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Difference between revisions of "EclipseLink/UserGuide/MOXy/Relationships/Shared Reference/Keys and Foreign Keys/Single Key"

Line 10: Line 10:
 
To model non-privately-owned relationships, your "target" objects must have IDs (keys) defined, and your "source" object must use these IDs to map the relationship.
 
To model non-privately-owned relationships, your "target" objects must have IDs (keys) defined, and your "source" object must use these IDs to map the relationship.
  
−
Relationships represented with keys use the '''XmlID''' and '''XmlIDREF''' annotations.  Although the JAXB specification requires that the property marked with '''@XmlID''' be a '''String''', MOXy JAXB does not enforce this restriction.  
+
Relationships represented with keys use the '''@XmlID''' and '''@XmlIDREF''' annotations.  Although the JAXB specification requires that the property marked with '''@XmlID''' be a '''String''', MOXy JAXB does not enforce this restriction.  
  
 
In this example, each '''Employee''' has ''one'' '''manager''' but ''multiple'' '''reports'''.
 
In this example, each '''Employee''' has ''one'' '''manager''' but ''multiple'' '''reports'''.
 
<source lang="java">
 
<source lang="java">
−
import java.util.ArrayList;
 
−
import java.util.List;
 
−
 
−
import javax.xml.bind.annotation.XmlAccessorType;
 
−
import javax.xml.bind.annotation.XmlAccessType;
 
−
import javax.xml.bind.annotation.XmlAttribute;
 
−
import javax.xml.bind.annotation.XmlElement;
 
−
import javax.xml.bind.annotation.XmlID;
 
−
import javax.xml.bind.annotation.XmlIDREF;
 
−
 
 
@XmlAccessorType(XmlAccessType.FIELD)
 
@XmlAccessorType(XmlAccessType.FIELD)
 
public class Employee {
 
public class Employee {
−
 
 
     @XmlAttribute
 
     @XmlAttribute
 
     @XmlID
 
     @XmlID
Line 40: Line 29:
 
     @XmlIDREF
 
     @XmlIDREF
 
     private List<Employee> reports;
 
     private List<Employee> reports;
−
+
 
−
     public Employee() {
+
     ...
−
        reports = new ArrayList<Employee>();
+
−
    }
+
−
+
 
}
 
}
 
</source>
 
</source>
  
 
Would produce the following XML:
 
Would produce the following XML:
 +
 
<source lang="xml">
 
<source lang="xml">
 
<company>
 
<company>
Line 63: Line 50:
 
</company>  
 
</company>  
 
</source>
 
</source>
−
The manager and reports are marshalled with the ID of the employee instance they are referencing.
 
  
−
Because the '''@XmlIDREF''' annotation is also compatible with the '''@XmlList''' annotation, the Employee object could be modeled as:
+
The '''manager''' and '''reports''' elements contain the IDs of the '''Employee''' instances they are referencing.
 +
 
 +
Because the '''@XmlIDREF''' annotation is also compatible with the '''@XmlList''' annotation, the '''Employee''' object could be modeled as:
 +
 
 
<source lang="java">
 
<source lang="java">
−
package blog.shared;
 
−
 
−
import java.util.ArrayList;
 
−
import java.util.List;
 
−
 
−
import javax.xml.bind.annotation.XmlAccessorType;
 
−
import javax.xml.bind.annotation.XmlAccessType;
 
−
import javax.xml.bind.annotation.XmlAttribute;
 
−
import javax.xml.bind.annotation.XmlID;
 
−
import javax.xml.bind.annotation.XmlIDREF;
 
−
import javax.xml.bind.annotation.XmlList;
 
−
 
−
@XmlAccessorType(XmlAccessType.FIELD)
 
 
public class Employee {
 
public class Employee {
−
 
 
     @XmlID
 
     @XmlID
 
     @XmlAttribute
 
     @XmlAttribute
Line 95: Line 70:
 
     @XmlList
 
     @XmlList
 
     private List<Employee> reports;
 
     private List<Employee> reports;
−
+
 
−
     public Employee() {
+
     ...
−
        reports = new ArrayList<Employee>();
+
−
    }
+
−
+
 
}
 
}
 
</source>  
 
</source>  

Revision as of 11:11, 16 March 2011



Single Key

To model non-privately-owned relationships, your "target" objects must have IDs (keys) defined, and your "source" object must use these IDs to map the relationship.

Relationships represented with keys use the @XmlID and @XmlIDREF annotations. Although the JAXB specification requires that the property marked with @XmlID be a String, MOXy JAXB does not enforce this restriction.

In this example, each Employee has one manager but multiple reports. 

@XmlAccessorType(XmlAccessType.FIELD)
public class Employee {
    @XmlAttribute
    @XmlID
    private String id;
 
    @XmlAttribute
    private String name;
 
    @XmlIDREF
    private Employee manager;
 
    @XmlElement(name="report")
    @XmlIDREF
    private List<Employee> reports;
 
    ...
}

Would produce the following XML: 

<company>
    <employee id="1" name="Jane Doe">
        <report>2</report>
        <report>3</report>
    </employee>
    <employee id="2" name="John Smith">
        <manager>1</manager>
    </employee>
    <employee id="3" name="Anne Jones">
        <manager>1</manager>
    </employee>
</company>

The manager and reports elements contain the IDs of the Employee instances they are referencing.

Because the @XmlIDREF annotation is also compatible with the @XmlList annotation, the Employee object could be modeled as: 

public class Employee {
    @XmlID
    @XmlAttribute
    private String id;
 
    @XmlAttribute
    private String name;
 
    @XmlIDREF
    private Employee manager;
 
    @XmlIDREF
    @XmlList
    private List<Employee> reports;
 
    ... 
}

Which would produce the following XML: 

<company>
   <employee id="1" name="Jane Doe">
      <reports>2 3</reports>
   </employee>
   <employee id="2" name="John Smith">
      <manager>1</manager>
   </employee>
   <employee id="3" name="Anne Jones">
      <manager>1</manager>
   </employee>
</company>

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