[java] Java Persistence API (JPA) Entity Rule: Public or Protected No-Arg Constructor

Proposed Rule Name: JPANoArgumentConstructor

Proposed Category: Bug

Description:

When a class is annotated with JPA's @Entity, there are certain requirements placed on the class. Please create a rule that requires a no-argument constructor. The constructor must have public or protected access.

Code Sample:

The following class will cause a problem at runtime because it does not have a no-argument constructor.

@Entity
class MyEntity
{
   public MyEntity(int value)
   {
      ...
   }
}

The following class is correct.

@Entity
class MyEntity
{
   protected MyEntity()
   {
      ...
   }

   public MyEntity(int value)
   {
      ...
   }
}

Possible Properties:

• allowPackage: Hibernate allows for package protected no-argument constructors

No source files, tests, or entry points are named. Start by locating the Java rule implementation and test conventions for annotation-based rules, then verify the behavior against the two constructor examples and the optional package-private setting described in the issue.