不存在，则创建一个新文档和一个新的根元素。之后，您可以继续使用您显示的代码。
Create a class Productto hold product data. Passing product data each as argument to a method is a no-go.
创建一个类Product来保存产品数据。将每个产品数据作为参数传递给方法是不行的。
Product class (for simplicity all fields are public, this not a good practice, you should make them at least protected and for each a getter and a setter method)
产品类（为简单起见，所有字段都是公开的，这不是一个好习惯，您应该至少使它们受保护，并为每个字段设置一个 getter 和一个 setter 方法）
public class Product {
public String categorie;
public String code;
public String naamartikel;
public String beschrijvingartikel;
public double prijz;
public String imgurl;
public String imgurl2;
public String imgurl3;
public String imgurl4;
public String imgurl5;
}
Writer method
写法
public static void Writer(Product product) throws JDOMException, IOException {
Document document = null;
Element root = null;
File xmlFile = new File("products.xml");
if(xmlFile.exists()) {
// try to load document from xml file if it exist
// create a file input stream
FileInputStream fis = new FileInputStream(xmlFile);
// create a sax builder to parse the document
SAXBuilder sb = new SAXBuilder();
// parse the xml content provided by the file input stream and create a Document object
document = sb.build(fis);
// get the root element of the document
root = document.getRootElement();
fis.close();
} else {
// if it does not exist create a new document and new root
document = new Document();
root = new Element("productlist");
}
String prijs = String.valueOf(product.prijz);
String naamelement = "naam";
String categorieelement = "category";
String descriptionelement = "description";
Element child = new Element("product");
child.addContent(new Element(categorieelement).setText(product.categorie));
child.addContent(new Element("code").setText(product.code));
child.addContent(new Element(naamelement).setText(product.naamartikel));
child.addContent(new Element(descriptionelement).setText(product.beschrijvingartikel));
child.addContent(new Element("price").setText(prijs));
child.addContent(new Element("image").setText(product.imgurl));
child.addContent(new Element("image").setText(product.imgurl2));
child.addContent(new Element("image").setText(product.imgurl3));
child.addContent(new Element("image").setText(product.imgurl4));
child.addContent(new Element("image").setText(product.imgurl5));
root.addContent(child);
document.setContent(root);
try {
FileWriter writer = new FileWriter("products.xml");
XMLOutputter outputter = new XMLOutputter();
outputter.setFormat(Format.getPrettyFormat());
outputter.output(document, writer);
outputter.output(document, System.out);
writer.close(); // close writer
} catch (IOException e) {
e.printStackTrace();
}
}
and finally a little test
最后是一个小测试
public static void main(String[] args) throws JDOMException, IOException {
Product product = null;
product = new Product();
product.categorie = "cat1";
product.code = "code1";
product.naamartikel = "naam1";
product.beschrijvingartikel = "beschrijving1";
product.prijz = 100d;
product.imgurl = "http://localhost/img1.png";
product.imgurl2 = "http://localhost/img2.png";
product.imgurl3 = "http://localhost/img3.png";
product.imgurl4 = "http://localhost/img5.png";
product.imgurl5 = "http://localhost/img5.png";
Writer(product);
product = new Product();
product.categorie = "cat2";
product.code = "code2";
product.naamartikel = "naam2";
product.beschrijvingartikel = "beschrijving2";
product.prijz = 200d;
product.imgurl = "http://localhost/img21.png";
product.imgurl2 = "http://localhost/img22.png";
product.imgurl3 = "http://localhost/img23.png";
product.imgurl4 = "http://localhost/img25.png";
product.imgurl5 = "http://localhost/img25.png";
Writer(product);
product = new Product();
product.categorie = "cat3";
product.code = "code3";
product.naamartikel = "naam3";
product.beschrijvingartikel = "beschrijving3";
product.prijz = 300d;
product.imgurl = "http://localhost/img31.png";
product.imgurl2 = "http://localhost/img32.png";
product.imgurl3 = "http://localhost/img33.png";
product.imgurl4 = "http://localhost/img35.png";
product.imgurl5 = "http://localhost/img35.png";
Writer(product);
}
Also, file name products.xmlshould not be hard coded in java file; instead pass it as an argument when you run the program.
此外，文件名products.xml不应硬编码在 java 文件中；而是在运行程序时将其作为参数传递。
回答by gxet4n
Replace root=document.getRootElement();by
替换root=document.getRootElement();为
root = document.detachRootElement();
because an Element can be associated to only one document in jdom.
因为一个 Element 在 jdom 中只能关联到一个文档。
回答by gxet4n
Before setting root as the content of document use:
在将 root 设置为文档内容之前使用：
root = root.detach();
because an Element can be associated to only one document in jdom.
因为一个 Element 在 jdom 中只能关联到一个文档。
