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Builder deserailizer: in-compatible type exception when return type is super type #761

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agavrilov76 opened this issue Apr 19, 2015 · 0 comments
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Builder deserailizer: in-compatible type exception when return type is super type #761

agavrilov76 opened this issue Apr 19, 2015 · 0 comments
Milestone
2.5.3

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@agavrilov76
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Based on the following stack overflow question: http://stackoverflow.com/questions/29724859/jackson-deserialization-with-builder-pattern-build-method-has-bad-return-type

The builder deserailizer throws the "Build method has bad return type, not compatible with POJO type” exception if the build method return type is a super type of the POJO type. Here is a complete example:

public class JacksonBuilder {
    public interface FooInterface {
    }

    public static class Foo implements FooInterface {
        public static final class Builder {
            @JsonProperty
            public Builder valueA(String value) { return this; }
            @JsonProperty
            public Builder valueB(String value) { return this; }
            public FooInterface build() { return new Foo() {}; }
        }
    }

    @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
    @JsonSubTypes({
            @JsonSubTypes.Type(value = Foo.class, name = "foo")})
    public static abstract class FooInterfaceMixin {}

    @JsonTypeName("foo")
    @JsonDeserialize(builder=Foo.Builder.class)
    public static abstract class FooMixin {}

    public static void main(String[] args) throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        mapper.addMixIn(FooInterface.class, FooInterfaceMixin.class);
        mapper.addMixIn(Foo.class, FooMixin.class);

        final String jsonString = "{\"type\":\"foo\", \"valueA\":\"a\", \"valueB\":\"b\"}";
        FooInterface foo = mapper.readValue(jsonString, FooInterface.class);
    }
}

Output:

Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: Build method 'stackoverflow.JacksonBuilder$Foo$Builder#build(0 params) has bad return type (stackoverflow.JacksonBuilder$FooInterface), not compatible with POJO type (stackoverflow.JacksonBuilder$Foo)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:270)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCacheValueDeserializer(DeserializerCache.java:245)
    at com.fasterxml.jackson.databind.deser.DeserializerCache.findValueDeserializer(DeserializerCache.java:143)
    at com.fasterxml.jackson.databind.DeserializationContext.findContextualValueDeserializer(DeserializationContext.java:406)
    at com.fasterxml.jackson.databind.jsontype.impl.TypeDeserializerBase._findDeserializer(TypeDeserializerBase.java:176)
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer._deserializeTypedForId(AsPropertyTypeDeserializer.java:110)
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer.deserializeTypedFromObject(AsPropertyTypeDeserializer.java:95)
    at com.fasterxml.jackson.databind.deser.AbstractDeserializer.deserializeWithType(AbstractDeserializer.java:131)
    at com.fasterxml.jackson.databind.deser.impl.TypeWrappedDeserializer.deserialize(TypeWrappedDeserializer.java:42)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3562)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2578)
    at stackoverflow.JacksonBuilder.main(JacksonBuilder.java:48)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)
Caused by: java.lang.IllegalArgumentException: Build method 'stackoverflow.JacksonBuilder$Foo$Builder#build(0 params) has bad return type (stackoverflow.JacksonBuilder$FooInterface), not compatible with POJO type (stackoverflow.JacksonBuilder$Foo)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBuilder.buildBuilderBased(BeanDeserializerBuilder.java:378)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.buildBuilderBasedDeserializer(BeanDeserializerFactory.java:297)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.createBuilderBasedDeserializer(BeanDeserializerFactory.java:155)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer(DeserializerCache.java:351)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:265)
    ... 16 more

It seems that the condition at

jackson-databind/src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializerBuilder.java

Line 377 in f757415

if (!valueType.getRawClass().isAssignableFrom(rawBuildType)) {
should be reversed to:

!rawBuildType.isAssignableFrom(valueType.getRawClass())

to allow rawBuildType be a super type of the valueType.
agavrilov76 added a commit to agavrilov76/jackson-databind that referenced this issue Apr 20, 2015
@agavrilov76
In-compatible type exception when build method return super type
e1159f8 
Issue FasterXML#761
@agavrilov76 agavrilov76 mentioned this issue Apr 20, 2015
Merged
cowtowncoder added a commit that referenced this issue Apr 21, 2015
@cowtowncoder
Minor tweak for #761 fix
2c9fa0e
@cowtowncoder cowtowncoder added this to the 2.5.0 milestone Apr 21, 2015
cowtowncoder added a commit that referenced this issue Apr 21, 2015
@cowtowncoder
Backport #761 fix in 2.5(.3)
3470803
@cowtowncoder cowtowncoder modified the milestones: 2.5.0, 2.5.3 Apr 22, 2015
@ctas582 ctas582 mentioned this issue Feb 22, 2017
Closed
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