在上一篇文章中，我们实现了基于Java的aws lambda函数，并使用CloudFront进行了部署。 由于我们已经设置了lambda函数，因此我们将使用AWS API Gateway将其与http端点集成。

Amazon API Gateway是一项完全托管的服务，使开发人员可以轻松地创建，发布，维护，监控和保护各种规模的API。 在AWS管理控制台中单击几下，您可以创建一个API，充当应用程序从后端服务访问数据，业务逻辑或功能（例如在Amazon Elastic Compute Cloud上运行的工作负载）的“前门”。 （Amazon EC2），在AWS Lambda或任何Web应用程序上运行的代码

对于此示例，将API网关想象为一个HTTP连接器。 我们将更改原始功能以实现划分。

package com.gkatzioura.deployment.lambda;import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;import java.math.BigDecimal;
import java.util.Map;
import java.util.logging.Logger;/*** Created by gkatzioura on 9/10/2016.*/
public class RequestFunctionHandler implements RequestHandler<Map<String,String>,String> {private static final String NUMERATOR_KEY = "numerator";private static final String DENOMINATOR_KEY = "denominator";private static final Logger LOGGER = Logger.getLogger(RequestFunctionHandler.class.getName());public String handleRequest(Map <String,String> values, Context context) {LOGGER.info("Handling request");if(!values.containsKey(NUMERATOR_KEY)||!values.containsKey(DENOMINATOR_KEY)) {return "You need both numberator and denominator";}try {BigDecimal numerator = new BigDecimal(values.get(NUMERATOR_KEY));BigDecimal denominator= new BigDecimal(values.get(DENOMINATOR_KEY));return  numerator.divide(denominator).toString();} catch (Exception e) {return "Please provide valid values";}}}

然后，我们将更改lambda代码并在s3上对其进行更新。

aws s3 cp build/distributions/JavaLambdaDeployment.zip s3://lambda-functions/JavaLambdaDeployment.zip

下一步是更新我们的CloudFormation模板，并将api网关转发请求添加到我们的lambda函数。

首先，我们必须声明我们的Rest API

"AGRA16PAA": {"Type": "AWS::ApiGateway::RestApi","Properties": {"Name": "CalculationApi"}}

然后，我们需要添加一个休息资源。 在DependsOn元素内，我们可以看到rest api的ID。 因此，cloudwatch将在创建其余api后创建资源。

"AGR2JDQ8": {"Type": "AWS::ApiGateway::Resource","Properties": {"RestApiId": {"Ref": "AGRA16PAA"},"ParentId": {"Fn::GetAtt": ["AGRA16PAA","RootResourceId"]},"PathPart": "divide"},"DependsOn": ["AGRA16PAA"]}

另一个关键部分是添加权限，以便能够调用我们的lambda函数。

"LPI6K5": {"Type": "AWS::Lambda::Permission","Properties": {"Action": "lambda:invokeFunction","FunctionName": {"Fn::GetAtt": ["LF9MBL", "Arn"]},"Principal": "apigateway.amazonaws.com","SourceArn": {"Fn::Join": ["",["arn:aws:execute-api:", {"Ref": "AWS::Region"}, ":", {"Ref": "AWS::AccountId"}, ":", {"Ref": "AGRA16PAA"}, "/*"]]}}}

最后一步是添加api网关方法，以便能够从api网关调用我们的lambda函数。 此外，我们将添加api网关部署说明。

"Deployment": {"Type": "AWS::ApiGateway::Deployment","Properties": {"RestApiId": { "Ref": "AGRA16PAA" },"Description": "First Deployment","StageName": "StagingStage"},"DependsOn" : ["AGM25KFD"]},"AGM25KFD": {"Type": "AWS::ApiGateway::Method","Properties": {"AuthorizationType": "NONE","HttpMethod": "POST","ResourceId": {"Ref": "AGR2JDQ8"},"RestApiId": {"Ref": "AGRA16PAA"},"Integration": {"Type": "AWS","IntegrationHttpMethod": "POST","IntegrationResponses": [{"StatusCode": 200}],"Uri": {"Fn::Join": ["",["arn:aws:apigateway:",{"Ref": "AWS::Region"},":lambda:path/2015-03-31/functions/",{"Fn::GetAtt": ["LF9MBL", "Arn"]},"/invocations"]]}},"MethodResponses": [{"StatusCode": 200}]}

