1158: Add backend for AWS JShell

Author: surajkumar

jshell-aws-backend/README.md

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+# JShell AWS Backend
+This module contains the infrastructure and code to create an AWS Lambda hosted JShell API. 
+The API is used to evaluate Java code in AWS using JShell.
+
+Sample request that can be made to this API:
+
+```curl
+curl -X POST "https://<FUNCTION_ID>.lambda-url.<AWS_REGION>>.on.aws/" \
+     -H "Content-Type: application/json" \
+     -d '{"code": "System.out.println(\"Hello, World\");"}'
+```
+
+## Getting Started
+To use this project in your own AWS account, you first need an AWS account and an [AWS authenticated CLI](https://docs.aws.amazon.com/cli/v1/userguide/cli-chap-authentication.html).
+
+### Required CLI tools
+* [AWS ClI](https://aws.amazon.com/cli/) 
+* [SAM CLI](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html)
+* [cfn-lint](https://github.com/aws-cloudformation/cfn-lint) (this is for CloudFormation linting)
+
+Once your terminal is all setup and authenticated, the easiest way to deploy this application is by running the `./deploy.sh`. 
+This will compile and upload the project to AWS, it will then create a stack called "jshell" in your AWS account. The Lambda URL will be printed to the console.
+
+If you prefer to deploy without the help of the `./deploy.sh` you can do it manually:
+1. `cd infrastructure`
+2. `sam build`
+3. `sam deploy`
+
+To delete the stack, this can be done either in CloudFormation via the AWS website or using the CLI command:
+```bash
+aws cloudformation delete-stack --stack-name jshell
+```
+
+## Testing Locally
+To test the Lambda locally without the need to use an AWS account you can use the SAM Local to invoke the Lambda directly.
+
+First build the project:
+1. `cd infrastructure`
+2. `sam build`
+
+Now you can directly send events to the Lambda e.g.
+```bash
+echo '{"body": "{\"code\": \"System.out.println(\\\"Hello, World!\\\");\"}"}' | sam local invoke "CodeRunnerFunction" -e -
+```
+We pass `body` in this request unlike how we do in AWS because we need to match how AWS would send the request to the function.
+
+**Note:** This requires [Docker](https://www.docker.com/) to be installed on your machine.
+
+If you want to test locally using a web server (e.g. testing the integration with TJ Bot) you can run the `start-local.sh`
+
+This will spin up a web server locally. To test you can use the following cURL:
+```curl
+curl -X POST http://127.0.0.1:3000/jshell \
+     -H "Content-Type: application/json" \
+     -d '{"code": "System.out.println(\"Hello, World!\");"}'
+```
+**Note:** This is using the SAM CLI web server, and it can be very slow to serve requests. 
+This also requires [Docker](https://www.docker.com/) to be installed on your machine.

jshell-aws-backend/build.gradle

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+plugins {
+    id 'java'
+}
+
+group = 'org.togetherjava'
+version = '1.0'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation 'com.amazonaws:aws-lambda-java-core:1.2.3'
+    implementation 'com.amazonaws:aws-lambda-java-events:3.13.0'
+
+    implementation 'com.fasterxml.jackson.core:jackson-core:2.17.2'
+    implementation 'com.fasterxml.jackson.core:jackson-annotations:2.17.2'
+    implementation 'com.fasterxml.jackson.core:jackson-databind:2.17.2'
+
+    implementation 'org.apache.logging.log4j:log4j-api:2.23.1'
+    implementation 'org.apache.logging.log4j:log4j-core:2.23.1'
+
+    testImplementation platform('org.junit:junit-bom:5.10.3')
+    testImplementation  'org.junit.jupiter:junit-jupiter'
+    testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
+    testImplementation 'org.mockito:mockito-core:5.12.0'
+}
+
+test {
+    useJUnitPlatform()
+    testLogging {
+        events "passed", "skipped", "failed"
+    }
+}
+
+sourceSets {
+    test {
+        java {
+            srcDirs 'src/test/integration', 'src/test/unit'
+        }
+    }
+}

jshell-aws-backend/deploy.sh

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+#!/usr/bin/env bash
+
+cfn-lint -t infrastructure/template.yaml
+sam validate -t infrastructure/template.yaml --region eu-west-2
+sam validate -t infrastructure/template.yaml --lint
+sam build -t infrastructure/template.yaml --parallel
+
+sam deploy --stack-name "jshell" \
+  --no-fail-on-empty-changeset \
+  --no-confirm-changeset \
+  --resolve-s3 \
+  --s3-prefix "jshell" \
+  --region "${AWS_REGION:-eu-west-2}" \
+  --capabilities CAPABILITY_IAM \
+  --template infrastructure/template.yaml

