Red Hat Summit Red Hat SummitSupportConsoleDéveloppeursCommencer un essaiContact

Ce contenu n'est pas disponible dans la langue sélectionnée.

3.5. Constraints

You can use constraints in a multitude of locations in your rule flow. You can, for example use them in a Split node using OR or XOR decisions, or as a constraint for a State node. The Rules Flow Engine supports two types of constraints:
  • Code constraints are Boolean expressions, evaluated directly immediately upon arrival. You can write them in either of these two dialects: Java and MVEL. Both have direct access to the globals and variables defined in the process.
    Here is an example of a constraint written in Java, person being a variable in the process: 
    return person.getAge() > 20;
    Copy to Clipboard Toggle word wrap
    Here is the same constraint written in MVEL: 
    return person.age > 20;
    Copy to Clipboard Toggle word wrap
  • Rule constraints are the same as normal JBoss Rules conditions. They use the JBoss Rules Rule Language's syntax to express what are potentially very complex constraints. These rules can, (like any other rule), refer to data in the working memory. You can also refer to globals directly.
    Here is an example of a valid rule constraint: 
    Person( age > 20 )
    Copy to Clipboard Toggle word wrap
    This searches the working memory for people older than twenty.
Rule constraints do not have direct access to variables that have been defined inside the rule flow. You can, however, possible to refer to the current process instance inside a rule constraint, by adding the process instance to the working memory and matching it to the process instance in your rule constraint.
Red Hat has added special logic to make sure that a processInstance variable of the type WorkflowProcessInstance will only match the current process instance and not to other process instances in the working memory. You, however, are responsible for inserting the process instance into the session and, updating it, using, for example, either Java code or an on-entry or on-exit or explicit process action.
The following example of a rule constraint will search for a person with the same name as the value stored in the process variable name: 
processInstance : WorkflowProcessInstance()
Person( name == ( processInstance.getVariable("name") ) )
# add more constraints here ...
Copy to Clipboard Toggle word wrap
Red Hat logoGithubredditYoutubeTwitter

Apprendre

Essayez, achetez et vendez

Communautés

À propos de la documentation Red Hat

Nous aidons les utilisateurs de Red Hat à innover et à atteindre leurs objectifs grâce à nos produits et services avec un contenu auquel ils peuvent faire confiance. Découvrez nos récentes mises à jour.

Rendre l’open source plus inclusif

Red Hat s'engage à remplacer le langage problématique dans notre code, notre documentation et nos propriétés Web. Pour plus de détails, consultez le Blog Red Hat.

À propos de Red Hat

Nous proposons des solutions renforcées qui facilitent le travail des entreprises sur plusieurs plates-formes et environnements, du centre de données central à la périphérie du réseau.

Theme

© 2026 Red HatRetour au début