[jackson] serialize/deserialize java 8 java.time with Jackson JSON mapper

How do I use Jackson JSON mapper with Java 8 LocalDateTime?

org.codehaus.jackson.map.JsonMappingException: Can not instantiate value of type [simple type, class java.time.LocalDateTime] from JSON String; no single-String constructor/factory method (through reference chain: MyDTO["field1"]->SubDTO["date"])

If you are using Jackson Serializer, here is a way to use the date modules:

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;
import org.apache.kafka.common.serialization.Serializer;

public class JacksonSerializer<T> implements Serializer<T> {

    private final ObjectMapper mapper = new ObjectMapper()
            .registerModule(new ParameterNamesModule())
            .registerModule(new Jdk8Module())
            .registerModule(new JavaTimeModule());

    @Override
    public byte[] serialize(String s, T object) {
        try {
            return mapper.writeValueAsBytes(object);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }
}

I had a similar problem while using Spring boot. With Spring boot 1.5.1.RELEASE all I had to do is to add dependency:

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-jsr310</artifactId>
</dependency>

If any one having problem while using SpringBoot here is how I fixed the issue without adding new dependency.

In Spring 2.1.3 Jackson expects date string 2019-05-21T07:37:11.000 in this yyyy-MM-dd HH:mm:ss.SSS format to de-serialize in LocalDateTime. Make sure date string separates the date and time with T not with space. seconds (ss) and milliseconds(SSS) could be ommitted.

@JsonProperty("last_charge_date")
public LocalDateTime lastChargeDate;

If you are using Jersey then you need to add the Maven dependency (jackson-datatype-jsr310) as the others suggested and register your object mapper instance like so:

@Provider
public class JacksonObjectMapper implements ContextResolver<ObjectMapper> {

  final ObjectMapper defaultObjectMapper;

  public JacksonObjectMapper() {
    defaultObjectMapper = createDefaultMapper();
  }

  @Override
  public ObjectMapper getContext(Class<?> type) {
    return defaultObjectMapper;
  }

  private static ObjectMapper createDefaultMapper() {
    final ObjectMapper mapper = new ObjectMapper();    
    mapper.registerModule(new JavaTimeModule());
    return mapper;
  }
}

When registering Jackson in your resources, you need to add this mapper like so:

final ResourceConfig rc = new ResourceConfig().packages("<your package>");
rc
  .register(JacksonObjectMapper.class)
  .register(JacksonJaxbJsonProvider.class);

This is just an example how to use it in a unit test that I hacked to debug this issue. The key ingredients are

• mapper.registerModule(new JavaTimeModule());
• maven dependency of <artifactId>jackson-datatype-jsr310</artifactId>

Code:

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import org.testng.Assert;
import org.testng.annotations.Test;

import java.io.IOException;
import java.io.Serializable;
import java.time.Instant;

class Mumu implements Serializable {
    private Instant from;
    private String text;

    Mumu(Instant from, String text) {
        this.from = from;
        this.text = text;
    }

    public Mumu() {
    }

    public Instant getFrom() {
        return from;
    }

    public String getText() {
        return text;
    }

    @Override
    public String toString() {
        return "Mumu{" +
                "from=" + from +
                ", text='" + text + '\'' +
                '}';
    }
}
public class Scratch {


    @Test
    public void JacksonInstant() throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerModule(new JavaTimeModule());

        Mumu before = new Mumu(Instant.now(), "before");
        String jsonInString = mapper.writeValueAsString(before);


        System.out.println("-- BEFORE --");
        System.out.println(before);
        System.out.println(jsonInString);

        Mumu after = mapper.readValue(jsonInString, Mumu.class);
        System.out.println("-- AFTER --");
        System.out.println(after);

        Assert.assertEquals(after.toString(), before.toString());
    }

}

I use this time format: "{birthDate": "2018-05-24T13:56:13Z}" to deserialize from json into java.time.Instant (see screenshot)

If you are using ObjectMapper class of fasterxml, by default ObjectMapper do not understand the LocalDateTime class, so, you need to add another dependency in your gradle/maven :

compile 'com.fasterxml.jackson.datatype:jackson-datatype-jsr310:2.7.3'

Now you need to register the datatype support offered by this library into you objectmapper object, this can be done by following :

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.findAndRegisterModules();

Now, in your jsonString, you can easily put your java.LocalDateTime field as follows :

