Any function similar to jackson's objectMapper.readValue?

[ZhaiMo15]

When using jackson, one can use

JsonFactory jsonFactory = new JsonFactory();
ObjectMapper objectMapper = new ObjectMapper(jsonFactory);
objectMapper.readValue(jsonString, TYPE);

to transfer json to Object or using writeValueAsString vice versa.

I'd like to know is there any function in simdjson can do the same thing?

[piotrrzysko]

Currently, there is no such function. However, there are plans to add it.

[ZhaiMo15]

Thx. Looking forward to this feature.

[ZhaiMo15]

Additionally, I saw toString() in JsonValue.java:

@Override
public String toString() {
    switch (tape.getType(tapeIdx)) {
        case INT64 -> {
            return String.valueOf(asLong());
        }
        case DOUBLE -> {
            return String.valueOf(asDouble());
        }
        case TRUE_VALUE, FALSE_VALUE -> {
            return String.valueOf(asBoolean());
        }
        case STRING -> {
            return asString();
        }
        case NULL_VALUE -> {
            return "null";
        }
        case START_OBJECT -> {
            return "<object>";
        }
        case START_ARRAY -> {
            return "<array>";
        }
        default -> {
            return "unknown";
        }
    }
}

IMHO START_OBJECT is the part I mentioned before. But how about array? If we have elements in json which type is array, we cannot use get to get the value of the array?

[piotrrzysko]

Do you mean something like this:

JsonValue json = parser.parse(...);
JsonValue[] array = json.getArray();

?

If that's the case, then currently it's not available. The only option is to use JsonValue::arrayIterator.

[andyglow]

for toString currently I'm using this workaround

void stringify(JsonValue v, StringBuilder w) {
        if (v.isArray()) {
            w.append('[');
            final var iter = v.arrayIterator();
            while (iter.hasNext()) {
                final var element = iter.next();
                stringify(element, w);
            }
            w.append('[');
        } else if (v.isObject()) {
            w.append('{');
            final var iter = v.objectIterator();
            boolean first = true;
            while (iter.hasNext()) {
                if (!first) w.append(',');
                final var element = iter.next();
                w.append('\"');
                w.append(element.getKey());
                w.append('\"');
                w.append(':');
                stringify(element.getValue(), w);
                first = false;
            }
            w.append('}');
        } else if (v.isString()) {
            w.append('\"');
            // may try to find vectorized version
            w.append(com.fasterxml.jackson.core.util.BufferRecyclers.getJsonStringEncoder().quoteAsString(v.asString()));
            w.append('\"');
        } else {
            w.append(v);
        }
    }

so you can use it like

            JsonValue jsonNode = entry.getValue();
            if (jsonNode != null && !jsonNode.isNull()) {
                final var sb = new StringBuilder();
                stringify(jsonNode, sb);
                
                // ... use sb
            }

but this is slow. I wonder if there is a way to use stringBuffer or buffer of the JsonNode instead to achieve the same effect?

[ZhaiMo15]

I'm using the similar workaround as you by modifying toString() @andyglow

@Override
    public String toString() {
        switch (tape.getType(tapeIdx)) {
            case INT64 -> {
                return String.valueOf(asLong());
            }
            case DOUBLE -> {
                return String.valueOf(asDouble());
            }
            case TRUE_VALUE, FALSE_VALUE -> {
                return String.valueOf(asBoolean());
            }
            case STRING -> {
                return asString();
            }
            case NULL_VALUE -> {
                return "null";
            }
            case START_OBJECT -> {
                Iterator<Map.Entry<String, JsonValue>> it = this.objectIterator();
                String result = "{";
                boolean first = true;
                while (it.hasNext()) {
                    if(!first)
                        result += ", ";
                    Map.Entry<String, JsonValue> field = it.next();
                    result += field.getKey() + "=" + field.getValue().toString();
                    first = false;
                }
                result += "}";
                return result;
            }
            case START_ARRAY -> {
                Iterator<JsonValue> it = this.arrayIterator();
                String result = "[";
                boolean first = true;
                while (it.hasNext()) {
                    if(!first)
                        result += ", ";
                    JsonValue field = it.next();
                    result += field.toString();
                    first = false;
                }
                result += "]";
                return result;
            }
            default -> {
                return "unknown";
            }
        }
    }

I think you have a little typo mistake, line 9 of stringify() should be w.append(']');