How do I make fields in DTO optional using lombok?-CodePudding

So I have a DTO like this,

@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
@Builder
@ToString
@JsonIgnoreProperties(ignoreUnknown=true)
public class PersonDTO {
  private String name;
  private String address;
  private String phone;
  private String other;
}

I am passing the following payload to an external API

{
    "name": "John",
    "phone": "123",
    "address": "abc"
}

This is throwing me 500 internal error:

HttpClientErrorException$NotFound: 404: "{<EOL> "status": "Error", <EOL> "message": "Error validating JSON. Error: - Invalid type Null, expected String."}"

If I comment out other property in DTO then I will successfully get 200 response. I thought @JsonIgnoreProperties annotation is supposed to ignore the properties that are not present but it seems that's not working.

CodePudding user response：

you are using lombok's @NoArgsConstructor and @AllArgsConstructor. So you have to use one or the other. If you don't want an all args constructor you'll have to implement your own.

@NoArgsConstructor
@Getter
@Setter
@Builder
@ToString
@JsonIgnoreProperties(ignoreUnknown=true)
public class PersonDTO {
  private String name;
  private String address;
  private String phone;
  private String other;

  public PersonDTO(String name, String address, String phone) {
    super(name, address, phone, "");
  }

  public PersonDTO(String name, String address, String phone, String other) {
    this.name = name;
    this.address = address;
    this.phone = phone;
    this.other = other
  }

}

Or if you have control over AND this is a spring boot app, you could try using required=false in your controller so you can continue to use an all arg constructor.

public PersonDTO getPerson(
      @PathVariable(value = "name") String name,
      @PathVariable(value = "address") String address
      @PathVariable(value = "phone") String phone
      @PathVariable(value = "other", required = false) String other) { 

 ....

}

CodePudding user response：

The error says that they can't parse Null into String. That's very interesting error and fooled me first. Your json object with other field null probably looks like this:

{
    "name": "John",
    "phone": "123",
    "address": "abc"
}

So somehow this API can't just wrap quotes around null and tells you it's not able to parse this.

Therefore I guess you need to set the value of other to an empty string:

@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
@Builder
@ToString
@JsonIgnoreProperties(ignoreUnknown=true)
public class PersonDTO {
  private String name;
  private String address;
  private String phone;
  private String other = ""; //empty because external api can't handle null
}

CodePudding user response：

If attributes are nullable then you can use @JsonInclude(Include.NON_NULL). This will allow to set null value in the attributes. I guess, by default it doesn't allow null value.

CodePudding user response：

Adding @JsonInclude(JsonInclude.Include.NON_NULL) is the solution as you said in the comment. This annotation tells the serializer to ignore fields that are null. If you don't add this the payload will look like this:

{
    "name": "John",
    "phone": "123",
    "address": "abc",
    "other": null
}