src/test/java/com/fasterxml/jackson/databind/deser/merge/MapPolymorphicMerge2336Test.java

package com.fasterxml.jackson.databind.deser.merge;

import java.util.LinkedHashMap;
import java.util.Map;

import com.fasterxml.jackson.annotation.*;

import com.fasterxml.jackson.databind.*;

public class MapPolymorphicMerge2336Test extends BaseMapTest
{
    private final ObjectMapper MAPPER = sharedMapper();

    @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "discriminator")
    @JsonSubTypes({@JsonSubTypes.Type(value = SomeClassA.class, name = "FirstConcreteImpl")})
    @JsonInclude(JsonInclude.Include.NON_NULL)
    public static abstract class SomeBaseClass {
        private String name;

        @JsonCreator
        public SomeBaseClass(@JsonProperty("name") String name) {
            this.name = name;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }
    }

    @JsonTypeName("FirstConcreteImpl")
    public static class SomeClassA extends SomeBaseClass {
        private Integer a;
        private Integer b;

        @JsonCreator
        public SomeClassA(@JsonProperty("name") String name, @JsonProperty("a") Integer a, @JsonProperty("b") Integer b) {
            super(name);
            this.a = a;
            this.b = b;
        }

        public Integer getA() {
            return a;
        }

        public void setA(Integer a) {
            this.a = a;
        }

        public Integer getB() {
            return b;
        }

        public void setB(Integer b) {
            this.b = b;
        }
    }

    public static class SomeOtherClass {
        String someprop;

        @JsonCreator
        public SomeOtherClass(@JsonProperty("someprop") String someprop) {
            this.someprop = someprop;
        }

        @JsonMerge
        Map<String, SomeBaseClass> data = new LinkedHashMap<>();

        public void addValue(String key, SomeBaseClass value) {
            data.put(key, value);
        }

        public Map<String, SomeBaseClass> getData() {
            return data;
        }

        public void setData(
                Map<String, SomeBaseClass> data) {
            this.data = data;
        }
    }

    // [databind#2336]
    public void testPolymorphicMapMerge() throws Exception
    {
        // first let's just get some valid JSON
        SomeOtherClass baseValue = new SomeOtherClass("house");
        baseValue.addValue("SOMEKEY", new SomeClassA("fred", 1, null));

        // now create a reader specifically for merging
        ObjectReader reader = MAPPER.readerForUpdating(baseValue);

        
        SomeOtherClass toBeMerged = new SomeOtherClass("house");
        toBeMerged.addValue("SOMEKEY", new SomeClassA("jim", null, 2));
        String jsonForMerging = MAPPER.writeValueAsString(toBeMerged);

        assertEquals("fred", baseValue.data.get("SOMEKEY").getName());
        
        // now try to do the merge and it blows up
        SomeOtherClass mergedResult = reader.readValue(jsonForMerging);

        // First of all, should update main POJO (since it's "value to update")
        assertSame(baseValue, mergedResult);
        // as well as Map within
        assertSame(baseValue.data, mergedResult.data);

        assertEquals(1, mergedResult.data.size());
        // but entry value has changed by necessity
        assertEquals(SomeClassA.class, mergedResult.data.get("SOMEKEY").getClass());

        assertEquals("jim", mergedResult.data.get("SOMEKEY").getName());
    }
}