Example lightweight DynamoDB integration that limits AWS Lambda cold starts for Java. It is pure-Java8 implementation without third-part libraries that increases fat JAR size and cold starts time.
It uses DynamoDB Low-Level API described on https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_Operations_Amazon_DynamoDB.html
This example assumes that there is DynamoDB Table Test created with Primary Key uuid with String type. It uses JSR-374 JSONP as JSON parser (https://javaee.github.io/jsonp/) for better readibility during preparing JSON requests.
JSON request in the following format:
{
"uuid": "NEW_UUID"
}Maven dependencies:
<dependencies>
<dependency>
<groupId>com.amazonaws</groupId>
<artifactId>aws-lambda-java-core</artifactId>
<version>1.2.0</version>
</dependency>
<dependency>
<groupId>pl.r6lab.aws</groupId>
<artifactId>rapid-dynamodb</artifactId>
<version>0.1.0</version>
</dependency>
<dependency>
<groupId>javax.json</groupId>
<artifactId>javax.json-api</artifactId>
<version>1.1.2</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.json</artifactId>
<version>1.1.2</version>
</dependency>
</dependencies>Example AWS Lambda handler that accepts request with uuid and after successful PutItem operation performs Scan and return all items:
public class RapidDynamoDBLambda implements RequestHandler<Map<String, String>, String> {
public String handleRequest(Map<String, String> event, Context context) {
RapidDynamoDBClient rapidDynamoDBClient = RapidDynamoDBClient.envAware();
DynamoDBRequest putItemRequest = DynamoDBRequest.of(Action.PUT_ITEM, getItemJson(event.get("uuid")));
DynamoDBResponse response = rapidDynamoDBClient.execute(putItemRequest);
if (response.isSuccess()) {
DynamoDBRequest scanRequest = DynamoDBRequest.of(Action.SCAN, scanJson());
return rapidDynamoDBClient.execute(scanRequest).getPayload();
} else {
context.getLogger().log(response.getPayload());
throw new IllegalStateException("Unable to put item into DynamoDB");
}
}
private String getItemJson(String uuid) {
JsonObject getItemJson = Json.createObjectBuilder()
.add("TableName", "Test")
.add("Item", Json.createObjectBuilder()
.add("uuid", Json.createObjectBuilder()
.add("S", uuid)))
.build();
return getItemJson.toString();
}
private String scanJson() {
JsonObject getItemJson = Json.createObjectBuilder()
.add("TableName", "Test")
.add("ReturnConsumedCapacity", "TOTAL")
.build();
return getItemJson.toString();
}
}