Cannot serialize classes that have generic signatures referencing each other

[tailg8nj]

Affects versions: 2.8.0
Worked with version: 2.7.5

java.lang.NullPointerException
    at com.fasterxml.jackson.databind.type.ResolvedRecursiveType.equals(ResolvedRecursiveType.java:103)
    at com.fasterxml.jackson.databind.type.TypeBindings$AsKey.equals(TypeBindings.java:458)
    at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:940)
    at com.fasterxml.jackson.databind.util.LRUMap.get(LRUMap.java:68)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromClass(TypeFactory.java:1211)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromParamType(TypeFactory.java:1384)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromAny(TypeFactory.java:1154)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromVariable(TypeFactory.java:1409)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromAny(TypeFactory.java:1164)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromParamType(TypeFactory.java:1380)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromAny(TypeFactory.java:1154)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromParamType(TypeFactory.java:1380)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromAny(TypeFactory.java:1154)
    at com.fasterxml.jackson.databind.type.TypeFactory._resolveSuperClass(TypeFactory.java:1285)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromClass(TypeFactory.java:1246)
    at com.fasterxml.jackson.databind.type.TypeFactory._fromAny(TypeFactory.java:1150)
    at com.fasterxml.jackson.databind.type.TypeFactory.constructType(TypeFactory.java:618)
    at com.fasterxml.jackson.databind.cfg.MapperConfig.constructType(MapperConfig.java:290)
    at com.fasterxml.jackson.databind.cfg.MapperConfig.introspectClassAnnotations(MapperConfig.java:320)
    at com.fasterxml.jackson.databind.ser.BasicSerializerFactory.createTypeSerializer(BasicSerializerFactory.java:264)
    at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.findPropertyTypeSerializer(BeanSerializerFactory.java:324)
    at com.fasterxml.jackson.databind.ser.BeanSerializerFactory._constructWriter(BeanSerializerFactory.java:817)
    at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.findBeanProperties(BeanSerializerFactory.java:611)
    at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.constructBeanSerializer(BeanSerializerFactory.java:390)
    at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.findBeanSerializer(BeanSerializerFactory.java:273)
    at com.fasterxml.jackson.databind.ser.BeanSerializerFactory._createSerializer2(BeanSerializerFactory.java:225)
    at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.createSerializer(BeanSerializerFactory.java:159)
    at com.fasterxml.jackson.databind.SerializerProvider._createUntypedSerializer(SerializerProvider.java:1272)
    at com.fasterxml.jackson.databind.SerializerProvider._createAndCacheUntypedSerializer(SerializerProvider.java:1222)
    at com.fasterxml.jackson.databind.SerializerProvider.findValueSerializer(SerializerProvider.java:499)
    at com.fasterxml.jackson.databind.SerializerProvider.findTypedValueSerializer(SerializerProvider.java:697)
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:270)
    at com.fasterxml.jackson.databind.ObjectMapper._configAndWriteValue(ObjectMapper.java:3672)
    at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:3048)
    at com.fasterxml.jackson.databind.CircularGenericsTest.testWrite(CircularGenericsTest.java:20)

package com.fasterxml.jackson.databind;

import org.junit.Test;

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.databind.ObjectMapper;

public class CircularGenericsTest {

    @Test
    public void testWrite() throws Exception {
        final Class<?>[] types = new Class[] { Bean.class, Nested.class };
        Bean bean = new Bean();
        bean.name = "NAME";
        bean.nested = new Nested<>();
        bean.nested.bean = bean;
        bean.nested.value = "VALUE";
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerSubtypes(types);
        System.out.println(mapper.writeValueAsString(bean));
    }


    public static abstract class AbstractBean<B extends AbstractBean<B, N>, N extends AbstractNested<B, N>> {
        public N nested;
    }

    public static abstract class AbstractNested<B extends AbstractBean<B, N>, N extends AbstractNested<B, N>> {
        @JsonIgnore
        public B bean;
    }

    public static class Nested<B extends AbstractBean<B, Nested<B>>> extends AbstractNested<B, Nested<B>> {
        public String value;
    }

    public static class Bean extends AbstractBean<Bean, Nested<Bean>> {
        public String name;
    }

}

[cowtowncoder]

Thank you for reporting this. I think it is very likely same as #1302 for which fix is in master, and will be resolved in 2.8.1. If you can try 2.8.1-SNASPHOT (either via Sonatype snapshots, or locally built) it should be easy to see if it works.

[tailg8nj]

Confirmed fixed in master, 2.8.1-SNAPSHOT. Thanks, didn't see 1302, it was already fixed!