example41 - Handling Bidirectional Relationships in Jackson to Prevent Infinite Recursion

I wanted to check for myself what kind of information gets stored in HttpSession, so I added in `SessionController.java`.
```
@RestController
@RequestMapping("/session")
public class SessionController {

private final HttpSession session;

@Autowired
public SessionController(HttpSession session) {
this.session = session;
}

@RequestMapping(method = RequestMethod.GET)
public Map getSessionAttributes() {
Map attributes = new HashMap<>();
Enumeration attributeNames = session.getAttributeNames();
while (attributeNames.hasMoreElements()) {
String name = attributeNames.nextElement();
attributes.put(name, session.getAttribute(name));
}
return attributes;
}
}
```

The results were nice and pretty

up until `session.setAttribute("eazyClass", eazyClass);` from `AdminController.java` was executed.
AdminController.java
```
@RequestMapping("/displayStudents")
public String displayStudents(Model model, @RequestParam int classId, HttpSession session, @RequestParam(required=false) String error){
Optional eazyClassOptional = eazyClassRepository.findById(classId);
EazyClass eazyClass = eazyClassOptional.get();
model.addAttribute("eazyClass", eazyClass);
session.setAttribute("eazyClass", eazyClass);
model.addAttribute("person", new Person());

String errorMessage = null;
if(error != null) {
errorMessage = "Invalid Email entered!!";
model.addAttribute("errorMessage", errorMessage);
}
return "students.html";
}
```

It seemed like the output kept repeating itself until it couldn't anymore and then just crashed.