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Add empty class support for deduction #3137

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531c9a7
Add empty class support for deduction
xJoeWoo Apr 30, 2021
cb64bcf
Remove lambda usage
xJoeWoo May 1, 2021
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78 changes: 51 additions & 27 deletions src/main/java/com/fasterxml/jackson/databind/jsontype/impl/AsDeductionTypeDeserializer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,8 @@ public class AsDeductionTypeDeserializer extends AsPropertyTypeDeserializer
// Bitmap of available fields in each subtype (including its parents)
private final Map<BitSet, String> subtypeFingerprints;

private static final String EMPTY_CLASS_MARKER = "";
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Needs Javadoc to explain use.

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One comment: empty String is actually valid property name in JSON -- is this problematic?


public AsDeductionTypeDeserializer(JavaType bt, TypeIdResolver idRes, JavaType defaultImpl,
DeserializationConfig config, Collection<NamedType> subtypes)
{
Expand Down Expand Up @@ -65,15 +67,14 @@ protected Map<BitSet, String> buildFingerprints(DeserializationConfig config, Co
List<BeanPropertyDefinition> properties = config.introspect(subtyped).findProperties();

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++);
if (properties.size() > 0) {
for (BeanPropertyDefinition property : properties) {
String name = property.getName();
if (ignoreCase) name = name.toLowerCase();
nextField = setField(fingerprint, name, nextField);
}
fingerprint.set(bitIndex);
} else {
nextField = setField(fingerprint, EMPTY_CLASS_MARKER, nextField);
}

String existingFingerprint = fingerprints.put(fingerprint, subtype.getType().getName());
Expand All @@ -88,6 +89,16 @@ protected Map<BitSet, String> buildFingerprints(DeserializationConfig config, Co
return fingerprints;
}

private int setField(BitSet fingerprint, String name, int nextField) {
Integer bitIndex = fieldBitIndex.get(name);
if (bitIndex == null) {
bitIndex = nextField;
fieldBitIndex.put(name, nextField++);
}
fingerprint.set(bitIndex);
return nextField;
}

@Override
public Object deserializeTypedFromObject(JsonParser p, DeserializationContext ctxt) throws IOException {

Expand All @@ -110,35 +121,48 @@ public Object deserializeTypedFromObject(JsonParser p, DeserializationContext ct
// Record processed tokens as we must rewind once after deducing the deserializer to use
@SuppressWarnings("resource")
TokenBuffer tb = new TokenBuffer(p, ctxt);
boolean ignoreCase = ctxt.isEnabled(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES);

for (; t == JsonToken.FIELD_NAME; t = p.nextToken()) {
String name = p.currentName();
if (ignoreCase) name = name.toLowerCase();

tb.copyCurrentStructure(p);

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)));
Object result = null;

// Next character of empty class is '}'
if (t == JsonToken.END_OBJECT) {
result = deserializeCandidates(EMPTY_CLASS_MARKER, candidates, p, ctxt, tb);
} else {
boolean ignoreCase = ctxt.isEnabled(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES);
for (; t == JsonToken.FIELD_NAME; t = p.nextToken()) {
String name = p.currentName();
if (ignoreCase) name = name.toLowerCase();
if ((result = deserializeCandidates(name, candidates, p, ctxt, tb)) != null) {
break;
}
}
}
if (result != null) {
return result;
}

// We have zero or multiple candidates, deduction has failed
String msgToReportIfDefaultImplFailsToo = String.format("Cannot deduce unique subtype of %s (%d candidates match)", ClassUtil.getTypeDescription(_baseType), candidates.size());
return _deserializeTypedUsingDefaultImpl(p, ctxt, tb, msgToReportIfDefaultImplFailsToo);
}

// 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();
private Object deserializeCandidates(String name, List<BitSet> candidates, JsonParser p, DeserializationContext ctxt, TokenBuffer tb) throws IOException {
Integer bit = fieldBitIndex.get(name);
// No empty class is registered
if (bit == null && name.equals(EMPTY_CLASS_MARKER)) {
return null;
}
if (bit != null) {
// field is known by at least one subtype
for (Iterator<BitSet> iter = candidates.iterator(); iter.hasNext(); ) {
if (!iter.next().get(bit)) {
iter.remove();
}
}
}
tb.copyCurrentStructure(p);
if (candidates.size() != 1) {
return null;
}
return _deserializeTypedForId(p, ctxt, tb, subtypeFingerprints.get(candidates.get(0)));
}
}
147 changes: 105 additions & 42 deletions src/test/java/com/fasterxml/jackson/databind/jsontype/TestPolymorphicDeduction.java
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Open in desktop
Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
package com.fasterxml.jackson.databind.jsontype;

import java.util.Iterator;
import java.util.List;
import java.util.Map;

