[SR] Map enum with mapstruct (#16163)

* Added enums for week day, its mapper and test.

* Added enums, mapping and tests for case transformation.

* Changed test names to follow BDD style.

* Renamed test class.

* Removed enum, mapper and test for weekdays.
Added same for traffic signal.

* Moved the source code and tests under its own package.

* Added link to article.

* Fixed readme

* Fixed readme

---------

Co-authored-by: sraverkar.encora <sraverkar.encora@centricsoftware.com>

mapstruct/src/main/java/com/baeldung/mapstruct/enums/mapper/TrafficSignalMapper.java

@@ -0,0 +1,208 @@
+package com.baeldung.mapstruct.enums.mapper;
+
+import com.baeldung.mapstruct.enums.model.*;
+import org.mapstruct.*;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * The Traffic signal mapper.
+ */
+@Mapper
+public interface TrafficSignalMapper {
+
+    /**
+     * The constant INSTANCE.
+     */
+    TrafficSignalMapper INSTANCE = Mappers.getMapper(TrafficSignalMapper.class);
+
+    /**
+     * Convert traffic signal to integer.
+     *
+     * @param source the source
+     * @return the integer
+     */
+    default Integer convertTrafficSignalToInteger(TrafficSignal source) {
+        Integer result = null;
+        switch (source) {
+            case Off:
+                result = 0;
+                break;
+            case Stop:
+                result = 1;
+                break;
+            case Go:
+                result = 2;
+                break;
+        }
+        return result;
+    }
+
+    /**
+     * Maps road sign to traffic signal.
+     *
+     * @param source the source
+     * @return the traffic signal
+     */
+    @ValueMapping(target = "Off", source = "Off")
+    @ValueMapping(target = "Go", source = "Move")
+    @ValueMapping(target = "Stop", source = "Halt")
+    TrafficSignal toTrafficSignal(RoadSign source);
+
+    /**
+     * Maps string to traffic signal.
+     *
+     * @param source the source
+     * @return the traffic signal
+     */
+    @ValueMapping(target = "Off", source = "Off")
+    @ValueMapping(target = "Go", source = "Move")
+    @ValueMapping(target = "Stop", source = "Halt")
+    TrafficSignal stringToTrafficSignal(String source);
+
+
+    /**
+     * Maps a traffic signal to string.
+     *
+     * @param source the source
+     * @return the traffic signal
+     */
+    @ValueMapping(target = "Off", source = "Off")
+    @ValueMapping(target = "Go", source = "Go")
+    @ValueMapping(target = "Stop", source = "Stop")
+    String trafficSignalToString(TrafficSignal source);
+
+    /**
+     * Maps a traffic signal to number.
+     *
+     * @param source the source
+     * @return the traffic signal number
+     */
+    @Mapping(target = "number", source = ".")
+    TrafficSignalNumber trafficSignalToTrafficSignalNumber(TrafficSignal source);
+
+    /**
+     * Maps traffic signal to simple traffic signal.
+     *
+     * @param source the source
+     * @return the simple traffic signal
+     */
+    @ValueMapping(target = "Off", source = "Off")
+    @ValueMapping(target = "On", source = "Go")
+    @ValueMapping(target = "Off", source = "Stop")
+    SimpleTrafficSignal toSimpleTrafficSignal(TrafficSignal source);
+
+    /**
+     * Maps traffic signal to simple traffic signal.
+     *
+     * @param source the source
+     * @return the simple traffic signal
+     */
+    @ValueMapping(target = "On", source = "Go")
+    @ValueMapping(target = "Off", source = MappingConstants.ANY_REMAINING)
+    SimpleTrafficSignal toSimpleTrafficSignalWithRemaining(TrafficSignal source);
+
+    /**
+     * Maps traffic signal to simple traffic signal.
+     *
+     * @param source the source
+     * @return the simple traffic signal
