Validate Json Request Schema

Question

So I have this Controller class that contain this method:

    @RequestMapping(value = "/x", method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE, consumes = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<MyRepsonseClass> get(
        @ApiParam(value = "x", required = true) @Valid @RequestBody MyRequestClass request
    ) throws IOException {
        //yada yada my logic here
        return something;
    }

The Json Request gets automatically Mapped to MyRequestClass.java

This is what that class looks like:

@lombok.ToString
@lombok.Getter
@lombok.Setter
@JsonInclude(JsonInclude.Include.NON_EMPTY)
@ApiModel(description = "description")
public class MyRequestClass {
    private List<SomeClass> attribute1;
    private SomeOtherClass attribute2;
    private YetAnotherClass attribute3;
}

This is an example of a valid json request:

{
    "attribute1": [
        {
            "key":"value"
        }
    ],
    "attribute3": {
        "key":"value"
    }
}

Now, my requirement is to return an Error Message when the request contains an attribute that doesn't exist in the MyRequestClass.java.

As such:

{
    "attribute1": [
        {
            "key":"value"
        }
    ],
    "attribute_that_doesnt_exist": {
        "key":"value"
    }
}

Right now it's not throwing any error. Rather, it's simply not mapping that attribute to anything. Are there annotations I can utilize that can make this happen quickly ?? Thank you.

Answer 1

Create a custom deserializer:

public class MyRequestClassDeserializer extends JsonDeserializer<MyRequestClass> {
    @Override
    public MyRequestClass deserialize(JsonParser jsonParser, DeserializationContext context) throws IOException, JsonProcessingException {
        MyRequestClass mrc = new MyRequestClass();
        ObjectMapper mapper = new ObjectMapper();
        JsonToken currentToken = null;
        while((currentToken = jsonParser.nextValue()) != null) {
            if(currentToken.equals(JsonToken.END_OBJECT) 
                    || currentToken.equals(JsonToken.END_ARRAY))
                continue;
            String currentName = jsonParser.getCurrentName();
            switch(currentName) {
                case "attribute1":
                    List<SomeClass> attr1 = Arrays.asList(mapper.readValue(jsonParser, SomeClass[].class));
                    mrc.setAttribute1(attr1);
                    break;
                case "attribute2":
                    mrc.setAttribute2(mapper.readValue(jsonParser, SomeOtherClass.class));
                    break;
                case "attribute3":
                    mrc.setAttribute3(mapper.readValue(jsonParser, YetAnotherClass.class));
                    break;
                // <cases for all the other expected attributes>
                default:// it's not an expected attribute
                    throw new JsonParseException(jsonParser, "bad request", jsonParser.getCurrentLocation());
            }
        }
        return mrc;
    }
}  

And add this annotation to your MyRequestClass class: @JsonDeserialize(using=MyRequestClassDeserializer.class)

The only "problem" is that manually deserializing jsons can be a hassle. I would have written the complete code for your case but I'm not good enough at it right now. I might update the answer in the future.

Edit: Done, now it's working code. I thought it was more complicated.

Answer 2

Did you try this annotation @JsonIgnoreProperties(ignoreUnknown = false)

If Spring boot, even better, use this property in application.properties(yaml)

spring.jackson.deserialization.fail-on-unknown-properties=true