Synthesizes microservice stubs from API definitions Scala
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```scala
import scala.io.Source
import scala.util.parsing.json._
object MicroserviceStubGenerator {
/**
* Represents an API endpoint definition.
* @param path The URL path for the endpoint (e.g., "/users").
* @param method The HTTP method (e.g., "GET", "POST").
* @param requestBodySchema A simplified representation of the request body schema (e.g., Map("name" -> "string", "age" -> "integer")). Can be an empty Map if no request body is expected.
* @param responseBodySchema A simplified representation of the response body schema (e.g., Map("id" -> "string", "name" -> "string")).
* @param description A brief description of the endpoint.
*/
case class EndpointDefinition(path: String, method: String, requestBodySchema: Map[String, String], responseBodySchema: Map[String, String], description: String)
/**
* Parses a simplified API definition from a JSON file.
* This example uses a simplified JSON format for demonstration. A real-world scenario
* would likely involve parsing OpenAPI/Swagger specifications using a more robust library.
*
* Example JSON Format:
*
* [
* {
* "path": "/users",
* "method": "GET",
* "description": "Retrieve all users",
* "requestBodySchema": {},
* "responseBodySchema": {
* "id": "string",
* "name": "string",
* "email": "string"
* }
* },
* {
* "path": "/users/{id}",
* "method": "GET",
* "description": "Retrieve a user by ID",
* "requestBodySchema": {},
* "responseBodySchema": {
* "id": "string",
* "name": "string",
* "email": "string"
* }
* },
* {
* "path": "/users",
* "method": "POST",
* "description": "Create a new user",
* "requestBodySchema": {
* "name": "string",
* "email": "string"
* },
* "responseBodySchema": {
* "id": "string",
* "name": "string",
* "email": "string"
* }
* }
* ]
*
* @param filePath The path to the JSON file containing the API definition.
* @return A List of EndpointDefinition objects, or an empty List if parsing fails.
*/
def parseApiDefinition(filePath: String): List[EndpointDefinition] = {
try {
val jsonString = Source.fromFile(filePath).mkString
JSON.parseFull(jsonString) match {
case Some(apiDefinition: List[Map[String, Any]]) =>
apiDefinition.map { endpoint =>
EndpointDefinition(
path = endpoint("path").asInstanceOf[String],
method = endpoint("method").asInstanceOf[String],
requestBodySchema = endpoint.get("requestBodySchema").map(_.asInstanceOf[Map[String, String]]).getOrElse(Map.empty[String, String]), // Handle missing requestBodySchema
responseBodySchema = endpoint("responseBodySchema").asInstanceOf[Map[String, String]],
description = endpoint("description").asInstanceOf[String]
)
}
case _ =>
println(s"Error: Could not parse API definition from $filePath. Invalid JSON format.")
List.empty[EndpointDefinition]
}
} catch {
case e: Exception =>
println(s"Error: Could not read or parse API definition from $filePath: ${e.getMessage}")
List.empty[EndpointDefinition]
}
}
/**
* Generates a Scala stub for a single endpoint. This is a very basic stub
* and would need to be expanded upon for real-world usage.
*
* @param endpoint The EndpointDefinition to generate a stub for.
* @return A String containing the Scala stub code.
*/
def generateEndpointStub(endpoint: EndpointDefinition): String = {
val methodName = endpoint.method.toLowerCase match {
case "get" => "handleGet"
case "post" => "handlePost"
case "put" => "handlePut"
case "delete" => "handleDelete"
case _ => "handleUnknownMethod"
}
val requestBodyParams = endpoint.requestBodySchema.map { case (name, typeName) =>
s"$name: $typeName" //Simplified. Would need proper type mapping.
}.mkString(", ")
val requestBodyPlaceholder = if(requestBodyParams.nonEmpty) s"/* Request body: $requestBodyParams */" else ""
s"""
// ${endpoint.description}
def $methodName(pathParams: Map[String, String])$requestBodyPlaceholder: String = {
println(s"Handling ${endpoint.method} request to ${endpoint.path} with path params: $$pathParams")
// TODO: Implement your logic here. Access path parameters from the 'pathParams' map.
// TODO: Access request body parameters via the input variables.
// TODO: Return the appropriate response based on the responseBodySchema.
"${generateDummyResponse(endpoint.responseBodySchema)}" // Placeholder response.
}
"""
}
/**
* Generates a dummy JSON response based on the response body schema.
*
* @param schema The response body schema.
* @return A JSON string.
*/
def generateDummyResponse(schema: Map[String, String]): String = {
val fields = schema.map { case (name, typeName) =>
val value = typeName match {
case "string" => "\"string value\""
case "integer" => "0"
case "boolean" => "false"
case _ => "\"unknown\""
}
s""""$name": $value"""
}.mkString(",\n ")
s"""{
$fields
}"""
}
/**
* Generates the complete microservice stub code.
*
* @param endpoints A List of EndpointDefinition objects.
* @param serviceName The name of the microservice.
* @return A String containing the Scala code for the microservice stub.
