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BAEL-5115 Deduction-Based Polymorphism in Jackson 2.12 (eugenp#11732)
* BAEL-5115 Deduction-Based Polymorphism in Jackson 2.12 * Fix pmd * Code review changes * Improvements * Code review * Code review * fix typo * Rename package * Apply formatter * Add old deduction * revert
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‎jackson-modules/jackson-annotations/src/main/java/com/baeldung/jackson/deductionbasedpolymorphism/Character.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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import com.fasterxml.jackson.annotation.JsonSubTypes;
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import com.fasterxml.jackson.annotation.JsonSubTypes.Type;
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import com.fasterxml.jackson.annotation.JsonTypeInfo;
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import com.fasterxml.jackson.annotation.JsonTypeInfo.Id;
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@JsonTypeInfo(use = Id.DEDUCTION)
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@JsonSubTypes({ @Type(ImperialSpy.class), @Type(King.class), @Type(Knight.class) })
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public interface Character {
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}

‎jackson-modules/jackson-annotations/src/main/java/com/baeldung/jackson/deductionbasedpolymorphism/ControlledCharacter.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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public class ControlledCharacter {
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private Character character;
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public Character getCharacter() {
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return character;
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}
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public void setCharacter(Character character) {
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this.character = character;
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}
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}

‎jackson-modules/jackson-annotations/src/main/java/com/baeldung/jackson/deductionbasedpolymorphism/ImperialSpy.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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public class ImperialSpy implements Character {
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}

‎jackson-modules/jackson-annotations/src/main/java/com/baeldung/jackson/deductionbasedpolymorphism/King.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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public class King extends NamedCharacter {
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private String land;
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public String getLand() {
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return land;
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}
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public void setLand(String land) {
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this.land = land;
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}
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}

‎jackson-modules/jackson-annotations/src/main/java/com/baeldung/jackson/deductionbasedpolymorphism/Knight.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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public class Knight extends NamedCharacter {
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private String weapon;
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public String getWeapon() {
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return weapon;
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}
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public void setWeapon(String weapon) {
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this.weapon = weapon;
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}
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}

‎jackson-modules/jackson-annotations/src/main/java/com/baeldung/jackson/deductionbasedpolymorphism/NamedCharacter.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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public class NamedCharacter implements Character {
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private String name;
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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}

‎jackson-modules/jackson-annotations/src/test/java/com/baeldung/jackson/deductionbasedpolymorphism/CaseInsensitiveInferenceUnitTest.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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import static com.baeldung.jackson.deductionbasedpolymorphism.JsonStringFormatterUtil.formatJson;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertSame;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import org.junit.jupiter.api.Test;
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import com.fasterxml.jackson.databind.MapperFeature;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import com.fasterxml.jackson.databind.json.JsonMapper;
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class CaseInsensitiveInferenceUnitTest {
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private final ObjectMapper objectMapper = JsonMapper.builder()
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.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true)
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.build();
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@Test
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void givenACaseInsensitiveKnight_whenMapping_thenExpectKnight() throws Exception {
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String knightJson = formatJson("{'NaMe':'Ostrava, of Boletaria', 'WeaPON':'Rune Sword'}");
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Character character = objectMapper.readValue(knightJson, Character.class);
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assertTrue(character instanceof Knight);
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assertSame(character.getClass(), Knight.class);
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Knight knight = (Knight) character;
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assertEquals("Ostrava, of Boletaria", knight.getName());
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assertEquals("Rune Sword", knight.getWeapon());
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}
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}

