如何使用JSTL将ModelAndView中的Hashmap的键和值（在UserDefinedClass中）循环到JSP

Question

I am having a problem showing my key and value from my HashMap in which the value is in User Defined Class here is the error that shows

Student.class :

class Student 
{
   private String name;
   private int age;
   //getter and setter
}

My CONTROLLER:

@RequestMapping(value = "/showStudent", method = RequestMethod.GET)
public ModelAndView retrievesession(HttpSession session) 
{
    ModelAndView mav = new ModelAndView("ShowStudent");
    Map<String,ArrayList<Student>> classList = new HashMap<String,ArrayList<Student>>();
    ArrayList<Student> student = new ArrayList<Student>();

    String nameUser = (String) session.getAttribute("name");
    String trackUser = (String) session.getAttribute("track");

    if(nameUser.equals("Kakashi") && trackUser.equals("Konoha"))
    {
        student.add(new Student("Naruto",12));
        student.add(new Student("Sasuke",13));
        classList.put("Ninja", student);

        mav.addObject("classList", classList);
    }

    else if(nameUser.equals("Goku") && trackUser.equals("Earth"))
    {
        student.add(new Student("Gohan",25));
        student.add(new Student("Goten",13));
        classList.put("Fighter", student);

        mav.addObject("classList", classList);
    }

    else if(nameUser.equals("Ryuk") && trackUser.equals("Killer"))
    {
        student.add(new Student("Kira",22));
        student.add(new Student("L",21));
        classList.put("Reaper", student);

        mav.addObject("classList", classList);
    }

    return mav;
}

My JSP:

<h3>Name: ${name}</h3>  
<h3>Track: ${track}</h3><br/><br/><br/>
<h3>Your student from ${classList.key}</h3>
<c:if test="${not empty classList}">
    <table>
    <c:forEach items="${classList}" var="classList">
       <tr>
           <td>${classList.value.name}</td>
           <td>${classList.value.age}</td>
       </tr>
    </c:forEach>
    </table>
</c:if>

I don't know if I'm doing it correctly, it is just showing the values that I am having a problem with, and also can I add an else statement, so if the session is null it will return to the login page?

Answer 1

Iterating over the map you'll get one more collection you need to iterate in another loop before you can get properties of the object.

<table>
<c:forEach items="${classList}" var="list">
  <tr><td><h3>Your student from ${list.key}</h3></td></tr>
  <tr><td>
   <table>
   <c:forEach items="${list.value}" var="student">
       <tr>
           <td>${student.name}</td>
           <td>${student.age}</td>
       </tr>
    </c:forEach>
   </table>
  </td></tr>
</c:forEach>
</table>

Answer 2

Use the code as:-

<h3>Name: ${name}</h3>  
<h3>Track: ${track}</h3><br/><br/><br/>
<h3>Your student from ${classList.key}</h3>
<c:if test="${not empty classList}">
   <table>
<c:forEach items="${classList}" var="class">
   <tr>
       <td>${class.name}</td>
       <td>${class.age}</td>
   </tr>
</c:forEach>
</table>