Cannot make converter from byte[] to String

[magnusar]

The examples for how to use an OverrideConverter for Calendar objects, for example described here #359 works fine for us.

But I'm unable to make a converter work for the type byte[] that outputs it as a String. How can this be achieved? The following does not work:

OverrideConverter converter = new OverrideConverter();
converter.add("array[byte]", jsonString);
ModelConverters.addConverter(converter, true);

Our property looks like this:
@ApiModelProperty(value = "base64 encoded string", notes = "base64 string", required = true)
private byte[] myBytes;

We are using com.wordnik:swagger-jaxrs_2.11:1.3.10 in a Dropwizard project.

[webron]

Instead of using a converter, have you tried the following?

@ApiModelProperty(value = "base64 encoded string", dataType="string", notes = "base64 string", required = true)
private byte[] myBytes;

I'm not entirely sure it'll work with string, but if not, you can also try String or java.lang.String.

[magnusar]

Yes I've already tried that. It doesn't work. It produces a Scala match error "scala.MatchError: string (of class java.lang.String)"

(Using just byte in combination with dataType="string" works fine and the output is a string. It's the byte[] that I can't make work.)

[webron]

You've tried all 3 variants?
Also, not that it should matter, can you also try changing your dependency to swagger-jersey-jaxrs instead?

[webron]

Hmm, it looks like this is related to #334 unfortunately.
I'm not sure you can assign a converter to an array, but @fehguy will have to comment on that.

[magnusar]

Sorry, what are the three variants? Yeah I can try changing the dependency.

[webron]

Well, you can try string, String, or java.lang.String.

[fehguy]

I don't believe you can override datatypes in model properties, period.

[webron]

Theoretically, we allow it - https://github.com/wordnik/swagger-core/blob/master/modules/swagger-annotations/src/main/java/com/wordnik/swagger/annotations/ApiModelProperty.java#L67

[fehguy]

Yes, you can add the annotations, but I don't believe they're honored. I'd suggest checking the tests.

Per @webron's comment below, I was mistaken.

[webron]

Just tested it and it works fine. I've used @ApiModelProperty(dataType="string") on a getter of a long field and the specification came out as string.

@magnusar - if it doesn't work for you, could you please produce a test case I can check locally?

[magnusar]

@webron && @fehguy : I'm not surprised that the annotation worked for long -> String, since it worked for me with byte -> String. The problem is the array primitive. So if you can make anything primitive[] working (preferably byte[] since that is my case) that would probably solve it.

If I end up having to patch the code myself, do you please have any pointers as to how I would go about making a converter work for arrays of Java primitives? (I'm totally new to Scala...)

Thanx for the feeback.

[webron]

Okay, I did some further testing. The problem is not related with primitive arrays but rather with arrays or anything that translates to an array. The type can be a primitive or a class, and the array could be a java array or the collections we parse as arrays (List, Set...). And this is a bug the way I see it.

@fehguy - could you look into that please?

[fehguy]

it is impossible to support all overrides in this fashion. It's a string, and to read the annotation, we're instantiating the class. So "List[String]" is not only invalid syntax for java, but impossible to instantiate because List isn't a concrete class.

I suggest we document the behavior, add support for overrides in the property parsing, and start using concrete classes for overrides rather than string representations.

[webron]

With swagger-core 1.5 I don't think it's relevant anymore, but I'm not sure follow everything you say here.
I agree with the usage of concrete classes instead of a string (though it would be a problem with collections). But what is the actual problem with replacing a value type of array with another one?
Just to make sure we're on the same page, I'm referring to this:

@ApiModelProperty(dataType="string")
private byte[] myBytes;

vs

@ApiModelProperty(dataType="string")
private long date;

The first sample doesn't work, the second works fine.

[magnusar]

As an input to the discussion, when I look at the response body where we also have a byte[] it looks like this in the Swagger UI if I click the Model link:

MyClass {
anotherByteArray (array[byte]): base64 encoded byte array
}

So "array[byte]" is used as syntax at least in the output. I don't know if that's relevant but that's why I tried "converter.add("array[byte]", jsonString);" as stated in the issue.

[magnusar]

We absolutely need to make the byte[] => string conversion work. (In the worst case I will have to try and patch the code myself or we have to choose some other framwork.) Do you think you guys could add a fix for this in the near future?

[webron]

@magnusar - there is a workaround but that would require you to duplicate your model and may add a few additional annotations for the documentation. It may be enough for you for now.

[magnusar]

@webron could you please give me an example of that workaround and what extra annotations I should add?

[webron]

It's a bit difficult since I don't know how you use your model (as a body parameter, response type..).

For starters, you'd have to create a copy of the class and replace the byte[] field with a String field.

[magnusar]

Ok, here's a simplified version of the model:

MyView.java:

@DaTa
@AllArgsConstructor
@NoArgsConstructor
@apimodel(value = "Bla bla bla")
public class MyView {

@ApiModelProperty(value = "a name", required = true)
private String name;

@ApiModelProperty(value = "some text", dataType="", notes = "base64 string", required = true)
private byte[] byteArray;
}

And then we use it like this:

@post
@path("/someservice")
@ApiOperation(value = "bla, bla",
notes = "bla bla",
response = MyView.class)
public MyView doRequest(@ApiParam(value = "Parameters for ...", required = true) InputObject inputObject) {

return getNewMyViewInstance(inputObject);

}

[webron]

Okay, so you'd have something like this:

@ApiModel(value = "MyView")
public class MySwaggerView {

@ApiModelProperty(value = "a name", required = true)
private String name;

@ApiModelProperty(value = "some text", notes = "base64 string", required = true)
private String byteArray;
}

And:

@POST
@Path("/someservice")
@ApiOperation(value = "bla, bla",
notes = "bla bla",
response = MySwaggerView.class)
public MyView doRequest(@ApiParam(value = "Parameters for ...", required = true) InputObject inputObject) {

return getNewMyViewInstance(inputObject);

}

(I'm ignoring the fact that in the sample there are only private fields with no setters)

[magnusar]

Yeah, that works. Thanks! (The setters are generated automatically by the Lombok annotation @DaTa.)

I'm not sure this duplication of model classes will be acceptable as a solution but perhaps we can use it temporarily. Do you know if we can expect a fix for this issue in a future snapshot release of Swagger?

[webron]

As said it's a workaround. I can't comment as to if or when a different solution will be available.

[fehguy]

OK I've dug into this--you cannot change a model property with an override converter from an array to a simple type like string. I understand where it may be desirable but I think this is more of a design challenge in the API than a configuration in swagger.

You can do this:

@ApiModelProperty(dataType="string")
var myBytes: Array[Byte] = _

but the model will be this:

  "properties": {
    "myBytes": {
      "type": "array",
      "items": {
        "type": "string",
        "format": "byte"
      }
    }
  }

I have fixed the error message to not be so opaque, though, as you first reported:

2f2caca