Add support for SerializeWith annotation

configlib-core/src/main/java/de/exlll/configlib/SerializeWith.java

@@ -0,0 +1,63 @@
+package de.exlll.configlib;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Indicates that the annotated element should be serialized with the given serializer. Serializers
+ * provided by this annotation take precedence over all other serializers.
+ * <p>
+ * If the annotated element is an array, list, set, or map a nesting level can be set to apply the
+ * serializer not to the top-level type but to its elements. For maps, the serializer is applied to
+ * the values and not the keys.
+ * <p>
+ * The following example shows how {@code nesting} can be used to apply the serializer at
+ * different levels.
+ *
+ * <pre>
+ * {@code
+ * // MyListSerializer is applied to 'list'
+ * @SerializeWith(serializer = MyListSerializer.class)
+ * List<Set<String>> list;
+ *
+ * // MySetSerializer is applied to the Set<String> elements of 'list'
+ * @SerializeWith(serializer = MySetSerializer.class, nesting = 1)
+ * List<Set<String>> list;
+ *
+ * // MyStringSerializer is applied to the strings within the set elements of 'list'
+ * @SerializeWith(serializer = MyStringSerializer.class, nesting = 2)
+ * List<Set<String>> list;
+ *
+ * // MyMap0Serializer is applied to 'map'
+ * @SerializeWith(serializer = MyMap0Serializer.class)
+ * Map<Integer, Map<String, Double>> map;
+ *
+ * // MyMap1Serializer is applied to the Map<String, Double> values of 'map'
+ * @SerializeWith(serializer = MyMap1Serializer.class, nesting = 1)
+ * Map<Integer, Map<String, Double>> map;
+ *
+ * // MyDoubleSerializer is applied to the doubles within the nested values of 'map'
+ * @SerializeWith(serializer = MyDoubleSerializer.class, nesting = 2)
+ * Map<Integer, Map<String, Double>> map;
+ * }
+ * </pre>
+ */
+@Target({ElementType.FIELD, ElementType.RECORD_COMPONENT})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface SerializeWith {
+    /**
+     * Returns the type of the serializer to be used.
+     *
+     * @return the type of serializer to use
+     */
+    Class<? extends Serializer<?, ?>> serializer();
+
+    /**
+     * Returns the nesting level at which to apply the serializer.
+     *
+     * @return the nesting level
+     */
+    int nesting() default 0;
+}

configlib-core/src/main/java/de/exlll/configlib/SerializerSelector.java

@@ -50,12 +50,32 @@ final class SerializerSelector {
             Map.entry(URI.class, new UriSerializer())
     );
     private final ConfigurationProperties properties;
+    /**
+     * Holds the {@code SerializeWith} value of the last {@literal select}ed component. If the
+     * component is not annotated with {@code SerializeWith}, the value of this field is null.
+     */
+    private SerializeWith serializeWith;
+    /**
+     * The {@code currentNesting} is used to determine the nesting of a type and is incremented each
+     * time the {@code selectForType} method is called. It is reset when {@code select} is called.
+     * <p>
+     * For example, for a field {@code List<Set<String>>}, the nesting of {@code List} would be 0,
+     * the nesting of {@code Set} 1, and the nesting of {@code String} 2.
+     */
+    private int currentNesting = -1;
 
     public SerializerSelector(ConfigurationProperties properties) {
         this.properties = requireNonNull(properties, "configuration properties");
     }
 
