Python/Flask 服务器端 - Java/HttpURLConnection 客户端 - REST 实现

Question

我现在正在为我的网页应用程序实现一个REST接口，这个接口是为了配合一个桌面应用程序而设计的。我们使用Python和Flask来搭建这个REST服务器。

我们遇到一个问题，就是Java客户端会发送一个POST请求，而Python服务器端在处理这个请求时一切正常，直到需要连接MySQL数据库的时候。

这是Python/Flask的代码：

@app.route("/update_project/<project_data>", methods=['GET','POST'])
def updateWPProject(project_data):
    """project_data = user+++++pw+++++pj_jsondoc.
    This will update an existing project data or insert a non-existant project data item."""
    usrpw = project_data.split("+++++")
    dblogin = wplogin(usr=usrpw[0], pw=usrpw[1])
    if dblogin[0] == 'SUCCESS':
        db_name = dblogin[1][0].strip()
        db_user = dblogin[1][1].strip()
        db_pw = dblogin[1][2].strip()
        if flask.request.method == 'POST':
            fname = flask.request.form['fName']
            if fname:
                pj = Project()
                try:
                    pj = json.loads(fname)
                except TypeError:
                    sys.stdout.write("JSON conversion error...%s" % sys.exc_info()[0])
                except AttributeError:
                    sys.stdout.write("JSON conversion error...%s" % sys.exc_info()[0])

                updateProject(db_name,db_user,db_pw,pj)
                #return redirect(url_for('/'))
    else:
        return 'Login failure.'
    pass

在执行到'updateProject(db_name,db_user,db_pw,pj)'这一行之前，一切都很顺利。但当程序进入这个函数后，在'cursor=conn.cursor()'这一行就会返回一个500错误，函数没有执行完就结束了。

    def updateProject(dbname, dbuser, dbpw, pj):
        """Updates or inserts a project record is not exists. PJ passed as an argument is a Project object."""

        try:
            conn = getConnection(dbuser, dbpw, dbname)
            cursor = conn.cursor()
        except:
            sys.stdout.write("MySQL connection error...%s" % sys.exc_info()[0])

        sql_stmt = """INSERT INTO projects( projNo, projName, worksteplabel, workstep1label, workstep2label, workstep3label, resultlabel, result1label, result2label, result3label, projectowner, dbname, dblogin, dbpw, role, preference1, preference2, preference3 )
VALUES (
'projNo', 'projName', 'wslabel', 'wslabel', 'wslabel', 'wslabel', 'rlabel', 'rlabel', 'rlabel', 'rlabel', 'pjowner', 'dbname', 'dblogin', 'dbpw', 'role', 'pref1', 'pref2', 'pref3'
) ON DUPLICATE
KEY UPDATE projName = 'projName',
worksteplabel = 'wslabel',
workstep1label = 'wslabel',
workstep2label = 'wslabel',
workstep3label = 'wslabel',
resultlabel = 'rlabel',
result1label = 'rlabel',
result2label = 'rlabel',
result3label = 'rlabel',
projectowner = 'pjowner',
dbname = 'dbname',
dblogin = 'dblogin',
dbpw = 'dbpw',
role = 'role',
preference1 = 'pref1',
preference2 = 'pref2',
preference3 = 'pref3' )

        try:
            cursor.execute(sql_stmt)
            return 'SUCCESS'
        except MySQLdb.Error:
            sys.stdout.write("MySQLdb error...%s" % sys.exc_info()[0])
            return 'FAILURE'

在Java客户端那边，我用以下代码来发送POST请求和数据。

public void DB_NewProjectREST(ProjectData proj, WPUser usr) {
        // public static String excutePost(String targetURL, String urlParameters)
        //URL url;
        HttpURLConnection connection = null;  

        ///First, all the GSON/JSon stuff up front
        Gson gson = new Gson();
        //convert java object to JSON format
        String json = gson.toJson(proj);
      //Then credentials and send string
        String send_string = usr.getUserEmail()+"+++++"+usr.getUserHash();

        try {
          //Create connection
          URL url = new URL("http://127.0.0.1:5000/update_project/"+send_string);
          String urlParameters = "fName=" + URLEncoder.encode(json, "UTF-8");

          connection = (HttpURLConnection)url.openConnection();
          connection.setRequestMethod("POST");
          connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

          connection.setRequestProperty("Content-Length", "" + Integer.toString(urlParameters.getBytes().length));
          connection.setRequestProperty("Content-Language", "en-US");  

          connection.setUseCaches(false);
          connection.setDoInput(true);
          connection.setDoOutput(true);

          //Send request
          DataOutputStream wr = new DataOutputStream (connection.getOutputStream ());
          wr.writeBytes (urlParameters);
          wr.flush ();
          wr.close ();

          //Get Response    
          InputStream is = connection.getInputStream();
          BufferedReader rd = new BufferedReader(new InputStreamReader(is));
          String line;
          StringBuffer response = new StringBuffer(); 
          while((line = rd.readLine()) != null) {
            response.append(line);
            response.append('\r');
          }
          rd.close();
        } catch (Exception e) {
            e.printStackTrace();
            //return null;
        }finally {
            if(connection != null) {
                connection.disconnect(); 
            }
        }
    }

看起来我需要给客户端发送某种响应（用于输入流），而我的Python代码就是在这个地方突然返回了。（？）数据从Java客户端成功传到了Python/Flask代码中，所以有没有办法快速返回一个'OK'，然后继续处理数据库更新呢？或者说，Python的updateProject函数中的游标连接调用是否以某种方式干扰了HTTP连接？

任何帮助都非常感谢。

mysql java database connection rest api flask post request http request server-client architecture

Python/Flask 服务器端 - Java/HttpURLConnection 客户端 - REST 实现

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