Following example shows how to write custom serializer and deserializer and how to register them with ObjectMapper.

Example

Java Object

public class CurrencyRate {
    private String pair;
    private double rate;
    private LocalDateTime lastUpdated;
    .............
}

Custom JsonSerializer

package com.logicbig.example;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.time.format.FormatStyle;

public class LocalDateTimeSerializer extends JsonSerializer<LocalDateTime> {
    static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.MEDIUM);

    @Override
    public void serialize(LocalDateTime value, JsonGenerator gen, SerializerProvider provider)
            throws IOException {
        try {
            String s = value.format(DATE_FORMATTER);
            gen.writeString(s);
        } catch (DateTimeParseException e) {
            System.err.println(e);
            gen.writeString("");
        }
    }
}

Custom JsonDeserializer

package com.logicbig.example;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeParseException;

public class LocalDatetimeDeserializer extends JsonDeserializer<LocalDateTime> {

    @Override
    public LocalDateTime deserialize(JsonParser p, DeserializationContext ctx)
            throws IOException {
        String str = p.getText();
        try {
            return LocalDateTime.parse(str, LocalDateTimeSerializer.DATE_FORMATTER);
        } catch (DateTimeParseException e) {
            System.err.println(e);
            return null;
        }
    }
}

Main class

package com.logicbig.example;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;
import java.io.IOException;
import java.time.LocalDateTime;

public class ExampleMain {
    public static void main(String[] args) throws IOException {
        System.out.println("-- Java object to JSON --");
        CurrencyRate cr = new CurrencyRate();
        cr.setPair("USD/JPY");
        cr.setRate(109.15);
        cr.setLastUpdated(LocalDateTime.now());
        System.out.println("Java object: " + cr);

        ObjectMapper om = new ObjectMapper();

        //creating a module
        SimpleModule module = new SimpleModule();
        //adding our custom serializer and deserializer
        module.addSerializer(LocalDateTime.class ,new LocalDateTimeSerializer());
        module.addDeserializer(LocalDateTime.class, new LocalDatetimeDeserializer());
        //registering the module with ObjectMapper
        om.registerModule(module);

        String s2 = om.writeValueAsString(cr);
        System.out.println("JSON string: " + s2);

        System.out.println("-- JSON to Java object --");
        CurrencyRate cr2 = om.readValue(s2, CurrencyRate.class);
        System.out.println("Java Object: " + cr2);
    }
}

-- Java object to JSON --
Java object: CurrencyRate{pair='USD/JPY', rate=109.15, lastUpdated=2018-06-01T20:52:47.102579200}
JSON string: {"pair":"USD/JPY","rate":109.15,"lastUpdated":"Jun 1, 2018, 8:52:47 PM"}
-- JSON to Java object --
Java Object: CurrencyRate{pair='USD/JPY', rate=109.15, lastUpdated=2018-06-01T20:52:47}

Using @JsonSerialize and @JsonDeserialize

Instead of registering our custom Serializer and Deserializer with ObjectMapper, we can use @JsonSerialize and @JsonDeserialize, check out this example.

Example Project

Dependencies and Technologies Used:

• jackson-databind 2.9.5: General data-binding functionality for Jackson: works on core streaming API.
• JDK 10
• Maven 3.3.9