-    public Serializer<?, ?> select(Type type) {
+    public Serializer<?, ?> select(TypeComponent<?> component) {
+        this.currentNesting = -1;
+        this.serializeWith = component.annotation(SerializeWith.class);
+        return selectForType(component.genericType());
+    }
+
+    private Serializer<?, ?> selectForType(Type type) {
+        this.currentNesting++;
         final Serializer<?, ?> custom = selectCustomSerializer(type);
         if (custom != null)
             return custom;
@@ -78,6 +98,8 @@ final class SerializerSelector {
     }
 
     private Serializer<?, ?> selectCustomSerializer(Type type) {
+        if ((serializeWith != null) && (currentNesting == serializeWith.nesting()))
+            return Reflect.callNoParamConstructor(serializeWith.serializer());
         if (type instanceof Class<?> cls) {
             if (properties.getSerializers().containsKey(cls))
                 return properties.getSerializers().get(cls);
@@ -133,7 +155,7 @@ final class SerializerSelector {
         } else if (elementType == double.class) {
             return new PrimitiveDoubleArraySerializer();
         }
-        var elementSerializer = select(elementType);
+        var elementSerializer = selectForType(elementType);
         var inputNulls = properties.inputNulls();
         var outputNulls = properties.outputNulls();
         return new ArraySerializer<>(elementType, elementSerializer, outputNulls, inputNulls);
@@ -147,10 +169,10 @@ final class SerializerSelector {
         final var outputNulls = properties.outputNulls();
 
         if (Reflect.isListType(rawType)) {
-            var elementSerializer = select(typeArgs[0]);
+            var elementSerializer = selectForType(typeArgs[0]);
             return new ListSerializer<>(elementSerializer, outputNulls, inputNulls);
         } else if (Reflect.isSetType(rawType)) {
-            var elementSerializer = select(typeArgs[0]);
+            var elementSerializer = selectForType(typeArgs[0]);
             return properties.serializeSetsAsLists()
                     ? new SetAsListSerializer<>(elementSerializer, outputNulls, inputNulls)
                     : new SetSerializer<>(elementSerializer, outputNulls, inputNulls);
@@ -158,8 +180,8 @@ final class SerializerSelector {
             if ((typeArgs[0] instanceof Class<?> cls) &&
                 (DEFAULT_SERIALIZERS.containsKey(cls) ||
                  Reflect.isEnumType(cls))) {
-                var keySerializer = select(typeArgs[0]);
+                var keySerializer = selectForClass(cls);
-                var valSerializer = select(typeArgs[1]);
+                var valSerializer = selectForType(typeArgs[1]);
                 return new MapSerializer<>(keySerializer, valSerializer, outputNulls, inputNulls);
             }
             String msg = baseExceptionMessage(type) +

configlib-core/src/main/java/de/exlll/configlib/TypeComponent.java

@@ -14,7 +14,7 @@ import static de.exlll.configlib.Validator.requireNonNull;
  *
  * @param <T> the type of the component
  */
-sealed interface TypeComponent<T extends AnnotatedElement> {
+interface TypeComponent<T extends AnnotatedElement> {
     /**
      * Returns the component itself.
      *

configlib-core/src/main/java/de/exlll/configlib/TypeSerializer.java

@@ -37,7 +37,7 @@ sealed abstract class TypeSerializer<T, TC extends TypeComponent<?>>
         try {
             return components().stream().collect(Collectors.toMap(
                     TypeComponent::name,
-                    component -> selector.select(component.genericType())
+                    selector::select
             ));
         } catch (StackOverflowError error) {
             String msg = "Recursive type definitions are not supported.";

configlib-core/src/test/java/de/exlll/configlib/SerializerSelectorTest.java

@@ -4,6 +4,7 @@ import de.exlll.configlib.Serializers.*;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
+import org.mockito.Mockito;
 
 import java.awt.Point;
 import java.io.File;
@@ -28,6 +29,7 @@ import static de.exlll.configlib.TestUtils.*;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.*;
 
+@SuppressWarnings("unused")
 class SerializerSelectorTest {
     private static final SerializerSelector SELECTOR = new SerializerSelector(
             ConfigurationProperties.newBuilder().build()
@@ -38,10 +40,21 @@ class SerializerSelectorTest {
         return ls.getGenericType();
     }
 
