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Re: XML

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Mon, 8 Aug 2016 05:38:22 -0700 (PDT), Eric Douglas:
> On Sunday, August 7, 2016 at 12:04:28 PM UTC-4, Stanimir Stamenkov 
> wrote:
>
>> That's because your Customer class is not annotated as/bound to a 
>> top-level XML element type (it really helps understanding the XML 
>> Schema model in this context). Try using @XmlRootElement on it:
>>
>> @XmlRootElement
>> public class Customer extends DataRecord {
>>
>> I think @XmlSeeAlso(DataFile.class) on the Customer class is 
>> superfluous. In certain situations you may need it the other way 
>> around:
>>
>> @XmlSeeAlso(Customer.class)
>> public class DataRecord { 
>
> There are a number of confusing things in the JAXB, those are a 
> couple of them.
>
> Does it make any sense to put @XmlRootElement on Customer?

That what my remark about understanding the XML Schema model was. 
The @XmlRootElement declares a top-level element type which might be 
used as document root element, but might appear as a child in 
certain content models as well.  Because you've used this DataRecord 
abstraction you need to have top-level element types if you want 
different elements to appear in a List<DataRecord>.

> It appears to work the same with or without it, and when 
> marshalled to the file it will never be the root. DataFile is the 
> root, that is it's purpose. The only purpose of DataRecord is to 
> be something generic the DataFile can store as a collection. 
> Customer, and other classes, extend the DataRecord to define a 
> single record. One file starts with none of these, typically has 
> many Customers (or items, orders, etc).
>
> Does it make sense to use the @XmlSeeAlso?

I've finally tried the whole of your example and discovered more 
discrepancies – see my reworked example at the end.

> If I put the XmlSeeAlso on the Customer to point to the DataFile I 
> can just pass the Customer class to the JAXBContext.newInstance, 
> which can accept multiple classes, and gets the same output if I 
> add the DataFile class there instead. Perhaps this tag doesn't 
> make sense in either direction at this level, but to cascade 
> further down such as storing a collection of something ie shipping 
> addresses within each customer?
>
> Is every XML file supposed to have that 
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" at least on 
> the root node? I tried what methods I could find and couldn't get 
> it to go away, or write a different value. That looks like a 
> useful url but seems like a waste of space to write it to every file.

Try my example (single "JAXBtoXML.java" file):

import java.util.ArrayList;
import java.util.List;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementRef;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlSeeAlso;
import javax.xml.bind.annotation.XmlValue;

@XmlRootElement(name = "DataRecord")
@XmlSeeAlso(Customer.class)
class DataRecord {

     @XmlValue
     String text;

}

@XmlRootElement(name = "DataFile")
class DataFile<E> {

     List<DataRecord> records;

     public List<DataRecord> getRecords() {
         return records;
     }

     @XmlElementRef
     public void setRecords(List<DataRecord> newRecords) {
         records = newRecords;
     }

     public void add(DataRecord newRec) {
         if (records == null) {
             records = new ArrayList<>();
         }
         records.add(newRec);
     }
}

@XmlRootElement(name = "Customer")
class Customer extends DataRecord {

     String name;
     int age;
     int id;

     public String getName() {
         return name;
     }

     @XmlElement
     public void setName(final String name) {
         this.name = name;
     }

     public int getAge() {
         return age;
     }

     @XmlElement
     public void setAge(final int age) {
         this.age = age;
     }

     public int getId() {
         return id;
     }

     @XmlAttribute
     public void setId(final int id) {
         this.id = id;
     }

}

public class JAXBtoXML {

     public static void main(final String[] args) throws Exception {

         final Customer customer = new Customer();
         customer.setId(100);
         customer.setName("John Smith");
         customer.setAge(29);

         final Customer customer2 = new Customer();
         customer2.setId(101);
         customer2.setName("Jane Doe");
         customer2.setAge(30);

         final DataRecord generic = new DataRecord();
         generic.text = "Eric";

         final JAXBContext jaxbContext = JAXBContext.newInstance(DataFile.class);
         final Marshaller jaxbMarshaller = jaxbContext.createMarshaller();

         // output pretty printed
         jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

         DataFile<Customer> customerList = new DataFile();
         customerList.add(customer);
         customerList.add(customer2);
         customerList.add(generic);
         jaxbMarshaller.marshal(customerList, System.out);

     }
}

This produces the following output:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<DataFile>
     <Customer id="100">
         <age>29</age>
         <name>John Smith</name>
     </Customer>
     <Customer id="101">
         <age>30</age>
         <name>Jane Doe</name>
     </Customer>
     <DataRecord>Eric</DataRecord>
</DataFile>

See if that suits you.

-- 
Stanimir

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XML Eric Douglas <e.d.programmer@gmail.com> - 2016-07-29 13:25 -0700
  Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-07-29 19:46 -0400
  Re: XML Roedy Green <inquiry@mindprod.com> - 2016-07-30 17:09 -0700
    Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-07-30 21:49 -0400
      Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-07-30 22:35 -0400
      Re: XML Roedy Green <inquiry@mindprod.com> - 2016-07-31 21:39 -0700
        Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-01 05:19 -0700
          Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-08-01 08:51 -0400
            Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-05 06:07 -0700
              Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-05 10:17 -0700
              Re: XML Stanimir Stamenkov <s7an10@netscape.net> - 2016-08-07 19:04 +0300
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-08 05:38 -0700
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-08 07:19 -0700
                Re: XML Stanimir Stamenkov <s7an10@netscape.net> - 2016-08-09 23:57 +0300
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-10 05:37 -0700
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-10 10:39 -0700
                Re: XML Stanimir Stamenkov <s7an10@netscape.net> - 2016-08-10 22:05 +0300
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-10 13:29 -0700
                Re: XML Stanimir Stamenkov <s7an10@netscape.net> - 2016-08-11 02:18 +0300
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-11 05:15 -0700
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-11 05:50 -0700
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-11 12:24 -0700
                Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-08-13 15:38 -0400
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-16 11:49 -0700
                Re: XML Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-16 15:57 -0400
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-16 13:20 -0700
                Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-08-16 17:04 -0400
                Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-08-16 21:37 -0400
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-17 05:22 -0700
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-17 05:21 -0700
                Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-08-16 16:13 -0400
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-16 13:22 -0700
                Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-08-16 16:53 -0400
                Re: XML Eric Douglas <e.d.programmer@gmail.com> - 2016-08-16 13:32 -0700
                Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-08-16 16:47 -0400
                Re: XML Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-16 16:59 -0400
        Re: XML Arne Vajhøj <arne@vajhoej.dk> - 2016-08-01 08:46 -0400

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