{
    "user_id": 1,
    "score": 9,
    "date_time": "2016-05-28T17:39:44.937"
}

By doing all this, your Json file to Java object conversion will work fine, you can read the file by following :

objectMapper.readValue(jsonString, new TypeReference<List<User>>() {
            });

You may set this in your application.yml file to resolve Instant time, which is Date API in java8:

spring.jackson.serialization.write-dates-as-timestamps=false

If you can't use jackson-modules-java8 for whatever reasons you can (de-)serialize the instant field as long using @JsonIgnore and @JsonGetter & @JsonSetter:

public class MyBean {

    private Instant time = Instant.now();

    @JsonIgnore
    public Instant getTime() {
        return this.time;
    }

    public void setTime(Instant time) {
        this.time = time;
    }

    @JsonGetter
    private long getEpochTime() {
        return this.time.toEpochMilli();
    }

    @JsonSetter
    private void setEpochTime(long time) {
        this.time = Instant.ofEpochMilli(time);
    }
}

Example:

@Test
public void testJsonTime() throws Exception {
    String json = new ObjectMapper().writeValueAsString(new MyBean());
    System.out.println(json);
    MyBean myBean = new ObjectMapper().readValue(json, MyBean.class);
    System.out.println(myBean.getTime());
}

yields

{"epochTime":1506432517242}
2017-09-26T13:28:37.242Z

If you consider using fastjson, you can solve your problem, note the version

 <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.56</version>
 </dependency>

For those who use Spring Boot 2.x

There is no need to do any of the above - Java 8 LocalDateTime is serialised/de-serialised out of the box. I had to do all of the above in 1.x, but with Boot 2.x, it works seamlessly.

See this reference too JSON Java 8 LocalDateTime format in Spring Boot

If you're having this issue because of GraphQL Java Tools and trying to marshal an Java Instant from a date string, you need to setup your SchemaParser to use an ObjectMapper with certain configurations:

In your GraphQLSchemaBuilder class, inject ObjectMapper and add this modules:

        ObjectMapper objectMapper = 
    new ObjectMapper().registerModule(new JavaTimeModule())
            .configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);

and add it to the options:

final SchemaParserOptions options = SchemaParserOptions.newOptions()
            .objectMapperProvider(fieldDefinition -> objectMapper)
            .typeDefinitionFactory(new YourTypeDefinitionFactory())
            .build();

See https://github.com/graphql-java-kickstart/graphql-spring-boot/issues/32

Update: Leaving this answer for historical reasons, but I don't recommend it. Please see the accepted answer above.

Tell Jackson to map using your custom [de]serialization classes:

@JsonSerialize(using = LocalDateTimeSerializer.class)
@JsonDeserialize(using = LocalDateTimeDeserializer.class)
private LocalDateTime ignoreUntil;

provide custom classes:

public class LocalDateTimeSerializer extends JsonSerializer<LocalDateTime> {
    @Override
    public void serialize(LocalDateTime arg0, JsonGenerator arg1, SerializerProvider arg2) throws IOException {
        arg1.writeString(arg0.toString());
    }
}

public class LocalDateTimeDeserializer extends JsonDeserializer<LocalDateTime> {
    @Override
    public LocalDateTime deserialize(JsonParser arg0, DeserializationContext arg1) throws IOException {
        return LocalDateTime.parse(arg0.getText());
    }
}

random fact: if i nest above classes and don't make them static, the error message is weird: org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/json;charset=UTF-8' not supported

        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-parameter-names</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jdk8</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr310</artifactId>
        </dependency>

add these dependencies and enable these modules. that should help

    private static final ObjectMapper mapper = new ObjectMapper().findAndRegisterModules();

If you are using Spring boot and have this issue with the OffsetDateTime then need to use the registerModules as answered above by @greperror(answered May 28 '16 at 13:04) but note that there is one difference. The dependency mentioned doesn't need to be added as I am guessing that spring boot has it already. I was having this issue with Spring boot and it worked for me without adding this dependency.

This maven dependency will solve your problem:

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-jsr310</artifactId>
    <version>2.6.5</version>
</dependency>

One thing I've struggled is that for ZonedDateTime timezone being changed to GMT during deserialization. Turned out, that by default jackson replaces it with one from context.. To keep zone one must disable this 'feature'

Jackson2ObjectMapperBuilder.json()
    .featuresToDisable(DeserializationFeature.ADJUST_DATES_TO_CONTEXT_TIME_ZONE)

all you need to know is in Jackson Documentation https://www.baeldung.com/jackson-serialize-dates

Ad.9 quick solved the problem for me.

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JavaTimeModule());
mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);