spring - How to show values only from specific java classes? -

i have table contains sorts of attributes set in constructors of java classes. need show attributes when want easy way nullpointers. have tried jstl if , jstl choose trick.

<c:choose>     <c:when test="${empty animal.getearsize()}">         not set!     </c:when>     <c:otherwise>         ${animal.getearsize()}     </c:otherwise> </c:choose> 

but when try run http status 500 - exception occurred processing jsp page. animal variable in jstl loop , not animals have earsize in constructor.

what doing wrong here? there way or way jstl choose or if?

edit: i'm using method in controller gives map animal objects i'm looping through.

public africanelephant(string color, string bodycovering, string name, double weight, gender gender, int earsize) {     super(color, bodycovering, name, weight, gender, maxnumberofeggs, earsize); }  public parrot(string color, string bodycovering, string name, double weight, gender gender) {     super(color, bodycovering, name, weight, gender, maxnumberofeggs); } 

these 2 sample constructors in elephant constructor there variable earsize in parrot constructor there no variable earsize.

edit: have changed choose this:

<td>              <c:if test="${animal.getclass().name eq 'mypackage.mypath.africanelephant'}">${animal.earsize}</c:if> 

this fixes http status 500 error displays 0 in table instead of earsize set me.

my controller:

@controller("animalcontroller") 

public class animalcontroller {

 arraylist<animal> animals = new arraylist<animal>();  @requestmapping(value = "/animaloverview", method = requestmethod.get) public string animals(map<string, object> model, @requestparam(value = "race", required = false, defaultvalue = "") string race){     if(race.isempty()){          model.put("animals", zoo.getinstance().getallanimals());      }      else{         model.put("animals", zoo.getinstance().getanimalsbyrace(race));    }      return "animalkingdom"; } 

you cannot check way. el empty works empty string or null, not non-existent property. either add getearsize() method parrot returns null, or check if animal instanceof africanelephant , print ${animal.earsize} (not getearsize()!).

something like:

<c:if test="${animal.getclass().name eq 'package.path.africanelephant'}"> 

also, amit goel's answer wrong. el using getter method, , not accessing property directly (and should private). if have method e.g.: getfullsize() returns calculation's result, don't have fullsize property, can still ${animal.fullsize} , display result.