com.fasterxml.jackson.databind.node.MissingNode Maven / Gradle / Ivy
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.
*
* 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();
/**
*
* 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 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);
}
}