java Jackson ObjectCodec到字符串json

Question

有了Jackson，我如何安全地将JsonNode转换为JSON字符串

public class WrappedMessage extends JsonDeserializer<WrappedMessage> {
    @Override
    public WrappedMessage deserialize(JsonParser jp, DeserializationContext ctxt)
            throws IOException {
        ObjectCodec codec = jp.getCodec();

        JsonNode node = codec.readTree(jp);
        JsonNode payload = node.get("payload");
        // How to get the payload as JSON

        return new WrappedMessage();
    }
}

用ObjectMapper#writeValueAsString可以做到这一点，我知道在正常情况下ObjectCode可以被转换为ObjectMapper，但看起来不是很干净

也可以执行payload.toString()，但文档说明：

Method that will produce developer-readable representation of the node; which may or may not be as valid JSON. If you want valid JSON output (or output formatted using one of other Jackson supported data formats) make sure to use {@link ObjectMapper} or {@link ObjectWriter} to serialize an instance, for example: String json = objectMapper.writeValueAsString(rootNode);

所以这也不安全

我看到的最后一种可能性是构造一个新的ObjectMapper，但对我来说似乎不是很有效

Answer 1

一种可能是创建一个JsonGenerator并使用ObjectCodec.writeTree：

StringWriter writer = new StringWriter();
JsonGenerator jgen = codec.getFactory().createGenerator(writer);    
codec.writeTree(jgen, payload);
String jsonPayload = writer.toString();