StAX Parser 创建一个空的 XML 文件

Question

我正在学习 Java 中的解析器，现在我正在尝试使用 StAX Parser 和 XMLStreamWriter 以及 StringWriter 编写用于 XML 文件创建的代码。 但是我遇到了一个问题，即我的解析器创建了一个空的 XML 文件。 我认为问题在于使用 for 循环，但我不知道如何解决。 这是一段代码：

public class STAXParser4 {
...
public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException, TransformerException { 
...
        try (FileWriter fileWriter = new FileWriter("STAX1ShoesShop.xml")){
            StringWriter stringWriter = new StringWriter();
            XMLOutputFactory xmlOutputFactory = XMLOutputFactory.newInstance();
            XMLStreamWriter xmlStreamWriter = xmlOutputFactory.createXMLStreamWriter(stringWriter);
            
            xmlStreamWriter.writeStartDocument();
            xmlStreamWriter.writeStartElement("ss:ShoesShop");
            ShoesShop shoesShop = new ShoesShop();
            
            for(Shoes shoes: shoesShop.getShoes()){ 
                xmlStreamWriter.writeStartElement("ss:shoes");
                xmlStreamWriter.writeAttribute("id", String.valueOf(shoes.getId()));
                
                xmlStreamWriter.writeStartElement("ss:title");
                xmlStreamWriter.writeCharacters(shoes.getTitle());
                xmlStreamWriter.writeEndElement();
                
                xmlStreamWriter.writeStartElement("ss:brand");
                xmlStreamWriter.writeCharacters(shoes.getBrand().toString());
                xmlStreamWriter.writeEndElement();
                
                xmlStreamWriter.writeStartElement("ss:category");
                xmlStreamWriter.writeCharacters(shoes.getCategory().toString());
                xmlStreamWriter.writeEndElement();
                
                xmlStreamWriter.writeStartElement("ss:season");
                xmlStreamWriter.writeCharacters(shoes.getSeason().toString());
                xmlStreamWriter.writeEndElement();
                
                xmlStreamWriter.writeStartElement("ss:price");
                xmlStreamWriter.writeCharacters(String.valueOf(shoes.getPrice()));
                xmlStreamWriter.writeEndElement();
                
                xmlStreamWriter.writeEndElement();
            } 
            xmlStreamWriter.writeEndElement();
            xmlStreamWriter.writeEndDocument();
            
            xmlStreamWriter.flush();
            xmlStreamWriter.close();
        } catch (XMLStreamException | IOException e) {
            e.printStackTrace();
        }
        
    }
}

这里还有一个用于鞋类的 Java 类

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "Shoes", propOrder = {
    "title",
    "brand",
    "category",
    "season",
    "gender",
    "details",
    "price"
})
public class Shoes
    extends Entity
{
    @XmlElement(required = true)
    protected String title;
    @XmlElement(required = true)
    @XmlSchemaType(name = "string")
    protected Brand brand;
    @XmlElement(required = true)
    @XmlSchemaType(name = "string")
    protected Category category;
    @XmlElement(required = true)
    @XmlSchemaType(name = "string")
    protected Season season;
    @XmlElement(required = true)
    protected Shoes.Gender gender;
    @XmlElement(required = true)
    protected Shoes.Details details;
    protected double price;
    @XmlAttribute(name = "stock", required = true)
    protected boolean stock;
    @XmlAttribute(name = "mostWanted")
    protected Boolean mostWanted;

    public String getTitle() {
        return title;
    }

    public void setTitle(String value) {
        this.title = value;
    }
    
    public Brand getBrand(){
        return brand;
    }
    
    public void setBrand(Brand value){
        this.brand = value;
    }
    
    public Category getCategory(){
        return category;
    }
    
    public void setCategory(Category value){
        this.category = value;
    }
    
    public Season getSeason(){
        return season;
    }
    
    public void setSeason(Season value) {
        this.season = value;
    }

    public Shoes.Gender getGender() {
        return gender;
    }

    public void setGender(Shoes.Gender value) {
        this.gender = value;
    }

    public Shoes.Details getDetails() {
        return details;
    }

    public void setDetails(Shoes.Details value) {
        this.details = value;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double value) {
        this.price = value;
    }

    public boolean isStock() {
        return stock;
    }

    public void setStock(boolean value) {
        this.stock = value;
    }

    public Boolean isMostWanted() {
        return mostWanted;
    }

    public void setMostWanted(Boolean value) {
        this.mostWanted = value;
    }

    @XmlAccessorType(XmlAccessType.FIELD)
    @XmlType(name = "", propOrder = {

    })
    public static class Details {

        @XmlElement(required = true)
        protected String highlights;
        @XmlElement(required = true)
        protected String composition;

        public String getHighlights() {
            return highlights;
        }

        public void setHighlights(String value) {
            this.highlights = value;
        }

        public String getComposition() {
            return composition;
        }

        public void setComposition(String value) {
            this.composition = value;
        }

    }

    @XmlAccessorType(XmlAccessType.FIELD)
    @XmlType(name = "", propOrder = {
        "\u043c\u0443\u0436\u0441\u043a\u043e\u0439Or\u0416\u0435\u043d\u0441\u043a\u0438\u0439"
    })
    public static class Gender {

        @XmlElementRefs({
            @XmlElementRef(name = "\u0436\u0435\u043d\u0441\u043a\u0438\u0439", namespace = "http://www.example.org/ShoesShop", type = JAXBElement.class, required = false),
            @XmlElementRef(name = "\u043c\u0443\u0436\u0441\u043a\u043e\u0439", namespace = "http://www.example.org/ShoesShop", type = JAXBElement.class, required = false)
        })
        protected List<JAXBElement<String>> maleOrFemale;

        public List<JAXBElement<String>> getMaleOrFemale() {
            if (maleOrFemale == null) {
                maleOrFemale = new ArrayList<JAXBElement<String>>();
            }
            return this.maleOrFemale;
        }
    }
}

鞋子的数据： shoesShop.getShoes 我从另一个 XML 文件中获得。 这是该文件的一个片段：

<ss:ShoesShop xmlns:ss="http://www.example.org/ShoesShop" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://www.example.org/ShoesShop ShoesShop.xsd ">
      <ss:shoes id="1" stock="true">
        <ss:title>Baltrum</ss:title>
        <ss:brand>Gucci</ss:brand>
        <ss:category>Boots</ss:category>
        <ss:season>fall</ss:season>
        <ss:price>734.0</ss:price>
      </ss:shoes>
  <ss:shoes id="2" stock="true" mostWanted = "true">
    <ss:title>Amalfi</ss:title>
    <ss:brand>Dior</ss:brand>
    <ss:category>Mules</ss:category>
    <ss:season>winter</ss:season>
    <ss:price>364.0</ss:price>
  </ss:shoes>
</ss:ShoesShop>

Answer 1

问题是您正在将输出写入stringWriter但它与您的输出文件没有任何联系。
尝试用stringWriter替换fileWriter ，您将看到 xml 写入输出文件：

    try (FileWriter fileWriter = new FileWriter("STAX1ShoesShop.xml")){
        XMLOutputFactory xmlOutputFactory = XMLOutputFactory.newInstance();
        XMLStreamWriter xmlStreamWriter = xmlOutputFactory.createXMLStreamWriter(fileWriter);