Java Jaxb Unmarshaller如何处理片段XML – XML的部分读取和写入

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英文:

How does Java Jaxb Unmarshaller handle the fragment xml - the partial reading and writing of xml

问题

这一行会引发异常：

JAXBElement<Fruit> f_file = (JAXBElement<Fruit>) jaxbUnMarshallerFruit.unmarshal(new File("./fruit_in_basket.xml"));

异常的详细信息是：

  1. javax.xml.bind.UnmarshalException: unexpected element (uri:"http://www.lin.com/", local:"fruit"). Expected elements are <{http://www.lin.com/}Document>

从异常信息来看，我猜测 Java 的 jaxbUnMarshaller 无法正确解析泛型类的信息。UnMarshaller 不能只解释 Fruit 类。如何修复它？

另外，还有一个小问题：
jaxbContext = JAXBContext.newInstance(Basket.class);
如果我使用 Basket.class，在解组时会出现错误：

unexpected element (uri:"http://www.lin.com/", local:"Document"). Expected elements are (none)

如果我传递 "com.baeldung.springsoap.basket"，它可以正常工作。为什么？

（我已经搜索了一段时间，但也许我不能用准确的词语描述我的问题，所以我错过了一些东西。如果可能的话，请提供一些回答的链接。）

英文:

I have a XML file:

  1. &lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot; standalone=&quot;yes&quot;?&gt;
  2. &lt;Document xmlns=&quot;http://www.lin.com/&quot;&gt;
  3.     &lt;name&gt;basket1&lt;/name&gt;
  4.     &lt;fruits id=&quot;1&quot;&gt;
  5.         &lt;price&gt;9.99&lt;/price&gt;
  6.         &lt;n&gt;Banana&lt;/n&gt;
  7.     &lt;/fruits&gt;
  8.     &lt;fruits id=&quot;2&quot;&gt;
  9.         &lt;price&gt;19.99&lt;/price&gt;
  10.         &lt;n&gt;Apple&lt;/n&gt;
  11.     &lt;/fruits&gt;
  12. &lt;/Document&gt;

I have entity classes:

  1. package com.baeldung.springsoap.basket;
  3. @XmlType(name = &quot;Document&quot;, propOrder = {&quot;name&quot;, &quot;fruits&quot;})
  4. @XmlAccessorType(XmlAccessType.FIELD)
  5. public class Basket {
  6.     @XmlElement(name = &quot;name&quot;)
  7.     private String name;
  8.     @XmlElement(name = &quot;fruits&quot;, required = true)
  9.     private List&lt;Fruit&gt; fruits;
  11.     public String getName() {
  12.         return name;
  13.     }
  15.     public void setName(String name) {
  16.         this.name = name;
  17.     }
  19.     public List&lt;Fruit&gt; getFruits() {
  20.         return fruits;
  21.     }
  23.     public void setFruits(List&lt;Fruit&gt; fruits) {
  24.         this.fruits = fruits;
  25.     }
  26. }
  28. @XmlType(propOrder = {&quot;price&quot;, &quot;name&quot;})
  29. @XmlAccessorType(XmlAccessType.FIELD)
  30. public class Fruit {
  32.     @XmlAttribute
  33.     int id;
  35.     @XmlElement(name = &quot;n&quot;)
  36.     String name;
  38.     String price;
  40.     public int getId() {
  41.         return id;
  42.     }
  44.     public void setId(int id) {
  45.         this.id = id;
  46.     }
  48.     public String getName() {
  49.         return name;
  50.     }
  52.     public void setName(String name) {
  53.         this.name = name;
  54.     }
  56.     public String getPrice() {
  57.         return price;
  58.     }
  60.     public void setPrice(String price) {
  61.         this.price = price;
  62.     }
  63. }

ObjectFactory.java is:

  1. package com.baeldung.springsoap.basket;
  3. import javax.xml.bind.JAXBElement;
  4. import javax.xml.bind.annotation.XmlElementDecl;
  5. import javax.xml.bind.annotation.XmlRegistry;
  6. import javax.xml.namespace.QName;
  9. @XmlRegistry
  10. public class ObjectFactory {
  12.     private final static QName _Document_QNAME = new QName(&quot;http://www.lin.com/&quot;, &quot;Document&quot;);
  14.     public Fruit createFruit() {
  15.         return new Fruit();
  16.     }
  18.     @XmlElementDecl(namespace = &quot;http://www.lin.com/&quot;, name = &quot;Document&quot;)
  19.     public JAXBElement&lt;Basket&gt; createBasket(Basket value) {
  20.         return new JAXBElement&lt;Basket&gt;(_Document_QNAME, Basket.class, null, value);
  21.     }
  23. }

package-info.java is:

  1. @javax.xml.bind.annotation.XmlSchema(namespace = &quot;http://www.lin.com/&quot;, elementFormDefault = javax.xml.bind.annotation.XmlNsForm.QUALIFIED)
  2. package com.baeldung.springsoap.basket;

Java unmarshal and marshal code:

  1.     public static void run_fruit() {
  2.         try {
  3.             //jaxbContext = JAXBContext.newInstance(Basket.class); // If I use Basket.class,  when unmarshal, it got error: unexpected element (uri:&quot;http://www.lin.com/&quot;, local:&quot;Document&quot;). Expected elements are (none)
  4.             JAXBContext jaxbContext = JAXBContext.newInstance(&quot;com.baeldung.springsoap.basket&quot;); //
  6.             Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
  8.             JAXBElement&lt;Basket&gt; f = (JAXBElement&lt;Basket&gt;) jaxbUnmarshaller.unmarshal(new File(&quot;./basket_fruit.xml&quot;));
  10.             // get a piece of fruit info, will save to file later.
  11.             Basket bb = f.getValue();
  12.             Fruit fruit=bb.getFruits().get(0);
  14.             Marshaller jaxbMarshallerFruit = jaxbContext.createMarshaller();
  16.             // save a piece of fruit info into file
  17.             // in real scenario， we need get a fruit data from list, then save to db as row data.
  18.             JAXBElement&lt;Fruit&gt; jaxbFruit= new JAXBElement&lt;&gt;(new QName(&quot;http://www.lin.com/&quot;, &quot;fruits&quot;), Fruit.class,  fruit);
  19.             jaxbMarshallerFruit.marshal(jaxbFruit, new File(&quot;./fruit_in_basket.xml&quot;));
  21.             // read fruit info from file, convert to java object.
  22.             Unmarshaller jaxbUnMarshallerFruit = jaxbContext.createUnmarshaller();
  23.             JAXBElement&lt;Fruit&gt; f_file = (JAXBElement&lt;Fruit&gt;) jaxbUnMarshallerFruit.unmarshal(new File(&quot;./fruit_in_basket.xml&quot;)); // this line will throw an exception.
  24.             System.out.println(f_file);
  26.         } catch (JAXBException e) {
  27.             e.printStackTrace();
  28.         }
  29.     }

This line will throw an exception.

  1. JAXBElement&lt;Fruit&gt; f_file = (JAXBElement&lt;Fruit&gt;) jaxbUnMarshallerFruit.unmarshal(new File(&quot;./fruit_in_basket.xml&quot;));

The exception detail is:

  1. javax.xml.bind.UnmarshalException: unexpected element (uri:&quot;http://www.lin.com/&quot;, local:&quot;fruit&quot;). Expected elements are &lt;{http://www.lin.com/}Document&gt;
  2. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:726)
  3. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:247)
  4. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:242)
  5. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:109)
  6. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(UnmarshallingContext.java:1131)
  7. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:556)
  8. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:538)
  9. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:153)
  10. 	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:509)
  11. 	at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:374)
  12. 	at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(XMLNSDocumentScannerImpl.java:613)
  13. 	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3132)
  14. 	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:852)
  15. 	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:602)
  16. 	at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:112)
  17. 	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:505)
  18. 	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:842)
  19. 	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:771)
  20. 	at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
  21. 	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
  22. 	at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643)
  23. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:243)
  24. 	at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:214)
  25. 	at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:157)
  26. 	at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:162)
  27. 	at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:171)
  28. 	at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:189)
  29. 	at com.baeldung.springsoap.xxml.JaxbExampleBasket.run_fruit(JaxbExampleBasket.java:48)
  30. 	at com.baeldung.springsoap.xxml.JaxbExampleBasket.main(JaxbExampleBasket.java:21)

From the exception, I guess the Java jaxbUnMarshaller can't figure out the authentic generics class info. UnMarshaller can't only interpret Fruit class. How to fix it?

Another minor question is:

  1. jaxbContext = JAXBContext.newInstance(Basket.class);

If I use Basket.class, when unmarshal, it will get an error:

unexpected element (uri:&quot;http://www.lin.com/&quot;, local:&quot;Document&quot;). Expected elements are (none)

If I pass &quot;com.baeldung.springsoap.basket&quot;, it works. Why?

(I have searched for a while, but maybe I can't describe my question with accurate words, so I missed something. If possible, kindly provide some links to the answer.)

答案1

得分: 0

给 Fruit 类添加 XMLRootElement 应该能消除异常。

  1. @XmlRootElement(name = "fruits")
  2. @XmlType(propOrder = {"price", "name"})
  3. @XmlAccessorType(XmlAccessType.FIELD)
  4. public class Fruit {
  5.     // ...
  6. }
英文:

Give the Fruit class an XMLRootElement should eliminate the exception.

  1. @XmlRootElement(name = &quot;fruits&quot;)
  2. @XmlType(propOrder = {&quot;price&quot;, &quot;name&quot;})
  3. @XmlAccessorType(XmlAccessType.FIELD)
  4. public class Fruit {
  5. ....

huangapple
  • 本文由 发表于 2023年3月7日 18:23:40
  • 转载请务必保留本文链接：https://go.coder-hub.com/75660712.html
  • java
  • jaxb
  • xml
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