Date format Mapping to JSON Jackson

Question

I have a Date format coming from API like this    start time    2015-10-1 3 00 PM GMT 1 00    Which is YYYY-DD-MM HH MM am pm GMT timestamp   I am mapping this value to a Date variable in POJO  Obviously  its showing conversion error   I would like to know 2 things    What is the formatting I need to use to carry out conversion with Jackson  Is Date a good field type for this  In general  is there a way to process the variables before they get mapped to Object members by Jackson  Something like  changing the format  calculations  etc

User · Answer

If anyone has problems with using a custom dateformat for java.sql.Date, this is the simplest solution:

ObjectMapper mapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.addSerializer(java.sql.Date.class, new DateSerializer());
mapper.registerModule(module);

(This SO-answer saved me a lot of trouble: https://stackoverflow.com/a/35212795/3149048 )

Jackson uses the SqlDateSerializer by default for java.sql.Date, but currently, this serializer doesn't take the dateformat into account, see this issue: https://github.com/FasterXML/jackson-databind/issues/1407 . The workaround is to register a different serializer for java.sql.Date as shown in the code example.

User · Answer

Just a complete example for spring boot application with RFC3339 datetime format  package bj demo   import com fasterxml jackson databind ObjectMapper  import org springframework beans factory annotation Autowired  import org springframework boot SpringApplication  import org springframework boot autoconfigure SpringBootApplication  import org springframework boot context event ApplicationReadyEvent  import org springframework context ApplicationListener   import java text SimpleDateFormat          Created by BaiJiFeiLong gmail com at 2018 5 4 10 22      SpringBootApplication public class BarApp implements ApplicationListener lt ApplicationReadyEvent gt         public static void main String   args            SpringApplication run BarApp class  args               Autowired     private ObjectMapper objectMapper        Override     public void onApplicationEvent ApplicationReadyEvent applicationReadyEvent            objectMapper setDateFormat new SimpleDateFormat  yyyy-MM-dd T HH mm ssXXX

User · Answer

Building on  miklov-kriven s very helpful answer  I hope these two additional points of consideration prove helpful to someone    1  I find it a nice idea to include serializer and de-serializer as static inner classes in the same class   NB  using ThreadLocal for thread safety of SimpleDateFormat   public class DateConverter        private static final ThreadLocal lt SimpleDateFormat gt  sdf            ThreadLocal  lt SimpleDateFormat gt withInitial                     - gt   return new SimpleDateFormat  yyyy-MM-dd HH mm a z            public static class Serialize extends JsonSerializer lt Date gt             Override         public void serialize Date value  JsonGenerator jgen SerializerProvider provider  throws Exception               if  value    null                    jgen writeNull                              else                   jgen writeString sdf get   format value                                       public static class Deserialize extends JsonDeserializer lt Date gt             Overrride         public Date deserialize JsonParser jp  DeserializationContext ctxt  throws Exception               String dateAsString   jp getText                try                   if  Strings isNullOrEmpty dateAsString                         return null                                    else                       return new Date sdf get   parse dateAsString  getTime                                                 catch  ParseException pe                    throw new RuntimeException pe                                      2  As an alternative to using  JsonSerialize and  JsonDeserialize annotations on each individual class member you could also consider overriding Jackson s default serialization by applying the custom serialization at an application level  that is all class members of type Date will be serialized by Jackson using this custom serialization without explicit annotation on each field  If you are using Spring Boot for example one way to do this would as follows    SpringBootApplication public class Application       public static void main String   args            SpringApplication run Application class  args               Bean     public Module customModule             SimpleModule module   new SimpleModule            module addSerializer Date class  new DateConverter Serialize             module addDeserializer Date class  new Dateconverter Deserialize             return module

