Czy JAXB może najpierw bronić się przed powstrzymywaniem, a następnie przesyłać dalej przez @XmlIDREF w celu uzyskania kolejnych referencji?

Question

Zastanawiam się, czy możliwe jest dodawanie adnotacji do moich klas, tak aby po raz pierwszy, gdy marshaller napotka obiekt, generuje element XML odpowiedniego typu, ale każde kolejne odwołanie do tego obiektu przez cokolwiek innego będzie miało wpis XML IDREF stworzony?

Answer 1

można wykorzystać koncepcję JAXB na XmlAdapter zrobić coś jak następuje:

input.xml

Poniżej znajduje się dokument XML Użyję do tego przykładu. The 3rd phone-number wpis jest nawiązaniem do 1 phone-number wpisu, a 5th phone-number wpis jest nawiązaniem do 4 .:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> 
<customer> 
    <phone-number id="A"> 
     <number>555-AAAA</number> 
    </phone-number> 
    <phone-number id="B"> 
     <number>555-BBBB</number> 
    </phone-number> 
    <phone-number id="A"/> 
    <phone-number xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="work-phone-number" id="W"> 
     <number>555-WORK</number> 
     <extension>1234</extension> 
    </phone-number> 
    <phone-number xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="work-phone-number" id="W"/> 
</customer> 

klientów

Klasa klient utrzymuje kolekcję PhoneNumber obiektów. To samo wystąpienie numeru PhoneNumber może pojawić się wiele razy w kolekcji.

package forum7587095; 

import java.util.List; 

import javax.xml.bind.annotation.XmlElement; 
import javax.xml.bind.annotation.XmlRootElement; 

@XmlRootElement 
public class Customer { 

    private List<PhoneNumber> phoneNumbers; 

    @XmlElement(name="phone-number") 
    public List<PhoneNumber> getPhoneNumbers() { 
     return phoneNumbers; 
    } 

    public void setPhoneNumbers(List<PhoneNumber> phoneNumbers) { 
     this.phoneNumbers = phoneNumbers; 
    } 

} 

PhoneNumber

Jest to klasa, która może pojawić się zarówno w samym dokumencie lub jako odniesienie. Będzie to obsługiwane przy użyciu XmlAdapter. XmlAdapter jest skonfigurowany przy użyciu adnotacji @XmlJavaTypeAdapter. Ponieważ mamy określony adaptera na poziomie typu/klasy będzie ona miała zastosowanie do wszystkich właściwości odwołujących klasę PhoneNumber:

package forum7587095; 

import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter; 

@XmlJavaTypeAdapter(PhoneNumberAdapter.class) 
public class PhoneNumber { 

    private String id; 
    private String number; 

    public String getId() { 
     return id; 
    } 

    public void setId(String id) { 
     this.id = id; 
    } 

    public String getNumber() { 
     return number; 
    } 

    public void setNumber(String number) { 
     this.number = number; 
    } 

    @Override 
    public boolean equals(Object arg0) { 
     if(null == arg0 || arg0.getClass() != this.getClass()) { 
      return false; 
     } 
     PhoneNumber test = (PhoneNumber) arg0; 
     if(!equals(id, test.getId())) { 
      return false; 
     } 
     return equals(number, test.getNumber()); 
    } 

    protected boolean equals(String control, String test) { 
     if(null == control) { 
      return null == test; 
     } else { 
      return control.equals(test); 
     } 
    } 

    @Override 
    public int hashCode() { 
     return id.hashCode(); 
    } 

} 

WorkPhoneNumber

Oparte na Twój komentarz dodałem podklasę PhoneNumber.

package forum7587095; 

public class WorkPhoneNumber extends PhoneNumber { 

    private String extension; 

    public String getExtension() { 
     return extension; 
    } 

    public void setExtension(String extension) { 
     this.extension = extension; 
    } 

    @Override 
    public boolean equals(Object arg0) { 
     if(!super.equals(arg0)) { 
      return false; 
     } 
     return equals(extension, ((WorkPhoneNumber) arg0).getExtension()); 
    } 

} 

PhoneNumberAdapter

Poniżej jest realizacja XmlAdapter. Zauważ, że musimy zachować, jeśli obiekt PhoneNumber był wcześniej widziany. Jeśli tak jest, wypełniamy tylko część obiektu id obiektu .

package forum7587095; 

import java.util.ArrayList; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map; 

import javax.xml.bind.annotation.XmlAttribute; 
import javax.xml.bind.annotation.XmlSeeAlso; 
import javax.xml.bind.annotation.XmlType; 
import javax.xml.bind.annotation.adapters.XmlAdapter; 

public class PhoneNumberAdapter extends XmlAdapter<PhoneNumberAdapter.AdaptedPhoneNumber, PhoneNumber>{ 

    private List<PhoneNumber> phoneNumberList = new ArrayList<PhoneNumber>(); 
    private Map<String, PhoneNumber> phoneNumberMap = new HashMap<String, PhoneNumber>(); 