+     */
+    @ValueMapping(target = "On", source = "Go")
+    @ValueMapping(target = "Off", source = MappingConstants.ANY_UNMAPPED)
+    SimpleTrafficSignal toSimpleTrafficSignalWithUnmapped(TrafficSignal source);
+
+    /**
+     * Maps traffic signal with null handling.
+     *
+     * @param source the source
+     * @return the work day
+     */
+    @ValueMapping(target = "Off", source = MappingConstants.NULL)
+    @ValueMapping(target = "On", source = "Go")
+    @ValueMapping(target = MappingConstants.NULL, source = MappingConstants.ANY_UNMAPPED)
+    SimpleTrafficSignal toSimpleTrafficSignalWithNullHandling(TrafficSignal source);
+
+    /**
+     * Maps simple traffic signal to traffic signal with exception handling.
+     *
+     * @param source the source
+     * @return the work day
+     * @throws IllegalArgumentException if {@code source} is {@code Sat} or {@code Sun}.
+     */
+    @ValueMapping(target = "On", source = "Go")
+    @ValueMapping(target = MappingConstants.THROW_EXCEPTION, source = MappingConstants.NULL)
+    @ValueMapping(target = MappingConstants.THROW_EXCEPTION, source = MappingConstants.ANY_UNMAPPED)
+    SimpleTrafficSignal toSimpleTrafficSignalWithExceptionHandling(TrafficSignal source);
+
+    /**
+     * Apply suffix.
+     *
+     * @param source the source
+     * @return traffic signal suffixed
+     */
+    @EnumMapping(nameTransformationStrategy = MappingConstants.SUFFIX_TRANSFORMATION, configuration = "_Value")
+    TrafficSignalSuffixed applySuffix(TrafficSignal source);
+
+    /**
+     * Apply prefix.
+     *
+     * @param source the source
+     * @return the traffic signal prefixed
+     */
+    @EnumMapping(nameTransformationStrategy = MappingConstants.PREFIX_TRANSFORMATION, configuration = "Value_")
+    TrafficSignalPrefixed applyPrefix(TrafficSignal source);
+
+    /**
+     * Strip suffix.
+     *
+     * @param source the source
+     * @return the traffic signal
+     */
+    @EnumMapping(nameTransformationStrategy = MappingConstants.STRIP_SUFFIX_TRANSFORMATION, configuration = "_Value")
+    TrafficSignal stripSuffix(TrafficSignalSuffixed source);
+
+    /**
+     * Strip prefix.
+     *
+     * @param source the source
+     * @return the traffic signal
+     */
+    @EnumMapping(nameTransformationStrategy = MappingConstants.STRIP_PREFIX_TRANSFORMATION, configuration = "Value_")
+    TrafficSignal stripPrefix(TrafficSignalPrefixed source);
+
+    /**
+     * Apply lowercase to traffic signal.
+     *
+     * @param source the source
+     * @return the traffic signal lowercase
+     */
+    @EnumMapping(nameTransformationStrategy = MappingConstants.CASE_TRANSFORMATION, configuration = "lower")
+    TrafficSignalLowercase applyLowercase(TrafficSignal source);
+
+    /**
+     * Apply uppercase to traffic signal.
+     *
+     * @param source the source
+     * @return the traffic signal uppercase
+     */
+    @EnumMapping(nameTransformationStrategy = MappingConstants.CASE_TRANSFORMATION, configuration = "upper")
+    TrafficSignalUppercase applyUppercase(TrafficSignal source);
+
+    /**
+     * Underscore to string in capital case.
+     *
+     * @param source the source
+     * @return the string
+     */
+    @EnumMapping(nameTransformationStrategy = MappingConstants.CASE_TRANSFORMATION, configuration = "capital")
+    String underscoreToCapital(TrafficSignalUnderscore source);
+
+    /**
+     * Lowercase to capital traffic signal.
+     *
+     * @param source the source
+     * @return traffic signal
+     */
+    @EnumMapping(nameTransformationStrategy = MappingConstants.CASE_TRANSFORMATION, configuration = "capital")
+    TrafficSignal lowercaseToCapital(TrafficSignalLowercase source);
+}