User · Answer

Of course there is an automated way called serialization and deserialization and you can define it with specific annotations   JsonSerialize  JsonDeserialize  as mentioned by pb2q as well   You can use both java util Date and java util Calendar     and probably JodaTime as well   The  JsonFormat annotations not worked for me as I wanted  it has adjusted the timezone to different value  during deserialization  the serialization worked perfect     JsonFormat locale    hu   shape   JsonFormat Shape STRING  pattern    yyyy-MM-dd HH mm   timezone    CET     JsonFormat locale    hu   shape   JsonFormat Shape STRING  pattern    yyyy-MM-dd HH mm   timezone    Europe Budapest     You need to use custom serializer and custom deserializer instead of the  JsonFormat annotation if you want predicted result  I have found real good tutorial and solution here http   www baeldung com jackson-serialize-dates  There are examples for Date fields but I needed for Calendar fields so here is my implementation   The serializer class   public class CustomCalendarSerializer extends JsonSerializer lt Calendar gt         public static final SimpleDateFormat FORMATTER   new SimpleDateFormat  yyyy-MM-dd HH mm        public static final Locale LOCALE HUNGARIAN   new Locale  hu    HU        public static final TimeZone LOCAL TIME ZONE   TimeZone getTimeZone  Europe Budapest          Override     public void serialize Calendar value  JsonGenerator gen  SerializerProvider arg2              throws IOException  JsonProcessingException           if  value    null                gen writeNull              else               gen writeString FORMATTER format value getTime                          The deserializer class   public class CustomCalendarDeserializer extends JsonDeserializer lt Calendar gt          Override     public Calendar deserialize JsonParser jsonparser  DeserializationContext context              throws IOException  JsonProcessingException           String dateAsString   jsonparser getText            try               Date date   CustomCalendarSerializer FORMATTER parse dateAsString               Calendar calendar   Calendar getInstance                  CustomCalendarSerializer LOCAL TIME ZONE                   CustomCalendarSerializer LOCALE HUNGARIAN                            calendar setTime date               return calendar            catch  ParseException e                throw new RuntimeException e                       and the usage of the above classes   public class CalendarEntry         JsonSerialize using   CustomCalendarSerializer class       JsonDeserialize using   CustomCalendarDeserializer class      private Calendar calendar              additional things         Using this implementation the execution of the serialization and deserialization process consecutively results the origin value   Only using the  JsonFormat annotation the deserialization gives different result I think because of the library internal timezone default setup what you can not change with annotation parameters  that was my experience with Jackson library 2 5 3 and 2 6 3 version as well

User · Answer

To add characters such as T and Z in your date   JsonFormat shape   JsonFormat Shape STRING  pattern    yyyy-MM-dd T HH mm ss Z    private Date currentTime    output          currentTime    2019-12-11T11 40 49Z

User · Answer

I want to point out that setting a SimpleDateFormat like described in the other answer only works for a java util Date which I assume is meant in the question  But for java sql Date the formatter does not work  In my case it was not very obvious why the formatter did not work because in the model which should be serialized the field was in fact a java utl Date but the actual object ended up beeing a java sql Date  This is possible because  public class java sql extends java util Date   So this is actually valid  java util Date date   new java sql Date 1542381115815L     So if you are wondering why your Date field is not correctly formatted make sure that the object is really a java util Date   Here is also mentioned why handling java sql Date will not be added      This would then be breaking change  and I don t think that is warranted  If we were starting from scratch I would agree with the change  but as things are not so much

User · Answer

What is the formatting I need to use to carry out conversion with Jackson  Is Date a good field type for this    Date is a fine field type for this  You can make the JSON parse-able pretty easily by using ObjectMapper setDateFormat   DateFormat df   new SimpleDateFormat  yyyy-MM-dd HH mm a z    myObjectMapper setDateFormat df        In general  is there a way to process the variables before they get mapped to Object members by Jackson  Something like  changing the format  calculations  etc    Yes  You have a few options  including implementing a custom JsonDeserializer  e g  extending JsonDeserializer lt Date gt   This is a good start

User · Answer

Working for me  SpringBoot    import com alibaba fastjson annotation JSONField     JSONField format    yyyy-MM-dd HH mm ss      private Date createTime    output          createTime    2019-06-14 13 07 21

User · Answer

Since Jackson v2 0  you can use  JsonFormat annotation directly on Object members     JsonFormat shape   JsonFormat Shape STRING  pattern    yyyy-MM-dd HH mm a z   private Date date

[java] Date format Mapping to JSON Jackson

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