topic context.getprocessengineconfiguration() is null in evaluating expression in Alfresco Archive

context.getprocessengineconfiguration() is null in evaluating expression

mf — Sat, 13 Jun 2015 10:08:05 GMT

I have a helper method to evaluate expressions in an executionublic Object evaluateExpression(DelegateExecution execution, String expr) { Expression expression = expressionManager.createExpression(expr); return expression.getValue(execution);}‍‍‍‍‍‍but in calling this method, the expression.ge

Re: context.getprocessengineconfiguration() is null in evaluating expression

mf — Sat, 13 Jun 2015 10:19:12 GMT

In addition, the expressionManager is injected with Spring. but if i use:
<java>
ExpressionManager expressionManager = Context.getProcessEngineConfiguration() .getExpressionManager();
</java>
the Context.getProcessEngineConfiguration() is null and it throws NullPointerException.

Re: context.getprocessengineconfiguration() is null in evaluating expression

jbarrez — Tue, 16 Jun 2015 09:08:23 GMT

When are you executing this? The nullpointer should not happen when you call that code during an API call, and a valid CommandContext is created.

Re: context.getprocessengineconfiguration() is null in evaluating expression

mf — Tue, 16 Jun 2015 15:22:11 GMT

No api call is involved and no Command Context is created; because in my use-case, i need to evaluate some expressions manually. This issue is resolved by creating a custom command:

<java>
public class EvauluateExpressionCmd implements Command<Object>, Serializable {

private static final long serialVersionUID = 1L;

private Expression expression;
private VariableScope variableScope;

public EvauluateExpressionCmd(Expression expression, VariableScope variableScope) {
this.expression = expression;
this.variableScope = variableScope;
}

@Override
public Object execute(CommandContext commandContext) {
return expression.getValue(variableScope);
}
}
</java>
And execute it with ManagementService:
<java>
public Object getValue(String expr, DelegateExecution execution) {
Expression expression = expressionManager.createExpression(getEvaluableExpression(expr));
EvauluateExpressionCmd command = new EvauluateExpressionCmd(expression, execution);
return managementService.executeCommand(command);
}
</java>

But i can't figure out, when exactly we need to create custom commands??

Re: context.getprocessengineconfiguration() is null in evaluating expression

trademak — Wed, 17 Jun 2015 10:39:22 GMT

When you need to run logic against an Activiti entity like the ExecutionEntity you always need a custom command, because it will need to be able to lookup Context values and be able to run a query against the Activiti entities.

Best regards,