使用Jackson的反序列化器正确反序列化对象

Question

I need a custom deserializer for casting a string in a complex POJO. The deserialization works until the deserializer is used: in particular when the custom deserializer is used, the non-object properties of my object are not serialized.

I have a restful web service that has a pojo as a parameter.

public PreventivoResponse calculate(@FormParam(value = "preventivo") PreventivoWs preventivo) throws Exception;

So my class PreventivoWs requires a fromString(String) method. Here the class definition:

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
public class PreventivoWs implements Serializable{
    private static final long serialVersionUID = -554141724349909424L;
    private ClienteMultiSelect cliente;

    private String riferimento;
    private List<EmailWS> email;

    private String dataritiro;
    private String dataconsegna;
    private Long tipoconsegna;

    private IndirizzoWS partenza;

    private IndirizzoWS destinazione;

    List<ColloWs> colli;

    HashMap<Long, String> services;

...
}

Inside the jsonObject i have an enumeration defined as

{
  "value" : "A",
  "text"  : "Active"
}

but this object require a deserializer to be converted:

public class TipoPersonaFGJsonDeserializer extends JsonDeserializer<TipoPersonaFG> {

@Override
public TipoPersonaFG deserialize(JsonParser jsonParser, DeserializationContext context) 
        throws IOException, JsonProcessingException {

    JsonToken currentToken = null;
    while ((currentToken = jsonParser.nextValue()) != null) {
        switch (currentToken) {
            case VALUE_STRING:
                switch (jsonParser.getCurrentName()) {
                    case "value":
                        String name = jsonParser.getText();
                        return TipoPersonaFG.valueOf(name);
                }
                break;
            default:
                break;
        }
    }
    return null;
}
}

and it is annotated on the property:

@JsonDeserialize(using = TipoPersonaFGJsonDeserializer.class)
private TipoPersonaFG tipo;

The fromString method simply call the jackson ObjectMapper:

public static PreventivoWs fromString(String jsonString) throws IOException{
    ObjectMapper mapper = new ObjectMapper();
    PreventivoWs oggetto = mapper.readValue(jsonString, PreventivoWs.class);
    return oggetto;
}

If the enum is not specified in the jsonString, it works fine: the object is deserialized perfectly; If i add the enum in the jsonString, all the object-properties are deserialized (email, cliente, partenza, destinazione,...) but the other properties are ignored (dataritiro,dataconsegna,tipoconsegna).

Why? The custom deserializer broke the standard process of deserialization?

UPDATE: the parsing process is interrupted when the custom deserializer take place: i moved the cliente property (which contains the particular enum) at the end of the json object: now the fields dataconsegna, dataritiro and so on are deserialised.

So the deserialization process ends up when the custom deserializer take place (even the cliente object is interrupted)

Answer 1

Solved! As written in Jackson Wiki :

must NOT process any token beyond value being deserialized (no more, or no less)

So the problem was in the deserializer: you must stop when the END_OBJECT (}) is found, otherwhise the jsonParser go on until the end of the stream, consuming all the other tokens.

@Override
public TipoPersonaFG deserialize(JsonParser jsonParser, DeserializationContext context) 
        throws IOException, JsonProcessingException {

    JsonToken currentToken = null;
    String name = null;
    while ((currentToken = jsonParser.nextValue()) != null) {
        switch (currentToken) {
            case VALUE_STRING:
                switch (jsonParser.getCurrentName()) {
                    case "value":
                        name = jsonParser.getText();
                        break;
                }
                break;
            case END_OBJECT:
                if(name != null)
                    return TipoPersonaFG.valueOf(name);
                else 
                    return null;
        }
    }
    return TipoPersonaFG.valueOf(name);
}

I have added the case condition END_OBJECT for consuming only the first '}' and close correctly the parsing of the enum object. The return was moved in the END_OBJECT case because otherwise the '}' token will remain in the stream and it will go to close the parent of the enum.

So you need to parse your object from '{' token to '}' token