mapstruct/src/main/java/com/baeldung/mapstruct/enums/model/RoadSign.java

@@ -0,0 +1,19 @@
+package com.baeldung.mapstruct.enums.model;
+
+/**
+ * The enum road signal.
+ */
+public enum RoadSign {
+    /**
+     * Off signal.
+     */
+    Off,
+    /**
+     * Stop signal.
+     */
+    Halt,
+    /**
+     * Go signal.
+     */
+    Move
+}

mapstruct/src/main/java/com/baeldung/mapstruct/enums/model/SimpleTrafficSignal.java

@@ -0,0 +1,15 @@
+package com.baeldung.mapstruct.enums.model;
+
+/**
+ * The enum two-state Traffic Signal.
+ */
+public enum SimpleTrafficSignal {
+    /**
+     * Off signal.
+     */
+    Off,
+    /**
+     * Stop signal.
+     */
+    On
+}

mapstruct/src/main/java/com/baeldung/mapstruct/enums/model/TrafficSignal.java

@@ -0,0 +1,19 @@
+package com.baeldung.mapstruct.enums.model;
+
+/**
+ * The enum Traffic Signal.
+ */
+public enum TrafficSignal {
+    /**
+     * Off signal.
+     */
+    Off,
+    /**
+     * Stop signal.
+     */
+    Stop,
+    /**
+     * Go signal.
+     */
+    Go
+}

mapstruct/src/main/java/com/baeldung/mapstruct/enums/model/TrafficSignalLowercase.java

@@ -0,0 +1,19 @@
+package com.baeldung.mapstruct.enums.model;
+
+/**
+ * The enum Traffic Signal with lowercase.
+ */
+public enum TrafficSignalLowercase {
+    /**
+     * Off signal.
+     */
+    off,
+    /**
+     * Stop signal.
+     */
+    stop,
+    /**
+     * Go signal.
+     */
+    go
+}

mapstruct/src/main/java/com/baeldung/mapstruct/enums/model/TrafficSignalNumber.java

@@ -0,0 +1,26 @@
+package com.baeldung.mapstruct.enums.model;
+
+/**
+ * The traffic signal number.
+ */
+public class TrafficSignalNumber {
+    private Integer number;
+
+    /**
+     * Gets number.
+     *
+     * @return the number
+     */
+    public Integer getNumber() {
+        return number;
+    }
+
+    /**
+     * Sets number.
+     *
+     * @param number the number
+     */
+    public void setNumber(Integer number) {
+        this.number = number;
+    }
+}

mapstruct/src/main/java/com/baeldung/mapstruct/enums/model/TrafficSignalPrefixed.java

@@ -0,0 +1,19 @@
+package com.baeldung.mapstruct.enums.model;
+
+/**
+ * The enum Traffic Signal with prefix.
+ */
+public enum TrafficSignalPrefixed {
+    /**
+     * Off signal.
+     */
+    Value_Off,
+    /**
+     * Stop signal.
+     */
+    Value_Stop,
+    /**
+     * Go signal.
+     */
+    Value_Go
+}

mapstruct/src/main/java/com/baeldung/mapstruct/enums/model/TrafficSignalSuffixed.java

@@ -0,0 +1,19 @@
+package com.baeldung.mapstruct.enums.model;
+
+/**
+ * The enum Traffic Signal with suffix.
+ */
+public enum TrafficSignalSuffixed {
+    /**
+     * Off signal.
+     */
+    Off_Value,
+    /**
+     * Stop signal.
+     */
+    Stop_Value,
+    /**
+     * Go signal.
+     */
+    Go_Value
+}

mapstruct/src/main/java/com/baeldung/mapstruct/enums/model/TrafficSignalUnderscore.java

@@ -0,0 +1,19 @@
+package com.baeldung.mapstruct.enums.model;
+
+/**
+ * The enum Traffic Signal with uppercase.
+ */
+public enum TrafficSignalUnderscore {
+    /**
+     * Off signal.
+     */
+    OFF_VALUE,
+    /**
+     * Stop signal.
+     */
+    STOP_VALUE,
+    /**
+     * Go signal.
+     */
+    GO_VALUE
+}

mapstruct/src/main/java/com/baeldung/mapstruct/enums/model/TrafficSignalUppercase.java

@@ -0,0 +1,19 @@
+package com.baeldung.mapstruct.enums.model;
+
+/**
+ * The enum Traffic Signal with uppercase.
+ */
+public enum TrafficSignalUppercase {
+    /**
+     * Off signal.
+     */
+    OFF,
+    /**
+     * Stop signal.
+     */
+    STOP,
+    /**
+     * Go signal.
+     */
+    GO
+}

mapstruct/src/test/java/com/baeldung/mapstruct/enums/TrafficSignalMapperUnitTest.java

