Question

我创建了一个存储文件名的实体'Images'和一个用于存储图像的blob对象：

class Images(ndb.Model):
    file_name = ndb.StringProperty()
    blob = ndb.BlobProperty()

现在，我尝试在我的应用程序中显示'database.jpeg'图像，如下所示：

HTML表单

<html>
<head>
    <title>Template</title>
</head>
<body>
    <img src="/img_serve/database.jpeg" /> 
</body>
</html>

Python文件：

class ImgServe(Handler):
    def get(self, resource):
        image = ndb.Key('Images', resource).get()
        self.response.headers[b'Content-Type'] = mimetypes.guess_type(image.file_name)[0]
        self.response.write(image.blob)  

app = webapp2.WSGIApplication([('/', MainPage),
                                ('/signup', Register),
                                ('/login', Login),
                                ('/logout', Logout),
                                ('/mp', MP),
                                (r'/file_upload', FileUpload),
                                ('/blob', Blob),
                                (r'/img_serve/<resource:(.*)>', ImgServe),
                                ('/template', Template)], debug=True)

以下是“图片”实体的屏幕截图：

enter image description here

但是，我的应用程序中出现了损坏的图像。我的代码中似乎有什么问题？

整个代码：

main.py

import os
import re
import random
import hashlib
import hmac
from string import letters
import mimetypes
import webapp2
import jinja2

from google.appengine.ext import ndb

template_dir = os.path.join(os.path.dirname(__file__), 'templates')
jinja_env = jinja2.Environment(loader = jinja2.FileSystemLoader(template_dir),
                               autoescape = True)

secret = 'fart'

def render_str(template, **params):
    t = jinja_env.get_template(template)
    return t.render(params)

def make_secure_val(val):
    return '%s|%s' % (val, hmac.new(secret, val).hexdigest())

def check_secure_val(secure_val):
    val = secure_val.split('|')[0]
    if secure_val == make_secure_val(val):
        return val

class Handler(webapp2.RequestHandler):
    def write(self, *a, **kw):
        self.response.out.write(*a, **kw)

    def render_str(self, template, **params):
        params['user'] = self.user
        return render_str(template, **params)

    def render(self, template, **kw):
        self.write(self.render_str(template, **kw))

    def set_secure_cookie(self, name, val):
        cookie_val = make_secure_val(val)
        self.response.headers.add_header(
            'Set-Cookie',
            '%s=%s; Path=/' % (name, cookie_val))

    def read_secure_cookie(self, name):
        cookie_val = self.request.cookies.get(name)
        return cookie_val and check_secure_val(cookie_val)

    def login(self, user):
        self.set_secure_cookie('user_id', str(user.key().id()))

    def logout(self):
        self.response.headers.add_header('Set-Cookie', 'user_id=; Path=/')

    def initialize(self, *a, **kw):
        webapp2.RequestHandler.initialize(self, *a, **kw)
        uid = self.read_secure_cookie('user_id')
        self.user = uid and User.by_id(int(uid))

class MainPage(Handler):
    def get(self):
        self.render("home.html")

##### user stuff
def make_salt(length = 5):
    return ''.join(random.choice(letters) for x in xrange(length))

def make_pw_hash(name, pw, salt = None):
    if not salt:
        salt = make_salt()
    h = hashlib.sha256(name + pw + salt).hexdigest()
    return '%s,%s' % (salt, h)

def valid_pw(name, password, h):
    salt = h.split(',')[0]
    return h == make_pw_hash(name, password, salt)

def users_key(group = 'default'):
    return ndb.Key.from_path('users', group)

class Images(ndb.Model):
    file_name = ndb.StringProperty()
    blob = ndb.BlobProperty()

class User(ndb.Model):
    name = ndb.StringProperty(required = True)
    pw_hash = ndb.StringProperty(required = True)
    email = ndb.StringProperty()

    @classmethod
    def by_id(cls, uid):
        return User.get_by_id(uid, parent = users_key())

    @classmethod
    def by_name(cls, name):
        u = User.all().filter('name =', name).get()
        return u

    @classmethod
    def register(cls, name, pw, email = None):
        pw_hash = make_pw_hash(name, pw)
        return User(parent = users_key(),
                    name = name,
                    pw_hash = pw_hash,
                    email = email)

    @classmethod
    def login(cls, name, pw):
        u = cls.by_name(name)
        if u and valid_pw(name, pw, u.pw_hash):
            return u


USER_RE = re.compile(r"^[a-zA-Z0-9_-]{3,20}$")
def valid_username(username):
    return username and USER_RE.match(username)

PASS_RE = re.compile(r"^.{3,20}$")
def valid_password(password):
    return password and PASS_RE.match(password)

