How to restrict jackson from parsing millis to LocalDate in json request

Question

I need to validate LocalDate fields in json requests. What i want is to prevent deserializing numbers as miilis to LocalDate. Here is example:

I have an entity:

public class Test {

   @NotNull
   @JsonFormat(pattern = "yyyy-MM-dd")
   private LocalDate birthDate;

   //getter and setter of course

}

Jackson2ObjectMapperBuilder config:

@Bean
public Jackson2ObjectMapperBuilder objectMapperBuilder() {
    Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
    builder.serializationInclusion(JsonInclude.Include.NON_EMPTY);
    builder.featuresToEnable(DeserializationFeature.READ_ENUMS_USING_TO_STRING);
    builder.featuresToEnable(SerializationFeature.WRITE_ENUMS_USING_TO_STRING);
    builder.featuresToDisable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
    builder.modulesToInstall(new JavaTimeModule());
    return builder;
}

Now if i'm receiveing:

{
    "birthDate": 1
}

the result is birthDate=1970-01-02

I'm able to do so by setting leniency to false:

objectMapper.configOverride(LocalDate.class).setFormat(JsonFormat.Value.forLeniency(false));
objectMapper.configOverride(LocalDateTime.class).setFormat(JsonFormat.Value.forLeniency(false));

And then it's working by throwing MismatchedInputException

But it's a little brutal to backward compatibility of our service, because we need to change all our date patterns from "yyyy-MM-dd" to "uuuu-MM-dd" and i wonder is there some solution to say jackson "If you see numbers or anything different from the pattern while deserialization, throw an exception"

Turo · Accepted Answer · 2021-04-01T11:18:08.793

You could write a custom LocalDateDeserializer:

public class MyLocalDateDeserializer extends JsonDeserializer<LocalDate> implements ContextualDeserializer {

    private LocalDateDeserializer defaultDeserializer = new LocalDateDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd"));

    public MyLocalDateDeserializer() {
        super();
    }

    public MyLocalDateDeserializer(LocalDateDeserializer defaultDeserializer) {
        super();
        this.defaultDeserializer = defaultDeserializer;
    }


    @Override
    public LocalDate deserialize(JsonParser parser, DeserializationContext context) throws IOException
    {
        if (StringUtils.isNumeric(parser.getText())) {
            throw  JsonMappingException.from(parser, "Not a String representation of Date ");

        }
        return defaultDeserializer.deserialize(parser, context);
    }


    @Override
    public JsonDeserializer<?> createContextual(DeserializationContext ctxt,
            BeanProperty property) throws JsonMappingException
    {
        JsonFormat.Value format = findFormatOverrides(ctxt, property, handledType());
        return (format == null) ? this : new MyLocalDateDeserializer(new LocalDateDeserializer(DateTimeFormatter.ofPattern(format.getPattern())));
    }

    protected JsonFormat.Value findFormatOverrides(DeserializationContext ctxt,
            BeanProperty prop, Class<?> typeForDefaults)
    {
        if (prop != null) {
            return prop.findPropertyFormat(ctxt.getConfig(), typeForDefaults);
        }
        // even without property or AnnotationIntrospector, may have type-specific defaults
        return ctxt.getDefaultPropertyFormat(typeForDefaults);
    }

}

and register it when needed.

Here my simple Tests:

@Test()
public void testObjectMapperForLocalDate() throws IOException {
    Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
    JavaTimeModule javaTimeModule = new JavaTimeModule();
    javaTimeModule.addDeserializer(LocalDate.class, new MyLocalDateDeserializer());
    builder.modulesToInstall(javaTimeModule);
    ObjectMapper objectMapper =  builder.build();

       DateContainer container =  objectMapper.readValue("{\r\n" +
                "    \"birthDate\": \"1999-01-01\"\r\n" +
                "}", DateContainer.class);
           System.out.println(container.getBirthDate());
}

@Test()
public void testFailObjectMapperForLocalDate() throws IOException {
    Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
    JavaTimeModule javaTimeModule = new JavaTimeModule();
    javaTimeModule.addDeserializer(LocalDate.class, new MyLocalDateDeserializer());
    builder.modulesToInstall(javaTimeModule);
    ObjectMapper objectMapper =  builder.build();

    assertThrows(JsonMappingException.class, () -> {
       DateContainer container =  objectMapper.readValue("{\r\n" +
                "    \"birthDate\": 1\r\n" +
                "}", DateContainer.class);
           System.out.println(container.getBirthDate());
      });
}

EDIT

Deserializer uses Pattern

Thank you for your answer! That's the problem, we have different patterns in our services for dates, so ignoring annotattion with Pattern is not an option, unfortunately — Nikita, Apr 01 '21 at 09:01
This is ABSOLUTELY AWESOME! Thank you so much for this magic lesson! Now it works as it should — Nikita, Apr 03 '21 at 06:31

How to restrict jackson from parsing millis to LocalDate in json request

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