Jackson - Features for configuring Java-to-JSON mapping

Following on/off features are defined in SerializationConfig.Feature (for Jackson 1.x), or SerializationFeature (Jackson 2.x):

 

AUTO_DETECT_FIELDS (default: true)

Feature that determines whether non-static fields are recognized as properties. If yes, then all public member fields are considered as properties. If disabled, only fields explicitly annotated are considered property fields.

Note that this feature has lower precedence than per-class annotations, and is only used if there isn't more granular configuration available.

 

AUTO_DETECT_GETTERS (default: true)

Controls whether "getter" methods are automatically detected (as opposed to located by annotations); if enabled, public no-argument non-static no-argument methods are recognized as getters. If disabled, only ones explicitly annotated (using @JsonProperty, for example) are recognized as serializable properties

 

AUTO_DETECT_IS_GETTERS (default: true)

Controls whether "is-getter" methods (methods with name "isXxx()" that return boolean or java.lang.Boolean value) are automatically detected (as opposed to located by annotations); if enabled, such methods are detected as getters. If disabled, only ones explicitly annotated (using @JsonProperty, for example) are recognized as serializable properties

 

CAN_OVERRIDE_ACCESS_MODIFIERS (default: true)

Whether non-public fields and methods can be forced accessible (using JDK provided methods or not): if disabled, non-public fields and methods can not be used for properties. The main reason to disable this feature is if running on a security-restricted platform where trying to change access rights results in a runtime error.

 

CLOSE_CLOSEABLE (default: false) (since 1.6)

If enabled, ObjectMapper will call close() and root values that implement java.io.Closeable; including cases where exception is thrown and serialization does not completely succeed.

Can be useful for resource clean up; and specifically allows for building wrappers that can be useful when serializing referential values (like, say, serializing a java.io.File value by reading contents of a file and outputting as JSON String or base64-encoded binary)

 

DEFAULT_VIEW_INCLUSION (default: true) (since 1.5)

Controls what is the behavior of properties that have no matching JsonView annotation: if set to true, they are included in all views; if false, not included in any views. This only affects JSON View enabled processing (i.e. when Serialization View is specified)

 

FAIL_ON_EMPTY_BEANS (default: true) (since 1.4)

Controls whether exception is thrown if no serializer is found for a type (Class); and type has neither getters nor recognized annotations (ones configured AnnotationIntrospector recognizes, including JacksonJAXBAnnotations if JAXB introspector used). If enabled, exception is thrown; if disabled, will just output empty JSON Object.

 

FLUSH_AFTER_WRITE_VALUE (default: true) (since 1.7)

Determines whether JsonGenerator.flush() is automatically called after ObjectMapper's writeValue(JsonGenerator, ...) is called or not (note: does NOT affect methods that do not take JsonGenerator) -- if true flush() is called; if false, it is not called.

Main reason to disable this feature is performance; for network connections flushing may send message earlier than optimal, and with some compressing streams compression block may complete with flush().

 

INDENT_OUTPUT (default: false)

Controls whether output is indented using the default indentation ("pretty-printing") mechanism (2-space, platform linefeeds) or not.

 

REQUIRE_SETTERS_FOR_GETTERS (default: false)

Controls whether auto-detection of getter methods requires presence of mutators (setter / constructor argument / field) to include auto-detectable getters or not: if enabled, only getters with matching mutator are included via auto-detection (meaning: explicitly annotated getters are still included); if disabled, all auto-detectable getters are included.

NOTE: some frameworks such as JAXB behave as if this feature was enabled; and enabling it can help ensure that serialized JSON can be deserialized back -- conversely, for write-only use cases, this feature is usually best left disabled.

 

SORT_PROPERTIES_ALPHABETICALLY (default: false) (since 1.8)

Controls default ordering used for serializing POJO fields (note: does NOT apply to Maps!): if enabled, default ordering is alphabetic (similar to how @JsonPropertyOrder.alphabetic=true works; if disabled, default order is unspecified.

Note that explicit ordering annotations on type (class) override default settings.

 

USE_ANNOTATIONS (default: true) (since 1.2)

Controls whether any annotation introspection is used for configuring data binding: if disabled, all annotations are ignored (independent of setting for AnnotationIntrospector in use)

note: since 1.8, disable this feature will try to remove ALL annotation processing; this to help on platforms like Android, where trying to access unavailable annotation types (JAXB annotations for value types) can result in exception, even if not specifically looking for that annotation type.

 

USE_STATIC_TYPING (default: false)

Controls whether the type detection for serialization should be using actual dynamic runtime type or declared static type. Default value is false, to use dynamic runtime type.

This global default value can be overridden at class, or method/field level by using JsonSerialize annotation (its typing property)

 

WRAP_ROOT_Exception (default: false) (since 1.7)

Feature that determines whether Jackson code should catch and wrap Exceptions (but never Errors!) to add additional information about location (within input) of problem or not. If enabled, most exceptions will be caught and re-thrown (exception specifically being that IOExceptions may be passed as is, since they are declared as throwable); this can be convenient both in that all exceptions will be checked and declared, and so there is more contextual information. However, sometimes calling application may just want "raw" unchecked exceptions passed as is.

 

WRAP_ROOT_VALUE (default: false) (since 1.7)

When enabled, will wrap output in a single-property JSON Object. Name of wrapper property is based on class name of the serialized instance (or value type if static typing used or root type specified); or, if using JAXB annotations, name from @XmlRootElement.

 

WRITE_BIGDECIMAL_AS_PLAIN (default: false) (since 2.2)

If enabled, will prevent use of scientific notation (use of 'e' in value to normalize scale of mantisaa); if disabled, will use scientific notation when necessary.

 

WRITE_CHAR_ARRAYS_AS_JSON_ARRAYS (default: false) (since 1.6)

Controls how basic char[] values are serialized: if enabled, they will be serialized as full JSON Arrays, with JSON Strings (of length 1 character) as elements; if disabled (which is the default) as a single JSON String consisting of all characters of the array.

 

WRITE_DATES_AS_TIMESTAMPS (default: true)

Controls whether Date / Time values are to be written out as numeric (64-bit) timestamps (if true) or as Strings. If latter, format used is defined by SerializationConfig.getDateFormat

 

WRITE_DATE_KEY_AS_TIMESTAMPS (default: false)

Feature that determines whether Dates (and sub-types) used as Map keys are serialized as timestamps or not (if not, will be serialized as textual values).

Default value is 'false', meaning that Date-valued Map keys are serialized as textual (ISO-8601) values.

 

WRITE_EMPTY_JSON_ARRAYS (default: true) (since 1.9)

to allow suppressing serialization of empty Collections/arrays.

 

WRITE_ENUMS_USING_INDEX (default: false) (since 1.9)

Determines whether Enums are to be serialized as integers (true), or Strings (false): if integers, Enum.ordinal() value is used as serialization.

 

WRITE_ENUMS_USING_TO_STRING (default: false) (since 1.6)

Determines which method is used to determine expected serialization of an Enum (when serialized as String): if false (default), use Enum.name(); if true, Enum.toString().

 

WRITE_NULL_MAP_VALUES (default: true) (since 1.6)

Determines whether Map entries with value null are serialized or not.

 

WRITE_NULL_PROPERTIES (default: true) (NOTE: deprecated as of 1.1)

Controls where values of properties that have null as value are written out or not.

deprecated Use SerializationConfig#setSerializationInclusion instead

 

WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED (default: true) (since 2.0)

to change handling of single-element Arrays, java.util.Collections, so that such arrays/collections are serialized as "unwrapped" elements, not as JSON Arrays.