‎jackson-modules/jackson-annotations/src/test/java/com/baeldung/jackson/deductionbasedpolymorphism/ContainedInferenceUnitTest.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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import static com.baeldung.jackson.deductionbasedpolymorphism.JsonStringFormatterUtil.formatJson;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertNull;
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import static org.junit.jupiter.api.Assertions.assertSame;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import org.junit.jupiter.api.Test;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import com.fasterxml.jackson.databind.json.JsonMapper;
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class ContainedInferenceUnitTest {
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private final ObjectMapper objectMapper = JsonMapper.builder()
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.build();
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@Test
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void givenAKnightControlledCharacter_whenMapping_thenExpectAControlledCharacterWithKnight() throws Exception {
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String controlledCharacterJson = formatJson("{'character': {'name': 'Ostrava, of Boletaria', 'weapon': 'Rune Sword'}}");
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ControlledCharacter controlledCharacter = objectMapper.readValue(controlledCharacterJson, ControlledCharacter.class);
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Character character = controlledCharacter.getCharacter();
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assertTrue(character instanceof Knight);
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assertSame(character.getClass(), Knight.class);
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Knight knight = (Knight) character;
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assertEquals("Ostrava, of Boletaria", knight.getName());
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assertEquals("Rune Sword", knight.getWeapon());
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}
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@Test
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void givenAKingControlledCharacter_whenMapping_thenExpectAControlledCharacterWithKing() throws Exception {
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String controlledCharacterJson = formatJson("{'character': {'name': 'King Allant', 'land': 'Boletaria'}}");
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ControlledCharacter controlledCharacter = objectMapper.readValue(controlledCharacterJson, ControlledCharacter.class);
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Character character = controlledCharacter.getCharacter();
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assertTrue(character instanceof King);
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assertSame(character.getClass(), King.class);
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King king = (King) character;
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assertEquals("King Allant", king.getName());
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assertEquals("Boletaria", king.getLand());
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}
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@Test
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void givenAnEmptySubtype_whenMapping_thenExpectImperialSpy() throws Exception {
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String controlledCharacterJson = formatJson("{'character': {}}");
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ControlledCharacter controlledCharacter = objectMapper.readValue(controlledCharacterJson, ControlledCharacter.class);
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assertTrue(controlledCharacter.getCharacter() instanceof ImperialSpy);
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}
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@Test
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void givenANullCharacter_whenMapping_thenExpectNullCharacter() throws Exception {
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String controlledCharacterJson = formatJson("{'character': null}");
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ControlledCharacter controlledCharacter = objectMapper.readValue(controlledCharacterJson, ControlledCharacter.class);
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assertNull(controlledCharacter.getCharacter());
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}
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@Test
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void givenAAnAbsentCharacter_whenMapping_thenExpectNullCharacter() throws Exception {
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String controlledCharacterJson = formatJson("{}");
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ControlledCharacter controlledCharacter = objectMapper.readValue(controlledCharacterJson, ControlledCharacter.class);
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assertNull(controlledCharacter.getCharacter());
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}
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}

‎jackson-modules/jackson-annotations/src/test/java/com/baeldung/jackson/deductionbasedpolymorphism/JsonStringFormatterUtil.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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public class JsonStringFormatterUtil {
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public static String formatJson(String input) {
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return input.replaceAll("'", "\"");
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}
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}

‎jackson-modules/jackson-annotations/src/test/java/com/baeldung/jackson/deductionbasedpolymorphism/SimpleInferenceUnitTest.java‎

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package com.baeldung.jackson.deductionbasedpolymorphism;
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import static com.baeldung.jackson.deductionbasedpolymorphism.JsonStringFormatterUtil.formatJson;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertNull;
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import static org.junit.jupiter.api.Assertions.assertSame;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import org.junit.jupiter.api.Test;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import com.fasterxml.jackson.databind.json.JsonMapper;
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class SimpleInferenceUnitTest {
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private final ObjectMapper objectMapper = JsonMapper.builder()
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.build();
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@Test
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void givenAKnight_whenMapping_thenExpectAKnightType() throws Exception {
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String knightJson = formatJson("{'name':'Ostrava, of Boletaria', 'weapon':'Rune Sword'}");
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Character character = objectMapper.readValue(knightJson, Character.class);
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assertTrue(character instanceof Knight);
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assertSame(character.getClass(), Knight.class);
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Knight king = (Knight) character;
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assertEquals("Ostrava, of Boletaria", king.getName());
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assertEquals("Rune Sword", king.getWeapon());
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}
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@Test
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void givenAKing_whenMapping_thenExpectAKingType() throws Exception {
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String kingJson = formatJson("{'name':'Old King Allant', 'land':'Boletaria'}");
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Character character = objectMapper.readValue(kingJson, Character.class);
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assertTrue(character instanceof King);
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assertSame(character.getClass(), King.class);
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King king = (King) character;
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assertEquals("Old King Allant", king.getName());
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assertEquals("Boletaria", king.getLand());
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}
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@Test
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void givenAnEmptyObject_whenMapping_thenExpectAnImperialSpy() throws Exception {
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String imperialSpyJson = "{}";
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Character character = objectMapper.readValue(imperialSpyJson, Character.class);
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assertTrue(character instanceof ImperialSpy);
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}
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@Test
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void givenANullObject_whenMapping_thenExpectANullObject() throws Exception {
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Character character = objectMapper.readValue("null", Character.class);
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assertNull(character);
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}
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}

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