Jackson Mapper Serialize/Deserialize ObjectId

Question

My POJO is :

import org.jongo.marshall.jackson.id.Id;

public class User {    

    @Id
    private String id;
    private String name;
    private int age;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

I get user from mongo database and want to output him into a file with jackson mapper

ObjectMapper mapper = new ObjectMapper();
mapper.writerWithDefaultPrettyPrinter().writeValue(new File("c:/user.txt"), user);

and I get something like this in my file

{
    "name" : "John",
    "age" : 23,
    "_id" : {
      "time" : 1358443593000,
      "inc" : 660831772,
      "machine" : 2028353122,
      "new" : false,
      "timeSecond" : 1358443593
    }
}

I need id field to be stored into a file as string because when i deserialize this object my id field in pojo looks something like this

{
   "time":1358443593000,
   "inc":660831772,
   "machine":2028353122,
   "new":false,
   "timeSecond":1358443593
}

Any help will be apreciated

This cannot be all the code. Where did the `_id` attribute come from? — Perception, Jan 18 '13 at 06:48
Does this answer your question? [java spring MappingJacksonJsonView not doing toString on mongodb ObjectId](https://stackoverflow.com/questions/9065042/java-spring-mappingjacksonjsonview-not-doing-tostring-on-mongodb-objectid) — Kapil Bhagchandani, Dec 05 '19 at 09:09

score 19 · Accepted Answer · edited May 23 '17 at 11:54

19

Answering my own question. Found solution here Spring 3.2 and Jackson 2: add custom object mapper

I needed custom object mapper and ObjectId serializer.

public class ObjectIdSerializer extends JsonSerializer<ObjectId> {

    @Override
    public void serialize(ObjectId value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
        jgen.writeString(value.toString());
    }
}


public class CustomObjectMapper extends ObjectMapper {

    public CustomObjectMapper() {
        SimpleModule module = new SimpleModule("ObjectIdmodule");
        module.addSerializer(ObjectId.class, new ObjectIdSerializer());
        this.registerModule(module);
    }

}

edited May 23 '17 at 11:54

Community

1
1

answered Jan 18 '13 at 13:16

user1745356

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You can use the [`ToStringSerializer`](https://fasterxml.github.io/jackson-databind/javadoc/2.2.0/com/fasterxml/jackson/databind/ser/std/ToStringSerializer.html) provided by jackson. – fracz Apr 08 '16 at 07:23
1

Is their any other setting I need to make apart from writing this two classes. because it is still not working for me. – Pratik Jul 01 '19 at 17:08
Should I do any other additional steps? this doesn't work for me. I use it like below: CustomObjectMapper oMapper = new CustomObjectMapper(); return oMapper.convertValue(obj, Map.class); – Jafar Amini Mar 16 '22 at 11:39

score 3 · Answer 2 · answered Sep 02 '21 at 15:25

I found an easy attempt using springboot 2.5.4.

Just by adding a Jackson2ObjectMapperBuilderCustomizer bean will do the trick.

@Configuration
public class JacksonMapperConfiguration
{   
    @Bean
    public Jackson2ObjectMapperBuilderCustomizer jsonCustomizer() {
        return builder -> builder.serializerByType(ObjectId.class, new ToStringSerializer());
    }
}

score 0 · Answer 3 · answered Nov 08 '22 at 10:59

Here is a simple solution for serialization if you don't have a model for the object being stored:

client.getDatabase("db").getCollection("collection").find().onEach { it["_id"] = it["_id"].toString() }

"onEach" is a kotlin function. If you use Java, then change it to a simple foreach.

It's not efficient to iterate over the entire list just for the id. Only use it for small lists where performance is less important than short code.

Jackson Mapper Serialize/Deserialize ObjectId

3 Answers3

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