Expand All @@ -22,11 +23,12 @@
// for [databind#43], deduction-based polymorphism
public class TestPolymorphicDeduction extends BaseMapTest {

@JsonTypeInfo(use = DEDUCTION)
@JsonSubTypes( {@Type(LiveCat.class), @Type(DeadCat.class)})
public static class Cat {
public String name;
}
@JsonTypeInfo(use = DEDUCTION)
@JsonSubTypes({@Type(LiveCat.class), @Type(DeadCat.class)})
public static class Cat {
public String name;
public Flea flea;
}

static class DeadCat extends Cat {
public String causeOfDeath;
Expand All @@ -36,6 +38,18 @@ static class LiveCat extends Cat {
public boolean angry;
}

@JsonTypeInfo(use = DEDUCTION)
@JsonSubTypes({@Type(NoFlea.class), @Type(HasFlea.class)})
interface Flea {
}

static class NoFlea implements Flea {
}

static class HasFlea implements Flea {
public int count;
}

static class Box {
public Cat cat;
}
Expand All @@ -46,40 +60,60 @@ static class Box {
/**********************************************************
*/

private static final String deadCatJson = aposToQuotes("{'name':'Felix','causeOfDeath':'entropy'}");
private static final String liveCatJson = aposToQuotes("{'name':'Felix','angry':true}");
private static final String luckyCatJson = aposToQuotes("{'name':'Felix','angry':true,'lives':8}");
private static final String ambiguousCatJson = aposToQuotes("{'name':'Felix','age':2}");
private static final String box1Json = aposToQuotes("{'cat':" + liveCatJson + "}");
private static final String box2Json = aposToQuotes("{'cat':" + deadCatJson + "}");
private static final String arrayOfCatsJson = aposToQuotes("[" + liveCatJson + "," + deadCatJson + "]");
private static final String mapOfCatsJson = aposToQuotes("{'live':" + liveCatJson + "}");
private static final String deadCatJson = aposToQuotes("{'name':'Felix','flea':null,'causeOfDeath':'entropy'}");
private static final String liveCatJson = aposToQuotes("{'name':'Felix','flea':null,'angry':true}");
private static final String liveNoFleaCatJson = aposToQuotes("{'name':'Felix','flea':{},'angry':true}");
private static final String liveHasFleaCatJson = aposToQuotes("{'name':'Felix','flea':{'count':42},'angry':true}");
private static final String luckyCatJson = aposToQuotes("{'name':'Felix','flea':null,'angry':true,'lives':8}");
private static final String ambiguousCatJson = aposToQuotes("{'name':'Felix','age':2}");
private static final String box1Json = aposToQuotes("{'cat':" + liveCatJson + "}");
private static final String box2Json = aposToQuotes("{'cat':" + deadCatJson + "}");
private static final String arrayOfCatsJson = aposToQuotes("[" + liveCatJson + "," + deadCatJson + "," + liveNoFleaCatJson + "]");
private static final String mapOfCatsJson = aposToQuotes("{'live':" + liveCatJson + ",'noFlea':" + liveNoFleaCatJson + "}");

/*
/**********************************************************
/* Test methods
/**********************************************************
*/

public void testSimpleInference() throws Exception {
Cat cat = sharedMapper().readValue(liveCatJson, Cat.class);
assertTrue(cat instanceof LiveCat);
assertSame(cat.getClass(), LiveCat.class);
assertEquals("Felix", cat.name);
assertTrue(((LiveCat)cat).angry);
public void testSimpleInference() throws Exception {

cat = sharedMapper().readValue(deadCatJson, Cat.class);
assertTrue(cat instanceof DeadCat);
assertSame(cat.getClass(), DeadCat.class);
assertEquals("Felix", cat.name);
assertEquals("entropy", ((DeadCat)cat).causeOfDeath);
}
Cat cat = sharedMapper().readValue(liveCatJson, Cat.class);
assertTrue(cat instanceof LiveCat);
assertSame(cat.getClass(), LiveCat.class);
assertEquals("Felix", cat.name);
assertTrue(((LiveCat) cat).angry);

cat = sharedMapper().readValue(deadCatJson, Cat.class);
assertTrue(cat instanceof DeadCat);
assertSame(cat.getClass(), DeadCat.class);
assertEquals("Felix", cat.name);
assertEquals("entropy", ((DeadCat) cat).causeOfDeath);

