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Revision as of 14:19, 17 February 2010
XMLDirectMapping
Requirements
Provide support for XML direct mappings.
The following structures are to be extended to support XML direct mapping configuration:
Path-based mappings must be supported. Design notes are located here.
The following should be configurable:
- Positional Mappings
- Read only (boolean)
- Write only (boolean)
- CDATA (boolean)
- Converters
- Default null value
- Null policy
- Get/set method names
Design
Basic XML direct mapping support
We will use the xml-attribute
, xml-element
and xml-value
structures to support direct mappings. For example, the following XML metadata snippet would be used to setup a direct mapping for an empId
attribute:
<xml-attribute java-attribute="empId" />
If empId
was to be mapped to id
, then the following would be used:
<xml-attribute java-attribute="empId" name="id" />
The same example mapped to an id
element:
<xml-element java-attribute="empId" name="id" />
The same example mapped to a simple type:
<xml-value java-attribute="empId" />
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="personal-info/first-name/text()" xsi:type="node"/> </attribute-mapping> <attribute-mapping xsi:type="xml-direct-mapping"> <attribute-name>lastName</attribute-name> <field name="personal-info/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="projects/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"> <personal-info> <first-name>Joe</first-name> <last-name>Black</last-name> </personal-info> <projects> <prj:project managerId="99">XML External Metadata Support</prj:project> </projects> </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-wrapper name="personal-info" /> </xml-element> <xml-element java-attribute="lastName" name="last-name" > <xml-element-wrapper name="personal-info" /> </xml-element> <xml-attribute java-attribute="mgrId" name="managerId" > <xml-element-wrapper name="projects/prj:project" /> </xml-attribute> <xml-element java-attribute="projectName" name="project" namespace="http://www.example.com/projects" > <xml-element-wrapper name="projects" /> </xml-element> </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 |
---|---|---|
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 to handle multi-level paths, and 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.
|
3 | What is the expected behavior when namespace is set on an xml-element-wrapper that has a path set?
|
If namespace is set, it will be applied to any path element that is not prefixed.
|
4 | What is the expected behavior when required is set on an xml-element-wrapper that has a path set?
|
If required is set, it will be applied to the last element in the path.
|
5 | What is the expected behavior when nillable is set on an xml-element-wrapper that has a path set?
|
If nillable is set, it will be applied to the last element in the path.
|
6 | How can we support positional mappings? | Positional mappings will be supported by overloading the name attribute on xml-element / xml-value .
|
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 an additional attribute such that users who do not wish use the
name
attribute in a non-standard way are able to set a multi-level path.