わかりました、標準の文字列デシリアライザーをオーバーライドすることで機能しました。残念ながら、org/codehaus/jackson/map/deser/std/StringDeserializer.java
最終版であり拡張できないため、完全な実装をコピーする必要がありました。
public class FixesModule extends SimpleModule {
public FixesModule() {
super();
addDeserializer(String.class, new CustomStringDeserializer());
}
}
と
public class CustomStringDeserializer extends StdScalarDeserializer<String> {
private static final String NULL_STRING = "null";
public CustomStringDeserializer() {
super(String.class);
}
@Override
public String deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
JsonToken curr = jp.getCurrentToken();
// Usually should just get string value:
if (curr == JsonToken.VALUE_STRING) {
// BEGIN NULL_STRING fix
if (NULL_STRING.equals(jp.getText())) {
return null;
}
// END NULL_STRING fix
return jp.getText();
}
// [JACKSON-330]: need to gracefully handle byte[] data, as base64
if (curr == JsonToken.VALUE_EMBEDDED_OBJECT) {
Object ob = jp.getEmbeddedObject();
if (ob == null) {
return null;
}
if (ob instanceof byte[]) {
return Base64Variants.getDefaultVariant().encode((byte[]) ob, false);
}
// otherwise, try conversion using toString()...
return ob.toString();
}
// Can deserialize any scalar value, but not markers
if (curr.isScalarValue()) {
return jp.getText();
}
throw ctxt.mappingException(_valueClass, curr);
}
// 1.6: since we can never have type info ("natural type"; String, Boolean,
// Integer, Double):
// (is it an error to even call this version?)
@Override
public String deserializeWithType(JsonParser jp, DeserializationContext ctxt, TypeDeserializer typeDeserializer)
throws IOException, JsonProcessingException {
return deserialize(jp, ctxt);
}
}