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.
Invoke a Lambda 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-west-2:555556330391:function:HelloFunction. You can retrieve the value by looking at the function in the AWS 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 Lambda 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 Lambda 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-west-2:555556330391:function:HelloFunction. You can retrieve the value by looking at the function in the AWS 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