cat = sharedMapper().readValue(liveNoFleaCatJson, Cat.class);
assertTrue(cat instanceof LiveCat);
assertTrue(cat.flea instanceof NoFlea);
assertSame(cat.getClass(), LiveCat.class);
assertSame(cat.flea.getClass(), NoFlea.class);
assertEquals("Felix", cat.name);
assertTrue(((LiveCat) cat).angry);

cat = sharedMapper().readValue(liveHasFleaCatJson, Cat.class);
assertTrue(cat instanceof LiveCat);
assertTrue(cat.flea instanceof HasFlea);
assertSame(cat.getClass(), LiveCat.class);
assertSame(cat.flea.getClass(), HasFlea.class);
assertEquals("Felix", cat.name);
assertEquals(42, ((HasFlea) cat.flea).count);
assertTrue(((LiveCat) cat).angry);
}

public void testCaseInsensitiveInference() throws Exception {
Cat cat = JsonMapper.builder() // Don't use shared mapper!
.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true)
.build()
.readValue(deadCatJson.toUpperCase(), Cat.class);
.readValue(deadCatJson.toUpperCase().replace("NULL", "null"), Cat.class);
assertTrue(cat instanceof DeadCat);
assertSame(cat.getClass(), DeadCat.class);
assertEquals("FELIX", cat.name);
Expand Down Expand Up @@ -120,12 +154,18 @@ public void testListInference() throws Exception {
assertTrue(boxes.get(1) instanceof DeadCat);
}

public void testMapInference() throws Exception {
JavaType mapOfCats = TypeFactory.defaultInstance().constructParametricType(Map.class, String.class, Cat.class);
Map<String, Cat> map = sharedMapper().readValue(mapOfCatsJson, mapOfCats);
assertEquals(1, map.size());
assertTrue(map.entrySet().iterator().next().getValue() instanceof LiveCat);
}
public void testMapInference() throws Exception {
JavaType mapOfCats = TypeFactory.defaultInstance().constructParametricType(Map.class, String.class, Cat.class);
Map<String, Cat> map = sharedMapper().readValue(mapOfCatsJson, mapOfCats);
assertEquals(2, map.size());

Iterator<Map.Entry<String, Cat>> iterator = map.entrySet().iterator();
assertTrue(iterator.next().getValue() instanceof LiveCat);

Cat noFlea = iterator.next().getValue();
assertTrue(noFlea instanceof LiveCat);
assertTrue(noFlea.flea instanceof NoFlea);
}

public void testArrayInference() throws Exception {
Cat[] boxes = sharedMapper().readValue(arrayOfCatsJson, Cat[].class);
Expand Down Expand Up @@ -200,16 +240,39 @@ public void testDefaultImpl() throws Exception {
assertEquals("Felix", cat.name);
}

public void testSimpleSerialization() throws Exception {
// Given:
JavaType listOfCats = TypeFactory.defaultInstance().constructParametricType(List.class, Cat.class);
List<Cat> list = sharedMapper().readValue(arrayOfCatsJson, listOfCats);
Cat cat = list.get(0);
// When:
String json = sharedMapper().writeValueAsString(cat);
// Then:
assertEquals(liveCatJson, json);
}

@JsonTypeInfo(use = DEDUCTION)
@JsonSubTypes({@Type(HasFlea.class)})
abstract static class FleaMixin {

}
public void testNoEmptyClassRegistered() throws Exception {
JsonMapper mapper = JsonMapper.builder() // Don't use shared mapper!
.addMixIn(Flea.class, FleaMixin.class)
.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
.build();
try {
mapper.readValue(liveNoFleaCatJson, Cat.class);
} catch (InvalidTypeIdException e) {
verifyException(e, "Cannot deduce unique subtype");
}
}

public void testSimpleSerialization() throws Exception {
// Given:
JavaType listOfCats = TypeFactory.defaultInstance().constructParametricType(List.class, Cat.class);
List<Cat> list = sharedMapper().readValue(arrayOfCatsJson, listOfCats);
Cat liveCat = list.get(0);
Cat liveNoFleaCat = list.get(2);
// When:
String json = sharedMapper().writeValueAsString(liveCat);
String noFleaJson = sharedMapper().writeValueAsString(liveNoFleaCat);
// Then:
assertEquals(liveCatJson, json);
assertEquals(liveNoFleaCatJson, noFleaJson);
}



public void testListSerialization() throws Exception {
// Given:
Expand Down