feat(s3): add ParameterizedTypeReference support to S3Template

spring-cloud-aws-s3/src/main/java/io/awspring/cloud/s3/Jackson2JsonS3ObjectConverter.java

@@ -17,6 +17,7 @@
 
 import java.io.InputStream;
 import org.springframework.util.Assert;
+import org.springframework.core.ParametrizedTypeReference;
 import software.amazon.awssdk.core.sync.RequestBody;
 import tools.jackson.core.JacksonException;
 import tools.jackson.databind.json.JsonMapper;
@@ -58,6 +59,19 @@ public <T> T read(InputStream is, Class<T> clazz) {
 		}
 	}
 
+	@Override
+	public <T> T read(InputStream is, ParametrizedTypeReference<T> valueTypeRef) {
+		Assert.notNull(is, "InputStream is required");
+		Assert.notNull(valueTypeRef, "valueTypeRef is required");
+		try {
+			return jsonMapper.readValue(is, jsonMapper.constructType(valueTypeRef.getType()));
+		}
+		catch (IOException e) {
+			throw new S3Exception("Failed to deserialize object from JSON", e);
+		}
+	}
+
+
 	@Override
 	public String contentType() {
 		return "application/json";

spring-cloud-aws-s3/src/main/java/io/awspring/cloud/s3/LegacyJackson2JsonS3ObjectConverter.java

@@ -20,6 +20,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import org.springframework.util.Assert;
+import org.springframework.core.ParameterizedTypeReference;
 import software.amazon.awssdk.core.sync.RequestBody;
 
 /**
@@ -60,6 +61,18 @@ public <T> T read(InputStream is, Class<T> clazz) {
 		}
 	}
 
+	@Override
+	public <T> T read(InputStream is, ParametrizedTypeReference<T> valueTypeRef) {
+		Assert.notNull(is, "InputStream is required");
+		Assert.notNull(valueTypeRef, "valueTypeRef is required");
+		try {
+			return objectMapper.readValue(is, objectMapper.constructType(valueTypeRef.getType()));
+		}
+		catch (IOException e) {
+			throw new S3Exception("Failed to deserialize object from JSON", e);
+		}
+	}
+
 	@Override
 	public String contentType() {
 		return "application/json";

spring-cloud-aws-s3/src/main/java/io/awspring/cloud/s3/S3ObjectConverter.java

@@ -16,6 +16,7 @@
 package io.awspring.cloud.s3;
 
 import java.io.InputStream;
+import org.springframework.core.ParameterizedTypeReference;
 import software.amazon.awssdk.core.sync.RequestBody;
 
 /**
@@ -43,6 +44,15 @@ public interface S3ObjectConverter {
 	 */
 	<T> T read(InputStream is, Class<T> clazz);
 
+	/**
+	 * Reads S3 object from the input stream into a Java object.
+	 * @param is - the input stream
+	 * @param valueTypeRef - the type reference of the object
+	 * @param <T> - the the type of the object
+	 * @return deserialized object
+	 */
+	<T> T read(InputStream is, ParameterizedTypeReference<T> valueTypeRef);
+
 	/**
 	 * Supported content type.
 	 *

spring-cloud-aws-s3/src/main/java/io/awspring/cloud/s3/S3Operations.java

@@ -20,6 +20,7 @@
 import java.time.Duration;
 import java.util.List;
 import org.jspecify.annotations.Nullable;
+import org.springframework.core.ParameterizedTypeReference;
 import software.amazon.awssdk.services.s3.S3Client;
 import software.amazon.awssdk.services.s3.model.CreateBucketResponse;
 
@@ -132,6 +133,17 @@ public interface S3Operations {
 	 */
 	<T> T read(String bucketName, String key, Class<T> clazz);
 
+	/**
+	 * Reads a Java object from a S3 bucket. Uses {@link S3ObjectConverter} for deserialization.
+	 *
+	 * @param bucketName - the bucket name
+	 * @param key - the object key
+	 * @param valueTypeRef - the parameterized type reference of the read object
+	 * @param <T> - the type of the read object
+	 * @return an object
+	 */
+	<T> T read(String bucketName, String key, ParameterizedTypeReference<T> valueTypeRef);
+
 	/**
 	 * Uploads data from an input stream to a S3 bucket.
 	 *

spring-cloud-aws-s3/src/main/java/io/awspring/cloud/s3/S3Template.java

@@ -21,6 +21,7 @@
 import java.time.Duration;
 import java.util.List;
 import org.jspecify.annotations.Nullable;
+import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.util.Assert;
 import org.springframework.util.StreamUtils;
 import software.amazon.awssdk.services.s3.S3Client;
@@ -165,6 +166,21 @@ public <T> T read(String bucketName, String key, Class<T> clazz) {
 		}
 	}
 
+	@Override
+	public <T> T read(String bucketName, String key, ParameterizedTypeReference<T> valueTypeRef) {
+		Assert.notNull(bucketName, "bucketName is required");
+		Assert.notNull(key, "key is required");
+		Assert.notNull(valueTypeRef, "valueTypeRef is required");
+
+		try (InputStream is = s3Client.getObject(r -> r.bucket(bucketName).key(key))) {
+			return s3ObjectConverter.read(is, valueTypeRef);
+		}
+		catch (Exception e) {
+			throw new S3Exception(
+					String.format("Failed to read object with a key '%s' from bucket '%s'", key, bucketName), e);
+		}
+	}
+
 	@Override
 	public S3Resource upload(String bucketName, String key, InputStream inputStream,
 			@Nullable ObjectMetadata objectMetadata) {

spring-cloud-aws-s3/src/test/java/io/awspring/cloud/s3/S3TemplateIntegrationTests.java

@@ -41,6 +41,7 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.util.StreamUtils;
+import org.springframework.core.ParameterizedTypeReference;
 import software.amazon.awssdk.core.ResponseInputStream;
 import software.amazon.awssdk.core.sync.RequestBody;
 import software.amazon.awssdk.http.HttpStatusCode;
@@ -232,6 +233,20 @@ void readsObject() {
 		assertThat(person.lastName).isEqualTo("Doe");
 	}
 
+	@Test
+	void readsParameterizedTypeObject() {
+		client.putObject(r -> r.bucket(BUCKET_NAME).key("persons.json"),
+				RequestBody.fromString("[{\"firstName\":\"John\",\"lastName\":\"Doe\"}]"));
+
+		List<Person> persons = s3Template.read(BUCKET_NAME, "persons.json", new ParamaterizedTypeReference<List<Person>>(){});
+
+		assertThat(persons.size()).isEqualTo(1);
+
+		Person person = persons.get(0);
+		assertThat(person.firstName).isEqualTo("John");
+		assertThat(person.lastName).isEqualTo("Doe");
+	}
+
 	@Test
 	void uploadsFile() throws IOException {
 		try (InputStream is = new ByteArrayInputStream("hello".getBytes(StandardCharsets.UTF_8))) {