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Examples

Here are some solutions that use nativeTypes to define the behaviour of a SimpleValueType.

note

NativeTypes can only be defined as DataResources as part of an expansionResource.

Java Transport Class​

You can define the type used in Projections and other transport classes for a SimpleValueType. Add a NativeType with concern transport and technology JDK.

<dataResource type="elements::NativeType">
  <nativeType name="java:transport:net.demo.MyType">
    <technology name="JDK"/>
    <concern>transport</concern>
    <!-- Definition should contain the fully qualified class name of the transport type. -->
    <definition>net.demo.MyType</definition>
  </nativeType>
</dataResource>
tip

The FieldComposite class has a property javaType which contains a representation of the transport class. Consult the javadoc of net.democritus.valuetype.JavaType to find out how to use it.

JPA Transport Class​

Similarly, you can define the type used in JPA Entity classes (i.e. -Data classes). Use the technology JPA.

<dataResource type="elements::NativeType">
  <nativeType name="jpa:transport:net.demo.MyJpaType">
    <technology name="JDK"/>
    <concern>transport</concern>
    <!-- Definition should contain the fully qualified class name of the transport type. -->
    <definition>net.demo.MyJpaType</definition>
  </nativeType>
</dataResource>
tip

Several NativeTypes have already been defined for JPA and can be reused. E.g. String is represented by jpa:transport:String.

Converter Class​

Some types need dedicated logic to convert between transport types. This class will need to implement conversion methods that map between specific transport types and the java transport type.

<dataResource type="elements::NativeType">
  <nativeType name="java:converter:MyTypeConverter">
    <technology name="JDK"/>
    <concern>converter</concern>
    <!-- Definition should contain the fully qualified class name of the converter class. -->
    <definition>net.demo.MyTypeConverter</definition>
  </nativeType>
</dataResource>

Undefined Checks​

By default, value are seen as undefined only if they contain a null reference. It is possible to define another condition by adding a NativeType with the concern isUndefined and technology JDK.

<dataResource type="elements::NativeType">
  <nativeType name="java:isUndefined:myType:notPresent">
    <technology name="JDK"/>
    <concern>isUndefined</concern>
    <!--
      Describe the condition in the definition.
      $property$ will be replaced with the actual getter call for the value.
     -->
    <definition>$property$ == null || !$property$.isPresent()</definition>
  </nativeType>
</dataResource>

Default Value​

In constructors, values of SimpleValueTypes are initialized with the default constructor of the transport classes. This behaviour can be modified as necessary using the default concern.

<dataResource type="elements::NativeType">
  <nativeType name="java:default:MyType">
    <technology name="JDK"/>
    <concern>default</concern>
    <definition>MyType.empty()</definition>
  </nativeType>
</dataResource>

The option defaultValue allows developers to set a default value in the model. The value of this option will be inserted one to one into the constructor.

<dataResource type="elements::NativeType">
  <nativeType name="java:creation:MyType">
    <technology name="JDK"/>
    <concern>creation</concern>
    <!--
      Describe the code to construct a value in the definition.
      $value$ will be replaced with the value of the option.
     -->
    <definition>new MyType("$value$")</definition>
  </nativeType>
</dataResource>