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Fix Enum deserialization with JsonFormat.Shape.OBJECT using both DELEGATING and PROPERTIES creator modes #3851

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merged 6 commits into from
Apr 1, 2023
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Fix Enum deserialization with JsonFormat.Shape.OBJECT using both DELEGATING and PROPERTIES creator modes #3851

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15e34c3
Fix
JooHyukKim Mar 29, 2023
5b01c7c
add comment
JooHyukKim Mar 29, 2023
c5add48
Reduce cognitive complexity
JooHyukKim Mar 29, 2023
fb7c843
Synchronize JsonParser
JooHyukKim Mar 31, 2023
8e38787
Remove transient keyword
JooHyukKim Mar 31, 2023
3bc0de2
construct _propCreatorRef lazily
JooHyukKim Mar 31, 2023
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28 changes: 17 additions & 11 deletions src/main/java/com/fasterxml/jackson/databind/deser/std/FactoryBasedEnumDeserializer.java
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package com.fasterxml.jackson.databind.deser.std;

import java.io.IOException;
import java.util.concurrent.atomic.AtomicReference;

import com.fasterxml.jackson.core.JacksonException;
import com.fasterxml.jackson.core.JsonParser;
Expand Down Expand Up @@ -40,10 +41,12 @@ class FactoryBasedEnumDeserializer

/**
* Lazily instantiated property-based creator.
* Introduced in 2.8 and wrapped with {@link AtomicReference} in 2.15
*
* @since 2.15
*
* @since 2.8
*/
private transient PropertyBasedCreator _propCreator;
private AtomicReference<PropertyBasedCreator> _propCreatorRef = new AtomicReference<>(null);

public FactoryBasedEnumDeserializer(Class<?> cls, AnnotatedMethod f, JavaType paramType,
ValueInstantiator valueInstantiator, SettableBeanProperty[] creatorProps)
Expand Down Expand Up @@ -132,18 +135,21 @@ public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOEx
// 30-Mar-2020, tatu: For properties-based one, MUST get JSON Object (before
// 2.11, was just assuming match)
if (_creatorProps != null) {
if (!p.isExpectedStartObjectToken()) {
if (p.isExpectedStartObjectToken()) {
_propCreatorRef.compareAndSet(null,
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But wouldn't this create (and try set) a new instance every time? :-D
(instead of trying to get() and only create-and-set if null)

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@JooHyukKim JooHyukKim Mar 31, 2023 •
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this create (and try set) a new instance every time? :-D
hmm, Not really my intention 😅

Could you check again? Take below as an example. Invoking get() and set separately wouldn't be atomic anymore 🤔.

    public void testAtomicRef() {
        Bean expected = new Bean(0);

        AtomicReference<Bean> reference = new AtomicReference<>(null);
        reference.compareAndSet(null, expected);
        reference.compareAndSet(null, new Bean(1));
        reference.compareAndSet(null, new Bean(2));

       // Passes
        assertEquals(0,reference.get().a);
    }

According to compareAndSet documentation,

Atomically sets the value to newValue if the current value == expectedValue, with memory effects

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Or we can do good-ol' double-checked locking like ones done in EnumDeserializer below.

jackson-databind/src/main/java/com/fasterxml/jackson/databind/deser/std/EnumDeserializer.java

Lines 432 to 445 in 68ba588

protected CompactStringObjectMap _getToStringLookup(DeserializationContext ctxt) {
CompactStringObjectMap lookup = _lookupByToString;
if (lookup == null) {
synchronized (this) {
lookup = _lookupByToString;
if (lookup == null) {
lookup = EnumResolver.constructUsingToString(ctxt.getConfig(), _enumClass())
.constructLookup();
_lookupByToString = lookup;
}
}
}
return lookup;
}

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No, my problem is that instead of only creating it if needed, it creates new instance every time and sets -- and never uses value. You are correct in that get + set is not atomic, but I am not worried about atomicity here; if instance gets created 2 or 3 times that's fine. They are all identical. Goal is just to avoid always creating instance eagerly.

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And no need to do double-locking with synchronized: just do get() from reference; if (and only if) null returned, construct instance, set() (or compareAndSet() against null). Use the props gotten or created.

