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

Jackson Annotations Source Code files are provided in the source packge (jackson-annotations-2.12.4-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Annotations Source Code below:

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

package com.fasterxml.jackson.databind.node;

import java.io.IOException;

import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.JsonSerializable;
import com.fasterxml.jackson.databind.SerializerProvider;

/**
 * Value node that contains a wrapped POJO, to be serialized as
 * a JSON constructed through data mapping (usually done by
 * calling {@link com.fasterxml.jackson.databind.ObjectMapper}).
 */
public class POJONode
    extends ValueNode
{
    private static final long serialVersionUID = 2L;

    protected final Object _value;

    public POJONode(Object v) { _value = v; }

    /*
    /**********************************************************
    /* Base class overrides
    /**********************************************************
     */

    @Override
    public JsonNodeType getNodeType() {
        return JsonNodeType.POJO;
    }

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

    /**
     * As it is possible that some implementations embed byte[] as POJONode
     * (despite optimal being {@link BinaryNode}), let's add support for exposing
     * binary data here too.
     */
    @Override
    public byte[] binaryValue() throws IOException
    {
        if (_value instanceof byte[]) {
            return (byte[]) _value;
        }
        return super.binaryValue();
    }
    
    /* 
    /**********************************************************
    /* General type coercions
    /**********************************************************
     */

    @Override
    public String asText() { return (_value == null) ? "null" : _value.toString(); }

    @Override public String asText(String defaultValue) {
        return (_value == null) ? defaultValue : _value.toString();
    }
    
    @Override
    public boolean asBoolean(boolean defaultValue)
    {
        if (_value != null && _value instanceof Boolean) {
            return ((Boolean) _value).booleanValue();
        }
        return defaultValue;
    }
    
    @Override
    public int asInt(int defaultValue)
    {
        if (_value instanceof Number) {
            return ((Number) _value).intValue();
        }
        return defaultValue;
    }

    @Override
    public long asLong(long defaultValue)
    {
        if (_value instanceof Number) {
            return ((Number) _value).longValue();
        }
        return defaultValue;
    }
    
    @Override
    public double asDouble(double defaultValue)
    {
        if (_value instanceof Number) {
            return ((Number) _value).doubleValue();
        }
        return defaultValue;
    }
    
    /*
    /**********************************************************
    /* Public API, serialization
    /**********************************************************
     */

    @Override
    public final void serialize(JsonGenerator gen, SerializerProvider ctxt) throws IOException
    {
        if (_value == null) {
            ctxt.defaultSerializeNull(gen);
        } else if (_value instanceof JsonSerializable) {
            ((JsonSerializable) _value).serialize(gen, ctxt);
        } else {
            // 25-May-2018, tatu: [databind#1991] do not call via generator but through context;
            //    this to preserve contextual information
            ctxt.defaultSerializeValue(_value, gen);
        }
    }

    /*
    /**********************************************************
    /* Extended API
    /**********************************************************
     */

    /**
     * Method that can be used to access the POJO this node wraps.
     */
    public Object getPojo() { return _value; }

    /*
    /**********************************************************
    /* Overridden standard methods
    /**********************************************************
     */

    @Override
    public boolean equals(Object o)
    {
        if (o == this) return true;
        if (o == null) return false;
        if (o instanceof POJONode) {
            return _pojoEquals((POJONode) o);
        }
        return false;
    }

    /**
     * @since 2.3
     */
    protected boolean _pojoEquals(POJONode other)
    {
        if (_value == null) {
            return other._value == null;
        }
        return _value.equals(other._value);
    }
    
    @Override
    public int hashCode() { return _value.hashCode(); }
}

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

 

⇒ Jackson Dataformat Extensions

⇐ Jackson Data Binding Source Code

⇑ Downloading and Reviewing jackson-*.jar

⇑⇑ Jackson - Java JSON library