+    private static TypeComponent<?> comp(Type type) {
+        TypeComponent<?> mock = Mockito.mock(TypeComponent.class);
+        Mockito.when(mock.genericType()).thenReturn(type);
+        return mock;
+    }
+
+    private static TypeComponent<?> comp(Class<?> type, String fieldName) {
+        Field field = getField(type, fieldName);
+        return new TypeComponent.ConfigurationField(field);
+    }
+
     @ParameterizedTest
     @ValueSource(classes = {boolean.class, Boolean.class})
     void selectSerializerBoolean(Class<?> cls) {
-        Serializer<?, ?> serializer = SELECTOR.select(cls);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(cls));
         assertThat(serializer, instanceOf(BooleanSerializer.class));
     }
 
@@ -52,99 +65,99 @@ class SerializerSelectorTest {
             float.class, Float.class, double.class, Double.class
     })
     void selectSerializerNumber(Class<?> cls) {
-        NumberSerializer serializer = (NumberSerializer) SELECTOR.select(cls);
+        NumberSerializer serializer = (NumberSerializer) SELECTOR.select(comp(cls));
         assertThat(serializer.getNumberClass(), equalTo(cls));
     }
 
     @ParameterizedTest
     @ValueSource(classes = {char.class, Character.class})
     void selectSerializerChar(Class<?> cls) {
-        Serializer<?, ?> serializer = SELECTOR.select(cls);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(cls));
         assertThat(serializer, instanceOf(CharacterSerializer.class));
     }
 
     @Test
     void selectSerializerString() {
-        Serializer<?, ?> serializer = SELECTOR.select(String.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(String.class));
         assertThat(serializer, instanceOf(StringSerializer.class));
     }
 
     @Test
     void selectSerializerBigInteger() {
-        Serializer<?, ?> serializer = SELECTOR.select(BigInteger.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(BigInteger.class));
         assertThat(serializer, instanceOf(BigIntegerSerializer.class));
     }
 
     @Test
     void selectSerializerBigDecimal() {
-        Serializer<?, ?> serializer = SELECTOR.select(BigDecimal.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(BigDecimal.class));
         assertThat(serializer, instanceOf(BigDecimalSerializer.class));
     }
 
     @Test
     void selectSerializerLocalDate() {
-        Serializer<?, ?> serializer = SELECTOR.select(LocalDate.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(LocalDate.class));
         assertThat(serializer, instanceOf(LocalDateSerializer.class));
     }
 
     @Test
     void selectSerializerLocalTime() {
-        Serializer<?, ?> serializer = SELECTOR.select(LocalTime.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(LocalTime.class));
         assertThat(serializer, instanceOf(LocalTimeSerializer.class));
     }
 
     @Test
     void selectSerializerLocalDateTime() {
-        Serializer<?, ?> serializer = SELECTOR.select(LocalDateTime.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(LocalDateTime.class));
         assertThat(serializer, instanceOf(LocalDateTimeSerializer.class));
     }
 
     @Test
     void selectSerializerInstant() {
-        Serializer<?, ?> serializer = SELECTOR.select(Instant.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(Instant.class));
         assertThat(serializer, instanceOf(InstantSerializer.class));
     }
 
     @Test
     void selectSerializerUuid() {
-        Serializer<?, ?> serializer = SELECTOR.select(UUID.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(UUID.class));
         assertThat(serializer, instanceOf(UuidSerializer.class));
     }
 
     @Test
     void selectSerializerFile() {
-        Serializer<?, ?> serializer = SELECTOR.select(File.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(File.class));
         assertThat(serializer, instanceOf(FileSerializer.class));
     }
 
     @Test
     void selectSerializerPath() {
-        Serializer<?, ?> serializer = SELECTOR.select(Path.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(Path.class));
         assertThat(serializer, instanceOf(PathSerializer.class));
     }
 
     @Test
     void selectSerializerUrl() {
-        Serializer<?, ?> serializer = SELECTOR.select(URL.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(URL.class));
         assertThat(serializer, instanceOf(UrlSerializer.class));
     }
 
