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package com.fasterxml.jackson.databind.deser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.util.AccessPattern;
/**
* Helper interface implemented by classes that are to be used as
* null providers during deserialization. Most importantly implemented by
* {@link com.fasterxml.jackson.databind.JsonDeserializer} (as a mix-in
* interface), but also by converters used to support more configurable
* null replacement.
*
* @since 2.9
*/
public interface NullValueProvider
{
/**
* Method called to possibly convert incoming `null` token (read via
* underlying streaming input source) into other value of type accessor
* supports. May return `null`, or value compatible with type binding.
*
* NOTE: if {@link #getNullAccessPattern()} returns `ALWAYS_NULL` or
* `CONSTANT`, this method WILL NOT use provided `ctxt` and it may thus
* be passed as `null`.
*/
public Object getNullValue(DeserializationContext ctxt) throws JsonMappingException;
/**
* Accessor that may be used to determine if and when provider must be called to
* access null replacement value.
*/
public AccessPattern getNullAccessPattern();
/**
* Method called to determine placeholder value to be used for cases
* where no value was obtained from input but we must pass a value
* nonetheless: the common case is that of Creator methods requiring
* passing a value for every parameter.
* Usually this is same as {@link #getNullValue} (which in turn
* is usually simply Java {@code null}), but it can be overridden
* for specific types: most notable scalar types must use "default"
* values.
*
* This method needs to be called every time a determination is made.
*
* Default implementation simply calls and returns {@link #getNullValue}.
*
* @since 2.13
*/
default Object getAbsentValue(DeserializationContext ctxt) throws JsonMappingException {
return getNullValue(ctxt);
}
}