Pave/Tutorials/Enablement

There are two aspects of enablement:

1. Enable the Apply Pattern action on your objects.

2. Enable a specific Pattern on already Pave enabled node.

1. To enable Apply Pattern ... action in your toolset, you have to specify the entry point and the enablement type.

For example if you want to enable it using context menu in a view or editor, you have to specify the necessary extension point and the conditions on which it will be enabled.

Various ways of doing so are: org.eclipse.ui.popup extension point, NavigatorContent extension point - for common navigators, and other view/editor specific ways.

The Pave Framework provides standard classes for some of these entry points:

   * Simple Action - ...pattern.application.framework.ui.popup.ApplyAction (org.eclipse.jface.action.Action)
   * Popup Object Delegate: ...pattern.application.framework.ui.popup.ApplyPatternAction&nbsp (org.eclipse.ui.IObjectActionDelegate)
   * Common Navigator Content - ...pattern.application.framework.ui.popup.PopupProvider (org.eclipse.ui.navigator.CommonActionProvider)

For every other case you can instantiate ApplyAction with the input object and run it:

(new ApplyAction(input)).run();

Important: Note that the framework is already enabled on: Project Explorer.

2. Enable specific Pattern on already Pave enabled node.

If you have 1. done, you can start to enable your pattern on specific input. This has to be done through using enablement on the Pattern definition itself.

Enablement accepts combination of the following restrictions.

<!ELEMENT enablement (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>
A generic root element. The element can be used inside an extension point to define its enablement expression. The children of an enablement expression are combined using the and operator.

<!ELEMENT not (not | and | or | instanceof | test | systemTest | equals | count | with | resolve | adapt | iterate | reference)>
This element represent a NOT operation on the result of evaluating it's sub-element expression.

<!ELEMENT and (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>
This element represent an AND operation on the result of evaluating all it's sub-elements expressions.

<!ELEMENT or (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>
This element represent an  OR operation on the result of evaluating all it's sub-element expressions.

<!ELEMENT instanceof EMPTY>
<!ATTLIST instanceof

value CDATA #REQUIRED>

This element is used to perform an instanceof check of the object in focus. The expression returns EvaluationResult.TRUE, if the object's type is a sub type of the type specified by the attribute value. Otherwise EvaluationResult.FALSE is returned.

    * value - a fully qualified name of a class or interface.

<!ELEMENT test EMPTY>
<!ATTLIST test

property              CDATA #REQUIRED

args                  CDATA #IMPLIED

value                 CDATA #IMPLIED

forcePluginActivation (true | false) >

This element is used to evaluate the property state of the object in focus. The set of properties ready for testing can be extended using the property tester extension point. The test expression returns EvaluationResult.NOT_LOADED if the property tester performing the actual testing is not loaded yet and the attribute forcePluginActivation is set to false. If forcePluginActivation is set to true and the evaluation context used to evaluate this expression supports plug-in activation then evaluating the property will result in activating the plug-in defining the tester.

    * property - the name of an object's property to test.
    * args- additional arguments passed to the property tester. Multiple arguments are separated by commas. Each individual argument is converted into a Java base type using the same rules as defined for the value attribute of the test expression.
    * value - the expected value of the property. It can be omitted if the property is a boolean property. The test expression is supposed to return EvaluationResult.TRUE if the property matches the value. Otherwise it returns EvaluationResult.FALSE. The value attribute is converted into a Java base type using the following rules:
          o the string "true" is converted into Boolean.TRUE
          o the string "false" is converted into Boolean.FALSE
          o if the string contains a dot, then the interpreter tries to convert the value into a Float object. If this fails, the string is treated as a java.lang.String
          o if the string only consists of numbers, then the interpreter converts the value in an Integer object
          o in all other cases the string is treated as a java.lang.String
          o the conversion of the string into a Boolean, Float, or Integer can be suppressed by surrounding the string with single quotes. For example, the attribute value="'true'" is converted into the string "true"
    * forcePluginActivation- a flag indicating whether the plug-in contributing the property tester should be loaded if necessary. As such, this flag should be used judiciously, in order to avoid unnecessary plug-in activations. Most clients should avoid setting this flag to true. This flag is only honored if the evaluation context used to evaluate this expression allows plug-in activation. Otherwise the flag is ignored and no plug-in loading takes place.

<!ELEMENT systemTest EMPTY>
<!ATTLIST systemTest

property CDATA #REQUIRED

value    CDATA #REQUIRED>

Tests a system property by calling the System.getProperty method and compares the result with the value specified through the value attribute.

