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Difference between revisions of "EclipseLink/UserGuide/MOXy/Relationships/Collections and Maps"

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==Default==
 
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==@XmlElement==
 
==@XmlElement==
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</customer>
 
</customer>
 
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== @XmlElementWrapper==
 
== @XmlElementWrapper==
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Use the '''@XmlElementWrapper''' annotation to add a grouping element to organize the collection:
  
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Sometimes we want to add a grouping element to organize our collection data.  This is done using the @XmlElementWrapper annotation.
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import java.util.*;
 
import java.util.*;
 
import javax.xml.bind.annotation.*;
 
import javax.xml.bind.annotation.*;
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}
  
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The following is the corresponding XML output:
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This will produce the following XML:
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<customer>
 
<customer>
 
     <email-addresses>
 
     <email-addresses>
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     </email-addresses>
 
     </email-addresses>
 
</customer>
 
</customer>
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</source>
  
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@XmlList
 
  
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We can also represent our collection data as space seperated text.  This is done using the @XmlList annotation.
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==@XmlList==
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Use the '''@XmlList''' annotation to represent the collection as space separated text.   
  
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import java.util.*;
 
import java.util.*;
 
import javax.xml.bind.annotation.*;
 
import javax.xml.bind.annotation.*;
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}
 
}
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</source>
  
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The following is the corresponding XML output:
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This will produce the following XML:
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<source lang="xml">
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<customer>
 
<customer>
 
     <emailAddresses>janed@example.com jdoe@example.org</emailAddresses>
 
     <emailAddresses>janed@example.com jdoe@example.org</emailAddresses>
 
</customer>
 
</customer>
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</source>
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@XmlList and @XmlAttribute
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==@XmlList and @XmlAttribute==
  
 
Since @XmlList allows us to represent a collection in a single piece of text it is also compatible with an XML attribute.
 
Since @XmlList allows us to represent a collection in a single piece of text it is also compatible with an XML attribute.

Revision as of 13:56, 5 April 2011

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Collections

JAXB contains several annotations to represent collections in XML:


Java Model

To demonstrate the annotations, refer to the following model: 

import java.util.*;
import javax.xml.bind.annotation.*;
 
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
 
    private List<String> emailAddresses;
 
    public Customer() {
        emailAddresses = new ArrayList<String>();
    }
 
    public List<String> getEmailAddresses() {
        return emailAddresses;
    }
 
    public void setEmailAddresses(List<String> emailAddresses) {
        this.emailAddresses = emailAddresses;
    }
 
}

By applying different JAXB annotations, you can produce different XML.


Demo Code

This sample code converts the Customer object to XML. 

 
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
 
public class Demo {
 
    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Customer.class);
 
        Customer customer = new Customer();
        customer.getEmailAddresses().add("janed@example.com");
        customer.getEmailAddresses().add("jdoe@example.org");
 
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(customer, System.out);
    }
}


Default

By default, JAXB marshalls each item in the collection to an XML element: 

 
<customer>
    <emailAddresses>janed@example.com</emailAddresses>
    <emailAddresses>jdoe@example.org</emailAddresses>
</customer>


@XmlElement

Use the @XmlElement to control the name of the XML element that a collection item is marshalled to: 

 
import java.util.*;
import javax.xml.bind.annotation.*;
 
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
 
    @XmlElement(name="email-address")
    private List<String> emailAddresses;
 
}

This will produce the following XML: 

 
<customer>
    <email-address>janed@example.com</email-address>
    <email-address>jdoe@example.org</email-address>
</customer>


@XmlElementWrapper

Use the @XmlElementWrapper annotation to add a grouping element to organize the collection: 

 
import java.util.*;
import javax.xml.bind.annotation.*;
 
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
 
    @XmlElementWrapper(name="email-addresses")
    @XmlElement(name="email-address")
    private List<String> emailAddresses;
 
}
 
This will produce the following XML:
<source lang="xml">	
<customer>
    <email-addresses>
        <email-address>janed@example.com</email-address>
        <email-address>jdoe@example.org</email-address>
    </email-addresses>
</customer>


@XmlList

Use the @XmlList annotation to represent the collection as space separated text. 

import java.util.*;
import javax.xml.bind.annotation.*;
 
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
 
    @XmlList
    private List<String> emailAddresses;
 
}

This will produce the following XML: 

 
<customer>
    <emailAddresses>janed@example.com jdoe@example.org</emailAddresses>
</customer>


@XmlList and @XmlAttribute

Since @XmlList allows us to represent a collection in a single piece of text it is also compatible with an XML attribute.

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import java.util.*; import javax.xml.bind.annotation.*;

@XmlRootElement @XmlAccessorType(XmlAccessType.FIELD) public class Customer { 

   @XmlList
   @XmlAttribute
   private List<String> emailAddresses;

}

The following is the corresponding XML output:

1 2

<customer 

   emailAddresses="janed@example.com jdoe@example.org"/>

@XmlList and @XmlValue

Since @XmlList allows us to represent a collection in a single piece of text it is also compatible with a single text node.

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import java.util.*; import javax.xml.bind.annotation.*;

@XmlRootElement @XmlAccessorType(XmlAccessType.FIELD) public class Customer { 

   @XmlList
   @XmlValue
   private List<String> emailAddresses;

}

The following is the corresponding XML output:

1

<customer>janed@example.com jdoe@example.org</customer>


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