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;


This singleton value class is used to contain explicit JSON null value.
/** * This singleton value class is used to contain explicit JSON null * value. */
public class NullNode extends ValueNode { // // Just need a fly-weight singleton private static final long serialVersionUID = 1L; public final static NullNode instance = new NullNode();

NOTE: visibility raised to `protected` in 2.9.3 to allow custom subtypes.

/** *<p> * NOTE: visibility raised to `protected` in 2.9.3 to allow custom subtypes. */
protected NullNode() { } // To support JDK serialization, recovery of Singleton instance protected Object readResolve() { return instance; } public static NullNode getInstance() { return instance; } @Override public JsonNodeType getNodeType() { return JsonNodeType.NULL; } @Override public JsonToken asToken() { return JsonToken.VALUE_NULL; } @Override public String asText(String defaultValue) { return defaultValue; } @Override public String asText() { return "null"; } @SuppressWarnings("unchecked") @Override public JsonNode requireNonNull() { return _reportRequiredViolation("requireNonNull() called on `NullNode`"); } // as with MissingNode, not considered number node; hence defaults are returned if provided /* public int asInt(int defaultValue); public long asLong(long defaultValue); public double asDouble(double defaultValue); public boolean asBoolean(boolean defaultValue); */ @Override public final void serialize(JsonGenerator g, SerializerProvider provider) throws IOException { provider.defaultSerializeNull(g); } @Override public boolean equals(Object o) { // 29-Aug-2019, tatu: [databind#2433] Since custom sub-classes are allowed (bad idea probably), // need to do better comparison return (o == this) || (o instanceof NullNode); } @Override public int hashCode() { return JsonNodeType.NULL.ordinal(); } }