Interface to implement
For a generic expression you have to implement the interface
com.coremedia.workflow.WfExpression.
Such an expression must return a java.lang.Comparable value. If you want to use
the result of your expression for further evaluation, you should return a
WfValue
because this is what all built-in expressions operate on.
Convenience classes
For convenience you can subclass from
com.coremedia.workflow.common.expressions.AbstractExpression
and implement the evaluate() method, which is called by the
CoreMedia Workflow Server. See
Example 5.7, “Example of a generic expression” for a simple example of an
expression.
Define expressions
The following XML fragment shows, how to define your expressions in the workflow definition.
.
.
<Variable name="comment" type="String">
<String value="TestString"/>
</Variable>
.
.
<If name="One">
<Condition>
<Less>
<Expression class="com.coremedia.example.
expression.DemoExpression"/>
<Get variable="comment"/>
</Less>
</Condition>
<Then successor="True"/>
<Else successor="False"/>
</If>
.
.
Example 5.6. Use a generic expression in the workflow definition
Example generic expression
The following code example shows a simple expression which returns a
StringValue.
public class SampleExpression extends AbstractExpression {
public String getName() {return "SampleExpression";}
public Comparable evaluate(WfInstance instance,
Map localVariables) {
return new StringValue("ConstantValue");
}
}
Example 5.7. Example of a generic expression
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