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/json/JsonWriteContext.java

package com.fasterxml.jackson.core.json;

import com.fasterxml.jackson.core.*;

/**
 * Extension of {@link JsonStreamContext}, which implements
 * core methods needed, and also exposes
 * more complete API to generator implementation classes.
 */
public class JsonWriteContext extends JsonStreamContext
{
    // // // Return values for writeValue()

    public final static int STATUS_OK_AS_IS = 0;
    public final static int STATUS_OK_AFTER_COMMA = 1;
    public final static int STATUS_OK_AFTER_COLON = 2;
    public final static int STATUS_OK_AFTER_SPACE = 3; // in root context
    public final static int STATUS_EXPECT_VALUE = 4;
    public final static int STATUS_EXPECT_NAME = 5;

    /**
     * Parent context for this context; null for root context.
     */
    protected final JsonWriteContext _parent;

    // // // Optional duplicate detection

    protected DupDetector _dups;

    /*
    /**********************************************************
    /* Simple instance reuse slots; speed up things a bit (10-15%)
    /* for docs with lots of small arrays/objects
    /**********************************************************
     */

    protected JsonWriteContext _child;

    /*
    /**********************************************************
    /* Location/state information (minus source reference)
    /**********************************************************
     */

    /**
     * Name of the field of which value is to be written; only
     * used for OBJECT contexts
     */
    protected String _currentName;

    /**
     * @since 2.5
     */
    protected Object _currentValue;

    /**
     * Marker used to indicate that we just wrote a name, and
     * now expect a value to write
     */
    protected boolean _gotName;

    /*
    /**********************************************************
    /* Life-cycle
    /**********************************************************
     */

    protected JsonWriteContext(int type, JsonWriteContext parent, DupDetector dups) {
        super();
        _type = type;
        _parent = parent;
        _dups = dups;
        _index = -1;
    }

    /* @since 2.10 */
    protected JsonWriteContext(int type, JsonWriteContext parent, DupDetector dups,
            Object currValue) {
        super();
        _type = type;
        _parent = parent;
        _dups = dups;
        _index = -1;
        _currentValue = currValue;
    }

    /**
     * Internal method to allow instance reuse: DO NOT USE unless you absolutely
     * know what you are doing.
     * Clears up state (including "current value"), changes type to one specified;
     * resets current duplicate-detection state (if any).
     * Parent link left as-is since it is {@code final}.
     *<p>
     * NOTE: Public since 2.12.
     *
     * @param type Type to assign to this context node
     *
     * @return This context instance to allow call-chaining
     */
    public JsonWriteContext reset(int type) {
        _type = type;
        _index = -1;
        _currentName = null;
        _gotName = false;
        _currentValue = null;
        if (_dups != null) { _dups.reset(); }
        return this;
    }

    /**
     * Internal method to allow instance reuse: DO NOT USE unless you absolutely
     * know what you are doing.
     * Clears up state, changes type to one specified, assigns "current value";
     * resets current duplicate-detection state (if any).
     * Parent link left as-is since it is {@code final}.
     *<p>
     * NOTE: Public since 2.12.
     *
     * @param type Type to assign to this context node
     * @param currValue Current value to assign to this context node
     *
     * @return This context instance to allow call-chaining
     *
     * @since 2.10
     */
    public JsonWriteContext reset(int type, Object currValue) {
        _type = type;
        _index = -1;
        _currentName = null;
        _gotName = false;
        _currentValue = currValue;
        if (_dups != null) { _dups.reset(); }
        return this;
    }

    public JsonWriteContext withDupDetector(DupDetector dups) {
        _dups = dups;
        return this;
    }

    @Override
    public Object getCurrentValue() {
        return _currentValue;
    }

    @Override
    public void setCurrentValue(Object v) {
        _currentValue = v;
    }

    /*
    /**********************************************************
    /* Factory methods
    /**********************************************************
     */

    /**
     * @deprecated Since 2.3; use method that takes argument
     *
     * @return Context instance created
     */
    @Deprecated
    public static JsonWriteContext createRootContext() { return createRootContext(null); }

    public static JsonWriteContext createRootContext(DupDetector dd) {
        return new JsonWriteContext(TYPE_ROOT, null, dd);
    }

    public JsonWriteContext createChildArrayContext() {
        JsonWriteContext ctxt = _child;
        if (ctxt == null) {
            _child = ctxt = new JsonWriteContext(TYPE_ARRAY, this,
                    (_dups == null) ? null : _dups.child());
            return ctxt;
        }
        return ctxt.reset(TYPE_ARRAY);
    }

