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JacksonFeatures
Features configurable via ObjectMapper
, ObjectWriter
and ObjectReader
are divide into two main categories: high-level settings that affect jackson-databind
components directly; and low-level settings
that affect behavior of Streaming API behavior (JsonParser
, JsonGenerator
).
For core databinding, features are divided further in 3 categories:
- [Mapper features](Mapper Features)
- [Serialization features](Serialization Features) (writing POJOs as JSON and other formats)
- [Deserialization features](Deserialization Features) (reading JSON and other formats as POJOs)
Of these, Mapper Features can only be modified before using ObjectMapper
: changes after use
may or may not take effects. If you need different configured mapper (or ObjectWriter
or ObjectReader
), you will need a new mapper instance: you can do this with ObjectMapper.copy()
-- it will copy current settings, but allow changes to Mapper Features.
Both Serialization and Deserialization features may, however, be configured by constructing new ObjectReader
and ObjectWriter
instances like so:
ObjectWriter w = mapper.write(SerializationFeature.WRAP_ROOT_VALUE);
ObjectWriter w2 = w.without(SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS);
ObjectReader r = mapper.reader(DeserializationFeature.USE_BIG_DECIMAL_FOR_FLOATS);
ObjectReader r2 = r2.with(DeserializationFeature.USE_JAVA_ARRAY_FOR_JSON_ARRAY)
.without(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
Since both ObjectReader
/ ObjectWriter
are immutable, methods will create new readers/writers and configuration is fully thread-safe. Cost of these instances is minimal (unlike cost of creating ObjectMapper
s, which is substantial) so while they may be freely shared and pooled, this is typically not necessary nor improve performance measurably.
Additional notes:
- Most databind features do NOT affect Tree Model (
JsonNode
) since Tree Model is meant to be 1-to-1 representation of underlying physical content, and as such, minimal amount of converting is done on purpose.
Similarly, low-level features are divided in 3 categories:
- Factory features
- Generator features (generating content encoded as JSON and other supported data formats)
- Parser features (decoding content encoded as JSON and other supported data formats)
Similar to databind features, Factory Features may only be changed after constructing factory (either directly, or automatically via ObjectMapper
), but before usage.
Parser and Generator Features may be modified dynamically between calls, using ObjectReader
and ObjectWriter
methods similar to how Serialization and Deserialization features may be enabled and disabled.