问题描述
我正在学习如何用Java编写解析器,并且在编写新的SAX XML解析器时遇到了问题。这是我得到的错误:
线程“ main”中的异常java.lang.NullPointerException
在 org.example.shoesshop.parser.SAXParser.characters(SAXParser.java:112) 在 com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.characters(AbstractSAXParser.java:546) 在 com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.characters(XMLSchemaValidator.java:812) 在 com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:455) 在 com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:841) 在 com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:770) 在 com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141) 在 com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213) 在 com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl $ JAXPSAXParser.parse(SAXParserImpl.java:643) 在 com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl.parse(SAXParserImpl.java:327) 在javax.xml.parsers.SAXParser.parse(SAXParser.java:195)在 org.example.shoesshop.parser.SAXParser.parse(SAXParser.java:61)在 org.example.shoesshop.parser.SAXParser.main(SAXParser.java:136)
这是SAX Parser的代码:
public class SAXParser extends DefaultHandler{
private static boolean logEnabled = true;
public static void log(Object o) {
if (logEnabled) {
System.out.println(o);
}
}
private String current;
private Brand brand;
private Category category;
private Gender gender;
private Season season;
private Shoes shoes;
private Shoes.Details details;
private ShoesShop shoesShop;
private String titleParent;
public ShoesShop getShoesShop(){
return shoesShop;
}
@Override
public void error(org.xml.sax.SAXParseException e) throws SAXException {
throw e;
};
public List<ShoesShop> parse(InputStream in) throws ParserConfigurationException,SAXException,IOException{
List<ShoesShop> shoesShop = new ArrayList<>();
SAXParserFactory factory = SAXParserFactory.newInstance();
factory.setNamespaceAware(true);
factory.setFeature("http://xml.org/sax/features/validation",true);
factory.setFeature("http://apache.org/xml/features/validation/schema",true);
javax.xml.parsers.SAXParser parser = factory.newSAXParser();
parser.parse(in,this); //line 61 error
return shoesShop;
}
@Override
public void startElement(String uri,String localName,String qName,Attributes attributes) throws SAXException{
System.out.println(localName);
current = localName;
if("ShoesShop".equals(current)){
shoesShop = new ShoesShop();
return;
}
if("Shoes".equals(current)){
shoes = new Shoes();
return;
}
}
@Override
public void characters(char[] ch,int start,int length) throws SAXException {
String elementText = new String(ch,start,length);
if (elementText.isEmpty()){
System.out.println("empty");
return;
}
else if ("title".equals(current)) {
if ("title".equals(titleParent)){
shoes.setTitle(new String (new String(ch,length)));
return;
}
}
else if("category".equals(current)){
shoes.setCategory(Category.fromValue(new String(ch,length)));
return;
}
else if ("brand".equals(current)) {
shoes.setBrand(Brand.fromValue(new String(ch,length))); // line 112 error
return;
}
else if("season".equals(current)){
shoes.setSeason(Season.fromValue(new String(ch,length)));
return;
}
else if("price".equals(current)) {
shoes.setPrice(new Double(new String(ch,length)));
return;
}
}
@Override
public void endElement(String uri,String qName) throws SAXException {
if("ShoesShop".equals(localName)){
shoesShop.getShoes().add(shoes);
return;
}
}
public static void main(String[] args) throws FileNotFoundException,ParserConfigurationException,IOException,TransformerException {
SAXParser parser = new SAXParser();
parser.parse(new FileInputStream("ShoesShop.xml")); // line 136 error
ShoesShop shoesShop = parser.getShoesShop();
String outputXmlFile = "sax.xml";
System.out.println("SAX Parser");
System.out.println();
System.out.println("Result: \n" + shoesShop);
System.out.println();
}
}
这是XML文件
<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:ShoesShop>
这是鞋类
@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",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();
}
}
解决方法
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