    @XmlSeeAlso(AdaptedWorkPhoneNumber.class) 
    @XmlType(name="phone-number") 
    public static class AdaptedPhoneNumber { 
     @XmlAttribute public String id; 
     public String number; 

     public AdaptedPhoneNumber() { 
     } 

     public AdaptedPhoneNumber(PhoneNumber phoneNumber) { 
      id = phoneNumber.getId(); 
      number = phoneNumber.getNumber(); 
     } 

     public PhoneNumber getPhoneNumber() { 
      PhoneNumber phoneNumber = new PhoneNumber(); 
      phoneNumber.setId(id); 
      phoneNumber.setNumber(number); 
      return phoneNumber; 
     } 

    } 

    @XmlType(name="work-phone-number") 
    public static class AdaptedWorkPhoneNumber extends AdaptedPhoneNumber { 

     public String extension; 

     public AdaptedWorkPhoneNumber() { 
     } 

     public AdaptedWorkPhoneNumber(WorkPhoneNumber workPhoneNumber) { 
      super(workPhoneNumber); 
      extension = workPhoneNumber.getExtension(); 
     } 

     @Override 
     public WorkPhoneNumber getPhoneNumber() { 
      WorkPhoneNumber phoneNumber = new WorkPhoneNumber(); 
      phoneNumber.setId(id); 
      phoneNumber.setNumber(number); 
      phoneNumber.setExtension(extension); 
      return phoneNumber; 
     } 
} 

    @Override 
    public AdaptedPhoneNumber marshal(PhoneNumber phoneNumber) throws Exception { 
     AdaptedPhoneNumber adaptedPhoneNumber; 
     if(phoneNumberList.contains(phoneNumber)) { 
      if(phoneNumber instanceof WorkPhoneNumber) { 
       adaptedPhoneNumber = new AdaptedWorkPhoneNumber(); 
      } else { 
       adaptedPhoneNumber = new AdaptedPhoneNumber(); 
      } 
      adaptedPhoneNumber.id = phoneNumber.getId(); 
     } else { 
      if(phoneNumber instanceof WorkPhoneNumber) { 
       adaptedPhoneNumber = new AdaptedWorkPhoneNumber((WorkPhoneNumber)phoneNumber); 
      } else { 
       adaptedPhoneNumber = new AdaptedPhoneNumber(phoneNumber); 
      } 
      phoneNumberList.add(phoneNumber); 
     } 
     return adaptedPhoneNumber; 
    } 

    @Override 
    public PhoneNumber unmarshal(AdaptedPhoneNumber adaptedPhoneNumber) throws Exception { 
     PhoneNumber phoneNumber = phoneNumberMap.get(adaptedPhoneNumber.id); 
     if(null != phoneNumber) { 
      return phoneNumber; 
     } 
     phoneNumber = adaptedPhoneNumber.getPhoneNumber(); 
     phoneNumberMap.put(phoneNumber.getId(), phoneNumber); 
     return phoneNumber; 
    } 

} 

Demo

Aby zapewnić tę samą instancję XmlAdapter służy do całych marshal i unmarshal operacji musimy szczegółowo określone wystąpienie XmlAdapter zarówno na Marshaller i Unmarshaller:

package forum7587095; 

import java.io.File; 

import javax.xml.bind.JAXBContext; 
import javax.xml.bind.Marshaller; 
import javax.xml.bind.Unmarshaller; 

public class Demo { 

    public static void main(String[] args) throws Exception { 
     JAXBContext jc = JAXBContext.newInstance(Customer.class); 

     Unmarshaller unmarshaller = jc.createUnmarshaller(); 
     unmarshaller.setAdapter(new PhoneNumberAdapter()); 
     File xml = new File("src/forum7587095/input.xml"); 
     Customer customer = (Customer) unmarshaller.unmarshal(xml); 

     System.out.println(customer.getPhoneNumbers().get(0) == customer.getPhoneNumbers().get(2)); 
     System.out.println(customer.getPhoneNumbers().get(3) == customer.getPhoneNumbers().get(4)); 

     Marshaller marshaller = jc.createMarshaller(); 
     marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); 
     marshaller.setAdapter(new PhoneNumberAdapter()); 
     marshaller.marshal(customer, System.out); 
    } 

} 

Wyjście

true 
true 
<?xml version="1.0" encoding="UTF-8" standalone="yes"?> 
<customer> 
    <phone-number id="A"> 
     <number>555-AAAA</number> 
    </phone-number> 
    <phone-number id="B"> 
     <number>555-BBBB</number> 
    </phone-number> 
    <phone-number id="A"/> 
    <phone-number xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="work-phone-number" id="W"> 
     <number>555-WORK</number> 
     <extension>1234</extension> 
    </phone-number> 
    <phone-number xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="work-phone-number" id="W"/> 
</customer> 

Aby uzyskać więcej informacji

• http://blog.bdoughan.com/2011/09/mixing-nesting-and-references-with.html
• http://blog.bdoughan.com/2010/10/jaxb-and-shared-references-xmlid-and.html
• http://blog.bdoughan.com/search/label/XmlAdapter
• http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-xsitype.html
• http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-substitution.html