@JsonAnySetter verson

import com.fasterxml.jackson.annotation.*;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test;

import static org.junit.Assert.assertTrue;

import java.io.IOException;
import java.net.URISyntaxException;
import java.util.Objects;

public class TestClass {

    @Test
    public void testBoth() throws IOException, URISyntaxException {
        ClassLoader classLoader = getClass().getClassLoader();
        String json = "{\n" +
                "    \"classA\":{\n" +
                "        \"aField\":\"A\",\n" +
                "        \"baseField\":\"baseA\"\n" +
                "    },\n" +
                "    \"classB\":{\n" +
                "        \"baseField\":\"baseB\",\n" +
                "        \"bField\":\"B\"\n" +
                "    }\n" +
                "}";//new String(Files.readAllBytes(Paths.get(classLoader.getResource("test/so-example.json").toURI())));
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerSubtypes(SubClassA.class, SubClassB.class);

        SubClassTestObject testObj = mapper.readValue(json, SubClassTestObject.class); //Fails here
        SubClassA a = testObj.getA();
        SubClassB b = testObj.getB();

        assertTrue(a.getBaseField().equals("baseA"));
        assertTrue(b.getBaseField().equals("baseB"));
        assertTrue(a.getaField().equals("A"));
        assertTrue(b.getbField().equals("B"));

    }

    @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.WRAPPER_OBJECT)
    @JsonSubTypes({
            @JsonSubTypes.Type(value = SubClassA.class, name = "classA"),
            @JsonSubTypes.Type(value = SubClassB.class, name = "classB")
    })

    @JsonIgnoreProperties(ignoreUnknown = true)
    public static abstract class AbstractSimpleClass {
        String baseField;

        public String getBaseField() {
            return baseField;
        }

        public void setBaseField(String baseField) {
            this.baseField = baseField;
        }
    }

    public static class SubClassA extends AbstractSimpleClass {
        String aField;

        public String getaField() {
            return aField;
        }

        public void setaField(String aField) {
            this.aField = aField;
        }
    }

    public static class SubClassB extends AbstractSimpleClass {
        String bField;

        public String getbField() {
            return bField;
        }

        public void setbField(String bField) {
            this.bField = bField;
        }

    }

    @JsonIgnoreProperties(ignoreUnknown = true)
    public static class SubClassTestObject {

        SubClassA a;

        SubClassB b;

        public SubClassA getA() {
            return a;
        }

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

        public SubClassB getB() {
            return b;
        }

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

        @JsonAnySetter
        public void jsonAnySetter(String key, JsonNode obj) {
            if (Objects.equals(key, "classA")) {
                a = new SubClassA();
                a.setaField(obj.get("aField").asText());
                a.setBaseField(obj.get("baseField").asText());
            }else if (Objects.equals(key, "classB")) {
                b = new SubClassB();
                b.setbField(obj.get("bField").asText());
                b.setBaseField(obj.get("baseField").asText());
            }
        }
    }
}

With JsonTypeInfo

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test;
import static org.junit.Assert.assertTrue;

import java.io.IOException;
import java.net.URISyntaxException;

public class TestClass {

    @Test
    public void testBoth() throws IOException, URISyntaxException {
        ClassLoader classLoader = getClass().getClassLoader();
        String json = "{\n" +
                "    \"classA\":{\n" +
                "        \"aField\":\"A\",\n" +
                "        \"baseField\":\"baseA\"\n" +
                "    },\n" +
                "    \"classB\":{\n" +
                "        \"baseField\":\"baseB\",\n" +
                "        \"bField\":\"B\"\n" +
                "    }\n" +
                "}";//new String(Files.readAllBytes(Paths.get(classLoader.getResource("test/so-example.json").toURI())));
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerSubtypes(SubClassA.class, SubClassB.class);

        SubClassTestObject testObj = mapper.readValue(json, SubClassTestObject.class); //Fails here
        SubClassA a = testObj.getA();
        SubClassB b = testObj.getB();

        assertTrue(a.getBaseField().equals("baseA"));
        assertTrue(b.getBaseField().equals("baseB"));
        assertTrue(a.getaField().equals("A"));
        assertTrue(b.getbField().equals("B"));

