Transition rule EL Expression fails [Solved]

[dondragon2]

I am using the default expression language to evaluate the rules for my transitions. But, I am getting the following exception each time it tries to process a rule in my decision node.

org.jbpm.api.JbpmException: expression condition ' #{response['resultSet'] != null && response['resultSet'][0][3] > 0}' did not return a boolean:  true

        at org.jbpm.pvm.internal.model.ExpressionCondition.evaluate(ExpressionCondition.java:45)

        at org.jbpm.jpdl.internal.activity.DecisionConditionActivity.findTransitionUsingConditions(DecisionConditionActivity.java:62)

org.jbpm.api.JbpmException: expression condition ' #{response['resultSet'] != null && response['resultSet'][0][3] > 0}' did not return a boolean:  true

        at org.jbpm.pvm.internal.model.ExpressionCondition.evaluate(ExpressionCondition.java:45)

        at org.jbpm.jpdl.internal.activity.DecisionConditionActivity.findTransitionUsingConditions(DecisionConditionActivity.java:62)

Why is result a string instead of a boolean?

How can I get around this?

[rebody]

Hi Donald,

  Which verion of jbpm did you used?

  Could you show us a testcase which could re-produce this problem.  This will be helpful for investigating it.

  Thank you very much.

[dondragon2]

I am using version 4.4

The issue is in the ExpressionCondition class

public boolean evaluate(OpenExecution execution) {

        Object result = Expression.create(expression, language).evaluate();

        if (result instanceof Boolean) {

            return ((Boolean) result).booleanValue();

        }

             throw new JbpmException("expression condition '" + expression + "' did not return a boolean: " + result);

    }

Apparently the value that is returned by the Expression.create is a String " true " which would fail based on the conditions above. I had to modify the code to reflect the following.

public boolean evaluate(OpenExecution execution) {

        Object result = Expression.create(expression, language).evaluate();

        if (result instanceof Boolean) {

            return ((Boolean) result).booleanValue();

        }

        if (result instanceof String) {

            if(result == null)

                return false;

            return Boolean.valueOf(((String) result).trim());

        }

        throw new JbpmException("expression condition '" + expression + "' did not return a boolean: " + result);

    }

After doing that it is evaluated properly. This an issue that needs to resolved in the official distribution.

public boolean evaluate(OpenExecution execution) {

        Object result = Expression.create(expression, language).evaluate();

        if (result instanceof Boolean) {

            return ((Boolean) result).booleanValue();

        }

        if (result instanceof String) {

            if(result == null)

                return false;

            return Boolean.valueOf(((String) result).trim());

        }

        throw new JbpmException("expression condition '" + expression + "' did not return a boolean: " + result);

    }

[rebody]

Hi Donald.

   Unfortunately, I cannot reproduce this problem,  I upload a testcase for this scenario.  Could you have a look at it?  Thank you very much.

http://anonsvn.jboss.org/repos/jbpm/jbpm4/trunk/modules/pvm/src/test/java/org/jbpm/pvm/internal/expr/UelExpressionTest.java

[milnauf]

Hello,

I running into problems when I try evaluating an expression during runtime (yeah - using internal APIs  :s ). What I'm doing is essentially try to find possible execution path using transition's condition.
The problem is that the method org.jbpm.pvm.internal.model.ExpressionCondition.evaluate(OpenExecution execution) - invokes evaluate() on created expression - rather than evaluate(execution). The problem is that the execution variables are not found - because in the subsequent call to JbpmElFactoryImpl.createCompositeResolver - if the scopeInstance is null - which it is in this case - the JbpmVariableElResolver is not added.

So a cosmetic change of the org.jbpm.pvm.internal.model.ExpressionCondition evaluate to invoke evaluate with execution parameter rather than without it - should fix the problem. Unless of course there's a good reason for not passing current execution.

At the bottom I attach a stacktrace for the error that I'm getting -> resulting directly from not using the OpenExecution to evaluate the expression.

The resulting code would be similar to the below:

public class org.jbpm.pvm.internal.model.ExpressionCondition {

public boolean evaluate(OpenExecution execution) {

    Object result = Expression.create(expression, language).evaluate(execution);

    if (result instanceof Boolean) {

      return ((Boolean) result).booleanValue();

    }

    throw new JbpmException("expression condition '" + expression + "' did not return a boolean: "+result);

  }

  ...

}

Stack trace:

javax.el.PropertyNotFoundException: Cannot resolve identifier 'task1'

    at de.odysseus.el.tree.impl.ast.AstIdentifier.eval(AstIdentifier.java:86)

    at de.odysseus.el.tree.impl.ast.AstEval.eval(AstEval.java:51)

    at de.odysseus.el.tree.impl.ast.AstNode.getValue(AstNode.java:28)

    at de.odysseus.el.TreeValueExpression.getValue(TreeValueExpression.java:122)

    at org.jbpm.pvm.internal.el.UelValueExpression.evaluateInScope(UelValueExpression.java:52)

    at org.jbpm.pvm.internal.el.Expression.evaluate(Expression.java:108)

    at org.jbpm.pvm.internal.model.ExpressionCondition.evaluate(ExpressionCondition.java:41)

...

caused by a call to:

boolean followPath = transition.getCondition().evaluate(openExecution);