Creating entities rules

Question

I'd like to know the answer to this simple question.

When I create an entity object and I want to restrict a setting of an attribute (for example I don't want to allow anyone to set an integer value less then 1 to an attribute), should I implement it in the setter of this attribute or should I check this restriction latter in a class that handles these objects ? Generally, can I implement getters and setters however I want as long as my getters return and setters set attributes ?

I know there are some rules (code conventions) in java, so I don't want to break any of them.

Thanks in advance, hope that my question is clear enough and sorry for any grammar mistakes I might have made :/ .

Answer 1

Yes getters/setters are useful for that.

for example:

public void setAge(int age){
 if(age < 0){
  throw new IllegalArgumentException("Invalid age : " + age);
  //or if you don't want to throw an exception you can handle it otherways too
 }
}

You can also use Java-EE's Bean Validators for this

public class Person{

   @Min(value = 0)
   @Max(value = 99)
   private Integer age;

   //some other code
}