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/MissingNode.java

package com.fasterxml.jackson.databind.node;

import java.io.IOException;

import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.jsontype.TypeSerializer;

/**
 * This singleton node class is generated to denote "missing nodes"
 * along paths that do not exist. For example, if a path via
 * element of an array is requested for an element outside range
 * of elements in the array; or for a non-array value, result
 * will be reference to this node.
 *<p>
 * In most respects this placeholder node will act as {@link NullNode};
 * for example, for purposes of value conversions, value is considered
 * to be null and represented as value zero when used for numeric
 * conversions. 
 */
public final class MissingNode
    extends ValueNode
{
    private static final long serialVersionUID = 1L;

    private final static MissingNode instance = new MissingNode();

    /**
     *<p>
     * NOTE: visibility raised to `protected` in 2.9.3 to allow custom subtypes
     * (which may not be greatest idea ever to have but was requested)
     */
    protected MissingNode() { }

    // To support JDK serialization, recovery of Singleton instance
    protected Object readResolve() {
        return instance;
    }
    
    @Override
    public boolean isMissingNode() {
        return true;
    }

    // Immutable: no need to copy
    @SuppressWarnings("unchecked")
    @Override
    public <T extends JsonNode> T deepCopy() { return (T) this; }

    public static MissingNode getInstance() { return instance; }
    
    @Override
    public JsonNodeType getNodeType()
    {
        return JsonNodeType.MISSING;
    }

    @Override public JsonToken asToken() { return JsonToken.NOT_AVAILABLE; }

    @Override public String asText() { return ""; }

    @Override public String asText(String defaultValue) { return defaultValue; }
    
    // // Note: not a numeric node, hence default 'asXxx()' are fine:
    
    /*
    public int asInt(int defaultValue);
    public long asLong(long defaultValue);
    public double asDouble(double defaultValue);
    public boolean asBoolean(boolean defaultValue);
    */

    /*
    /**********************************************************
    /* Serialization: bit tricky as we don't really have a value
    /**********************************************************
     */
    
    @Override
    public final void serialize(JsonGenerator g, SerializerProvider provider)
        throws IOException
    {
        /* Nothing to output... should we signal an error tho?
         * Chances are, this is an erroneous call. For now, let's
         * not do that; serialize as explicit null. Why? Because we
         * cannot just omit a value as JSON Object field name may have
         * been written out.
         */
        g.writeNull();
    }

    @Override
    public void serializeWithType(JsonGenerator g, SerializerProvider provider,
            TypeSerializer typeSer)
        throws IOException
    {
        g.writeNull();
    }

    /*
    /**********************************************************
    /* Jackson 2.10 improvements for validation
    /**********************************************************
     */
    
    @SuppressWarnings("unchecked")
    @Override
    public JsonNode require() {
        return _reportRequiredViolation("require() called on `MissingNode`");
    }

    @SuppressWarnings("unchecked")
    @Override
    public JsonNode requireNonNull() {
        return _reportRequiredViolation("requireNonNull() called on `MissingNode`");
    }

    @Override
    public int hashCode() {
        return JsonNodeType.MISSING.ordinal();
    }

    /*
    /**********************************************************
    /* Standard method overrides
    /**********************************************************
     */

    // 10-Dec-2019, tatu: Bit tricky case, see [databind#2566], but seems
    //    best NOT to produce legit JSON.
    @Override
    public String toString() {
        return "";
    }

    @Override
    public String toPrettyString() {
        return "";
    }
    
    @Override
    public boolean equals(Object o)
    {
        /* Hmmh. Since there's just a singleton instance, this fails in all cases but with
         * identity comparison. However: if this placeholder value was to be considered
         * similar to SQL NULL, it shouldn't even equal itself?
         * That might cause problems when dealing with collections like Sets...
         * so for now, let's let identity comparison return true.
         */
        return (o == this);
    }
}

⏎ com/fasterxml/jackson/databind/node/MissingNode.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
Download 

⇒ Jackson Annotations Source Code

⇐ Download and Install Jackson Binary Package

⇑ Downloading and Reviewing jackson-*.jar

⇑⇑ Jackson - Java JSON library