java执行python代码（java远程调用python脚本讲解）

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 result

if __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_directory

app = 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 &