java - 连接 Java 和 Python Flask

Question

我有一个简单的 Flask API:

from flask import Flask, jsonify

app = Flask(__name__)


@app.route('/')
def hello_world():
    return 'Hello World!'

@app.route('/add/<params>', methods = ['GET'])
def add_numbers(params):
    #params is expected to be a dictionary: {'x': 1, 'y':2}
    params = eval(params)
    return jsonify({'sum': params['x'] + params['y']})

if __name__ == '__main__':
    app.run(debug=True)

现在，我想从 Java 调用此方法并提取结果。我尝试过使用 java.net.URL 和 java.net.HttpURLConnection;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;


public class MyClass {
    public static void main(String[] args) {
        try {
            URL url = new URL("http://127.0.0.1:5000/add/{'x':100, 'y':1}");
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setRequestProperty("Accept", "application/json");

            if (conn.getResponseCode() != 200) {
                throw new RuntimeException("Failed : HTTP error code : "
                        + conn.getResponseCode());
            }

            BufferedReader br = new BufferedReader(new InputStreamReader(
                    (conn.getInputStream())));

            String output;
            System.out.println("Output from Server .... \n");
            while ((output = br.readLine()) != null) {
                System.out.println(output);
            }

            conn.disconnect();

        } catch (MalformedURLException e) {
            e.printStackTrace();
        }catch (IOException e){
e.printStackTrace();
        }
    }
}

但是这不起作用。在 Flask 服务器中，我收到一条错误消息:

code 400, message Bad request syntax ("GET /add/{'x':100, 'y':1} HTTP/1.1")

"GET /add/{'x':100, 'y':1} HTTP/1.1" HTTPStatus.BAD_REQUEST -

在 Java 代码中，我收到错误:

Exception in thread "main" java.lang.RuntimeException: Failed : HTTP error code : -1 at MyClass.main(MyClass.java:17)

我做错了什么？

我的最终目标是将字典对象传递给我的Python函数并将函数的响应返回给java。该词典可以包含超过一千个单词的文本值。我怎样才能实现这个目标？

编辑

根据评论和答案，我更新了 Flask 代码以避免使用 eval 并获得更好的设计:

@app.route('/add/', methods = ['GET'])
def add_numbers():
    params = {'x': int(request.args['x']), 'y': int(request.args['y']), 'text': request.args['text']}
    print(params['text'])
    return jsonify({'sum': params['x'] + params['y']})

现在我的网址是:“http://127.0.0.1:5000/add?x=100&y=12&text='Test'”

这样更好吗？

Answer 1

根据上面 @TallChuck 的评论，您需要替换或删除 URL 中的空格

URL url = new URL("http://127.0.0.1:5000/add?x=100&y=12&text='Test'");

我建议使用请求对象来检索 GET 调用中的参数。

The Request Object

To access the incoming data in Flask, you have to use the request object. The request object holds all incoming data from the request, which includes the mimetype, referrer, IP address, raw data, HTTP method, and headers, among other things. Although all the information the request object holds can be useful we'll only focus on the data that is normally directly supplied by the caller of our endpoint.

正如评论中提到的发布大量参数和数据，此任务更合适的实现可能是使用 POST 方法。

下面是关于后端 POST 的相同实现的示例:

from flask import Flask, jsonify, request
import json

app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello World!'

@app.route('/add/', methods = ['POST'])
def add_numbers():
    if request.method == 'POST':
        decoded_data = request.data.decode('utf-8')
        params = json.loads(decoded_data)
        return jsonify({'sum': params['x'] + params['y']})

if __name__ == '__main__':
    app.run(debug=True)

这是使用 cURL 测试 POST 后端的简单方法:

 curl -d '{"x":5, "y":10}' -H "Content-Type: application/json" -X POST http://localhost:5000/add

使用Java发布请求:

import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.StandardCharsets;

public class PostClass {
    public static void main(String args[]){
        HttpURLConnection conn = null;
        DataOutputStream os = null;
        try{
            URL url = new URL("http://127.0.0.1:5000/add/"); //important to add the trailing slash after add
            String[] inputData = {"{\"x\": 5, \"y\": 8, \"text\":\"random text\"}",
                    "{\"x\":5, \"y\":14, \"text\":\"testing\"}"};
            for(String input: inputData){
                byte[] postData = input.getBytes(StandardCharsets.UTF_8);
                conn = (HttpURLConnection) url.openConnection();
                conn.setDoOutput(true);
                conn.setRequestMethod("POST");
                conn.setRequestProperty("Content-Type", "application/json");
                conn.setRequestProperty( "charset", "utf-8");
                conn.setRequestProperty("Content-Length", Integer.toString(input.length()));
                os = new DataOutputStream(conn.getOutputStream());
                os.write(postData);
                os.flush();

                if (conn.getResponseCode() != 200) {
                    throw new RuntimeException("Failed : HTTP error code : "
                            + conn.getResponseCode());
                }

                BufferedReader br = new BufferedReader(new InputStreamReader(
                        (conn.getInputStream())));

                String output;
                System.out.println("Output from Server .... \n");
                while ((output = br.readLine()) != null) {
                    System.out.println(output);
                }
                conn.disconnect();
            }
    } catch (MalformedURLException e) {
        e.printStackTrace();
    }catch (IOException e){
        e.printStackTrace();
    }finally
        {
            if(conn != null)
            {
                conn.disconnect();
            }
        }
    }
}