Add ObjectArrayToJsonConverter interface specifying a contract to convert an array of Objects to JSON.

Resolves gh-67.

spring-geode/src/main/java/org/springframework/geode/data/json/converter/ObjectArrayToJsonConverter.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+package org.springframework.geode.data.json.converter;
+
+import java.util.Arrays;
+
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.data.gemfire.util.ArrayUtils;
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
+
+/**
+ * A Spring {@link Converter} interface extension defining a contract to convert
+ * an {@link Iterable} or an array of {@link Object Objects} into {@link String JSON}.
+ *
+ * @author John Blum
+ * @see java.lang.FunctionalInterface
+ * @see java.lang.Iterable
+ * @see java.lang.Object
+ * @see java.lang.String
+ * @see org.springframework.core.convert.converter.Converter
+ * @since 1.3.0
+ */
+@FunctionalInterface
+public interface ObjectArrayToJsonConverter extends Converter<Iterable<?>, String> {
+
+	/**
+	 * Converts the given array of {@link Object Objects} into {@link String JSON}.
+	 *
+	 * @param array array of {@link Object Objects} to convert into {@link String JSON}.
+	 * @return {@link String JSON} generated from the given array of {@link Object Objects}.
+	 * @see #convert(Object)
+	 */
+	default @NonNull String convert(@Nullable Object... array) {
+		return convert(Arrays.asList(ArrayUtils.nullSafeArray(array, Object.class)));
+	}
+}

spring-geode/src/test/java/org/springframework/geode/data/json/converter/ObjectArrayToJsonConverterUnitTests.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+package org.springframework.geode.data.json.converter;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.doCallRealMethod;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import java.util.Arrays;
+import java.util.Collections;
+
+import org.junit.Test;
+import org.mockito.ArgumentMatchers;
+
+import example.app.crm.model.Customer;
+
+/**
+ * Unit Tests for {@link ObjectArrayToJsonConverter}.
+ *
+ * @author John Blum
+ * @see org.junit.Test
+ * @see org.mockito.Mockito
+ * @see org.springframework.geode.data.json.converter.ObjectArrayToJsonConverter
+ * @since 1.3.0
+ */
+public class ObjectArrayToJsonConverterUnitTests {
+
+	@Test
+	public void convertObjectArrayCallsConvertIterable() {
+
+		String json = "[{ \"name\": \"Jon Doe\"}, { \"name\": \"Jane Doe\"}]";
+
+		ObjectArrayToJsonConverter mockConverter = mock(ObjectArrayToJsonConverter.class);
+
+		doCallRealMethod().when(mockConverter).convert(ArgumentMatchers.<Object[]>any());
+		doReturn(json).when(mockConverter).convert(any(Iterable.class));
+
+		Customer jonDoe = Customer.newCustomer(1L, "Jon Doe");
+		Customer janeDoe = Customer.newCustomer(2L, "Jane Doe");
+
+		assertThat(mockConverter.convert(jonDoe, janeDoe)).isEqualTo(json);
+
+		verify(mockConverter, times(1)).convert(eq(Arrays.asList(jonDoe, janeDoe)));
+	}
+
+	@Test
+	public void convertEmptyObjectArrayToEmptyJsonArray() {
+
+		String json = "[]";
+
+		ObjectArrayToJsonConverter mockConverter = mock(ObjectArrayToJsonConverter.class);
+
+		doCallRealMethod().when(mockConverter).convert(ArgumentMatchers.<Object[]>any());
+		doReturn(json).when(mockConverter).convert(any(Iterable.class));
+
+		assertThat(mockConverter.convert()).isEqualTo(json);
+
+		verify(mockConverter, times(1)).convert(eq(Collections.emptyList()));
+	}
+
+	@Test
+	public void convertNullObjectArrayIsNullSafeAndReturnsEmptyJsonArray() {
+
+		String json = "[]";
+
+		ObjectArrayToJsonConverter mockConverter = mock(ObjectArrayToJsonConverter.class);
+
+		doCallRealMethod().when(mockConverter).convert(ArgumentMatchers.<Object[]>any());
+		doReturn(json).when(mockConverter).convert(any(Iterable.class));
+
+		assertThat(mockConverter.convert((Object[]) null)).isEqualTo(json);
+
+		verify(mockConverter, times(1)).convert(eq(Collections.emptyList()));
+	}
+}