Jackson is "the Java JSON library" or "the best JSON parser for Java". Or simply as "JSON for Java".

Jackson Core Source Code files are provided in the source packge (jackson-core-2.14.0-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Core Source Code below:

⏎ com/fasterxml/jackson/core/StreamReadFeature.java

package com.fasterxml.jackson.core;

import java.io.InputStream;
import java.io.Reader;

import com.fasterxml.jackson.core.util.JacksonFeature;

/**
 * Token reader (parser) features not-specific to any particular format backend.
 * Eventual replacement for non-JSON-specific {@link com.fasterxml.jackson.core.JsonParser.Feature}s.
 *
 * @since 2.10
 */
public enum StreamReadFeature
    implements JacksonFeature // since 2.12
{
    // // // Low-level I/O handling features:

    /**
     * Feature that determines whether parser will automatically
     * close underlying input source that is NOT owned by the
     * parser. If disabled, calling application has to separately
     * close the underlying {@link InputStream} and {@link Reader}
     * instances used to create the parser. If enabled, parser
     * will handle closing, as long as parser itself gets closed:
     * this happens when end-of-input is encountered, or parser
     * is closed by a call to {@link JsonParser#close}.
     *<p>
     * Feature is enabled by default.
     */
    AUTO_CLOSE_SOURCE(JsonParser.Feature.AUTO_CLOSE_SOURCE),

    // // // Validity checks
    
    /**
     * Feature that determines whether {@link JsonParser} will explicitly
     * check that no duplicate JSON Object field names are encountered.
     * If enabled, parser will check all names within context and report
     * duplicates by throwing a {@link JsonParseException}; if disabled,
     * parser will not do such checking. Assumption in latter case is
     * that caller takes care of handling duplicates at a higher level:
     * data-binding, for example, has features to specify detection to
     * be done there.
     *<p>
     * Note that enabling this feature will incur performance overhead
     * due to having to store and check additional information: this typically
     * adds 20-30% to execution time for basic parsing.
     */
    STRICT_DUPLICATE_DETECTION(JsonParser.Feature.STRICT_DUPLICATE_DETECTION),

    /**
     * Feature that determines what to do if the underlying data format requires knowledge
     * of all properties to decode (usually via a Schema), and if no definition is
     * found for a property that input content contains.
     * Typically most textual data formats do NOT require schema information (although
     * some do, such as CSV), whereas many binary data formats do require definitions
     * (such as Avro, protobuf), although not all (Smile, CBOR, BSON and MessagePack do not).
     * Further note that some formats that do require schema information will not be able
     * to ignore undefined properties: for example, Avro is fully positional and there is
     * no possibility of undefined data. This leaves formats like Protobuf that have identifiers
     * that may or may not map; and as such Protobuf format does make use of this feature.
     *<p>
     * Note that support for this feature is implemented by individual data format
     * module, if (and only if) it makes sense for the format in question. For JSON,
     * for example, this feature has no effect as properties need not be pre-defined.
     *<p>
     * Feature is disabled by default, meaning that if the underlying data format
     * requires knowledge of all properties to output, attempts to read an unknown
     * property will result in a {@link JsonProcessingException}
     */
    IGNORE_UNDEFINED(JsonParser.Feature.IGNORE_UNDEFINED),

    // // // Other

    /**
     * Feature that determines whether {@link JsonLocation} instances should be constructed
     * with reference to source or not. If source reference is included, its type and contents
     * are included when `toString()` method is called (most notably when printing out parse
     * exception with that location information). If feature is disabled, no source reference
     * is passed and source is only indicated as "UNKNOWN".
     *<p>
     * Most common reason for disabling this feature is to avoid leaking
     * internal information; this may be done for security reasons.
     * Note that even if source reference is included, only parts of contents are usually
     * printed, and not the whole contents. Further, many source reference types can not
     * necessarily access contents (like streams), so only type is indicated, not contents.
     *<p>
     * Feature is enabled by default, meaning that "source reference" information is passed
     * and some or all of the source content may be included in {@link JsonLocation} information
     * constructed either when requested explicitly, or when needed for an exception.
     */
    INCLUDE_SOURCE_IN_LOCATION(JsonParser.Feature.INCLUDE_SOURCE_IN_LOCATION),

    /**
     * Feature that determines whether we use the built-in {@link Double#parseDouble(String)} code to parse
     * doubles or if we use {@link com.fasterxml.jackson.core.io.doubleparser}
     * instead.
     *<p>
     * This setting is disabled by default.
     *
     * @since 2.14
     */
    USE_FAST_DOUBLE_PARSER(JsonParser.Feature.USE_FAST_DOUBLE_PARSER)

    ;

    /**
     * Whether feature is enabled or disabled by default.
     */
    private final boolean _defaultState;

    private final int _mask;

    /**
     * For backwards compatibility we may need to map to one of existing {@link JsonParser.Feature}s;
     * if so, this is the feature to enable/disable.
     */
    final private JsonParser.Feature _mappedFeature;

    private StreamReadFeature(JsonParser.Feature mapTo) {
        // only for 2.x, let's map everything to legacy feature:
        _mappedFeature = mapTo;
        _mask = mapTo.getMask();
        _defaultState = mapTo.enabledByDefault();
    }

    /**
     * Method that calculates bit set (flags) of all features that
     * are enabled by default.
     *
     * @return Bit mask of all features that are enabled by default
     */
    public static int collectDefaults()
    {
        int flags = 0;
        for (StreamReadFeature f : values()) {
            if (f.enabledByDefault()) {
                flags |= f.getMask();
            }
        }
        return flags;
    }

    @Override
    public boolean enabledByDefault() { return _defaultState; }
    @Override
    public boolean enabledIn(int flags) { return (flags & _mask) != 0; }
    @Override
    public int getMask() { return _mask; }

    public JsonParser.Feature mappedFeature() { return _mappedFeature; }
}

⏎ com/fasterxml/jackson/core/StreamReadFeature.java

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File name: jackson-core-2.14.0-sources.jar
File size: 497693 bytes
Release date: 2022-11-05
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