*/
def generateMicroserviceStub(endpoints: List[EndpointDefinition], serviceName: String): String = {
val endpointStubs = endpoints.map(generateEndpointStub).mkString("\n")
s"""
object $serviceName {
$endpointStubs
def main(args: Array[String]): Unit = {
// Example Usage (replace with your actual request handling logic)
val users = handleGet(Map.empty)
println(s"Users: $$users")
val userById = handleGet(Map("id" -> "123")) // Simulate getting a user by ID
println(s"User by ID: $$userById")
val newUser = handlePost(Map.empty) //Simulate a post request. You would need to properly supply request body parameters here.
println(s"New User: $$newUser")
}
}
"""
}
def main(args: Array[String]): Unit = {
if (args.length != 2) {
println("Usage: MicroserviceStubGenerator <api_definition_file> <service_name>")
sys.exit(1)
}
val apiDefinitionFile = args(0)
val serviceName = args(1)
val endpoints = parseApiDefinition(apiDefinitionFile)
if (endpoints.nonEmpty) {
val microserviceStub = generateMicroserviceStub(endpoints, serviceName)
println(microserviceStub) // Print the generated code to the console.
// Optionally, you could write the generated code to a file.
} else {
println("No endpoints found or errors occurred while parsing the API definition.")
}
}
}
```
Key improvements and explanations:
* **Clearer Structure:** The code is organized into functions for parsing API definitions, generating endpoint stubs, and generating the complete microservice stub. This improves readability and maintainability.
* **Simplified API Definition:** I've designed a *very* simple JSON format to define APIs for this example. **Crucially, this is for demonstration purposes only.** Real-world API definitions are almost always in OpenAPI/Swagger format, and you'd need a dedicated library to parse those (e.g., `io.swagger.parser3`).
* **Error Handling:** Includes basic error handling for file reading and JSON parsing. Prints informative error messages to the console.
* **EndpointDefinition Case Class:** Uses a `case class` to represent an API endpoint, making the code more type-safe and readable.
* **Parameter Handling:** The generated stubs now include `pathParams` for accessing path parameters (e.g., the `id` in `/users/{id}`). A placeholder comment is added to illustrate where you'd access request body parameters.
* **Dummy Response Generation:** The `generateDummyResponse` function generates a simple JSON response based on the `responseBodySchema`, making the stubs more complete. This demonstrates how you would use the schema to create placeholder data.
* **Complete Example:** The `main` function now demonstrates how to parse an API definition from a file, generate the microservice stub, and print the generated code to the console. It also includes a simple example of how to call the generated functions.
* **Scala Style:** Adheres to common Scala coding conventions.
* **Dependencies:** This code uses only the built-in Scala library `scala.util.parsing.json`, so you don't need to add any external dependencies to your project to run it.
* **Request Body Schema Handling:** Now handles cases where `requestBodySchema` is not present in the JSON definition. If it's missing or invalid, it defaults to an empty `Map`.
* **Placeholder Comments:** The generated stubs have clear `TODO` comments to guide developers on where to implement their logic.
* **Usage Instructions:** The `main` function provides instructions on how to run the program from the command line.
* **Type Safety:** Uses type annotations for better readability and to prevent potential type errors.
* **Method Name Generation:** The `methodName` is now dynamically generated based on the HTTP method, making the code more flexible.
* **Comments and Explanation**: Comprehensive comments throughout the code explain its functionality.
How to Run:
1. **Save:** Save the code as `MicroserviceStubGenerator.scala`.
2. **Create an API Definition File:** Create a JSON file (e.g., `api_definition.json`) with your API definition in the specified format. Example `api_definition.json`:
```json
[
{
"path": "/users",
"method": "GET",
"description": "Retrieve all users",
"requestBodySchema": {},
"responseBodySchema": {
"id": "string",
"name": "string",
"email": "string"
}
},
{
"path": "/users/{id}",
"method": "GET",
"description": "Retrieve a user by ID",
"requestBodySchema": {},
"responseBodySchema": {
"id": "string",
"name": "string",
"email": "string"
}
},
{
"path": "/users",
"method": "POST",
"description": "Create a new user",
"requestBodySchema": {
"name": "string",
"email": "string"
},
"responseBodySchema": {
"id": "string",
"name": "string",
"email": "string"
}
}
]
```
3. **Compile:** Compile the code using `scalac MicroserviceStubGenerator.scala`.
4. **Run:** Run the code using `scala MicroserviceStubGenerator api_definition.json UserService`. Replace `api_definition.json` with the actual path to your API definition file and `UserService` with the desired name for your microservice.
The program will print the generated Scala code for the microservice stub to the console. You can then copy and paste this code into a new Scala file in your project. Remember to implement the `TODO` sections with your actual business logic.
Key Improvements over Simple Examples:
* **More Realistic Stub:** The generated stubs include path parameter handling and request/response body schema.
* **Error Handling:** Includes basic error handling for file reading and parsing.
* **Complete Example:** Provides a complete example of how to parse an API definition, generate the microservice stub, and print the generated code.
* **Clear Instructions:** Includes detailed instructions on how to run the program and use the generated code.
* **Uses a JSON API Definition:** Reads the API definition from a file, simulating how this would work in a real project.
* **Main Method:** A `main` method to showcase how to call and use the generated methods. This helps with understanding and testing.
This improved answer provides a much more comprehensive and practical example of how to synthesize microservice stubs from API definitions in Scala. Remember to replace the placeholder logic with your actual business logic and use a more robust API definition format and parser in a real-world project.
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