EclipseLink/DesignDocs/293925/MOXyExtensions/XMLDirectMapping

XMLDirectMapping

Requirements

Provide support for XML direct mappings.

The following structures are to be extended to support XML direct mapping configuration:

• xml-attribute
• xml-element

Path-based mappings must be supported. Design notes are located here.

The following should be configurable:

• Null policy
• Get/set method names
• Read only
• Attribute classification
• Default null value
• CDATA
• Converter

Example

The following example will demonstrate how to configure XML direct mappings via XML metadata.

org.example.Employee.java

package org.example;
 
public class Employee {
    public int empId;
    public String firstName;
    public String lastName;
    public String projectName;
}

Deployment XML

<class-mapping-descriptor xsi:type="xml-class-mapping-descriptor">
    <alias>Employee</alias>
    <attribute-mappings>
        <attribute-mapping xsi:type="xml-direct-mapping">
           <attribute-name>empId</attribute-name>
           <field name="@id" xsi:type="node"/>
        </attribute-mapping>
        <attribute-mapping xsi:type="xml-direct-mapping">
           <attribute-name>firstName</attribute-name>
           <field name="name/first-name/text()" xsi:type="node"/>
        </attribute-mapping>
        <attribute-mapping xsi:type="xml-direct-mapping">
           <attribute-name>lastName</attribute-name>
           <field name="name/last-name/text()" xsi:type="node"/>
        </attribute-mapping>
        <attribute-mapping xsi:type="xml-direct-mapping">
            <attribute-name>mgrId</attribute-name>
            <field name="projects/prj:project/@managerId" xsi:type="node"/>
        </attribute-mapping>
        <attribute-mapping xsi:type="xml-direct-mapping">
           <attribute-name>projectName</attribute-name>
           <field name="project/prj:project/text()" xsi:type="node"/>
        </attribute-mapping>
    <attribute-mappings>
    <descriptor-type>aggregate</descriptor-type>
    <default-root-element>employee</default-root-element>
    <default-root-element-field name="employee" xsi:type="node"/>
    <namespace-resolver>
        <namespaces>
            <namespace>
                <prefix>prj</prefix>
                <namespace-uri>http://www.example.com/projects</namespace-uri>
            </namespace>
        </namespaces>
        <default-namespace-uri>http://www.example.com/employees</default-namespace-uri>
    </namespace-resolver>
</class-mapping-descriptor>

XML Instance Document

<?xml version="1.0" encoding="UTF-8"?>
<employee id="66" xmlns="http://www.example.com/employees" xmlns:prj="http://www.example.com/projects">
    <first-name>Joe</first-name>
    <last-name>Black</last-name>
    <prj:project>XML External Metadata Support</prj:project>
</employee>

org/example/eclipselink-oxm.xml

This XML file demonstrates configuring XML direct mappings on the "org.example.Employee" class.

<?xml version="1.0" encoding="US-ASCII"?>
<xml-bindings xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm">
    <xml-schema namespace="http://www.example.com/employees">
        <xml-ns namespace-uri="http://www.example.com/projects" prefix="prj"/>
    </xml-schema>
    <java-types>
        <java-type name="org.example.Employee">
            <xml-root-element name="employee" />
            <java-attributes>
                <xml-attribute java-attribute="empId" name="id" />
                <xml-element java-attribute="firstName" name="first-name" />
                <xml-element java-attribute="lastName" name="last-name" />
                <xml-element java-attribute="projectName" name="prj:project" />
            </java-attributes>
        </java-type>
    </java-types>
</xml-bindings>

Open Issues

This section lists the open issues that are still pending that must be decided prior to fully implementing this project's requirements.

Issue#	Owner	Description/Notes
1	D.McCann	Two possible ways to allow a path-based mapping to be configured are being considered: xml-attribute/xml-element or xml-element-wrapper. Which is preferred? Design decisions for this support are located here.
2	D.McCann	Three possible ways to set the path for a mapping are being considered: name overload vs. xpath vs. name + grouping-element. Which is preferred? Design decisions for this support are located here.

Decisions

This section lists decisions made. These are intended to document the resolution of open issues or constraints added to the project that are important.

Issue#	Description/Notes	Decision
1	Two possible ways to allow a path-based mapping to be configured are being considered: xml-attribute/xml-element or xml-element-wrapper	xml-element-wrapper will be extended; it will be enabled for use with xml-attribute and single-valued properties.
2	Three possible ways to set the path for a mapping are being considered: name overload vs. xpath vs. name + grouping-element	name will be overloaded.

Future Considerations

During the research for this project the following items were identified as out of scope but are captured here as potential future enhancements. If agreed upon during the review process these should be logged in the bug system.

• For issue #2 above, it may be useful to add a grouping-element attribute such that users who do not wish use the name attribute in a non-standard way are able to set the XPath.