如何在Java/Groovy脚本任务中调用外部Python函数？

方案1：搭建Python API服务（推荐复杂逻辑/高复用场景） #

用FastAPI快速构建轻量API，步骤如下：

1. 安装依赖：

pip install fastapi uvicorn

2. 编写API代码（保存为word_count_api.py）：

from fastapi import FastAPI

app = FastAPI()

def getWordCount(string):
    return len(string.split())

@app.post("/count-words")
async def count_words(request: dict):
    input_str = request.get("string", "")
    return {"count": getWordCount(input_str)}

3. 启动API服务：

uvicorn word_count_api:app --host 0.0.0.0 --port 8000

4. Java调用示例：

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

public class PythonApiCaller {
    public static void main(String[] args) throws Exception {
        String testing = "This is a string.";
        
        JsonObject requestBody = new JsonObject();
        requestBody.addProperty("string", testing);
        
        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create("http://localhost:8000/count-words"))
                .header("Content-Type", "application/json")
                .POST(HttpRequest.BodyPublishers.ofString(requestBody.toString()))
                .build();
        
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
        JsonObject responseJson = JsonParser.parseString(response.body()).getAsJsonObject();
        int count = responseJson.get("count").getAsInt();
        
        System.out.println("Word count: " + count);
    }
}

5. Groovy简化调用示例：

import groovy.json.JsonBuilder
import groovy.json.JsonSlurper

def testing = "This is a string."
def requestBody = new JsonBuilder([string: testing]).toString()

def response = new URL("http://localhost:8000/count-words").openConnection()
response.setRequestMethod("POST")
response.setRequestProperty("Content-Type", "application/json")
response.doOutput = true
response.outputStream.write(requestBody.getBytes())

def result = new JsonSlurper().parseText(response.inputStream.text)
int count = result.count

println "Word count: ${count}"

方案2：Java/Groovy直接调用Python进程（适合简单场景/无需长期服务） #

如果工作流环境允许执行外部进程，可跳过API直接调用脚本：

1. 编写可独立运行的Python脚本（保存为word_counter.py）：

import sys

def getWordCount(string):
    return len(string.split())

if __name__ == "__main__":
    if len(sys.argv) > 1:
        input_str = sys.argv[1]
        print(getWordCount(input_str))

2. Java调用示例：

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class PythonProcessCaller {
    public static void main(String[] args) throws Exception {
        String testing = "This is a string.";
        
        ProcessBuilder pb = new ProcessBuilder("python", "/path/to/word_counter.py", testing);
        Process process = pb.start();
        
        BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        String output = reader.readLine();
        int count = Integer.parseInt(output);
        
        System.out.println("Word count: " + count);
        
        process.waitFor();
    }
}

3. Groovy简化调用示例：

def testing = "This is a string."
def process = ["python", "/path/to/word_counter.py", testing].execute()
process.waitFor()

int count = process.in.text.trim().toInteger()
println "Word count: ${count}"

注意事项 #

• 若涉及神经网络等重逻辑，API服务建议搭配Gunicorn做进程管理，避免单请求阻塞服务
• 生产环境需给API添加认证（如API Key），防止未授权访问
• 调用时需处理异常场景：API超时、脚本执行失败、输入参数格式错误等

内容的提问来源于stack exchange，提问作者Wilko