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Polymorphic subtype deduction from available fields (#2813)
Polymorphic deduction implemented
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src/main/java/com/fasterxml/jackson/databind/jsontype/impl/AsDeductionTypeDeserializer.java
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| @@ -0,0 +1,152 @@ | ||
| package com.fasterxml.jackson.databind.jsontype.impl; | ||
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| import java.io.IOException; | ||
| import java.util.BitSet; | ||
| import java.util.Collection; | ||
| import java.util.HashMap; | ||
| import java.util.Iterator; | ||
| import java.util.LinkedList; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
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| import com.fasterxml.jackson.annotation.JsonTypeInfo; | ||
| import com.fasterxml.jackson.core.JsonParser; | ||
| import com.fasterxml.jackson.core.JsonToken; | ||
| import com.fasterxml.jackson.databind.BeanProperty; | ||
| import com.fasterxml.jackson.databind.DeserializationConfig; | ||
| import com.fasterxml.jackson.databind.DeserializationContext; | ||
| import com.fasterxml.jackson.databind.JavaType; | ||
| import com.fasterxml.jackson.databind.MapperFeature; | ||
| import com.fasterxml.jackson.databind.exc.InvalidTypeIdException; | ||
| import com.fasterxml.jackson.databind.introspect.BeanPropertyDefinition; | ||
| import com.fasterxml.jackson.databind.jsontype.NamedType; | ||
| import com.fasterxml.jackson.databind.jsontype.TypeDeserializer; | ||
| import com.fasterxml.jackson.databind.jsontype.TypeIdResolver; | ||
| import com.fasterxml.jackson.databind.util.TokenBuffer; | ||
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| /** | ||
| * A {@link TypeDeserializer} capable of deducing polymorphic types based on the fields available. Deduction | ||
| * is limited to the <i>names</i> of child fields (not their values or, consequently, any nested descendants). | ||
| * Exceptions will be thrown if not enough unique information is present to select a single subtype. | ||
| */ | ||
| public class AsDeductionTypeDeserializer extends AsPropertyTypeDeserializer { | ||
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| // Fieldname -> bitmap-index of every field discovered, across all subtypes | ||
| private final Map<String, Integer> fieldBitIndex; | ||
| // Bitmap of available fields in each subtype (including its parents) | ||
| private final Map<BitSet, String> subtypeFingerprints; | ||
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| public AsDeductionTypeDeserializer(JavaType bt, TypeIdResolver idRes, JavaType defaultImpl, DeserializationConfig config, Collection<NamedType> subtypes) { | ||
| super(bt, idRes, null, false, defaultImpl); | ||
| fieldBitIndex = new HashMap<>(); | ||
| subtypeFingerprints = buildFingerprints(config, subtypes); | ||
| } | ||
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| public AsDeductionTypeDeserializer(AsDeductionTypeDeserializer src, BeanProperty property) { | ||
| super(src, property); | ||
| fieldBitIndex = src.fieldBitIndex; | ||
| subtypeFingerprints = src.subtypeFingerprints; | ||
| } | ||
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| @Override | ||
| public JsonTypeInfo.As getTypeInclusion() { | ||
| return null; | ||
| } | ||
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| @Override | ||
| public TypeDeserializer forProperty(BeanProperty prop) { | ||
| return (prop == _property) ? this : new AsDeductionTypeDeserializer(this, prop); | ||
| } | ||
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| protected Map<BitSet, String> buildFingerprints(DeserializationConfig config, Collection<NamedType> subtypes) { | ||
| boolean ignoreCase = config.isEnabled(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES); | ||
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| int nextField = 0; | ||
| Map<BitSet, String> fingerprints = new HashMap<>(); | ||
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| for (NamedType subtype : subtypes) { | ||
| JavaType subtyped = config.getTypeFactory().constructType(subtype.getType()); | ||
| List<BeanPropertyDefinition> properties = config.introspect(subtyped).findProperties(); | ||
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| BitSet fingerprint = new BitSet(nextField + properties.size()); | ||
| for (BeanPropertyDefinition property : properties) { | ||
| String name = property.getName(); | ||
| if (ignoreCase) name = name.toLowerCase(); | ||
| Integer bitIndex = fieldBitIndex.get(name); | ||
| if (bitIndex == null) { | ||
| bitIndex = nextField; | ||
| fieldBitIndex.put(name, nextField++); | ||
| } | ||
| fingerprint.set(bitIndex); | ||
| } | ||
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| String existingFingerprint = fingerprints.put(fingerprint, subtype.getType().getName()); | ||
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| // Validate uniqueness | ||
| if (existingFingerprint != null) { | ||
| throw new IllegalStateException( | ||
| String.format("Subtypes %s and %s have the same signature and cannot be uniquely deduced.", existingFingerprint, subtype.getType().getName()) | ||
| ); | ||
| } | ||
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| } | ||
| return fingerprints; | ||
| } | ||
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| @Override | ||
| public Object deserializeTypedFromObject(JsonParser p, DeserializationContext ctxt) throws IOException { | ||
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| JsonToken t = p.currentToken(); | ||
| if (t == JsonToken.START_OBJECT) { | ||
| t = p.nextToken(); | ||
| } else { | ||
| /* This is most likely due to the fact that not all Java types are | ||
| * serialized as JSON Objects; so if "as-property" inclusion is requested, | ||
| * serialization of things like Lists must be instead handled as if | ||
| * "as-wrapper-array" was requested. | ||
| * But this can also be due to some custom handling: so, if "defaultImpl" | ||
| * is defined, it will be asked to handle this case. | ||
| */ | ||
| return _deserializeTypedUsingDefaultImpl(p, ctxt, null); | ||
| } | ||
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| List<BitSet> candidates = new LinkedList<>(subtypeFingerprints.keySet()); | ||
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| // Record processed tokens as we must rewind once after deducing the deserializer to use | ||
| TokenBuffer tb = new TokenBuffer(p, ctxt); | ||
| boolean ignoreCase = ctxt.isEnabled(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES); | ||
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| for (; t == JsonToken.FIELD_NAME; t = p.nextToken()) { | ||
| String name = p.getCurrentName(); | ||
| if (ignoreCase) name = name.toLowerCase(); | ||
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| tb.copyCurrentStructure(p); | ||
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| Integer bit = fieldBitIndex.get(name); | ||
| if (bit != null) { | ||
| // field is known by at least one subtype | ||
| prune(candidates, bit); | ||
| if (candidates.size() == 1) { | ||
| return _deserializeTypedForId(p, ctxt, tb, subtypeFingerprints.get(candidates.get(0))); | ||
| } | ||
| } | ||
| } | ||
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| throw new InvalidTypeIdException( | ||
| p, | ||
| String.format("Cannot deduce unique subtype of %s (%d candidates match)", _baseType.toString(), candidates.size()), | ||
| _baseType | ||
| , "DEDUCED" | ||
| ); | ||
| } | ||
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| // Keep only fingerprints containing this field | ||
| private static void prune(List<BitSet> candidates, int bit) { | ||
| for (Iterator<BitSet> iter = candidates.iterator(); iter.hasNext(); ) { | ||
| if (!iter.next().get(bit)) { | ||
| iter.remove(); | ||
| } | ||
| } | ||
| } | ||
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| } |
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