Or leave as-is and I can add that as well, not a big deal.

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@JooHyukKim JooHyukKim Mar 31, 2023 •
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No, my problem is that instead of only creating it if needed, it creates new instance every time and sets -- and never uses value.

Oh, I think I understand now! Thank you for the explanation! 🙏🏼🙏🏼.

The code creates newly instance in compareAndSet(null, PropertyBasedCreator.construct()). The new intance will be ignored, but created "everytime" when _propCreator is not null anymore.

PropertyBasedCreator.construct(ctxt, _valueInstantiator, _creatorProps,
ctxt.isEnabled(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES)));

p.nextToken();
return deserializeEnumUsingPropertyBased(p, ctxt, _propCreatorRef.get());
}
// If value cannot possibly be delegating-creator,
if (!_valueInstantiator.canCreateFromString()) {
final JavaType targetType = getValueType(ctxt);
ctxt.reportInputMismatch(targetType,
"Input mismatch reading Enum %s: properties-based `@JsonCreator` (%s) expects JSON Object (JsonToken.START_OBJECT), got JsonToken.%s",
ClassUtil.getTypeDescription(targetType), _factory, p.currentToken());
}
if (_propCreator == null) {
_propCreator = PropertyBasedCreator.construct(ctxt, _valueInstantiator, _creatorProps,
ctxt.isEnabled(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES));
"Input mismatch reading Enum %s: properties-based `@JsonCreator` (%s) expects JSON Object (JsonToken.START_OBJECT), got JsonToken.%s",
ClassUtil.getTypeDescription(targetType), _factory, p.currentToken());
}
p.nextToken();
return deserializeEnumUsingPropertyBased(p, ctxt, _propCreator);
}
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@JooHyukKim JooHyukKim Mar 29, 2023 •
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Summary here,

  1. Simply flipped the p.isExpectedStartObjectToken() conditional (line 135)
  2. Allow pass-through of case for possible "delegating-creator" (line 144) -- in other words, "fail if f value cannot possibly be delegating-creator"


// 12-Oct-2021, tatu: We really should only get here if and when String
Expand Down
32 changes: 30 additions & 2 deletions ...n/failing/JsonCreatorModeForEnum3566.java → .../creators/JsonCreatorModeForEnum3566.java
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
package com.fasterxml.jackson.failing;
package com.fasterxml.jackson.databind.deser.creators;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonFormat;
Expand Down Expand Up @@ -98,7 +98,8 @@ public static EnumB fromString(String type) {
@JsonFormat(shape = JsonFormat.Shape.OBJECT)
enum EnumC {
A("AType"),
B("BType");
B("BType"),
C("CType");

private final String type;

Expand All @@ -121,6 +122,16 @@ public static EnumC create(@JsonProperty("type") String type) {
}
}

static class DelegatingCreatorEnumWrapper {
public EnumA enumA;
public EnumB enumB;
}

static class PropertiesCreatorEnumWrapper {
public EnumA enumA;
public EnumC enumC;
}

/*
/**********************************************************
/* Tests
Expand Down Expand Up @@ -179,4 +190,21 @@ public void testPojoCreatorModeDelegating() throws Exception {

assertEquals("properties", pojo1.name);
}

public void testDelegatingCreatorEnumWrapper() throws Exception {
DelegatingCreatorEnumWrapper wrapper = newJsonMapper()
.readValue(a2q("{'enumA':'AType', 'enumB': 'BType'}"), DelegatingCreatorEnumWrapper.class);

assertEquals(EnumA.A, wrapper.enumA);
assertEquals(EnumB.B, wrapper.enumB);
}

public void testPropertiesCreatorEnumWrapper() throws Exception {
PropertiesCreatorEnumWrapper wrapper = newJsonMapper()
.readValue(a2q("{'enumA':{'type':'AType'}, 'enumC': {'type':'CType'}}"), PropertiesCreatorEnumWrapper.class);

assertEquals(EnumA.A, wrapper.enumA);
assertEquals(EnumC.C, wrapper.enumC);
}

}