Swagger API consuming json with json validation

Question

I am using Swagger to generate a Restful API:

@POST
@Consumes({ "application/json" })
@Produces({ "application/json" })
@io.swagger.annotations.ApiOperation(value = "Create a task", notes = "", response = Tasks.class)
@io.swagger.annotations.ApiResponses(value = { 
    @io.swagger.annotations.ApiResponse(code = 200, message = "created task", response = Tasks.class),
    @io.swagger.annotations.ApiResponse(code = 404, message = "task not found", response = Tasks.class),
    @io.swagger.annotations.ApiResponse(code = 200, message = "unexpected error", response = Tasks.class) })
public Response createTask(@ApiParam(value = "The task to create" ,required=true ) NewTask newTask)
throws NotFoundException {
    return delegate.createTask(newTask);
}

This API accepts json strings and generates java objects from it. This is working quiet well with one exception: The API accepts any correct formed json string but ignores the content of the json which means i get an object created with default values.

So my question is: How can i validate the incoming jsonstring ( against a json schema) before the actual java object is generated?

How do perform the validation against the schema? You can receive your JSON as String, validate it and then create a object from it using Jackson, for example. But, since you are performing validations, have you considered Bean Validation? — cassiomolin
– cassiomolin, Commented Dec 1, 2015 at 13:53
The problem is, i would have to change the API to receive a json string instead of an object like public Response createTask(String jsonTask) in the methods parameters afaik but i would prefer to have the object there if its possible. — Gobliins
– Gobliins, Commented Dec 1, 2015 at 14:17

cassiomolin · Accepted Answer · 2015-12-01 14:39:33Z

1

Since you don't want to receive a JSON String in your methods and Bean Validation is not an option for your validation, you could try a MessageBodyWriter<T>.

JAX-RS uses MessageBodyWriter<T>s to parse incoming requests. Since you want something very specific, consider writing your own MessageBodyWriter<T>.

See the following example:

@Provider
@Produces("application/json")
public class CustomMessageBodyWriter implements MessageBodyWriter<Object> {

    @Override
    public boolean isWriteable(Class<?> type, Type genericType,
                               Annotation[] annotations, MediaType mediaType) {
        return true;
    }

    @Override
    public long getSize(MyBean myBean, Class<?> type, Type genericType,
                        Annotation[] annotations, MediaType mediaType) {

        // Deprecated by JAX-RS 2.0
        return 0;
    }

    @Override
    public void writeTo(Object object, Class<?> type, Type genericType,
                        Annotation[] annotations, MediaType mediaType,
                        MultivaluedMap<String, Object> httpHeaders,
                        OutputStream entityStream) throws IOException {

        // Read the entityStream
        // Perform the validation against your schema
        // Write to the object
    }
}

The @Provider annotation makes the class to be automatically discovered by the JAX-RS runtime during a provider scanning phase.

answered Dec 1, 2015 at 14:39

cassiomolin

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4 Comments

Gobliins Over a year ago

One question: I am using Swagger which brings its own MessageBodyWriter. link Would i need to change the swagger source? Or is there another way i could force the use of my own implementation (without reflection)?

cassiomolin Over a year ago

@Gobliins Annotating your MessageBodyWriter with @Provider or registering it to your Applicationor ResourceConfig class should be enough to it be recognized by Jersey/JAX-RS.

Gobliins Over a year ago

Err.. wouldn't i need the other way (DeSerializer)? Since the i want to verify an incoming json before mapping it to the model and not writing a model in a json stream?

cassiomolin Over a year ago

@Gobliins Jersey/JAX-RS already provide a MessageBodyReader<T> for JSON. You can write your own if the provided one doesn't fit your needs.

Sven Döring · Accepted Answer · 2019-10-03 09:39:40Z

0

There is the swagger-request-validator having several adapters for various frameworks, e.g.: Spring Web MVC

It is capable of validating requests and / or responses against Swagger / OpenAPI 2 or OpenAPI 3 schemes.

See here: Validating JSON messages against Swagger definition in Java for a more detailed answer.

answered Oct 3, 2019 at 9:39

Sven Döring

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