JsonReadFeatures

Jackson Streaming: JsonReadFeature

General

This set of features was added in Jackson 2.10, split off from earlier JsonParser.Feature. It contains features that are only relevant and usable on JSON backend.

Note: with 2.10 and later 2.x version there is overlap between new and old features: Jackson will keep "same" settings in sync so you can whichever; but recommendation is to use newer set of features to ease migration to 3.0.

Features

Settings can be divided in couple of loose categories, as follows.

Support for non-standard JSON content (deviations from JSON specification)

• ALLOW_BACKSLASH_ESCAPING_ANY_CHARACTER (default: false)
  • Maps to JsonParser.Feature.ALLOW_BACKSLASH_ESCAPING_ANY_CHARACTER
• ALLOW_JAVA_COMMENTS (default: false) (for textual formats with concept of comments)
  • Enabling the feature allows recognition and handling of "C comments" (/* ... */) and "C++ comments" (// ....)
  • Maps to JsonParser.Feature.ALLOW_COMMENTS (note naming difference!)
• ALLOW_YAML_COMMENTS (default: false)
  • For JSON: enabling the feature allows recognition and handling of "hash comments" (# .... )
  • Maps to JsonParser.Feature.ALLOW_YAML_COMMENTS
• ALLOW_UNQUOTED_FIELD_NAMES (default: false)
  • Feature that determines whether parser will allow use of unquoted field names (which is allowed by Javascript, for example, but not by JSON specification).
  • Maps to JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES
• ALLOW_SINGLE_QUOTES (default: false)
  • Feature that determines whether parser will allow use of single quotes (apostrophe, character "'") for quoting JSON Strings (names and String values). If so, this is in addition to other acceptable markers.
  • Maps to JsonParser.Feature.ALLOW_SINGLE_QUOTES
• ALLOW_UNESCAPED_CONTROL_CHARS (default: false)
  • Feature that determines whether parser will allow JSON Strings to contain unescaped control characters (ASCII characters with value less than 32, including tab and line feed characters) or not.
    • If feature is set false, an exception is thrown if such a character is encountered.
  • Maps to JsonParser.Feature.ALLOW_UNQUOTED_CONTROL_CHARS (Note the naming difference!)
• ALLOW_NON_NUMERIC_NUMBERS (default: false)
  • Feature that allows parser to recognize set of "Not-a-Number" (NaN) tokens as legal floating number values (similar to how many other data formats and programming language source code allows it).
  • Specific subset contains values that XML Schema (see section 3.2.4.1, Lexical Representation) allows (tokens are quoted contents, not including quotes):
    • "INF" (for positive infinity), as well as alias of "Infinity"
    • "-INF" (for negative infinity), alias "-Infinity"
    • "NaN" (for other not-a-numbers, like result of division by zero)
  • Maps to JsonParser.Feature.ALLOW_NON_NUMERIC_NUMBERS
• ALLOW_MISSING_VALUES (default: false)
  • Allow translation of "missing" values (white-space between two commas, in JSON Array context) into null values, instead of an exception
  • Maps to JsonParser.Feature.ALLOW_MISSING_VALUES
• ALLOW_LEADING_ZEROS_FOR_NUMBERS (default: false)
  • Feature that determines whether parser will allow JSON integral numbers to start with additional (ignorable) zeroes (like: 000001).
  • If enabled, no exception is thrown, and extra zeroes are silently ignored (and not included in textual representation exposed via JsonParser.getText().
  • Maps to JsonParser.Feature.ALLOW_NUMERIC_LEADING_ZEROS (Note the naming difference!)