Java 为什么在运行StAX解析器时会出现NullPointerException?
我正试图用Java编写一个STAXXML解析器,但总是得到NullPointerException错误。请帮我解决这个问题。完整问题: 线程“main”java.lang.NullPointerException中的异常位于 org.example.shoesshop.parser.STAXParser.parseXMLfile(STAXParser.java:68) 位于org.example.shoesshop.parser.STAXParser.main(STAXParser.java:101) 这里有一个用于StAX解析器的类:Java 为什么在运行StAX解析器时会出现NullPointerException?,java,xml,parsing,xml-parsing,stax,Java,Xml,Parsing,Xml Parsing,Stax,我正试图用Java编写一个STAXXML解析器,但总是得到NullPointerException错误。请帮我解决这个问题。完整问题: 线程“main”java.lang.NullPointerException中的异常位于 org.example.shoesshop.parser.STAXParser.parseXMLfile(STAXParser.java:68) 位于org.example.shoesshop.parser.STAXParser.main(STAXParser.java:1
public class STAXParser extends DefaultHandler {
private static List<Shoes> parseXMLfile(String fileName){
List<Shoes> shoesList = new ArrayList<>();
Shoes shoes = null;
XMLInputFactory xmlInputFactory = XMLInputFactory.newInstance();
try {
XMLEventReader reader = xmlInputFactory.createXMLEventReader(new FileInputStream(fileName));
while (reader.hasNext()){
XMLEvent xmlEvent = reader.nextEvent();
if(xmlEvent.isStartElement()){
StartElement startElement = xmlEvent.asStartElement();
if(startElement.getName().getLocalPart().equals("Shoes")){
shoes = new Shoes();
Attribute idAttr = startElement.getAttributeByName(new QName("id"));
if(idAttr != null){
shoes.setId(Integer.parseInt(idAttr.getValue()));
}
} else if (startElement.getName().getLocalPart().equals("title")){
xmlEvent = reader.nextEvent();
shoes.setTitle(xmlEvent.asCharacters().getData()); // error line 68
} else if (startElement.getName().getLocalPart().equals("brand")){
xmlEvent = reader.nextEvent();
shoes.setBrand(Brand.fromValue(xmlEvent.asCharacters().getData()));
} else if (startElement.getName().getLocalPart().equals("category")){
xmlEvent = reader.nextEvent();
shoes.setCategory(Category.fromValue(xmlEvent.asCharacters().getData()));
} else if (startElement.getName().getLocalPart().equals("season")){
xmlEvent = reader.nextEvent();
shoes.setSeason(Season.fromValue(xmlEvent.asCharacters().getData()));
} else if (startElement.getName().getLocalPart().equals("price")){
xmlEvent = reader.nextEvent();
shoes.setPrice(Double.parseDouble(xmlEvent.asCharacters().getData()));
}
}
if(xmlEvent.isEndElement()){
EndElement endElement = xmlEvent.asEndElement();
if(endElement.getName().getLocalPart().equals("Shoes")){
shoesList.add(shoes);
}
}
}
} catch (FileNotFoundException | XMLStreamException exc) {
exc.printStackTrace();
} return shoesList;
}
public static void main(String[] args) throws Exception {
System.out.println("STAX Parser");
System.out.println();
System.out.println("Result: \n");
System.out.println();
String fileName = "ShoesShop.xml";
List<Shoes> shoesList = parseXMLfile(fileName); //error line 101
for (Shoes shoes:shoesList){
System.out.println(shoes.toString());
}
}
}
公共类STAXParser扩展了DefaultHandler{
私有静态列表parseXMLfile(字符串文件名){
List shoesList=new ArrayList();
Shoes=null;
XMLInputFactory XMLInputFactory=XMLInputFactory.newInstance();
试一试{
XMLEventReader=xmlInputFactory.createXMLEventReader(新文件输入流(文件名));
while(reader.hasNext()){
XMLEvent=reader.nextEvent();
if(xmlEvent.isStartElement()){
StartElement StartElement=xmlEvent.asStartElement();
if(startElement.getName().getLocalPart().equals(“鞋”)){
鞋=新鞋();
Attribute idAttr=startElement.getAttributeByName(新的QName(“id”));
如果(idAttr!=null){
setId(Integer.parseInt(idAttr.getValue());
}
}else if(startElement.getName().getLocalPart().equals(“title”)){
xmlEvent=reader.nextEvent();
setTitle(xmlEvent.asCharacters().getData());//错误行68