jshell-aws-backend/infrastructure/samconfig.toml

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+version = 0.1
+[default.deploy.parameters]
+stack_name = "jshell"
+resolve_s3 = true
+s3_prefix = "jshell"
+region = "eu-west-2"
+capabilities = "CAPABILITY_IAM"
+image_repositories = []

jshell-aws-backend/infrastructure/template.yaml

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+AWSTemplateFormatVersion: '2010-09-09'
+Description: JShell Stack
+Transform: [ AWS::LanguageExtensions, AWS::Serverless-2016-10-31 ]
+
+Globals:
+  Function:
+    Timeout: 20
+    CodeUri: ..
+    MemorySize: 512
+    Runtime: java21
+    Architectures: [ arm64 ]
+
+Resources:
+  CodeRunnerFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: org.togetherjava.jshell.CodeRunner::handleRequest
+      SnapStart:
+        ApplyOn: PublishedVersions
+      AutoPublishAlias: live
+      FunctionUrlConfig:
+        AuthType: NONE
+        Cors:
+          AllowOrigins:
+            - '*'
+      Policies:
+        - AWSLambdaBasicExecutionRole
+        - Statement:
+            Effect: Allow
+            Action: lambda:InvokeFunctionUrl
+            Resource: '*'
+      Events:
+        Api:
+          Type: Api
+          Properties:
+            Path: /jshell
+            Method: POST
+
+  CodeRunnerFunctionLogGroup:
+    Type: AWS::Logs::LogGroup
+    Properties:
+      LogGroupName: !Sub /aws/lambda/${CodeRunnerFunction}
+      RetentionInDays: 7
+
+Outputs:
+  LambdaURL:
+    Value: !GetAtt CodeRunnerFunctionUrl.FunctionUrl

jshell-aws-backend/openapi_spec.yaml

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+openapi: 3.0.1
+info:
+  title: "JShell API"
+  version: "1.0"
+
+servers:
+  - url: https://33ykaxnvin5lusynogiwrevqgm0ovara.lambda-url.eu-west-2.on.aws/
+    description: AWS
+  - url: http://127.0.0.1:3000/jshell
+    description: localhost
+
+paths:
+  /:
+    post:
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                code:
+                  type: string
+                  example: "System.out.println(\"Hello, World!\");"
+      responses:
+        200:
+          description: "Successful invocation of the JShell API"
+          content: 
+            application/json:
+              examples:
+                Happy path:
+                  value:
+                    errorStream: ""
+                    outputStream: "Hello, World!"
+                    events: [
+                      statement: "System.out.println(\"Hello, World!\");",
+                      value: "",
+                      status: "VALID"
+                    ]
+                Syntax errors:
+                  value:
+                    errorStream: ""
+                    outputStream: ""
+                    events: [
+                      statement: "System.out.prinn(\"Hello, World!\");",
+                      value: null,
+                      status: "REJECTED"
+                    ]
+                System.err.println:
+                  value:
+                    errorStream: "Hello, World!"
+                    outputStream: ""
+                    events: [
+                      statement: "System.out.prinn(\"Hello, World!\");",
+                      value: "",
+                      status: "VALID"
+                    ]
+                Simple evaluation that provides a value:
+                  value:
+                    errorStream: ""
+                    outputStream: ""
+                    events: [
+                      statement: "1+1",
+                      value: "2",
+                      status: "VALID"
+                    ]
+        408:
+          description: "Execution took too long so it timed out"
+          content:
+            application/json:
+              examples:
+                Response:
+                  value:
+                    error: "Execution timed out"
+        400:
+          description: "Missing fields or the provided input is incorrect"
+          content:
+            application/json:
+              examples:
+                Invalid request payload:
+                  value:
+                    error: "Invalid input format"
+                Invalid code value:
+                  value:
+                    error: "Code field is empty or invalid"
+        500:
+          description: "Internal server error"
+          content:
+            application/json:
+              examples:
+                JShell exceptions:
+                  value:
+                    error: "Error during code execution"
+                InputStream error:
+                  value:
+                    error: "Failed to read the request stream"