    }

    @JsonTypeInfo(use=JsonTypeInfo.Id.NAME, include=JsonTypeInfo.As.WRAPPER_OBJECT)
    @JsonSubTypes({
            @JsonSubTypes.Type(value = SubClassA.class, name = "classA"),
            @JsonSubTypes.Type(value = SubClassB.class, name = "classB")
    })

    @JsonIgnoreProperties(ignoreUnknown = true)
    public static abstract class AbstractSimpleClass {
        String baseField;

        public String getBaseField() {
            return baseField;
        }

        public void setBaseField(String baseField) {
            this.baseField = baseField;
        }
    }

    public static class SubClassA extends AbstractSimpleClass {
        String aField;

        public String getaField() {
            return aField;
        }

        public void setaField(String aField) {
            this.aField = aField;
        }
    }

    public static class SubClassB extends AbstractSimpleClass {
        String bField;

        public String getbField() {
            return bField;
        }

        public void setbField(String bField) {
            this.bField = bField;
        }

    }
    @JsonIgnoreProperties(ignoreUnknown = true)
    public static class SubClassTestObject {
        @JsonProperty("classA")
        @JsonTypeInfo(use=JsonTypeInfo.Id.NONE)
        SubClassA a;

        @JsonProperty("classB")
        @JsonTypeInfo(use=JsonTypeInfo.Id.NONE)
        SubClassB b;

        public SubClassA getA() {
            return a;
        }
        public void setA(SubClassA a) {
            this.a = a;
        }
        public SubClassB getB() {
            return b;
        }
        public void setB(SubClassB b) {
            this.b = b;
        }
    }
}

Without JsonTypeInfo

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test;
import static org.junit.Assert.assertTrue;

import java.io.IOException;
import java.net.URISyntaxException;

public class TestClassv2 {

    @Test
    public void testBoth() throws IOException, URISyntaxException {
        ClassLoader classLoader = getClass().getClassLoader();
        String json = "{\n" +
                "    \"classA\":{\n" +
                "        \"aField\":\"A\",\n" +
                "        \"baseField\":\"baseA\"\n" +
                "    },\n" +
                "    \"classB\":{\n" +
                "        \"baseField\":\"baseB\",\n" +
                "        \"bField\":\"B\"\n" +
                "    }\n" +
                "}";//new String(Files.readAllBytes(Paths.get(classLoader.getResource("test/so-example.json").toURI())));
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerSubtypes(SubClassA.class, SubClassB.class);

        SubClassTestObject testObj = mapper.readValue(json, SubClassTestObject.class); //Fails here
        SubClassA a = testObj.getA();
        SubClassB b = testObj.getB();

        assertTrue(a.getBaseField().equals("baseA"));
        assertTrue(b.getBaseField().equals("baseB"));
        assertTrue(a.getaField().equals("A"));
        assertTrue(b.getbField().equals("B"));

    }


    @JsonIgnoreProperties(ignoreUnknown = true)
    public static abstract class AbstractSimpleClass {
        String baseField;

        public String getBaseField() {
            return baseField;
        }

        public void setBaseField(String baseField) {
            this.baseField = baseField;
        }
    }

    public static class SubClassA extends AbstractSimpleClass {
        String aField;

        public String getaField() {
            return aField;
        }

        public void setaField(String aField) {
            this.aField = aField;
        }
    }

    public static class SubClassB extends AbstractSimpleClass {
        String bField;

        public String getbField() {
            return bField;
        }

        public void setbField(String bField) {
            this.bField = bField;
        }

    }
    @JsonIgnoreProperties(ignoreUnknown = true)
    public static class SubClassTestObject {
        @JsonProperty("classA")
        SubClassA a;

        @JsonProperty("classB")
        SubClassB b;

        public SubClassA getA() {
            return a;
        }
        public void setA(SubClassA a) {
            this.a = a;
        }
        public SubClassB getB() {
            return b;
        }
        public void setB(SubClassB b) {
            this.b = b;
        }
    }
}

3 versons of the same classes than can path the test