Spring 4 MVC - Rest service - use default values in beans

Question

I am using Spring 4.1.4 and implementing a simple REST service. I do have a POST method which gets a Person object as request.

@ResponseStatus(value = HttpStatus.CREATED)
@RequestMapping(value = "", method = RequestMethod.POST, headers = "Accept=application/json", consumes = "application/json")
public void add(@Valid @RequestBody Person oPerson) throws Exception {
    //do the things
}

Bean:

public class Person {

    public Person(){ }

    private String firstname;

    private String lastname;

    private Integer activeState;

    //getter+setter
}

My question is - is there a possibility to set a default value for the properties in the bean. Something like this:

@Value(default=7)
private Integer activeState;

I know when using the @RequestParam annotation in a @RestController methode it is possible to set a default value with @RequestParam(value="activeState", required=false, defaultValue="2") but is there a possibility to do a similar thing on class level?

Solution

Your Person class is not really a spring bean. It is simply a class whose parameters are set when you make a call to your application endpoint due to the @RequestBody annotation. The parameters which are not in the body of your call will simply not get binded so to solve your problem you can do this:

1. Set default values for your person class like this (toString() is overridden for convenience:

   public class Person {
   
       public Person() {
       }
   
       private String firstName = "default";
       private String lastName = "default";
       private Integer activeState = 7;
   
       public String getFirstName() {
           return firstName;
       }
   
       public String getLastName() {
           return lastName;
       }
   
       public Integer getActiveState() {
           return activeState;
       }
   
       @Override
       public String toString() {
           return "Person{" +
                   "firstName='" + firstName + '\'' +
                   ", lastName='" + lastName + '\'' +
                   ", activeState=" + activeState +
                   '}';
       }
   }
   

2. Perform the request to your endpoint, for example with this json data:

   {
       "firstName": "notDefault"
   }
   

3. If you print out the person object in your controller, you'll notice that the firstName got the non-default value while others are default:

   public void add(@Valid @RequestBody Person oPerson) {
       System.out.println(oPerson);
   }
   

Console output: Person{firstName='notDefault', lastName='default', activeState=7}

Comments

[Ben]

Great, and what if your dto's are immutable? Also I don't believe it's the responsibility of dto object to dictate the behavior or controller endpoint

[Edd]

@Ben if they're immutable, then handle default value assignment in the controller method. That is, check which values are missing and make a new copy of your immutable object with them being assigned.

[Praytic]

This is not a good case when we have the same DTO for multiple endpoints. Some endpoints would like to have different default values or no default values at all.