@@ -0,0 +1,249 @@
+package com.baeldung.mapstruct.enums;
+
+import com.baeldung.mapstruct.enums.mapper.TrafficSignalMapper;
+import com.baeldung.mapstruct.enums.model.*;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+/**
+ * The traffic signal mapper test.
+ */
+class TrafficSignalMapperUnitTest {
+
+    /**
+     * To traffic signal.
+     */
+    @Test
+    void whenRoadSignIsMapped_thenGetTrafficSignal() {
+        RoadSign source = RoadSign.Move;
+        TrafficSignal target = TrafficSignalMapper.INSTANCE.toTrafficSignal(source);
+        assertEquals(TrafficSignal.Go, target);
+    }
+
+    /**
+     * String to traffic signal.
+     */
+    @Test
+    void whenStringIsMapped_thenGetTrafficSignal() {
+        String source = RoadSign.Move.name();
+        TrafficSignal target = TrafficSignalMapper.INSTANCE.stringToTrafficSignal(source);
+        assertEquals(TrafficSignal.Go, target);
+    }
+
+    /**
+     * String to unmapped traffic signal.
+     */
+    @Test
+    void whenStringIsUnmapped_thenGetException() {
+        String source = "Proceed";
+        Exception exception = assertThrows(IllegalArgumentException.class, () -> {
+            TrafficSignalMapper.INSTANCE.stringToTrafficSignal(source);
+        });
+        assertEquals("Unexpected enum constant: " + source, exception.getMessage());
+    }
+
+    /**
+     * Traffic signal to string.
+     */
+    @Test
+    void whenTrafficSignalIsMapped_thenGetString() {
+        TrafficSignal source = TrafficSignal.Go;
+        String targetTrafficSignalStr = TrafficSignalMapper.INSTANCE.trafficSignalToString(source);
+        assertEquals("Go", targetTrafficSignalStr);
+    }
+
+    /**
+     * Traffic signal to int.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected traffic signal number
+     */
+    @ParameterizedTest
+    @CsvSource({"Off,0", "Stop,1"})
+    void whenTrafficSignalIsMapped_thenGetInt(TrafficSignal source, int expected) {
+        Integer targetTrafficSignalInt = TrafficSignalMapper.INSTANCE.convertTrafficSignalToInteger(source);
+        TrafficSignalNumber targetTrafficSignalNumber = TrafficSignalMapper.INSTANCE.trafficSignalToTrafficSignalNumber(source);
+        assertEquals(expected, targetTrafficSignalInt.intValue());
+        assertEquals(expected, targetTrafficSignalNumber.getNumber().intValue());
+    }
+
+    /**
+     * Traffic signal to simple traffic signal.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected traffic signal
+     */
+    @ParameterizedTest
+    @CsvSource({"Off,Off", "Go,On", "Stop,Off"})
+    void whenTrafficSignalIsMapped_thenGetSimpleTrafficSignal(TrafficSignal source, SimpleTrafficSignal expected) {
+        SimpleTrafficSignal target = TrafficSignalMapper.INSTANCE.toSimpleTrafficSignal(source);
+        assertEquals(expected, target);
+    }
+
+    /**
+     * Traffic signal to working day.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected traffic signal
+     */
+    @ParameterizedTest
+    @CsvSource({"Off,Off", "Go,On", "Stop,Off"})
+    void whenTrafficSignalIsMappedWithRemaining_thenGetTrafficSignal(TrafficSignal source, SimpleTrafficSignal expected) {
+        SimpleTrafficSignal targetTrafficSignal = TrafficSignalMapper.INSTANCE.toSimpleTrafficSignalWithRemaining(source);
+        assertEquals(expected, targetTrafficSignal);
+    }
+
+    /**
+     * Traffic signal to working day.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected traffic signal
+     */
+    @ParameterizedTest
+    @CsvSource({"Off,Off", "Go,On", "Stop,Off"})
+    void whenTrafficSignalIsMappedWithUnmapped_thenGetTrafficSignal(TrafficSignal source, SimpleTrafficSignal expected) {
+        SimpleTrafficSignal target = TrafficSignalMapper.INSTANCE.toSimpleTrafficSignalWithUnmapped(source);
+        assertEquals(expected, target);
+    }
+
+    /**
+     * Traffic signal to simple traffic signal with null handling.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected traffic signal
+     */
+    @ParameterizedTest
+    @CsvSource({",Off", "Go,On", "Stop,"})
+    void whenTrafficSignalIsMappedWithNull_thenGetTrafficSignal(TrafficSignal source, SimpleTrafficSignal expected) {
+        SimpleTrafficSignal targetTrafficSignal = TrafficSignalMapper.INSTANCE.toSimpleTrafficSignalWithNullHandling(source);
+        assertEquals(expected, targetTrafficSignal);
+    }
+
+    /**
+     * Traffic signal to traffic signal with exception handling.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected traffic signal
