Create Json from a Java Swagger model

Question

Suppose I have an object of class io.swagger.models.Swagger, from the library io.swagger:swagger-models:1.5.24. How do I transform it into JSON?

My goal is to create a json file from our REST API definition. We're using Finch/Finagle in Scala, and this will be a brand new capability; I'd like it to be as generic as possible. I have an idea for the design, but it requires turning the Java model into JSON, and I haven't found that facility in Swagger yet.

This is swagger v2. Don't know what version of OpenAPI it is. It would be appreciated if there was also a method for generating swagger v3 and the related OpenAPI, but swagger v2 is an absolute necessity here.

It turns out to be very easy to do this with Gson. I'll post an answer to this question shortly. — Larry B.

Larry B. Larry B. · Accepted Answer · 2019-11-07T02:18:28

You can use the Gson library to encode the Java object. I used "com.google.code.gson" % "gson" % "2.8.6" in my build.sbt file.

The Scala code looks like this:

def getServerJson: String = {
    val gson = (new GsonBuilder).setPrettyPrinting().create
    val swag = new Swagger()

    val op = new Operation
    op.setVendorExtensions(null)
    op.setSummary("Updates a pet in the store with form data")
    op.consumes("application/x-www-form-urlencoded")
    val p = new Path
    p.setVendorExtensions(null)
    p.setPost(op)
    swag.path("/pet/{petId}",p)

    gson.toJson(swag)
  }

It's stateful, which is kind of annoying. Maybe there are immutable model objects that would be easier to manipulate in a functional program. That's not too big a deal, it satisfied my immediate need. The Json produced looks like:

{
  "swagger": "2.0",
  "paths": {
    "/pet/{petId}": {
      "post": {
        "summary": "Updates a pet in the store with form data",
        "consumes": [
          "application/x-www-form-urlencoded"
        ],
        "parameters": []
      }
    }
  }
}

Create Json from a Java Swagger model

1 Answers