}else if(startElement.getName().getLocalPart().equals(“品牌”)){
xmlEvent=reader.nextEvent();
setBrand(Brand.fromValue(xmlEvent.asCharacters().getData());
}else if(startElement.getName().getLocalPart().equals(“类别”)){
xmlEvent=reader.nextEvent();
setCategory(Category.fromValue(xmlEvent.asCharacters().getData());
}else if(startElement.getName().getLocalPart().equals(“季节”)){
xmlEvent=reader.nextEvent();
Season(Season.fromValue(xmlEvent.asCharacters().getData());
}else if(startElement.getName().getLocalPart().equals(“price”)){
xmlEvent=reader.nextEvent();
setPrice(Double.parseDouble(xmlEvent.asCharacters().getData());
}
}
if(xmlEvent.isEndElement()){
EndElement EndElement=xmlEvent.asEndElement();
如果(endElement.getName().getLocalPart().equals(“鞋”)){
鞋类列表。添加(鞋子);
}
}
}
}catch(FileNotFoundException | XMLStreamException exc){
exc.printStackTrace();
}退货清单;
}
公共静态void main(字符串[]args)引发异常{
System.out.println(“STAX解析器”);
System.out.println();
System.out.println(“结果:\n”);
System.out.println();
字符串fileName=“shoessshop.xml”;
List shoesList=parseXMLfile(文件名);//错误行101
用于(鞋:鞋列表){
System.out.println(shoes.toString());
}
}
}
这是一个XML文件
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type = "text/xsl" href = "ShoesShop.xsl"?>
<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:gender>
<ss:male>male</ss:male>
</ss:gender>
<ss:details>
<ss:highlights>Highlights text 1</ss:highlights>
<ss:composition>Composition text 1</ss:composition>
</ss:details>
<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:gender>
<ss:female>female</ss:female>
</ss:gender>
<ss:details>
<ss:highlights>Highlights text 2</ss:highlights>
<ss:composition>Composition text 2</ss:composition>
</ss:details>
<ss:price>364.0</ss:price>
</ss:shoes>
<ss:shoes id="3" stock="true" mostWanted = "true">
<ss:title>Korfu</ss:title>
<ss:brand>Mary Katrantzou</ss:brand>
<ss:category>Sneakers</ss:category>
<ss:season>spring</ss:season>
<ss:gender>
<ss:female>female</ss:female>
</ss:gender>
<ss:details>
<ss:highlights>Highlights text 3</ss:highlights>
<ss:composition>Composition text 3</ss:composition>
</ss:details>
<ss:price>173.0</ss:price>
</ss:shoes>
</ss:ShoesShop>
香脂
古琦
靴子
落下
男性的
突出显示文本1
作文课文1
734
阿马尔菲
迪奥
骡子
冬天
女的
突出显示文本2
作文课文2
364
科夫岛
玛丽·卡特兰佐
运动鞋
春天
女的
突出显示文本3
作文课文3
173
这里还有一个鞋的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;
}
}
@Override
public String toString(){
StringBuilder builder = new StringBuilder();
builder.append("[title=");
builder.append(title);
builder.append(", brand=");
builder.append(brand);
builder.append(", category=");
builder.append(category);
builder.append(", season=");
builder.append(season);
builder.append(", price=");
builder.append(price);
builder.append("]");
return builder.toString();
}
}
@xmlacessortype(xmlacesstype.FIELD)
@XmlType(name=“Shoes”,比例器={
“头衔”,
“品牌”,
“类别”,
“季节”,
“性别”,
“详情”,
“价格”
})
公营鞋
扩展实体
{
@XmlElement(必需=true)
受保护的字符串标题;
@XmlElement(必需=true)
@XmlSchemaType(name=“string”)
保护品牌;
@XmlElement(必需=true)
@XmlSchemaType(name=“string”)
保护类别;
@XmlElement(必需=true)
@XmlSchemaType(name=“string”)
保护季节;
@XmlElement(必需=true)
保护鞋。性别;
@XmlElement(必需=true)
保护鞋。细节;
保护双重价格;
@xmltattribute(name=“stock”,required=true)
受保护股票;
@XmlAttribute(name=“mostWanted”)
受保护的布尔mostWanted;
公共字符串getTitle(){
返回标题;
}
公共void setTitle(字符串值){
this.title=值;
}
公共品牌{
回归品牌;
}
公共品牌(品牌价值){
这个品牌=价值;
}
公共类别getCategory(){
退货类别;
}
公共无效集合类别(类别值){
这个类别=价值;
}
公众季节{
回归季节;
}
公共无效设置季节(季节值){
这个季节=价值;
}
公共鞋{
返回性别;
}
公共空间设置性别(Shoes.Gender值){
性别=价值;
}
公共鞋。详细信息getDetails(){
退货详情;
}
public void setDetails(Shoes.Details值){
this.details=值;
}
公开双价{
退货价格;
}
公共定价(双倍值){
价格=价值;
}
公共布尔值isStock(){
退货;
}
公共v