     @Test
     void selectSerializerUri() {
-        Serializer<?, ?> serializer = SELECTOR.select(URI.class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(URI.class));
         assertThat(serializer, instanceOf(UriSerializer.class));
     }
 
     @Test
     void selectSerializerEnum() {
         enum E {}
-        EnumSerializer serializer = (EnumSerializer) SELECTOR.select(E.class);
+        EnumSerializer serializer = (EnumSerializer) SELECTOR.select(comp(E.class));
         assertThat(serializer.getEnumCls(), equalTo(E.class));
     }
 
     @Test
     void selectSerializerArray() {
-        var serializer = (ArraySerializer<?, ?>) SELECTOR.select(String[][].class);
+        var serializer = (ArraySerializer<?, ?>) SELECTOR.select(comp(String[][].class));
         assertThat(serializer.getComponentType(), equalTo(String[].class));
 
         var elementSerializer = (ArraySerializer<?, ?>) serializer.getElementSerializer();
@@ -154,49 +167,49 @@ class SerializerSelectorTest {
 
     @Test
     void selectSerializerPrimitiveBooleanArray() {
-        Serializer<?, ?> serializer = SELECTOR.select(boolean[].class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(boolean[].class));
         assertThat(serializer, instanceOf(PrimitiveBooleanArraySerializer.class));
     }
 
     @Test
     void selectSerializerPrimitiveCharacterArray() {
-        Serializer<?, ?> serializer = SELECTOR.select(char[].class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(char[].class));
         assertThat(serializer, instanceOf(PrimitiveCharacterArraySerializer.class));
     }
 
     @Test
     void selectSerializerPrimitiveByteArray() {
-        Serializer<?, ?> serializer = SELECTOR.select(byte[].class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(byte[].class));
         assertThat(serializer, instanceOf(PrimitiveByteArraySerializer.class));
     }
 
     @Test
     void selectSerializerPrimitiveShortArray() {
-        Serializer<?, ?> serializer = SELECTOR.select(short[].class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(short[].class));
         assertThat(serializer, instanceOf(PrimitiveShortArraySerializer.class));
     }
 
     @Test
     void selectSerializerPrimitiveIntegerArray() {
-        Serializer<?, ?> serializer = SELECTOR.select(int[].class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(int[].class));
         assertThat(serializer, instanceOf(PrimitiveIntegerArraySerializer.class));
     }
 
     @Test
     void selectSerializerPrimitiveLongArray() {
-        Serializer<?, ?> serializer = SELECTOR.select(long[].class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(long[].class));
         assertThat(serializer, instanceOf(PrimitiveLongArraySerializer.class));
     }
 
     @Test
     void selectSerializerPrimitiveFloatArray() {
-        Serializer<?, ?> serializer = SELECTOR.select(float[].class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(float[].class));
         assertThat(serializer, instanceOf(PrimitiveFloatArraySerializer.class));
     }
 
     @Test
     void selectSerializerPrimitiveDoubleArray() {
-        Serializer<?, ?> serializer = SELECTOR.select(double[].class);
+        Serializer<?, ?> serializer = SELECTOR.select(comp(double[].class));
         assertThat(serializer, instanceOf(PrimitiveDoubleArraySerializer.class));
     }
 
@@ -206,14 +219,14 @@ class SerializerSelectorTest {
         class A<T> {
             int i;
         }
-        var serializer = (ConfigurationSerializer<?>) SELECTOR.select(A.class);
+        var serializer = (ConfigurationSerializer<?>) SELECTOR.select(comp(A.class));
         assertThat(serializer.getConfigurationType(), equalTo(A.class));
     }
 
     @Test
     void selectSerializerRecord() {
         record R(int i) {}
-        var serializer = (RecordSerializer<?>) SELECTOR.select(R.class);
+        var serializer = (RecordSerializer<?>) SELECTOR.select(comp(R.class));
         assertThat(serializer.getRecordType(), equalTo(R.class));
     }
 
