Java平台调用Python平台已有算法（附源码及解析）

1. 问题描述

Java平台要调用Pyhon平台已有的算法，为了减少耦合度，采用Pyhon平台提供Restful 接口，Java平台负责来调用，采用Http+Json格式交互。

2. 解决方案

2.1 JAVA平台侧

2.1.1 项目代码

public static String invokeAlgorithm(String url, HashMap params) throws Exception { HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.parseMediaType("application/json; charset=UTF-8"));
headers.add("Accept", MediaType.APPLICATION_JSON.toString());
HttpEntity<String> httpEntity = new HttpEntity<>(JSONObject.toJSONString(params), headers);
RestTemplate rst = new RestTemplate(); ResponseEntity<String> stringResponseEntity = rst.postForEntity(url, httpEntity, String.class); return stringResponseEntity.getBody();
}


2.1.2 代码解析

两个入参：url为Python提供restful调用方法；params参数，项目中参数使用了map，然后将map转成了Json，与Python服务器约定Json格式传输。

2.2 python平台侧

经过反复调研与深思熟虑的考虑后，决定采用flask提供Rest接口， flask 是一款非常流行的python web框架，微框架、简洁，社区活跃等。（其实是因为安装的Anaconda自带了flask，一配置一启动好了，就是这么巧）

2.2.1 项目代码

# -*- coding: utf-8 -*-
from flask import Flask, request, send_from_directory
from k_means import exec
app = Flask(__name__)
import logging@app.route('/')
def index():
return "Hello, World!"# k-means算法
@app.route('/getKmeansInfoByPost', methods=['POST'])
def getKmeansInfoByPost():
try:
result = exec(request.get_json())
except IndexError as e:
logging.error(str(e))
return 'exception:' + str(e)
except KeyError as e:
logging.error(str(e))
return 'exception:' + str(e)
except ValueError as e:
logging.error(str(e))
return 'exception:' + str(e)
except Exception as e:
logging.error(str(e))
return 'exception:' + str(e)
else:
return result@app.route("/<path:filename>")
def getImages(filename):
return send_from_directory(dirpath, filename, as_attachment=True)if __name__ == '__main__':
app.run(host="0.0.0.0", port=5000, debug=True)

2.2.2 代码解析

代码为真实项目示例，去掉了一些配置而已，示例中包含三个方法，分别说一下

（1）最基本Rest接口：helloword

# -*- coding: utf-8 -*-
from flask import Flask
app = Flask(__name__)@app.route('/')
def index():
return "Hello, World!"if __name__ == '__main__':
app.run(host="0.0.0.0", port=5000, debug=True)


（2）调用其他python文件的Rest接口

# -*- coding: utf-8 -*-
from flask import Flask, request
from k_means import exec
app = Flask(__name__)
import logging# k-means算法
@app.route('/getKmeansInfoByPost', methods=['POST'])
def getKmeansInfoByPost():
try:
result = exec(request.get_json())
except IndexError as e:
logging.error(str(e))
return 'exception:' + str(e)
except KeyError as e:
logging.error(str(e))
return 'exception:' + str(e)
except ValueError as e:
logging.error(str(e))
return 'exception:' + str(e)
except Exception as e:
logging.error(str(e))
return 'exception:' + str(e)
else:
return resultif __name__ == '__main__':
app.run(host="0.0.0.0", port=5000, debug=True)


说明：1.接收POST方法；2. 从request获取java传过来的参数，对应上面的java调用代码

（3） 文件下载Rest接口

# -*- coding: utf-8 -*-
from flask import Flask, send_from_directoryapp = Flask(__name__)@app.route("/<path:filename>")
def getImages(filename):
return send_from_directory(dirpath, filename, as_attachment=True)if __name__ == '__main__':
app.run(host="0.0.0.0", port=5000, debug=True)


说明：1.还是flask框架提供的：send_from_directory

​ 2.dirpath目录，一般可以给个固定存放目录，调用的时候只用给文件名称就可以直接下载对应文件。

2.3 Linux服务器启动python服务

nohup python restapi.py &


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