Struts Action class 中的不可序列化属性

Question

I am working on refactoring our code according to Sonar and Kiuwan analyzers recommendations. Our architecture is standard MVC Java Web App based on Struts 2.x framework deployed on Apache Tomcat 9.x. App itself is basically an information system that allows users to browse pdf documents and perform actions on them.

I have run into a design flaw which I am not sure how to solve or if it even is an problem all togther.

During http request processing we set set up Hibernate's Entity Manager instance in Interceptor class before Struts Actions are called. We are using this EM instance for the whole lifecycle of the Struts action. When the action finishes the interceptor closes the EM instance. The EM instance is saved into instance of action class as an class attribute. Snippet below.

class BaseAction extends ActionSupport implements EntityManagerAware { //EntityManagerAware my interface that allows interceptor to inject em instance into underlying Action class
    private EntityManager em;
    private String someParam;

    @Action(value = "welcome", results = {@Result(name = SUCCESS, type = "tiles", location = "welcome")})
    public String input() {
        em.doStuffWithEntities();
        log.trace("Some param": + someParam);
        return SUCCESS;
    }

...
}

I have always thought this is solution is OK, but now we introduced Sonar. Sonar marks em attribute as - Make "em" transient or serializable. I understand that Sonar thinks it is an attribute that might be passed during HttpRequests, line someParam attribute in the snippet above.

My question is do Struts action attributes need to be Serializable (even the ones like "em")? Can I somehow solve this with perhaps Struts annotation or simply with transient flag? When does serialization of Action class instance occur? Can it occur?

Basically can somebody explain this in greater detail (I can always just mark this Sonar issue as false positive, but I really do not know how this works)? I have googled and googled but came up empty handed.

Thank you very much,

Jiri

Answer 1

EntityManager should be a persistent dependency , for example:

 @PersistenceUnit(unitName = "QueryPersistenceUnit") private EntityManagerFactory entityManagerFactory; public EntityManager getEntityManager() { return entityManagerFactory.createEntityManager(); }