@@ -221,14 +234,14 @@ class SerializerSelectorTest {
     void recordSerializerTakesPrecedenceOverConfigurationSerializer() {
         @Configuration
         record R(int i) {}
-        var serializer = (RecordSerializer<?>) SELECTOR.select(R.class);
+        var serializer = (RecordSerializer<?>) SELECTOR.select(comp(R.class));
         assertThat(serializer.getRecordType(), equalTo(R.class));
     }
 
     @Test
     void selectSerializerMissingType() {
         assertThrowsConfigurationException(
-                () -> SELECTOR.select(Object.class),
+                () -> SELECTOR.select(comp(Object.class)),
                 "Missing serializer for type class java.lang.Object.\nEither annotate the type with " +
                 "@Configuration or provide a custom serializer by adding it to the properties."
         );
@@ -240,7 +253,7 @@ class SerializerSelectorTest {
                 .addSerializer(Point.class, POINT_SERIALIZER)
                 .build();
         SerializerSelector selector = new SerializerSelector(properties);
-        var pointSerializer = selector.select(Point.class);
+        var pointSerializer = selector.select(comp(Point.class));
         assertThat(pointSerializer, sameInstance(POINT_SERIALIZER));
     }
 
@@ -250,7 +263,7 @@ class SerializerSelectorTest {
                 .addSerializer(BigInteger.class, CUSTOM_BIG_INTEGER_SERIALIZER)
                 .build();
         SerializerSelector selector = new SerializerSelector(properties);
-        var bigIntegerSerializer = selector.select(BigInteger.class);
+        var bigIntegerSerializer = selector.select(comp(BigInteger.class));
         assertThat(bigIntegerSerializer, instanceOf(TestUtils.CustomBigIntegerSerializer.class));
         assertThat(bigIntegerSerializer, sameInstance(CUSTOM_BIG_INTEGER_SERIALIZER));
     }
@@ -261,7 +274,7 @@ class SerializerSelectorTest {
                 .addSerializerByCondition(t -> t == Point.class, POINT_SERIALIZER)
                 .build();
         SerializerSelector selector = new SerializerSelector(properties);
-        var pointSerializer = selector.select(Point.class);
+        var pointSerializer = selector.select(comp(Point.class));
         assertThat(pointSerializer, sameInstance(POINT_SERIALIZER));
     }
 
@@ -271,7 +284,7 @@ class SerializerSelectorTest {
                 .addSerializerByCondition(t -> t == BigInteger.class, CUSTOM_BIG_INTEGER_SERIALIZER)
                 .build();
         SerializerSelector selector = new SerializerSelector(properties);
-        var bigIntegerSerializer = selector.select(BigInteger.class);
+        var bigIntegerSerializer = selector.select(comp(BigInteger.class));
         assertThat(bigIntegerSerializer, instanceOf(TestUtils.CustomBigIntegerSerializer.class));
         assertThat(bigIntegerSerializer, sameInstance(CUSTOM_BIG_INTEGER_SERIALIZER));
     }
@@ -285,7 +298,7 @@ class SerializerSelectorTest {
                 .addSerializer(int.class, serializer2)
                 .build();
         SerializerSelector selector = new SerializerSelector(properties);
-        var serializer = selector.select(int.class);
+        var serializer = selector.select(comp(int.class));
         assertThat(serializer, instanceOf(IdentifiableSerializer.class));
         assertThat(serializer, sameInstance(serializer2));
     }
@@ -295,7 +308,7 @@ class SerializerSelectorTest {
         class A {
             List<String> ls;
         }
-        var serializer = (ListSerializer<?, ?>) SELECTOR.select(getGenericType(A.class, "ls"));
+        var serializer = (ListSerializer<?, ?>) SELECTOR.select(comp(getGenericType(A.class, "ls")));
         assertThat(serializer.getElementSerializer(), instanceOf(StringSerializer.class));
     }
 
