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

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

You can also browse Jackson Databind Source Code below:

⏎ com/fasterxml/jackson/databind/node/TreeTraversingParser.java

package com.fasterxml.jackson.databind.node;

import java.io.IOException;
import java.io.OutputStream;
import java.math.BigDecimal;
import java.math.BigInteger;

import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.core.base.ParserMinimalBase;
import com.fasterxml.jackson.core.util.JacksonFeatureSet;
import com.fasterxml.jackson.databind.JsonNode;

/**
 * Facade over {@link JsonNode} that implements {@link JsonParser} to allow
 * accessing contents of JSON tree in alternate form (stream of tokens).
 * Useful when a streaming source is expected by code, such as data binding
 * functionality.
 */
public class TreeTraversingParser extends ParserMinimalBase
{
    /*
    /**********************************************************
    /* Configuration
    /**********************************************************
     */

    protected ObjectCodec _objectCodec;

    /**
     * Traversal context within tree
     */
    protected NodeCursor _nodeCursor;

    /*
    /**********************************************************
    /* State
    /**********************************************************
     */

    /**
     * Flag that indicates whether parser is closed or not. Gets
     * set when parser is either closed by explicit call
     * ({@link #close}) or when end-of-input is reached.
     */
    protected boolean _closed;

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

    public TreeTraversingParser(JsonNode n) { this(n, null); }

    public TreeTraversingParser(JsonNode n, ObjectCodec codec)
    {
        super(0);
        _objectCodec = codec;
        _nodeCursor = new NodeCursor.RootCursor(n, null);
    }

    @Override
    public void setCodec(ObjectCodec c) {
        _objectCodec = c;
    }

    @Override
    public ObjectCodec getCodec() {
        return _objectCodec;
    }

    @Override
    public Version version() {
        return com.fasterxml.jackson.databind.cfg.PackageVersion.VERSION;
    }

    @Override
    public JacksonFeatureSet<StreamReadCapability> getReadCapabilities() {
        // Defaults are fine
        return DEFAULT_READ_CAPABILITIES;
    }

    /*
    /**********************************************************
    /* Closeable implementation
    /**********************************************************
     */

    @Override
    public void close() throws IOException
    {
        if (!_closed) {
            _closed = true;
            _nodeCursor = null;
            _currToken = null;
        }
    }

    /*
    /**********************************************************
    /* Public API, traversal
    /**********************************************************
     */

    @Override
    public JsonToken nextToken() throws IOException
    {
        _currToken = _nodeCursor.nextToken();
        if (_currToken == null) {
            _closed = true; // if not already set
            return null;
        }
        switch (_currToken) {
        case START_OBJECT:
            _nodeCursor = _nodeCursor.startObject();
            break;
        case START_ARRAY:
            _nodeCursor = _nodeCursor.startArray();
            break;
        case END_OBJECT:
        case END_ARRAY:
            _nodeCursor = _nodeCursor.getParent();
        default:
        }
        return _currToken;
    }

    // default works well here:
    //public JsonToken nextValue() throws IOException

    @Override
    public JsonParser skipChildren() throws IOException
    {
        if (_currToken == JsonToken.START_OBJECT) {
            _nodeCursor = _nodeCursor.getParent();
            _currToken = JsonToken.END_OBJECT;
        } else if (_currToken == JsonToken.START_ARRAY) {
            _nodeCursor = _nodeCursor.getParent();
            _currToken = JsonToken.END_ARRAY;
        }
        return this;
    }

    @Override
    public boolean isClosed() {
        return _closed;
    }

    /*
    /**********************************************************
    /* Public API, token accessors
    /**********************************************************
     */

    @Override public String getCurrentName() {
        NodeCursor crsr = _nodeCursor;
        if (_currToken == JsonToken.START_OBJECT || _currToken == JsonToken.START_ARRAY) {
            crsr = crsr.getParent();
        }
        return (crsr == null) ? null : crsr.getCurrentName();
    }

    @Override public void overrideCurrentName(String name) {
        NodeCursor crsr = _nodeCursor;
        if (_currToken == JsonToken.START_OBJECT || _currToken == JsonToken.START_ARRAY) {
            crsr = crsr.getParent();
        }
        if (crsr != null) {
            crsr.overrideCurrentName(name);
        }
    }

    @Override
    public JsonStreamContext getParsingContext() {
        return _nodeCursor;
    }

    @Override
    public JsonLocation getTokenLocation() {
        return JsonLocation.NA;
    }

    @Override
    public JsonLocation getCurrentLocation() {
        return JsonLocation.NA;
    }

    /*
    /**********************************************************
    /* Public API, access to textual content
    /**********************************************************
     */

