template.yaml<\/span>. It describes the serverless application. Again unfortunately SAM CLI hard codes the word “hello world” everywhere in this template. So let’s first modify this as per our needs so that it looks like the following:<\/p>\n\n\n\nAWSTemplateFormatVersion: '2010-09-09'\nTransform: AWS::Serverless-2016-10-31\nDescription: >\n java-sam-api-example\n\n Sample SAM Template for java-sam-api-example\n\nGlobals:\n Function:\n Timeout: 20\n\nResources:\n SAMExampleFunction:\n Type: AWS::Serverless::Function \n Properties:\n CodeUri: SAMExampleFunction\n Handler: samexample.App::handleRequest\n Runtime: java11\n Architectures:\n - x86_64\n MemorySize: 512\n Environment: \n Variables:\n PARAM1: VALUE\n JAVA_TOOL_OPTIONS: -XX:+TieredCompilation -XX:TieredStopAtLevel=1\n Events:\n SAMExample:\n Type: Api \n Properties:\n Path: \/hello\n Method: get\n\nOutputs:\n SAMExampleApi:\n Description: \"API Gateway endpoint URL for Prod stage for Hello World function\"\n Value: !Sub \"https:\/\/${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com\/Prod\/hello\/\"\n SAMExampleFunction:\n Description: \"Hello World Lambda Function ARN\"\n Value: !GetAtt SAMExampleFunction.Arn\n SAMExampleFunctionIamRole:\n Description: \"Implicit IAM Role created for Hello World function\"\n Value: !GetAtt SAMExampleFunctionRole.Arn\n<\/pre>\n\n\n\nAt this point you can build and run the application locally using the commands:<\/p>\n\n\n
sam build\nsam local start-api<\/code><\/span><\/pre>\n\n\nNow of you test the API using following command:<\/p>\n\n\n
curl --location --request GET 'http:\/\/127.0.0.1:3000\/hello'<\/span><\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\nYou should see following output:<\/p>\n\n\n
{ \"message\"<\/span>: \"hello world\"<\/span>, \"location\"<\/span>: \"103.254.55.17\"<\/span> }<\/code><\/span>Code language:<\/span> JSON \/ JSON with Comments<\/span> (<\/span>json<\/span>)<\/span><\/small><\/pre>\n\n\nAs you may already know, to expose a lambda function as HTTP endpoint, you need AWS API Gateway to be configured. In this “hello world” template, it uses an implicit gateway resource named: ServerlessRestApi<\/span>. As it turns out to support CORS you need to modify the API gateway resource. So we can’t use this implicit API gateway resource. So we will create a API resource in our template.yaml file:<\/p>\n\n\n\nAWSTemplateFormatVersion: '2010-09-09'\nTransform: AWS::Serverless-2016-10-31\nDescription: >\n java-sam-api-example\n\n Sample SAM Template for java-sam-api-example\n\nGlobals:\n Function:\n Timeout: 20\n\nResources:\n SAMExampleApi:\n Type: AWS::Serverless::Api\n Properties:\n StageName: Prod\n Cors:\n AllowMethods: \"'GET,POST,OPTIONS,PUT,PATCH,DELETE'\"\n AllowHeaders: \"'content-type'\"\n AllowOrigin: \"'*'\"\n AllowCredentials: \"'*'\"\n SAMExampleFunction:\n Type: AWS::Serverless::Function\n Properties:\n CodeUri: SAMExampleFunction\n Handler: samexample.App::handleRequest\n Runtime: java11\n Architectures:\n - x86_64\n MemorySize: 512\n Environment:\n Variables:\n PARAM1: VALUE\n JAVA_TOOL_OPTIONS: -XX:+TieredCompilation -XX:TieredStopAtLevel=1\n Events:\n SAMExample:\n Type: Api\n Properties:\n Path: \/hello\n Method: get\n RestApiId: !Ref SAMExampleApi\n\nOutputs:\n SAMExampleApi:\n Description: \"API Gateway endpoint URL for Prod stage for Hello World function\"\n Value: !Sub \"https:\/\/${SAMExampleApi}.execute-api.${AWS::Region}.amazonaws.com\/Prod\/hello\/\"\n SAMExampleFunction:\n Description: \"Hello World Lambda Function ARN\"\n Value: !GetAtt SAMExampleFunction.Arn\n SAMExampleFunctionIamRole:\n Description: \"Implicit IAM Role created for Hello World function\"\n Value: !GetAtt SAMExampleFunctionRole.Arn\n<\/pre>\n\n\n\nHere as you can notice we have added a new resource:<\/p>\n\n\n\n
SAMExampleApi:\n Type: AWS::Serverless::Api\n Properties:\n StageName: Prod\n Cors:\n AllowMethods: \"'GET,POST,OPTIONS,PUT,PATCH,DELETE'\"\n AllowHeaders: \"'content-type,X-Custom-Header'\"\n AllowOrigin: \"'*'\"\n AllowCredentials: \"'*'\"\n<\/pre>\n\n\n\nHere I am using all HTTP methods in the “AllowMethods” <\/span> and allowing “*” (any) origin in the “AllowOrigin” header. However for production deployments you should restrict the HTTP methods to the methods your API supports and the origin to your “production” domain only. In the AllowHeaders, you need to mention all the custom headers your API supports.<\/p>\n\n\n\nThen in the Events under “SAMExampleFunction” we have added new line:<\/p>\n\n\n
RestApiId: !Ref SAMExampleApi<\/code><\/span><\/pre>\n\n\nAlso in the “Outputs” section we have updated the “Value” for the “SAMExampleApi” like follows:<\/p>\n\n\n
Value: !Sub \"https:\/\/${SAMExampleApi}.execute-api.${AWS::Region}.amazonaws.com\/Prod\/hello\/\"<\/span><\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\nTo support CORS we will need to make some changes to our Java code also. So we need to add the following lines in the “handleReuest” <\/span> method of the App.java file:<\/p>\n\n\nheaders.put(\"Access-Control-Allow-Origin\"<\/span>, \"*\"<\/span>);\nheaders.put(\"Access-Control-Allow-Methods\"<\/span>, \"GET,POST,OPTIONS,PUT,PATCH,DELETE\"<\/span>);\nheaders.put(\"Access-Control-Allow-Headers\"<\/span>, \"content-type,X-Custom-Header\"<\/span>);<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\njust below the line:<\/p>\n\n\n
headers.put(\"X-Custom-Header\"<\/span>, \"application\/json\"<\/span>);<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\nAt this point we are ready to deploy our application so let’s run the following commands:<\/p>\n\n\n
sam build\nsam deploy --guided<\/code><\/span><\/pre>\n\n\nAt this point SAM CLI will ask you a bunch of questions about how to deploy your serverless application. Here are the answers I provided:<\/p>\n\n\n
Setting default<\/span> arguments for<\/span> 'sam deploy'<\/span>\n=========================================\nStack Name [sam-app]: java-sam-api-example \nAWS Region [us-west-2<\/span>]:\n