    /* @since 2.10 */
    public JsonWriteContext createChildArrayContext(Object currValue) {
        JsonWriteContext ctxt = _child;
        if (ctxt == null) {
            _child = ctxt = new JsonWriteContext(TYPE_ARRAY, this,
                    (_dups == null) ? null : _dups.child(), currValue);
            return ctxt;
        }
        return ctxt.reset(TYPE_ARRAY, currValue);
    }

    public JsonWriteContext createChildObjectContext() {
        JsonWriteContext ctxt = _child;
        if (ctxt == null) {
            _child = ctxt = new JsonWriteContext(TYPE_OBJECT, this,
                    (_dups == null) ? null : _dups.child());
            return ctxt;
        }
        return ctxt.reset(TYPE_OBJECT);
    }

    /* @since 2.10 */
    public JsonWriteContext createChildObjectContext(Object currValue) {
        JsonWriteContext ctxt = _child;
        if (ctxt == null) {
            _child = ctxt = new JsonWriteContext(TYPE_OBJECT, this,
                    (_dups == null) ? null : _dups.child(), currValue);
            return ctxt;
        }
        return ctxt.reset(TYPE_OBJECT, currValue);
    }

    @Override public final JsonWriteContext getParent() { return _parent; }
    @Override public final String getCurrentName() { return _currentName; }
    // @since 2.9
    @Override public boolean hasCurrentName() { return _currentName != null; }

    /**
     * Method that can be used to both clear the accumulated references
     * (specifically value set with {@link #setCurrentValue(Object)})
     * that should not be retained, and returns parent (as would
     * {@link #getParent()} do). Typically called when closing the active
     * context when encountering {@link JsonToken#END_ARRAY} or
     * {@link JsonToken#END_OBJECT}.
     *
     * @return Parent context of this context node, if any; {@code null} for root context
     *
     * @since 2.7
     */
    public JsonWriteContext clearAndGetParent() {
        _currentValue = null;
        // could also clear the current name, but seems cheap enough to leave?
        return _parent;
    }

    public DupDetector getDupDetector() {
        return _dups;
    }

    /**
     * Method that writer is to call before it writes a name of Object property.
     *
     * @param name Property name being written
     *
     * @return Index of the field entry (0-based)
     *
     * @throws JsonProcessingException if duplicate check restriction is violated
     */
    public int writeFieldName(String name) throws JsonProcessingException {
        if ((_type != TYPE_OBJECT) || _gotName) {
            return STATUS_EXPECT_VALUE;
        }
        _gotName = true;
        _currentName = name;
        if (_dups != null) { _checkDup(_dups, name); }
        return (_index < 0) ? STATUS_OK_AS_IS : STATUS_OK_AFTER_COMMA;
    }

    private final void _checkDup(DupDetector dd, String name) throws JsonProcessingException {
        if (dd.isDup(name)) {
            Object src = dd.getSource();
            throw new JsonGenerationException("Duplicate field '"+name+"'",
                    ((src instanceof JsonGenerator) ? ((JsonGenerator) src) : null));
        }
    }
    
    public int writeValue() {
        // Most likely, object:
        if (_type == TYPE_OBJECT) {
            if (!_gotName) {
                return STATUS_EXPECT_NAME;
            }
            _gotName = false;
            ++_index;
            return STATUS_OK_AFTER_COLON;
        }

        // Ok, array?
        if (_type == TYPE_ARRAY) {
            int ix = _index;
            ++_index;
            return (ix < 0) ? STATUS_OK_AS_IS : STATUS_OK_AFTER_COMMA;
        }
        
        // Nope, root context
        // No commas within root context, but need space
        ++_index;
        return (_index == 0) ? STATUS_OK_AS_IS : STATUS_OK_AFTER_SPACE;
    }
}

⏎ com/fasterxml/jackson/core/json/JsonWriteContext.java

Or download all of them as a single archive file:

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