    * property - the name of an system property to test.
    * value - the expected value of the property. The value is interpreted as a string value.


<!ELEMENT equals EMPTY>
<!ATTLIST equals

value CDATA #REQUIRED>

This element is used to perform an equals check of the object in focus. The expression returns EvaluationResult.TRUE if the object is equal to the value provided by the attribute value. Otherwise EvaluationResult.FALSE is returned.

    * value - the expected value. The value provided as a string is converted into a Java base type using the same rules as for the value attribute of the test expression.


<!ELEMENT count EMPTY>
<!ATTLIST count

value CDATA #REQUIRED>

This element is used to test the number of elements in a collection.

    * value - an expression to specify the number of elements in a list. The following wildcard characters can be used: *any number of elements?no elements or one element+one or more elements!no elementsinteger value the list must contain the exact number of elements




<!ELEMENT with (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>
<!ATTLIST with

variable CDATA #REQUIRED>

This element changes the object to be inspected for all its child element to the object referenced by the given variable. If the variable cannot be resolved then the expression will throw a ExpressionException when evaluating it. The children of a with expression are combined using the and operator.

    * variable - the name of the variable to be used for further inspection. It is up to the evaluator of an extension point to provide the variable in the variable pool.

<!ELEMENT resolve (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>
<!ATTLIST resolve

variable CDATA #REQUIRED

args     CDATA #IMPLIED>

This element changes the object to be inspected for all its child element to the object referenced by the given variable. If the variable cannot be resolved then the expression will throw a ExpressionException when evaluating it. The children of a with expression are combined using the "and" operator.

    * variable - the name of the variable to be resolved. This variable is then used as the object in focus for child element evaluation. It is up to the evaluator of an extension point to provide a corresponding variable resolver (refer to IVariableResolver) through the evaluation context passed to the root expression element when evaluating the expression.
    * args - additional arguments passed to the variable resolver. Multiple arguments are separated by commas. Each individual argument is converted into a Java base type using the same rules as defined for the value attribute of the test expression.

<!ELEMENT adapt (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>
<!ATTLIST adapt

type CDATA #REQUIRED>

This element is used to adapt the object in focus to the type specified by the attribute type. The expression returns not loaded if either the adapter or the type referenced is not loaded yet. It throws a ExpressionException during evaluation if the type name does not exist at all. The children of an adapt expression are combined using the and operator.

    * type - the type to which the object in focus is to be adapted.

<!ELEMENT iterate (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>
<!ATTLIST iterate

operator (or|and)

ifEmpty  (true | false) >

This element is used to iterate over a variable that is of type java.util.Collection. If the object in focus is not of type java.util.Collection then an ExpressionException will be thrown while evaluating the expression.

    * operator - either "and" or "or". The operator defines how the child elements will be combined. If not specified, "and" will be used.
    * ifEmpty - the value returned from the iterate expression if the collection is empty. If not specified then true is returned when the operator equals "and" and false is return if the operator equals "or".

<!ELEMENT reference EMPTY>
<!ATTLIST reference

definitionId IDREF #REQUIRED>

This element is used to reference an expression from the org.eclipse.core.expressions.definitions extension point. The expression definition will be evaluated within the current expression element using the current evaluation context.

    * definitionId - The unique ID of an expression from org.eclipse.core.expressions.definitions. 

Instance of Example:

<enablement>
  <and>
  <instanceof
     value="org.eclipse.jdt.core.IJavaProject">
  </instanceof>
  </and>
</enablement>

Complex example:

 <enablement>
	<and>
	   <instanceof
			 value="org.eclipse.jdt.core.IJavaProject">
	   </instanceof>
	   <adapt
			 type="org.eclipse.jdt.core.IJavaElement">
	   </adapt>
	   <or>
		  <test
				forcePluginActivation="false"
				property="pattern.application.fwk.test_CoreDev_stream.test1">
		  </test>
	   </or>
	</and>
 </enablement>

Property Tester Example:

<extension
         point="org.eclipse.core.expressions.propertyTesters">
      <propertyTester
            class="javaee.patterns.crud.CrudApplicable"
            id="CrudTester"
            namespace="javaee.patterns"
            properties="crudApplicable"
            type="java.lang.Object">
      </propertyTester>
   </extension>

 <enablement>
            <or>
               <test
                     forcePluginActivation="true"
                     property="javaee.patterns.crudApplicable">
               </test></or>
         </enablement>