EMAIL_RE  = re.compile(r'^[\S]+@[\S]+\.[\S]+$')
def valid_email(email):
    return not email or EMAIL_RE.match(email)

class Signup(Handler):
    def get(self):
        self.render("signup-form.html")

    def post(self):
        have_error = False
        self.username = self.request.get('username')
        self.password = self.request.get('password')
        self.verify = self.request.get('verify')
        self.email = self.request.get('email')

        params = dict(username = self.username,
                      email = self.email)

        if not valid_username(self.username):
            params['error_username'] = "That's not a valid username."
            have_error = True

        if not valid_password(self.password):
            params['error_password'] = "That wasn't a valid password."
            have_error = True
        elif self.password != self.verify:
            params['error_verify'] = "Your passwords didn't match."
            have_error = True

        if not valid_email(self.email):
            params['error_email'] = "That's not a valid email."
            have_error = True

        if have_error:
            self.render('signup-form.html', **params)
        else:
            self.done()

    def done(self, *a, **kw):
        raise NotImplementedError

class Register(Signup):
    def done(self):
        #make sure the user doesn't already exist
        u = User.by_name(self.username)
        if u:
            msg = 'That user already exists.'
            self.render('signup-form.html', error_username = msg)
        else:
            u = User.register(self.username, self.password, self.email)
            u.put()

            self.login(u)
            self.redirect('/')

class Login(Handler):
    def get(self):
        self.render('login-form.html')

    def post(self):
        username = self.request.get('username')
        password = self.request.get('password')

        u = User.login(username, password)
        if u:
            self.login(u)
            frontuser = username
            self.render('home.html', frontuser = frontuser)
        else:
            msg = 'Invalid login'
            self.render('login-form.html', error = msg)

class Logout(Handler):
    def get(self):
        self.logout()
        self.redirect('/')

class MP(Handler):
    def get(self):
        self.render('mp.html')

class FileUpload(Handler):
    def post(self):
        file_upload = self.request.POST.get("file", None)
        file_name = file_upload.filename
        image = Images(id=file_name, file_name=file_name, blob=file_upload.file.read())
        image.put()

        self.response.headers[b'Content-Type'] = mimetypes.guess_type(image.file_name)[0]
        self.response.write(image.blob)

class ImgServe(Handler):
    def get(self, resource):
        image = ndb.Key('Images', resource).get()
        self.response.headers[b'Content-Type'] = mimetypes.guess_type(image.file_name)[0]
        self.response.write(image.blob)            

class Blob(Handler):
    def get(self):
        self.render("blob.html")

class Template(Handler):
    def get(self):
        self.render('template.html')


app = webapp2.WSGIApplication([('/', MainPage),
                                ('/signup', Register),
                                ('/login', Login),
                                ('/logout', Logout),
                                ('/mp', MP),
                                (r'/file_upload', FileUpload),
                                ('/blob', Blob),
                                (r'/img_serve/<resource:(.*)>', ImgServe),
                                ('/template', Template)], debug=True)

blob.html

<!DOCTYPE HTML>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Image Upload</title>
</head>
<body>
<form action="/file_upload" enctype="multipart/form-data" method="post">
    <div><input type="file" name="file"/></div>
    <div><input type="submit" value="Upload"></div>
</form>
</body>
</html>

template.html

<html>
<head>
    <title>Template</title>
</head>
<body>
    <img src="/img_serve/database.jpeg" /> 
</body>
</html>

此外，这是我得到的而不是图像：

enter image description here

Answer 1

使用App引擎SDK 1.9.0和Python 27，在使用您的上传代码和file_name：clock.png上传图像后，SDK数据存储应该如下所示： enter image description here

在您的代码中：class FileUpload(Handler)和class ImgServe(Handler):

但为什么不使用webapp2.RequestHandler for Handler？

使用此静态HTML：

<!DOCTYPE HTML>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Image Serving</title>
</head>
<body>
   <img src="/img_serve/clock.png" alt="clock" >
</body>
</html>

这个处理程序：

class ImgServe(webapp2.RequestHandler):

    def get(self, resource):
        image = ndb.Key('Images', resource).get()
        self.response.headers[b'Content-Type'] = mimetypes.guess_type(image.file_name)[0]
        self.response.write(image.blob)

路由：

    webapp2.Route(r'/img_serve/<resource:(.*)>', handler=....ImgServe)

Answer 2

我建议您使用Blobstore存储图像 - 它更便宜，并且专门针对此目的进行了优化。

更好的是，您可以将图像存储在Google云端存储中。它甚至比Blobstore便宜。

这两种解决方案都有额外的好处 - 浏览器可以缓存这些图像。

Google App Engine：显示存储在数据存储区中的图像

2 个答案: