Jackson + Builder Pattern?

Question

I'd like Jackson to deserialize a class with the following constructor:

public Clinic(String name, Address address)

Deserializing the first argument is easy. The problem is that Address is defined as:

public class Address {
  private Address(Map<LocationType, String> components)
  ...

  public static class Builder {
    public Builder setCity(String value);
    public Builder setCountry(String value);
    public Address create();
  }
}

and is constructed like this: new Address.Builder().setCity("foo").setCountry("bar").create();

Is there a way to get key-value pairs from Jackson in order to construct the Address myself? Alternatively, is there a way to get Jackson to use the Builder class itself?

score 164 · Accepted Answer · edited Aug 09 '16 at 12:24

164

As long as you are using Jackson 2+, then there is now built in support for this.

First you need to add this annotation to your Address class:

@JsonDeserialize(builder = Address.Builder.class)

Then you need to add this annotation to your Builder class:

@JsonPOJOBuilder(buildMethodName = "create", withPrefix = "set")

You can skip this second annotation if you are happy to rename your Builder's create method to build, and your Builder's setters to be prefixed to with, instead of set.

Full example:

@JsonDeserialize(builder = Address.Builder.class)
public class Address
{
  private Address(Map<LocationType, String> components)
  ...

  @JsonPOJOBuilder(buildMethodName = "create", withPrefix = "set")
  public static class Builder
  {
    public Builder setCity(String value);
    public Builder setCountry(String value);
    public Address create();
  }
}

edited Aug 09 '16 at 12:24

Ekruten

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answered Feb 07 '14 at 10:01

Rupert Madden-Abbott

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If it is desired to get rid of the `@JsonPOJOBuilder` annotation all together, rename "create" to "build" and annotate each of the builder setters with `@JsonProperty`. – Sam Berry Oct 22 '14 at 05:14
this is golden. Thanks. – Mukul Goel May 18 '17 at 11:20
1

This is now outdated, with Lombok 1.18.4 you can use `@Jacksonized` which replaces the inner builder and the jackson annotations with a single thing – Randakar Oct 15 '20 at 12:20
2

@Randakar I don't think this is outdated because a) `@Jackonized` is a just released experimental feature in Lombok. I don't think it is a good idea to unnecessarily encourage adoption of experimental features. b) the question doesn't mention or use Lombok. I don't think it is a good idea to unnecessarily introduce a dependency to solve a problem. – Rupert Madden-Abbott Oct 16 '20 at 13:32
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Fair enough. I was updating another answer with this information where lombok *was* relevant, apparently I cast too wide a net. – Randakar Jan 12 '21 at 16:12

score 25 · Answer 2 · answered Aug 01 '14 at 17:35

The answer from @Rupert Madden-Abbott works. However, if you have a non-default constructor, e.g.,

Builder(String city, String country) {...}

Then you should annotate the parameters as below:

@JsonCreator
Builder(@JsonProperty("city")    String city, 
        @JsonProperty("country") String country) {...}

score 14 · Answer 3 · edited Mar 06 '18 at 07:32

14

A solution which was suitable for me in this case (I used "Lombok" builder annotation).

@Getter
@Builder(builderMethodName = "builder")
@NoArgsConstructor(access = AccessLevel.PRIVATE)
@AllArgsConstructor(access = AccessLevel.PRIVATE)
@JsonAutoDetect(
    fieldVisibility = JsonAutoDetect.Visibility.ANY,
    creatorVisibility = JsonAutoDetect.Visibility.ANY
)

I hope would be useful for u too.

edited Mar 06 '18 at 07:32

Ram Koti

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answered Mar 06 '18 at 06:50

JustK K

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This is now outdated, with Lombok 1.18.4 you can use `@Jacksonized` which replaces the inner builder and the jackson annotations with a single thing – Randakar Oct 15 '20 at 12:21
1

But if you can't upgrade our library due to company rules. This is continue to working fine for me – Davide Castronovo Mar 18 '22 at 14:10

score 7 · Answer 4 · answered Feb 14 '11 at 03:53

I ended up implementing this using the @JsonDeserialize as follows:

@JsonDeserialize(using = JacksonDeserializer.class)
public class Address
{...}

@JsonCachable
static class JacksonDeserializer extends JsonDeserializer<Address>
{
    @Override
    public Address deserialize(JsonParser parser, DeserializationContext context)
        throws IOException, JsonProcessingException
    {
        JsonToken token = parser.getCurrentToken();
        if (token != JsonToken.START_OBJECT)
        {
            throw new JsonMappingException("Expected START_OBJECT: " + token, parser.getCurrentLocation());
        }
        token = parser.nextToken();
        Builder result = new Builder();
        while (token != JsonToken.END_OBJECT)
        {
            if (token != JsonToken.FIELD_NAME)
            {
                throw new JsonMappingException("Expected FIELD_NAME: " + token, parser.getCurrentLocation());
            }
            LocationType key = LocationType.valueOf(parser.getText());

            token = parser.nextToken();
            if (token != JsonToken.VALUE_STRING)
            {
                throw new JsonMappingException("Expected VALUE_STRING: " + token, parser.getCurrentLocation());
            }
            String value = parser.getText();

            // Our Builder allows passing key-value pairs
            // alongside the normal setter methods.
            result.put(key, value);
            token = parser.nextToken();
        }
        return result.create();
    }
}

This may be how you ended up implementing it, but this answer doesn't actually answer the question as posed. The answer posted by @Rupert Madden-Abbott should be marked as the accepted one. — kelnos, Feb 27 '19 at 10:08

score 4 · Answer 5 · answered Dec 12 '19 at 08:56

This worked for me: @NoArgsConstructor The only drawback of this, is that one can do = new ADTO() again. But, hey, I dont like de code police anyhow, telling me how to use someones code :-) So, use my POJO DTOS the way you like it. With or without builder. I suggest: do it with a Builder, but be my guest...

@Data
@Builder
//Dont forget this! Otherwise no Jackson serialisation possible!
@NoArgsConstructor
@AllArgsConstructor
public class ADTO {
.....
}

score 3 · Answer 6 · answered Feb 13 '11 at 07:21

3

There is no support currently for builder pattern, although it has been requested quite a while ago (and finally Jira issue http://jira.codehaus.org/browse/JACKSON-469 was filed) -- it is something that may be added for 1.8 release if there is enough demand (make sure to vote at Jira!). It is a reasonable additional feature, and only delayed by amount of time developers have. But I think it would be great addition.

answered Feb 13 '11 at 07:21

StaxMan

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Codehaus no longer has Jira available but the linked issue is described here: http://wiki.fasterxml.com/JacksonFeatureBuilderPattern – Paul Feb 26 '16 at 14:10
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Support for Builder pattern has been long since added, at something like Jackson 2.2. – StaxMan Mar 16 '16 at 05:17

Jackson + Builder Pattern?

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