@@ -304,7 +317,7 @@ class SerializerSelectorTest {
         class A {
             List<List<String>> lls;
         }
-        var serializer = (ListSerializer<?, ?>) SELECTOR.select(getGenericType(A.class, "lls"));
+        var serializer = (ListSerializer<?, ?>) SELECTOR.select(comp(getGenericType(A.class, "lls")));
         var elementSerializer = (ListSerializer<?, ?>) serializer.getElementSerializer();
         assertThat(elementSerializer.getElementSerializer(), instanceOf(StringSerializer.class));
     }
@@ -317,7 +330,7 @@ class SerializerSelectorTest {
         SerializerSelector selector = new SerializerSelector(
                 ConfigurationProperties.newBuilder().serializeSetsAsLists(false).build()
         );
-        var serializer = (SetSerializer<?, ?>) selector.select(getGenericType(A.class, "ss"));
+        var serializer = (SetSerializer<?, ?>) selector.select(comp(getGenericType(A.class, "ss")));
         assertThat(serializer.getElementSerializer(), instanceOf(StringSerializer.class));
     }
 
@@ -326,7 +339,7 @@ class SerializerSelectorTest {
         class A {
             Set<String> ss;
         }
-        var serializer = (SetAsListSerializer<?, ?>) SELECTOR.select(getGenericType(A.class, "ss"));
+        var serializer = (SetAsListSerializer<?, ?>) SELECTOR.select(comp(getGenericType(A.class, "ss")));
         assertThat(serializer.getElementSerializer(), instanceOf(StringSerializer.class));
     }
 
@@ -335,7 +348,7 @@ class SerializerSelectorTest {
         class A {
             Map<Integer, String> mis;
         }
-        var serializer = (MapSerializer<?, ?, ?, ?>) SELECTOR.select(getGenericType(A.class, "mis"));
+        var serializer = (MapSerializer<?, ?, ?, ?>) SELECTOR.select(comp(getGenericType(A.class, "mis")));
         var numberSerializer = (NumberSerializer) serializer.getKeySerializer();
         assertThat(numberSerializer.getNumberClass(), equalTo(Integer.class));
         assertThat(serializer.getValueSerializer(), instanceOf(StringSerializer.class));
@@ -347,7 +360,7 @@ class SerializerSelectorTest {
         class A {
             Map<E, Set<List<E>>> mesle;
         }
-        var serializer = (MapSerializer<?, ?, ?, ?>) SELECTOR.select(getGenericType(A.class, "mesle"));
+        var serializer = (MapSerializer<?, ?, ?, ?>) SELECTOR.select(comp(getGenericType(A.class, "mesle")));
 
