By Nobukimi Sasaki (2023-04-24) Continued from API Gateway + Lambda + DynamoDB (Configuration)

Dependency for AWS Lambda

        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-lambda-java-core</artifactId>
            <version>1.1.0</version>
        </dependency>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-lambda-java-events</artifactId>
            <version>2.0.2</version>
        </dependency>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-java-sdk-dynamodb</artifactId>
            <version>1.11.271</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.14.1</version>
        </dependency>

The main class receive the request:APIGatewayProxyRequestEvent::getHttpMethod.

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBScanExpression;
import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;
import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;

public class LambdaHandler implements RequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyResponseEvent> {

    @Override
    public APIGatewayProxyResponseEvent handleRequest ( APIGatewayProxyRequestEvent apiGatewayRequest, Context context ) {

        EmployeeService employeeService = new EmployeeService();

        switch (apiGatewayRequest.getHttpMethod()) {

            case "POST":
                return employeeService.saveEmployee( apiGatewayRequest, context );

            case "GET":
                if (apiGatewayRequest.getPathParameters() != null) {
                    return employeeService.getEmployeeById( apiGatewayRequest, context );
                }
                return employeeService.getEmployees( apiGatewayRequest, context );
            case "DELETE":
                if (apiGatewayRequest.getPathParameters() != null) {
                    return employeeService.deleteEmployeeById( apiGatewayRequest, context );
                }
            default:
                throw new Error( "Unsupported Methods:::" + apiGatewayRequest.getHttpMethod() );

        }
    }
}

The 1st parameter, APIGatewayProxyRequestEvent contains:
This getHttpMethod returns String httpMethod that is “GET”, “POST”, “PUT”,,,,

The 2nd parameter, Context contains:

The response class “APIGatewayProxyResponseEvent” contains:

Saving data:

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBScanExpression;
import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;
import com.app.easy2excel.entity.Employee;

import java.util.List;
import java.util.Map;

public class EmployeeService {

    private DynamoDBMapper dynamoDBMapper;
    private static String jsonBody = null;

    public APIGatewayProxyResponseEvent saveEmployee ( APIGatewayProxyRequestEvent apiGatewayRequest, Context context ) {
        initDynamoDB();
        Employee employee = Utility.convertStringToObj( apiGatewayRequest.getBody(), context );
        dynamoDBMapper.save( employee );
        jsonBody = Utility.convertObjToString( employee, context );
        context.getLogger().log( "data saved successfully to dynamodb:::" + jsonBody );
        return createAPIResponse( jsonBody, 201, Utility.createHeaders() );
    }
....

Within the createAPIResponse, it returns the APIGatewayProxyResponseEvent:

    private APIGatewayProxyResponseEvent createAPIResponse ( String body, int statusCode, Map<String, String> headers ) {
        APIGatewayProxyResponseEvent responseEvent = new APIGatewayProxyResponseEvent();
        responseEvent.setBody( body );
        responseEvent.setHeaders( headers );
        responseEvent.setStatusCode( statusCode );
        return responseEvent;
    }

The entity model:

import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBAttribute;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBHashKey;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBTable;

@DynamoDBTable(tableName = "employee")
public class Employee {

    @DynamoDBHashKey(attributeName = "empId")
    private String empId;

    @DynamoDBAttribute(attributeName = "name")
    private String name;

    @DynamoDBAttribute(attributeName = "email")
    private String email;
....

How to deploy the code:
Go to intellij terminal, as command line >mvn clean install

The jar file is created under target:

After specifying the built jar file, then upload.
Lambda > Functions > RestApiLambda (your function name) … There is a “Upload From” button:

Scroll down and under Runtime settings > Edit

Edit the header info as:

1. Package path
2. Class name
3. Method name
Then Save! Now the API is ready to run

In Postman, the POST request went succesfully:

Go to dashboard DynamoDB > Tables

1. Tables
2. Check
3. Click the table name
4. Explore the items
5. You will see the data created