Error writing java.util.date into Json file

问题

I have a Json writer class EntrenadorWriter that writes the entity data produced from a RestFul service into a Json file. Then, the file is consumed by Json reader class. One of the fields that has to be written into the Json is a Java.util.Date Date. But I'm having serious trouble to write-read the Date.

WriteTo method from Json writer class:

 @Override
            public void writeTo(Usuario t, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> httpHeaders,
                    OutputStream entityStream) throws IOException, WebApplicationException {
                JsonGenerator gen = Json.createGenerator(entityStream);
                DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
                gen.writeStartObject()
                        .write("Dni", t.getDni())
                        .write("PassWord", t.getPassWord())
                        .write("Login", t.getLogin())
                        .write("Email", t.getEmail())
                        .write("NombreCompleto", t.getNombreCompleto())
                        .write("Telefono", t.getTelefono())
                        .write("FechaNacimiento", df.format(t.getFechaNacimiento()))
                        .writeEnd();
                gen.flush();
            }

And here is where the problem starts:

.write("FechaNacimiento", df.format(t.getFechaNacimiento()))

t.getFechaNacimiento() returns a java.util.Date and df.format() parses it to String with the format specified in the DateFormatter (yyyy-MM-dd).

The json is written and sent.

ReadTo method from Json reader class:

  public Usuario readFrom(Class<Usuario> type,
                Type genericType,
                Annotation[] annotations,
                MediaType mediaType,
                MultivaluedMap<String, String> httpHeaders,
                InputStream entityStream)
                throws IOException, WebApplicationException {
                Usuario usuario = new Usuario();
                JsonParser parser = Json.createParser(entityStream);
                while (parser.hasNext()) {
                    switch (parser.next()) {
                         case KEY_NAME:
                             String key = parser.getString();
                             parser.next();
                             switch (key) {
                                case "Dni":
                                   usuario.setDni(key);
                                   break;
                                case "FechaNacimiento": 
                                   DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
                                   LocalDate localDate = LocalDate.parse(key, formatter);
                                   usuario.setFechaNacimiento(java.sql.Date.valueOf(localDate)); 
                                   break;
                                default:
                                   break;
                              }
                        break;
                    default:
                        break;
                }
            }
            return usuario;
        }

The reader consumes the date field from the Json and parses string date into a LocalDate object.

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
LocalDate localDate = LocalDate.parse(key, formatter);

I've made this convertion by looking in the internet and what i found was, that so as to parse Dates with "yyyy-MM-dd" format, without the time zone part, is more correct in this way than using directly a convertion to a Date Object. Then DateTime object is parsed into a java.sql.date java.sql.Date.valueOf(localDate).

The error is the following one:

 javax.ws.rs.client.ResponseProcessingException: javax.json.bind.JsonbException: Error parsing date from value: 1998-04-19

回答1:

If key is already in the format, yyyy-MM-dd, you do not need DateTimeFormatter object to parse it to LocalDate. You can simply do it as:

LocalDate localDate = LocalDate.parse(key);

Also, why are you using the broken java.util.Date and outdated DateFormat?

Change the type of fechaNacimiento to LocalDate in Usuario and then

case "FechaNacimiento": 
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    LocalDate localDate = LocalDate.parse(key, formatter);
    usuario.setFechaNacimiento(localDate); 
    break;

And inside, writeTo:

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
...
...
...
.write("FechaNacimiento", formatter.format(t.getFechaNacimiento()))
.writeEnd();

来源：https://stackoverflow.com/questions/61974822/error-writing-java-util-date-into-json-file