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

问题

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?

回答1:

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:

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 +
                '}';
    }
}

Perform the request to your endpoint, for example with this json data:
```
{
    "firstName": "notDefault"
}
```
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}

回答2:

Adding to @Edd answer, if you want to override the default values from the input, then we have to annotate the bean with @JsonAutoDetect, as follows:

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;

@JsonAutoDetect(fieldVisibility = Visibility.ANY, getterVisibility = Visibility.NONE, setterVisibility = Visibility.NONE)
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 +
                '}';
    }
}

来源：https://stackoverflow.com/questions/35499575/spring-4-mvc-rest-service-use-default-values-in-beans

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java

Spring

rest

spring-mvc

spring-4