    @Override
    public String getText()
    {
        if (_currToken == null) {
            return null;
        }
        // need to separate handling a bit...
        switch (_currToken) {
        case FIELD_NAME:
            return _nodeCursor.getCurrentName();
        case VALUE_STRING:
            return currentNode().textValue();
        case VALUE_NUMBER_INT:
        case VALUE_NUMBER_FLOAT:
            return String.valueOf(currentNode().numberValue());
        case VALUE_EMBEDDED_OBJECT:
            JsonNode n = currentNode();
            if (n != null && n.isBinary()) {
                // this will convert it to base64
                return n.asText();
            }
        default:
            return _currToken.asString();
        }
    }

    @Override
    public char[] getTextCharacters() throws IOException {
        return getText().toCharArray();
    }

    @Override
    public int getTextLength() throws IOException {
        return getText().length();
    }

    @Override
    public int getTextOffset() throws IOException {
        return 0;
    }

    @Override
    public boolean hasTextCharacters() {
        // generally we do not have efficient access as char[], hence:
        return false;
    }
    
    /*
    /**********************************************************
    /* Public API, typed non-text access
    /**********************************************************
     */

    //public byte getByteValue() throws IOException

    @Override
    public NumberType getNumberType() throws IOException {
        JsonNode n = currentNumericNode();
        return (n == null) ? null : n.numberType();
    }

    @Override
    public BigInteger getBigIntegerValue() throws IOException
    {
        return currentNumericNode().bigIntegerValue();
    }

    @Override
    public BigDecimal getDecimalValue() throws IOException {
        return currentNumericNode().decimalValue();
    }

    @Override
    public double getDoubleValue() throws IOException {
        return currentNumericNode().doubleValue();
    }

    @Override
    public float getFloatValue() throws IOException {
        return (float) currentNumericNode().doubleValue();
    }

    @Override
    public int getIntValue() throws IOException {
        final NumericNode node = (NumericNode) currentNumericNode();
        if (!node.canConvertToInt()) {
            reportOverflowInt();
        }
        return node.intValue();
    }

    @Override
    public long getLongValue() throws IOException {
        final NumericNode node = (NumericNode) currentNumericNode();
        if (!node.canConvertToLong()) {
            reportOverflowLong();
        }
        return node.longValue();
    }

    @Override
    public Number getNumberValue() throws IOException {
        return currentNumericNode().numberValue();
    }

    @Override
    public Object getEmbeddedObject()
    {
        if (!_closed) {
            JsonNode n = currentNode();
            if (n != null) {
                if (n.isPojo()) {
                    return ((POJONode) n).getPojo();
                }
                if (n.isBinary()) {
                    return ((BinaryNode) n).binaryValue();
                }
            }
        }
        return null;
    }

    @Override
    public boolean isNaN() {
        if (!_closed) {
            JsonNode n = currentNode();
            if (n instanceof NumericNode) {
                return ((NumericNode) n).isNaN();
            }
        }
        return false;
    }

    /*
    /**********************************************************
    /* Public API, typed binary (base64) access
    /**********************************************************
     */

    @Override
    public byte[] getBinaryValue(Base64Variant b64variant)
        throws IOException
    {
        // Multiple possibilities...
        JsonNode n = currentNode();
        if (n != null) {
            // [databind#2096]: although `binaryValue()` works for real binary node
            // and embedded "POJO" node, coercion from TextNode may require variant, so:
            if (n instanceof TextNode) {
                return ((TextNode) n).getBinaryValue(b64variant);
            }
            return n.binaryValue();
        }
        // otherwise return null to mark we have no binary content
        return null;
    }


    @Override
    public int readBinaryValue(Base64Variant b64variant, OutputStream out)
        throws IOException
    {
        byte[] data = getBinaryValue(b64variant);
        if (data != null) {
            out.write(data, 0, data.length);
            return data.length;
        }
        return 0;
    }

    /*
    /**********************************************************
    /* Internal methods
    /**********************************************************
     */

    protected JsonNode currentNode() {
        if (_closed || _nodeCursor == null) {
            return null;
        }
        return _nodeCursor.currentNode();
    }

    protected JsonNode currentNumericNode()
        throws JacksonException
    {
        JsonNode n = currentNode();
        if (n == null || !n.isNumber()) {
            JsonToken t = (n == null) ? null : n.asToken();
            throw _constructError("Current token ("+t+") not numeric, cannot use numeric value accessors");
        }
        return n;
    }

    @Override
    protected void _handleEOF() {
        _throwInternal(); // should never get called
    }
}

⏎ com/fasterxml/jackson/databind/node/TreeTraversingParser.java

Or download all of them as a single archive file:

File name: jackson-databind-2.14.0-sources.jar
File size: 1187952 bytes
Release date: 2022-11-05
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