GH-1043 Add support for communicating type via MimeType parameter for JsonMessageConverter

Resolves #1043

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/config/JsonMessageConverterTests.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2023-2023 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.cloud.function.context.config;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.cloud.function.json.JacksonMapper;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHeaders;
+import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.util.MimeTypeUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ *
+ * @author Oleg Zhurakousky
+ *
+ */
+public class JsonMessageConverterTests {
+
+	@Test
+	public void testTypeInference() {
+		JsonMessageConverter converter = new JsonMessageConverter(new JacksonMapper(new ObjectMapper()));
+
+		Message<String> message = MessageBuilder.withPayload("{\"name\":\"bill\"}").build();
+		assertThat(converter.canConvertFrom(message, Person.class)).isTrue();
+
+		message = MessageBuilder.withPayload("{\"name\":\"bill\"}").setHeader(MessageHeaders.CONTENT_TYPE, MimeTypeUtils.APPLICATION_JSON).build();
+		assertThat(converter.canConvertFrom(message, Person.class)).isTrue();
+		assertThat(converter.canConvertFrom(message, Object.class)).isFalse();
+		assertThat(converter.canConvertFrom(message, null)).isFalse();
+		assertThat(converter.convertFromInternal(message, Person.class, null)).isInstanceOf(Person.class);
+
+		message = MessageBuilder.withPayload("{\"name\":\"bill\"}")
+				.setHeader(MessageHeaders.CONTENT_TYPE, MimeTypeUtils.APPLICATION_JSON.toString() + ";type=" + Person.class.getName()).build();
+		assertThat(converter.canConvertFrom(message, Object.class)).isTrue();
+		assertThat(converter.canConvertFrom(message, null)).isTrue();
+		assertThat(converter.convertFromInternal(message, Person.class, null)).isInstanceOf(Person.class);
+		assertThat(converter.convertFromInternal(message, Object.class, null)).isInstanceOf(Person.class);
+		assertThat(converter.convertFromInternal(message, null, null)).isInstanceOf(Person.class);
+	}
+
+	public static class Person {
+		private String name;
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+	}
+}