Support retrieving lower bound from TypeVariable in Collection attrib…

…ute (#580)

Support retrieving lower bound from TypeVariable in Collection attribute

src/main/java/org/eclipse/yasson/internal/ReflectionUtils.java

@@ -240,6 +240,14 @@ public static Type resolveTypeArguments(ParameterizedType typeToResolve, Type ty
                 }
                 resolvedArgs[i] = new VariableTypeInheritanceSearch()
                         .searchParametrizedType(typeToSearch, (TypeVariable<?>) variableType);
+
+                if (resolvedArgs[i] == null) {
+                    Type[] bounds = ((TypeVariable<?>) variableType).getBounds();
+                    if (Objects.nonNull(bounds) && bounds.length > 0) {
+                        resolvedArgs[i] = bounds[0];
+                    }
+                }
+
                 if (resolvedArgs[i] == null) {
                     if (typeToSearch instanceof Class) {
                         return Object.class;

src/test/java/org/eclipse/yasson/defaultmapping/generics/GenericsTest.java

@@ -29,6 +29,8 @@
 import jakarta.json.bind.Jsonb;
 import jakarta.json.bind.JsonbBuilder;
 import jakarta.json.bind.JsonbConfig;
+import java.lang.reflect.Field;
+import java.util.Collection;
 import org.eclipse.yasson.TestTypeToken;
 import org.eclipse.yasson.adapters.model.GenericBox;
 import org.eclipse.yasson.defaultmapping.generics.model.AnotherGenericTestClass;
@@ -54,6 +56,7 @@
 import org.junit.jupiter.api.Test;
 
 import static org.eclipse.yasson.Jsonbs.defaultJsonb;
+import org.eclipse.yasson.defaultmapping.generics.model.LowerBoundTypeVariableWithCollectionAttributeClass;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -446,6 +449,32 @@ public void multipleGenericLevels() {
         assertEquals(concreteContainer, finalGenericWrapper);
     }
 
+    @Test
+    public void lowerBoundTypeVariableInCollectionAttribute() throws Exception {
+
+        Shape shape = new Shape();
+        shape.setArea(5D);
+
+        AnotherGenericTestClass<Integer, Shape> anotherGenericTestClass = new AnotherGenericTestClass<>();
+        anotherGenericTestClass.field1 = 6;
+        anotherGenericTestClass.field2 = shape;
+
+        List<AnotherGenericTestClass<Integer, Shape>> asList = Arrays.asList(anotherGenericTestClass);
+
+        Jsonb jsonb = JsonbBuilder.create();
+        String toJson = jsonb.toJson(asList);
+
+        Field field = LowerBoundTypeVariableWithCollectionAttributeClass.class.getDeclaredField("value");
+
+        Type genericType = field.getGenericType();
+
+        List<AnotherGenericTestClass<Integer, Shape>> fromJson = jsonb.fromJson(toJson, genericType);
+
+        assertEquals(5, fromJson.get(0).field2.getArea());
+        assertEquals(6, fromJson.get(0).field1);
+
+    }
+
     public interface FunctionalInterface<T> {
         T getValue();
     }

src/test/java/org/eclipse/yasson/defaultmapping/generics/model/LowerBoundTypeVariableWithCollectionAttributeClass.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2015, 2022 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0,
+ * or the Eclipse Distribution License v. 1.0 which is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
+ */
+
+package org.eclipse.yasson.defaultmapping.generics.model;
+
+import java.util.Collection;
+
+/**
+ * @author Alessandro Moscatelli
+ */
+public class LowerBoundTypeVariableWithCollectionAttributeClass<T extends Shape> {
+
+    private Collection<AnotherGenericTestClass<Integer, T>> value;
+
+    public Collection<AnotherGenericTestClass<Integer, T>> getValue() {
+        return value;
+    }
+
+    public void setValue(Collection<AnotherGenericTestClass<Integer, T>> value) {
+        this.value = value;
+    }
+
+}