Parsing OpenAPI definitions results in error

[Blaž Ocepek]

Hello 

I have a strange issue when importing OpenAPI definition for our server when passing it via http://localhost:60000/swagger/v1/swagger.json an error is thrown:
[ZAP-Import-OpenAPI-1] WARN  org.zaproxy.zap.extension.openapi.ExtensionOpenApi - class io.swagger.v3.oas.models.media.JsonSchema cannot be cast to class io.swagger.v3.oas.models.media.ArraySchema (io.swagger.v3.oas.models.media.JsonSchema and io.swagger.v3.oas.models.media.ArraySchema are in unnamed module of loader org.zaproxy.zap.control.AddOnClassLoader @4559cdc2)
java.lang.ClassCastException: class io.swagger.v3.oas.models.media.JsonSchema cannot be cast to class io.swagger.v3.oas.models.media.ArraySchema (io.swagger.v3.oas.models.media.JsonSchema and io.swagger.v3.oas.models.media.ArraySchema are in unnamed module of loader org.zaproxy.zap.control.AddOnClassLoader @4559cdc2)
at org.zaproxy.zap.extension.openapi.generators.DataGenerator.generateArrayValue(DataGenerator.java:153)
at org.zaproxy.zap.extension.openapi.generators.DataGenerator.generateParam(DataGenerator.java:136)
at org.zaproxy.zap.extension.openapi.generators.DataGenerator.generate(DataGenerator.java:75)
at org.zaproxy.zap.extension.openapi.generators.PathGenerator.generateFullPath(PathGenerator.java:43)
at org.zaproxy.zap.extension.openapi.converter.swagger.RequestModelConverter.generatePath(RequestModelConverter.java:60)
at org.zaproxy.zap.extension.openapi.converter.swagger.RequestModelConverter.convert(RequestModelConverter.java:46)
at org.zaproxy.zap.extension.openapi.converter.swagger.SwaggerConverter.convertToRequest(SwaggerConverter.java:208)
at org.zaproxy.zap.extension.openapi.converter.swagger.SwaggerConverter.getRequestModels(SwaggerConverter.java:202)
at org.zaproxy.zap.extension.openapi.ExtensionOpenApi$1.run(ExtensionOpenApi.java:427)


It took me a while to find the difference if i cppy te content of swagger.json and imoprt as a file there are no issues. 
The difference i found tis this part :
NOT FAILING WITH FILE :
"/api/....." : {
      "get" : {
        "tags" : [ "...." ],
        "summary" : "...",
        "parameters" : [ {
          "name" : "code",
          "in" : "path",
          "description" : "Code desc",
          "required" : true,
          "schema" : {
            "type" : "string"
          }
        }, {
          "name" : "previewSizes",
          "in" : "query",
          "description" : "Preview size desc",
          "schema" : {
            "type" : "array",
            "items" : {
              "type" : "string"
            }
          }
        }, {
          "name" : "attachmentIds",
          "in" : "query",
          "description" : "Attachemnt id desc",
          "schema" : {
            "type" : "array",
            "items" : {
              "type" : "string",
              "format" : "uuid"
            }
          }
        } ],
        "responses" : {...}
      }


FAILING WHEN IMPORTING FOMR URI:

"/api/...": {
      "get": {
        "tags": ["..."],
        "summary": "...",
        "parameters": [{
          "name": "code",
          "in": "path",
          "description": "Code desc",
          "required": true,
          "style": "simple",
          "explode": false,
          "schema": {}
        }, {
          "name": "previewSizes",
          "in": "query",
          "description": "Preview size desc",
          "required": false,
          "style": "form",
          "explode": true,
          "schema": {
            "items": {}
          }
        }, {
          "name": "attachmentIds",
          "in": "query",
          "description": "Attachemnt id desc",
          "required": false,
          "style": "form",
          "explode": true,
          "schema": {
            "items": {
              "format": "uuid"
            }
          }
        }],
        "responses": {...}
        }
      },


The important part is the `previewSize` parameter the difference in schema definition.

How I got to this JSON output is this additional line to openApi add-on attached photo

[Simon Bennetts]

Hiya,

Can you provide a full OpenAPI example file which shows this problem?

If we can reproduce it then we can look at fixing it :)

In theory would could recreate full examples from fragments, but this takes time and so might not be something we get around to quickly.

Cheers,

Simon

[Blaž Ocepek]

Hello

The issue is that when I import the whole OpenPAI via file just copied from the server response there are no issues. When I am back in office I can try to create a valid OpenAPI definition that will reproduce the issue. 

V V čet., 12. feb. 2026 ob 13:14 je oseba Simon Bennetts <psi...@gmail.com> napisala:

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Lep pozdrav

Blaž Ocepek

031-217-120

[Blaž Ocepek]

Hello sorry it took a while to prepare a nice example.

This is the JSON Open Api definition. 

{

  "openapi": "3.1.1",
  "info": {
    "title": "API Documentation",
    "description": "Broken open api definition.",
    "version": "v1"
  },
  "paths": {
    "/api/someApiEndpoint/attachments": {
      "get": {
        "parameters": [
          {
            "name": "parameterName",
            "in": "query",

            "schema": {
              "type": "array",
              "items": {
                "type": "string"
              }
            }
          }

        ]
      }
    }
  }
}

To reproduce service this json on a local server and then import that open api definition from the server.

In other words use the local server to import the open api definition like so:
 

[Blaž Ocepek]

Hello

Any update on this?