         var keySerializer = (EnumSerializer) serializer.getKeySerializer();
         assertThat(keySerializer.getEnumCls(), equalTo(E.class));
@@ -365,7 +378,7 @@ class SerializerSelectorTest {
         }
         Type type = getGenericType(A.class, "mlss");
         assertThrowsConfigurationException(
-                () -> SELECTOR.select(type),
+                () -> SELECTOR.select(comp(type)),
                 "Cannot select serializer for type '" + type + "'.\nMap keys can only be " +
                 "of simple or enum type."
         );
@@ -378,7 +391,7 @@ class SerializerSelectorTest {
         }
         Type type = getGenericType(A.class, "mps");
         assertThrowsConfigurationException(
-                () -> SELECTOR.select(type),
+                () -> SELECTOR.select(comp(type)),
                 "Cannot select serializer for type '" + type + "'.\nMap keys can only be " +
                 "of simple or enum type."
         );
@@ -392,7 +405,7 @@ class SerializerSelectorTest {
         }
         Type type = getGenericType(A.class, "box");
         assertThrowsConfigurationException(
-                () -> SELECTOR.select(type),
+                () -> SELECTOR.select(comp(type)),
                 "Cannot select serializer for type '" + type + "'.\nParameterized " +
                 "types other than lists, sets, and maps cannot be serialized."
         );
@@ -405,7 +418,7 @@ class SerializerSelectorTest {
         }
         Type type = getGenericType(A.class, "ga");
         assertThrowsConfigurationException(
-                () -> SELECTOR.select(type),
+                () -> SELECTOR.select(comp(type)),
                 "Cannot select serializer for type 'java.util.List<?>[]'.\n" +
                 "Generic array types cannot be serialized."
         );
@@ -419,7 +432,7 @@ class SerializerSelectorTest {
         ParameterizedType ptype = (ParameterizedType) getGenericType(A.class, "les");
         Type type = ptype.getActualTypeArguments()[0];
         assertThrowsConfigurationException(
-                () -> SELECTOR.select(type),
+                () -> SELECTOR.select(comp(type)),
                 "Cannot select serializer for type '? extends java.lang.String'.\n" +
                 "Wildcard types cannot be serialized."
         );
@@ -433,7 +446,7 @@ class SerializerSelectorTest {
         ParameterizedType ptype = (ParameterizedType) getGenericType(A.class, "lw");
         Type type = ptype.getActualTypeArguments()[0];
         assertThrowsConfigurationException(
-                () -> SELECTOR.select(type),
+                () -> SELECTOR.select(comp(type)),
                 "Cannot select serializer for type '?'.\n" +
                 "Wildcard types cannot be serialized."
         );
@@ -446,9 +459,143 @@ class SerializerSelectorTest {
         }
         Type type = getGenericType(A.class, "t");
         assertThrowsConfigurationException(
-                () -> SELECTOR.select(type),
+                () -> SELECTOR.select(comp(type)),
                 "Cannot select serializer for type 'T'.\n" +
                 "Type variables cannot be serialized."
         );
     }
-}
+
+    static final class SerializeWithTests {
+        static class Z {
+            @SerializeWith(serializer = IdentitySerializer.class)
+            String string;
+            @SerializeWith(serializer = IdentitySerializer.class)
+            List<Set<String>> list1;
+            @SerializeWith(serializer = IdentitySerializer.class, nesting = 1)
+            List<Set<String>> list2;
+            @SerializeWith(serializer = IdentitySerializer.class, nesting = 2)
+            List<Set<String>> list3;
+            @SerializeWith(serializer = IdentitySerializer.class)
+            Set<List<String>> set1;
+            @SerializeWith(serializer = IdentitySerializer.class, nesting = 1)
+            Set<List<String>> set2;
+            @SerializeWith(serializer = IdentitySerializer.class, nesting = 2)
+            Set<List<String>> set3;
+            @SerializeWith(serializer = IdentitySerializer.class)
+            Map<Integer, Map<String, Double>> map1;
+            @SerializeWith(serializer = IdentitySerializer.class, nesting = 1)
+            Map<Integer, Map<String, Double>> map2;
+            @SerializeWith(serializer = IdentitySerializer.class, nesting = 2)
+            Map<Integer, Map<String, Double>> map3;
+            @SerializeWith(serializer = IdentitySerializer.class)
+            String[][] array1;
+            @SerializeWith(serializer = IdentitySerializer.class, nesting = 1)
+            String[][] array2;
+            @SerializeWith(serializer = IdentitySerializer.class, nesting = 2)
+            String[][] array3;
+        }
+
+        @Test
+        void selectCustomSerializerForField() {
+            var serializer = SELECTOR.select(comp(Z.class, "string"));