+     */
+    @ParameterizedTest
+    @CsvSource({",", "Go,On", "Stop,"})
+    void whenTrafficSignalIsMappedWithException_thenGetTrafficSignal(TrafficSignal source, SimpleTrafficSignal expected) {
+        if (source == TrafficSignal.Go) {
+            SimpleTrafficSignal targetTrafficSignal = TrafficSignalMapper.INSTANCE.toSimpleTrafficSignalWithExceptionHandling(source);
+            assertEquals(expected, targetTrafficSignal);
+        } else {
+            Exception exception = assertThrows(IllegalArgumentException.class, () -> {
+                TrafficSignalMapper.INSTANCE.toSimpleTrafficSignalWithExceptionHandling(source);
+            });
+            assertEquals("Unexpected enum constant: " + source, exception.getMessage());
+        }
+    }
+
+    /**
+     * Apply suffix.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected result
+     */
+    @ParameterizedTest
+    @CsvSource({"Off,Off_Value", "Go,Go_Value"})
+    void whenTrafficSignalIsMappedWithSuffix_thenGetTrafficSignalSuffixed(TrafficSignal source, TrafficSignalSuffixed expected) {
+        TrafficSignalSuffixed result = TrafficSignalMapper.INSTANCE.applySuffix(source);
+        assertEquals(expected, result);
+    }
+
+    /**
+     * Apply prefix.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected result
+     */
+    @ParameterizedTest
+    @CsvSource({"Off,Value_Off", "Go,Value_Go"})
+    void whenTrafficSignalIsMappedWithPrefix_thenGetTrafficSignalPrefixed(TrafficSignal source, TrafficSignalPrefixed expected) {
+        TrafficSignalPrefixed result = TrafficSignalMapper.INSTANCE.applyPrefix(source);
+        assertEquals(expected, result);
+    }
+
+    /**
+     * Strip suffix.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected result
+     */
+    @ParameterizedTest
+    @CsvSource({"Off_Value,Off", "Go_Value,Go"})
+    void whenTrafficSignalSuffixedMappedWithStripped_thenGetTrafficSignal(TrafficSignalSuffixed source, TrafficSignal expected) {
+        TrafficSignal result = TrafficSignalMapper.INSTANCE.stripSuffix(source);
+        assertEquals(expected, result);
+    }
+
+    /**
+     * Strip prefix.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected result
+     */
+    @ParameterizedTest
+    @CsvSource({"Value_Off,Off", "Value_Stop,Stop"})
+    void whenTrafficSignalPrefixedMappedWithStripped_thenGetTrafficSignal(TrafficSignalPrefixed source, TrafficSignal expected) {
+        TrafficSignal result = TrafficSignalMapper.INSTANCE.stripPrefix(source);
+        assertEquals(expected, result);
+    }
+
+    /**
+     * Apply lowercase.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected result
+     */
+    @ParameterizedTest
+    @CsvSource({"Off,off", "Go,go"})
+    void whenTrafficSignalMappedWithLower_thenGetTrafficSignalLowercase(TrafficSignal source, TrafficSignalLowercase expected) {
+        TrafficSignalLowercase result = TrafficSignalMapper.INSTANCE.applyLowercase(source);
+        assertEquals(expected, result);
+    }
+
+    /**
+     * Apply uppercase.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected result
+     */
+    @ParameterizedTest
+    @CsvSource({"Off,OFF", "Go,GO"})
+    void whenTrafficSignalMappedWithUpper_thenGetTrafficSignalUppercase(TrafficSignal source, TrafficSignalUppercase expected) {
+        TrafficSignalUppercase result = TrafficSignalMapper.INSTANCE.applyUppercase(source);
+        assertEquals(expected, result);
+    }
+
+    /**
+     * Underscore to capital.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected result
+     */
+    @ParameterizedTest
+    @CsvSource({"OFF_VALUE,Off_Value", "GO_VALUE,Go_Value"})
+    void whenTrafficSignalUnderscoreMappedWithCapital_thenGetStringCapital(TrafficSignalUnderscore source, String expected) {
+        String result = TrafficSignalMapper.INSTANCE.underscoreToCapital(source);
+        assertEquals(expected, result);
+    }
+
+    /**
+     * Lowercase to capital.
+     *
+     * @param source   the traffic signal
+     * @param expected the expected result
+     */
+    @ParameterizedTest
+    @CsvSource({"off,Off", "go,Go"})
+    void whenTrafficSignalLowercaseMappedWithCapital_thenGetTrafficSignal(TrafficSignalLowercase source, TrafficSignal expected) {
+        TrafficSignal result = TrafficSignalMapper.INSTANCE.lowercaseToCapital(source);
+        assertEquals(expected, result);
+    }
+}