Adds removeEmployee method to Project

src/main/java/dgpena/siexample/persistence/Project.java

@@ -20,7 +20,7 @@ public class Project {
 	
 	private String name;
 	
-	@OneToMany(mappedBy="project", cascade = {CascadeType.REMOVE, CascadeType.PERSIST})
+	@OneToMany(mappedBy="project", cascade = {CascadeType.REMOVE, CascadeType.PERSIST}, orphanRemoval = true)
 	private Set<ProjectAssignment> projectAssignments = new HashSet<>();
 	
 	public int getId() {
@@ -54,9 +54,19 @@ public class Project {
 		// the ProjectAssignment is automatically persisted due to CascadeType.PERSIST
 	}
 
+	public void removeEmployee(Employee e) {
+		for (ProjectAssignment pa: this.projectAssignments) {
+			if (pa.getEmployee().equals(e)) {
+				// this will call internalRemoveProjectAssignment
+				pa.setProject(null);
+
+				// the project assignment will be also removed from the DB due to "orphanRemoval"
+			}
+		}
+	}
+
 	void internalRemoveProjectAssignment(ProjectAssignment projectAssignment) {
 		this.projectAssignments.remove(projectAssignment);
-		
 	}
 
 	void internalAddProjectAssignment(ProjectAssignment projectAssignment) {

src/test/java/dgpena/siexample/persistence/ProjectsTest.java

@@ -69,6 +69,39 @@ public class ProjectsTest extends SQLBasedTest {
 		assertEquals(1, res.getInt("total"));
 	}
 
+	@Test
+	public void testRemoveEmployeeFromProject() throws SQLException {
+		// insert a project previously with JDBC
+		int projectId = insertAProject();
+
+		// insert an employee previously with JDBC
+		int employeeId = insertAnEmployee();
+
+		// assign the employee to the project (which should be removed due to CascadeType.REMOVE
+		// in Project.projectAssignments)
+		Statement statement = jdbcConnection.createStatement();
+		statement.executeUpdate("INSERT INTO ProjectAssignment(project_id, employee_id) values("+projectId+", "
+				+employeeId+")", Statement
+				.RETURN_GENERATED_KEYS);
+
+		EntityManager em = emf.createEntityManager();
+
+		em.getTransaction().begin();
+			Project p = new Projects(em).findById(projectId);
+			Employee e = new Employees(em).findById(employeeId);
+
+			p.removeEmployee(e);
+		em.getTransaction().commit();
+
+
+		// ensure that the project assignment does not exist
+		statement = jdbcConnection.createStatement();
+		ResultSet res = statement.executeQuery("SELECT COUNT(*) as total from ProjectAssignment where employee_id = " +
+				""+employeeId+" and project_id = "+projectId);
+		res.next();
+		assertEquals(0, res.getInt("total"));
+	}
+	
 	@Test
 	public void testCreateProjectAssignment() throws SQLException {
 		// insert a project previously with JDBC