Create Enrollment entity model and Data Access Object

[aolguin89]

User Story

As a developer
I want to implement the Enrollment entity and DAO layer
So that the application can manage student course enrollments

Description

Implement Enrollment POJO and DAO layer to handle the many-to-many relationship between users and courses.

Tasks

Enrollment Model (POJO)

• Create Enrollment.java in model/ package
• Add all fields matching enrollments table schema
• Implement constructors
• Implement getters and setters
• Override toString()
• Add Javadoc documentation

Enrollment DAO Interface

• Create EnrollmentDAO.java interface in dao/ package
• Define method signatures for enrollment operations
• Add Javadoc documentation

Enrollment DAO Implementation

• Create EnrollmentDAOImpl.java in dao/ package
• Implement enroll(int userId, int courseId) - create enrollment
• Implement unenroll(int userId, int courseId) - remove enrollment
• Implement isEnrolled(int userId, int courseId) - check if enrolled
• Implement findByUser(int userId) - user's enrollments
• Implement findByCourse(int courseId) - course's enrollments
• Implement countByCourse(int courseId) - enrollment count
• Handle duplicate enrollment attempts
• Handle capacity validation
• Close resources correctly

Testing

• Test enroll() creates enrollment record
• Test duplicate enrollment is prevented
• Test isEnrolled() returns correct status
• Test countByCourse() returns correct count
• Test capacity limit enforcement

Acceptance Criteria

• Enrollment.java includes all fields from schema
• EnrollmentDAO implements all operations
• Cannot enroll twice in same course (unique constraint)
• Capacity validation works (if implemented)
• All methods handle errors gracefully
• Code includes Javadoc