Feedback please. I am sick of talking to myself

On  Jan 21, 2009, at 23:37, Emmanuel Bernard wrote:

I looked at the OVAL schema and as usual there are good stuffs here, I also added some missing elements

 - I forgot the flag to be able to ignore existing annotations

 - I forgot the @Valid equivalent

 - OVal has the ability to describe OVal specific constraints in a typesafe way but not custom user constraints (as far as I can see). 

Let me know what you think, especially on the constraints declarations options.

Ignore Annotation flag

Should the ignore-annotation flag be a <bean/> level attribute only or should a user be able to define it at the field/method/class level?

If set to true, annotations placed on the bean, field or getter will not be considered. If set to false, they will.

@Valid

<valid/>

will indicate that a field or a getter is to be cascaded

Constraints declarations

In the current schema proposal, here is how constraints are declared

           <constraint annotation="com.acme.validate.SafeCustomer">
               <attribute name="category">
                   <array-element>com.acme.validate.SecurityLevel.SECURED_COUNTRY</array-element>
                   <array-element>com.acme.validate.SecurityLevel.SECURED_ADDRESS</array-element>
                   <array-element>com.acme.validate.SecurityLevel.SECURED_FINANCIALS</array-element>
               </attribute>
               <attribute name="failPerCategory">false</attribute>
           </constraint>

           <constraint annotation="javax.validation.constraint.NotNull">

               <message>blah</message>

           </constraint>

We could enhance this in two ways:

 - provide type-safe support for built-in validations:

<not-null/>, 

<min>

  <value>3</value>

  <message>blah</message>

</min>

etc

 - allow custom constraints support in a type-safe way: 

The second point would work as followed

 - a constraint annotation would be associated with a given XML type eg. <Min/>

 - propose an abstract constraintType XML type that any constraint declared in XML would inherit (Min would extend ConstraintType)

 - thanks to that message and groups would be inherited

 - Min would have an attribute "annotation" fixed to the f.q.c.n of the corresponding annotation (I haven't find a way to hide it from the user but still have it present at parsing time)

 - subelements of a constraint XML element would represent attributes of the annotation (with the same name)

<?xml version="1.0" encoding="UTF-8"?>

<validation-mappings

  xmlns="http://jboss.com/java/validation-mapping"

  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

  xmlns:appval="http://acme.com/appval"

  xsi:schemaLocation="http://jboss.com/java/validation-mapping validation-mapping.xsd">

    <default-package>com.acme.dvdstore.model</default-package>

    <bean class="Customer" ignore-annotations="true">

        <class>

            <constraint annotation="com.acme.validate.SafeCustomer">

                <attribute name="category">

                    <array-element>com.acme.validate.SecurityLevel.SECURED_COUNTRY</array-element>

                    <array-element>com.acme.validate.SecurityLevel.SECURED_ADDRESS</array-element>

                    <array-element>com.acme.validate.SecurityLevel.SECURED_FINANCIALS</array-element>

                </attribute>

                <attribute name="failPerCategory">false</attribute>

            </constraint>

        </class>

        <fields>

            <field name="firstname">

                 <valid/>

                <appval:min annotation="javax.validation.constraint.Min">

                    <message>blah</message>

                    <value>4</value>

                </appval:min>

                <constraint annotation="javax.validation.Min">

                    <message>{error.tooSmall}</message>

                    <groups>

                        <group>javax.validation.groups.Default</group>

                    </groups>

                    <attribute name="value">45</attribute>

                </constraint>

            </field>

        </fields>

        <getters>

            <getter name="firstname">

                <ignore-annotations/>

                <stop-inheritance/>

                <constraint annotation="javax.validation.Min">

                    <message>{error.tooSmall}</message>

                    <groups>

                        <group>javax.validation.groups.Default</group>

                    </groups>

                    <attribute name="value">45</attribute>

                </constraint>

            </getter>

        </getters>

    </bean>

</validation-mappings>

where app:val is described in the XSD as 

<?xml version="1.0" encoding="UTF-8"?>

<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema" version="1.0"

        xmlns:bv="http://jboss.com/java/validation-mapping">

  <xs:element name="min" type="minType"/>

    <xs:complexType name="minType">

        <xs:complexContent>

            <xs:extension base="bv:AbstractConstraintType">

                <xs:sequence>

                    <xs:element name="value" type="xs:int" minOccurs="1"/>

                </xs:sequence>

                <xs:attribute name="annotation" use="required" fixed="javax.validation.constraint.Min"/>

            </xs:extension>

        </xs:complexContent>

    </xs:complexType>

</xs:schema>

On  Jan 19, 2009, at 19:35, Emmanuel Bernard wrote:

Here is my very first attempt to describe the constraint mapping XML schema.
I did not look at other product approach to avoid being tainted. If you have examples of alternative approach, I would appreciate a link.

A couple of comments:
- I would have preferred a Web Beans style XML approach but this kind of approach is getting some heavy resistance from some members of the expert committee. So I fell back to a more classic approach.
- constraints themselves cannot be defined: you have to write an actual annotation. I wonder if we should provide such model. At minimal we might want to provide a way to override the constraint validator for a given constraint.
- I used JPA 2 mapping schema as inspiration
- I stayed very close to the Java structure

Better names, enhancements, alternative proposals are welcome.

Emmanuel

<?xml version="1.0" encoding="UTF-8"?>
<validation-mappings>
  <package>com.acme.dvdstore.model</package>
  <bean class="Customer">
      <class>
          <constraint annotation="com.acme.validate.SafeCustomer">
              <attribute name="category">
                  <array-element>com.acme.validate.SecurityLevel.SECURED_COUNTRY</array-element>
                  <array-element>com.acme.validate.SecurityLevel.SECURED_ADDRESS</array-element>
                  <array-element>com.acme.validate.SecurityLevel.SECURED_FINANCIALS</array-element>
              </attribute>
              <attribute name="failPerCategory">false</attribute>
          </constraint>
      </class>
      <fields>
          <field name="firstname">
              <ignore-annotations/>
              <stop-inheritance/>
              <constraint annotation="javax.validation.Min">
                  <message>{error.tooSmall}</message>
                  <groups>
                      <group>javax.validation.groups.Default</group>
                  </groups>
                  <attribute name="value">45</attribute>
              </constraint>
          </field>
      </fields>
      <getters>
          <getter name="firstname">
              <ignore-annotations/>
              <stop-inheritance/>
              <constraint annotation="javax.validation.Min">
                  <message>{error.tooSmall}</message>
                  <groups>
                      <group>javax.validation.groups.Default</group>
                  </groups>
                  <attribute name="value">45</attribute>
              </constraint>
          </getter>
      </getters>
  </bean>
</validation-mappings>
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