examples-lambda.md

Invoking, Listing, and Deleting Lambda Functions

This section provides examples of programming with the Lambda service client by using the AWS SDK for Java. To learn how to create a Lambda function, see How to Create AWS Lambda functions.

Topics

• Invoke a function
• List functions
• Delete a function

Invoke a function

You can invoke a Lambda function by creating an AWSLambda object and invoking its invoke method. Create an InvokeRequest object to specify additional information such as the function name and the payload to pass to the Lambda function. Function names appear as arn:aws:lambda:us-east-1:555556330391:function:HelloFunction. You can retrieve the value by looking at the function in the AWS Management Console.

To pass payload data to a function, invoke the InvokeRequest object’s withPayload method and specify a String in JSON format, as shown in the following code example.

Imports

import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.lambda.AWSLambda;
import com.amazonaws.services.lambda.AWSLambdaClientBuilder;
import com.amazonaws.services.lambda.model.InvokeRequest;
import com.amazonaws.services.lambda.model.InvokeResult;
import com.amazonaws.services.lambda.model.ServiceException;

import java.nio.charset.StandardCharsets;

Code

The following code example demonstrates how to invoke a Lambda function.

        String functionName = args[0];

        InvokeRequest invokeRequest = new InvokeRequest()
                .withFunctionName(functionName)
                .withPayload("{\n" +
                        " \"Hello \": \"Paris\",\n" +
                        " \"countryCode\": \"FR\"\n" +
                        "}");
        InvokeResult invokeResult = null;

        try {
            AWSLambda awsLambda = AWSLambdaClientBuilder.standard()
                    .withCredentials(new ProfileCredentialsProvider())
                    .withRegion(Regions.US_WEST_2).build();

            invokeResult = awsLambda.invoke(invokeRequest);

            String ans = new String(invokeResult.getPayload().array(), StandardCharsets.UTF_8);

            //write out the return value
            System.out.println(ans);

        } catch (ServiceException e) {
            System.out.println(e);
        }

        System.out.println(invokeResult.getStatusCode());

See the complete example on Github.

List functions

Build an AWSLambda object and invoke its listFunctions method. This method returns a ListFunctionsResult object. You can invoke this object’s getFunctions method to return a list of FunctionConfiguration objects. You can iterate through the list to retrieve information about the functions. For example, the following Java code example shows how to get each function name.

Imports

import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.lambda.AWSLambda;
import com.amazonaws.services.lambda.AWSLambdaClientBuilder;
import com.amazonaws.services.lambda.model.FunctionConfiguration;
import com.amazonaws.services.lambda.model.ListFunctionsResult;
import com.amazonaws.services.lambda.model.ServiceException;
import java.util.Iterator;
import java.util.List;

Code

The following Java code example demonstrates how to retrieve a list of Lambda function names.

        ListFunctionsResult functionResult = null;

        try {
            AWSLambda awsLambda = AWSLambdaClientBuilder.standard()
                    .withCredentials(new ProfileCredentialsProvider())
                    .withRegion(Regions.US_WEST_2).build();

            functionResult = awsLambda.listFunctions();

            List<FunctionConfiguration> list = functionResult.getFunctions();

            for (Iterator iter = list.iterator(); iter.hasNext(); ) {
                FunctionConfiguration config = (FunctionConfiguration)iter.next();

                System.out.println("The function name is "+config.getFunctionName());
            }

        } catch (ServiceException e) {
            System.out.println(e);
        }

See the complete example on Github.

Delete a function

Build an AWSLambda object and invoke its deleteFunction method. Create a DeleteFunctionRequest object and pass it to the deleteFunction method. This object contains information such as the name of the function to delete. Function names appear as arn:aws:lambda:us-east-1:555556330391:function:HelloFunction. You can retrieve the value by looking at the function in the AWS Management Console.

Imports

import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.lambda.AWSLambda;
import com.amazonaws.services.lambda.AWSLambdaClientBuilder;
import com.amazonaws.services.lambda.model.ServiceException;
import com.amazonaws.services.lambda.model.DeleteFunctionRequest;

Code

The following Java code demonstrates how to delete a Lambda function.

        String functionName = args[0];
        try {
            AWSLambda awsLambda = AWSLambdaClientBuilder.standard()
                    .withCredentials(new ProfileCredentialsProvider())
                    .withRegion(Regions.US_WEST_2).build();

            DeleteFunctionRequest delFunc = new DeleteFunctionRequest();
            delFunc.withFunctionName(functionName);

            //Delete the function
            awsLambda.deleteFunction(delFunc);
            System.out.println("The function is deleted");

        } catch (ServiceException e) {
            System.out.println(e);
        }

See the complete example on Github.