How to format BigDecimal as "plain text" when serializing a JsonNode from a play controller ?

[Simon]

Hi !

In Jackson, there is a settings to output a BigDecimal as a plain string instead of the scientific annotation : SerializationFeature.WRITE_BIGDECIMAL_AS_PLAIN. With this settings enabled, the serializer will call BigDecimal.toPlainString() instead of BigDecimal.toString().

To achieve this in my Play (Java) application :

1) I use a custom GlobalSettings class in which I configure the play Json API :

@Override

public void onStart(Application app) {

    ObjectMapper mapper = new ObjectMapper();

    mapper.enable(SerializationFeature.WRITE_BIGDECIMAL_AS_PLAIN);

    Json.setObjectMapper(mapper);

}

2) I created a simple route that map /test to my controller method which is :

public static Result test() {

    return ok(Json.toJson(BigDecimal.valueOf(100)));

}

However, when testing this route, the output is : 

1E+2

I expected the output :

100

So it looks like the object mapper settings are not taken into account when serializing a JsonNode from a play controller...

Looking at the play source code, I found that a JsonNode is serialised via JsonNode.toString() method in the method JavaResults.writeJson() :

def writeJson(implicit codec: Codec): Writeable[com.fasterxml.jackson.databind.JsonNode] = Writeable(json => codec.encode(json.toString), Some(ContentTypes.JSON))

JsonNode.toString() delegates this operation to DecimalNode.asText() which in turn calls BigDecimal.toString(), which uses the scientific notation... My custom object mapper settings can't be use in this case !

Would it be possible to use ObjectMapper.writeValueAsString(Object) on a JsonNode instead of the JsonNode.toString() method ? 

For example :

def writeJson(implicit codec: Codec): Writeable[com.fasterxml.jackson.databind.JsonNode] = Writeable(json => codec.encode(mapper.writeValueAsString(json)), Some(ContentTypes.JSON))

What do you think of this solution ? Is there a workaround in the mean time ?

[amertum]

Are you sure the onStart method is call in your Global extends GlobalSettings ? (This object must be defined in the root package.)

If not, it is an issue as Json.setObjectMapper said that it should work.

As for a work around, why not use an ObjectMapper factory directly in your Controller ?

public static Result test() {

    return ok(mapperFactory().valueToTree(BigDecimal.valueOf(100)));

}

private static ObjectMapper mapperFactory() {

    ObjectMapper mapper = new ObjectMapper();

    mapper.enable(SerializationFeature.WRITE_BIGDECIMAL_AS_PLAIN);

    return mapper;

[Simon]

Hi,

Thank you to have taken the time to answer.

I am sure the onStart method is called. I added a log statement which is outputed in the console...

Your solution doesn't work, the response is still :

1E+2

This is because the problem arise when a JsonNode is converted into a JSON string, not when a Java object is converted into a JsonNode...

Your workaround should rather be something like this :

public Result test() {

    return ok(asJsonContent(BigDecimal.valueOf(100)));

}

private static Content asJsonContent(Object value) {

    String json;

    try {

        json = mapperFactory().writeValueAsString(value);

    } catch (JsonProcessingException e) {

        throw new RuntimeException(e);

    }

    return new Content() {

        @Override

        public String contentType() {

             return "application/json";

        }

        @Override

        public String body() {

            return json;

        }

    };

}

private static ObjectMapper mapperFactory() {

    ObjectMapper mapper = new ObjectMapper();

    mapper.enable(SerializationFeature.WRITE_BIGDECIMAL_AS_PLAIN);

    return mapper;

}

Could the framework do this workaround for me ? Should I open an issue ?

[ludo amertum]

Which version of play are you using ? I've used this code with play 2.1.5 and never had any problem with scientific notation.

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[Simon]

I am using play for Java 2.3.1 and Jackson 2.3.2.

[ludo amertum]

That should be fixed. if not, you should open an issue on jackson project.

cf. https://github.com/FasterXML/jackson-databind/issues/251

https://github.com/FasterXML/jackson-core/issues/85

https://github.com/FasterXML/jackson-databind/issues/232