因此，我们最终获得了新的cloudwatch配置。

{"AWSTemplateFormatVersion": "2010-09-09","Resources": {"LF9MBL": {"Type": "AWS::Lambda::Function","Properties": {"Code": {"S3Bucket": "lambda-functions","S3Key": "JavaLambdaDeployment.zip"},"FunctionName": "SimpleRequest","Handler": "com.gkatzioura.deployment.lambda.RequestFunctionHandler","MemorySize": 128,"Role": "arn:aws:iam::274402012893:role/lambda_basic_execution","Runtime": "java8"}},"Deployment": {"Type": "AWS::ApiGateway::Deployment","Properties": {"RestApiId": { "Ref": "AGRA16PAA" },"Description": "First Deployment","StageName": "StagingStage"},"DependsOn" : ["AGM25KFD"]},"AGM25KFD": {"Type": "AWS::ApiGateway::Method","Properties": {"AuthorizationType": "NONE","HttpMethod": "POST","ResourceId": {"Ref": "AGR2JDQ8"},"RestApiId": {"Ref": "AGRA16PAA"},"Integration": {"Type": "AWS","IntegrationHttpMethod": "POST","IntegrationResponses": [{"StatusCode": 200}],"Uri": {"Fn::Join": ["",["arn:aws:apigateway:",{"Ref": "AWS::Region"},":lambda:path/2015-03-31/functions/",{"Fn::GetAtt": ["LF9MBL","Arn"]},"/invocations"]]}},"MethodResponses": [{"StatusCode": 200}]},"DependsOn": ["LF9MBL","AGR2JDQ8","LPI6K5"]},"AGR2JDQ8": {"Type": "AWS::ApiGateway::Resource","Properties": {"RestApiId": {"Ref": "AGRA16PAA"},"ParentId": {"Fn::GetAtt": ["AGRA16PAA","RootResourceId"]},"PathPart": "divide"},"DependsOn": ["AGRA16PAA"]},"AGRA16PAA": {"Type": "AWS::ApiGateway::RestApi","Properties": {"Name": "CalculationApi"}},"LPI6K5": {"Type": "AWS::Lambda::Permission","Properties": {"Action": "lambda:invokeFunction","FunctionName": {"Fn::GetAtt": ["LF9MBL", "Arn"]},"Principal": "apigateway.amazonaws.com","SourceArn": {"Fn::Join": ["",["arn:aws:execute-api:", {"Ref": "AWS::Region"}, ":", {"Ref": "AWS::AccountId"}, ":", {"Ref": "AGRA16PAA"}, "/*"]]}}}}
}

最后但并非最不重要的一点是，我们必须更新以前的cloudformation堆栈。

所以我们上传了我们最新的模板

aws s3 cp cloudformationjavalambda2.template s3://cloudformation-templates/cloudformationjavalambda2.template

我们要做的就是更新堆栈。

aws cloudformation update-stack --stack-name JavaLambdaStack --template-url https://s3.amazonaws.com/cloudformation-templates/cloudformationjavalambda2.template

我们的堆栈刚刚更新。
我们可以到达我们的api网关端点并尝试发布帖子。

curl -H "Content-Type: application/json" -X POST -d '{"numerator":1,"denominator":"2"}' https://{you api gateway endpoint}/StagingStage/divide
"0.5"

您可以在github上找到源代码。

翻译自: https://www.javacodegeeks.com/2016/10/java-aws-cloud-using-lambda-api-gateway-cloudformation.html