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package com.fasterxml.jackson.jr.ob.api;
import com.fasterxml.jackson.jr.ob.impl.JSONReader;
import com.fasterxml.jackson.jr.ob.impl.JSONWriter;
import com.fasterxml.jackson.jr.ob.impl.POJODefinition;
/**
* API to implement to apply modifications to {@link ValueReader}s and
* {@link ValueWriter}s of all kinds (default scalar ones, custom ones,
* POJO ones).
*
* @since 2.11
*/
public abstract class ReaderWriterModifier
{
// // Basic POJO introspection
public POJODefinition pojoDefinitionForDeserialization(JSONReader readContext,
Class pojoType)
{
// use default
return null;
}
public POJODefinition pojoDefinitionForSerialization(JSONWriter writeContext,
Class pojoType) {
// use default
return null;
}
// // Reader handling
/**
* Method called after {@link ValueReader} to use has been constructed, but
* before it is to be used for the first time. Method may either return that
* reader as-is, or construct a different {@link ValueReader} and return that
* to be used.
*
* This method is often used to create a new {@link ValueReader} that needs to
* delegate to the original reader for some uses, but not all.
*
* @param readContext Context that may be used to access configuration
* @param type Type of values to read
* @param defaultReader {@link ValueReader} that is to be used
*
* @return either {@code defaultReader} as-is, or an alternate {@link ValueReader} to use.
*/
public ValueReader modifyValueReader(JSONReader readContext,
Class type, ValueReader defaultReader) {
return defaultReader;
}
// // Writer handling
/**
* Method called after {@link ValueWriter} to use has been constructed, but
* before it is to be used for the first time. Method may either return that
* writer as-is, or construct a different {@link ValueWriter} and return that
* to be used.
*
* Note that this method is NOT called for non-POJO JDK "standard" values that
* jackson-jr supports (such as {@link java.lang.Number}s, {@link java.lang.String}
* and {@link java.net.URL}); for these types, {@link #overrideStandardValueWriter}
* is called instead.
*
* This method is often used to create a new {@link ValueReader} that needs to
* delegate to the original reader for some uses, but not all.
*
* @param writeContext Context that may be used to access configuration
* @param type Type of values to write
* @param defaultWriter {@link ValueReader} that is to be used
*
* @return either {@code defaultReader} as-is, or an alternate {@link ValueWriter} to use;
* must not return {@code null}.
*/
public ValueWriter modifyValueWriter(JSONWriter writeContext,
Class type, ValueWriter defaultWriter) {
return defaultWriter;
}
/**
* Method called instead of {@link #modifyValueWriter} for set of non-POJO
* "standard" JDK types that do not have matching {@link ValueWriter} and are
* normally directly serialized by {@link JSONWriter} itself.
* Handler may either return {@code null} to indicate "no override" or return
* custom {@link ValueWriter} to use.
*
* @param writeContext Context that may be used to access configuration
* @param type Type of values to write
* @param stdTypeId Internal identifier of standard type (not usually useful,
* but could potentially be used for delegating)
*
* @return {@code null} if no override should occur, or {@link ValueWriter}
* to use.
*/
public ValueWriter overrideStandardValueWriter(JSONWriter writeContext,
Class type, int stdTypeId) {
return null;
}
/**
* Implementation that allows chaining of two modifiers, one (first) with higher precedence
* than the other (second).
*/
public static class Pair extends ReaderWriterModifier
{
protected final ReaderWriterModifier _primary, _secondary;
protected Pair(ReaderWriterModifier p, ReaderWriterModifier s) {
_primary = p;
_secondary = s;
}
/**
* Factory method for "combining" given 2 modifiers so that if neither is {@code null},
* a {@link Pair} is constructed; otherwise if one is non-null, that provider is returned;
* or if both are {@code null}s, {@code null} is returned.
*
* @param primary Primary provider
* @param secondary Secondary provider
*
* @return Provider instance either constructed (2 non-null providers), or non-null provider
* given as-is, or, if both nulls, {@code null}.
*/
public static ReaderWriterModifier of(ReaderWriterModifier primary, ReaderWriterModifier secondary) {
if (primary == null) {
return secondary;
}
if (secondary == null) {
return primary;
}
return new Pair(primary, secondary);
}
@Override
public POJODefinition pojoDefinitionForDeserialization(JSONReader ctxt,
Class pojoType) {
POJODefinition def = _primary.pojoDefinitionForDeserialization(ctxt, pojoType);
return (def == null) ? _secondary.pojoDefinitionForDeserialization(ctxt, pojoType) : def;
}
@Override
public POJODefinition pojoDefinitionForSerialization(JSONWriter ctxt,
Class pojoType) {
POJODefinition def = _primary.pojoDefinitionForSerialization(ctxt, pojoType);
return (def == null) ? _secondary.pojoDefinitionForSerialization(ctxt, pojoType) : def;
}
@Override
public ValueReader modifyValueReader(JSONReader ctxt,
Class type, ValueReader defaultReader) {
defaultReader = _primary.modifyValueReader(ctxt, type, defaultReader);
return _secondary.modifyValueReader(ctxt, type, defaultReader);
}
@Override
public ValueWriter modifyValueWriter(JSONWriter ctxt,
Class type, ValueWriter defaultWriter) {
defaultWriter = _primary.modifyValueWriter(ctxt, type, defaultWriter);
return _secondary.modifyValueWriter(ctxt, type, defaultWriter);
}
@Override
public ValueWriter overrideStandardValueWriter(JSONWriter ctxt,
Class type, int stdTypeId) {
ValueWriter w = _primary.overrideStandardValueWriter(ctxt, type, stdTypeId);
return (w == null) ? _secondary.overrideStandardValueWriter(ctxt, type, stdTypeId) : w;
}
}
}