+            assertThat(serializer, instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForListsWithNesting0() {
+            var serializer = SELECTOR.select(comp(Z.class, "list1"));
+            assertThat(serializer, instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForListsWithNesting1() {
+            var serializer = (ListSerializer<?, ?>) SELECTOR.select(comp(Z.class, "list2"));
+            assertThat(serializer.getElementSerializer(), instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForListsWithNesting2() {
+            var serializer1 = (ListSerializer<?, ?>) SELECTOR.select(comp(Z.class, "list3"));
+            var serializer2 = (SetAsListSerializer<?, ?>) serializer1.getElementSerializer();
+            assertThat(serializer2.getElementSerializer(), instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForSetsWithNesting0() {
+            var serializer = SELECTOR.select(comp(Z.class, "set1"));
+            assertThat(serializer, instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForSetsWithNesting1() {
+            var serializer = (SetAsListSerializer<?, ?>) SELECTOR.select(comp(Z.class, "set2"));
+            assertThat(serializer.getElementSerializer(), instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForSetsWithNesting2() {
+            var serializer1 = (SetAsListSerializer<?, ?>) SELECTOR.select(comp(Z.class, "set3"));
+            var serializer2 = (ListSerializer<?, ?>) serializer1.getElementSerializer();
+            assertThat(serializer2.getElementSerializer(), instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForMapsWithNesting0() {
+            var serializer = SELECTOR.select(comp(Z.class, "map1"));
+            assertThat(serializer, instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForMapsWithNesting1() {
+            var serializer = (MapSerializer<?, ?, ?, ?>) SELECTOR.select(comp(Z.class, "map2"));
+            assertThat(serializer.getKeySerializer(), instanceOf(NumberSerializer.class));
+            assertThat(serializer.getValueSerializer(), instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForMapsWithNesting2() {
+            var serializer1 = (MapSerializer<?, ?, ?, ?>) SELECTOR.select(comp(Z.class, "map3"));
+            var serializer2 = (MapSerializer<?, ?, ?, ?>) serializer1.getValueSerializer();
+            assertThat(serializer2.getKeySerializer(), instanceOf(StringSerializer.class));
+            assertThat(serializer2.getValueSerializer(), instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForArraysWithNesting0() {
+            var serializer = SELECTOR.select(comp(Z.class, "array1"));
+            assertThat(serializer, instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForArraysWithNesting1() {
+            var serializer = (ArraySerializer<?, ?>) SELECTOR.select(comp(Z.class, "array2"));
+            assertThat(serializer.getElementSerializer(), instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerForArraysWithNesting2() {
+            var serializer1 = (ArraySerializer<?, ?>) SELECTOR.select(comp(Z.class, "array3"));
+            var serializer2 = (ArraySerializer<?, ?>) serializer1.getElementSerializer();
+            assertThat(serializer2.getElementSerializer(), instanceOf(IdentitySerializer.class));
+        }
+
+        @Test
+        void selectCustomSerializerWithInvalidNestingNotSelected() {
+            class A {
+                @SerializeWith(serializer = IdentitySerializer.class, nesting = -1)
+                String s1;
+                @SerializeWith(serializer = IdentitySerializer.class)
+                String s2;
+                @SerializeWith(serializer = IdentitySerializer.class, nesting = 1)
+                String s3;
+                @SerializeWith(serializer = IdentitySerializer.class, nesting = 2)
+                List<String> list;
+            }
+            assertThat(SELECTOR.select(comp(A.class, "s1")), instanceOf(StringSerializer.class));
+            assertThat(SELECTOR.select(comp(A.class, "s2")), instanceOf(IdentitySerializer.class));
+            assertThat(SELECTOR.select(comp(A.class, "s3")), instanceOf(StringSerializer.class));
+            var serializer = (ListSerializer<?, ?>) SELECTOR.select(comp(A.class, "list"));
+            assertThat(serializer.getElementSerializer(), instanceOf(StringSerializer.class));
+        }
+    }
+}

configlib-core/src/testFixtures/java/de/exlll/configlib/TestUtils.java

@@ -127,6 +127,19 @@ public final class TestUtils {
         }
     }
 
+    public static final class IdentitySerializer implements Serializer<Object, Object> {
+        @Override
+        public Object serialize(Object element) {
+            return element;
+        }
+
+        @Override
+        public Object deserialize(Object element) {
+            return element;
+        }
+    }
+
+
     @SafeVarargs
     public static <E> Set<E> asSet(E... elements) {
         return new LinkedHashSet<>(Arrays.asList(elements));