CODEWITHSUNDEEP
javajsonrestapijersey
TheMonkWhoSoldHisCode
TheMonkWhoSoldHisCode

Reputation: 2332

Identifying if 'null' was deliberately set on the input JSON

We are creating a REST API for managing a resource. We are using Jersey framework.

Following is the structure of the JSON

cable {
  "id": 1,
  "name": "Cable 1",
  "description": "Test Cable",
  "Site": 4
}

The JSON should map to the below class.

public class CableDTO {

  private Long id;

  private String name;

  private String description;

  //private SiteDTO site;
  private Long siteID;

  .
  .
  .

  // Getters ans Setters

}

Site is actually a reference object. The input and output JSON, requires the CableDTO to contain Site id instead of the entire Site object. We have assemblers which convert the DTO's to Domain objects and vice-versa.

The sample assembler code is as below:

public class CableAssembler {

  //some code

  public void fillDomain(Cable cable, CableDto dto){
    if(dto.getId() != null) cable.setID(dto.getId());
    if(dto.getSiteID() != null) cable.setSiteId(dto.getSiteId())

    //some more code below
  }

}

This assembler works well when a brand new POST HTTP method is called. If the SiteID is not set in the input json, the site is set to null and all is hunky dory. However, on a PUT HTTP call, if the SiteID is not set, the existing SiteID is over written to null. This is because the same assembler is used in both PUT and POST call. The assembler checks if the siteID set in the DTO is null. If it is null, the existing siteID is overwritten. The problem is, I am not able to distinguish between whether the null value in the SiteID is because the value was not sent or the SiteID was indeed deliberately set to null (which is possible {"siteID":null} )

Any pointers on how to solve this?
We use Jackson for serialization/de-serialization.

Upvotes: 0

Views: 126

Answers (2)

mortalis
mortalis

Reputation: 2151

If I understood right your situation, my propositions are:

  • If you can, add a boolean field to JSON and DTO telling if the siteID was set and sent and check it in the assembler or other code;
  • Give the siteId another default value, different from null, like -1 or 0, if it's possible.

Upvotes: 1

Dmitry Gorkovets
Dmitry Gorkovets

Reputation: 2276

It seems that you use your PUT request like PATCH request. To use PUT request properly you should GET cable info, change some fields and PUT back. In this case your siteId field will remain unchanged.

Upvotes: 1

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