如何在GAE数据存储中显示图像？

Question

我看了教程和所有能找到的关于如何显示保存在数据存储中的图片的资料，但还是没能搞定。非常感谢任何帮助。这是我之前的问题.

下面的代码用于/displayimage，结果显示图片链接坏掉了；而/image则出现了BadKeyError: Invalid string key .。根据Nick Johnson在这里的回复，我可能传递了一个空字符串给img_id，但是在/display image中的日志显示这个键：(((result.key():)))) agpkZXZ-dGluZy0xcg8LEghIb21lUGFnZRjOCAw。谢谢你的帮助。

class HomePage(db.Model):
    thumbnail = db.BlobProperty()
    firm_name = db.StringProperty()

class ImageUpload(webapp.RequestHandler):
    def get(self):
...        
        self.response.out.write("""
        <form action="/imagesave" enctype="multipart/form-data" method="post">
        <div><label>firm name:</label> <input type="text" name="firm_name" size=40></div>
        <div><input type="file" name="img" /></div>
        <div><input type="submit" value="Upload image"></div>
        </form>
        """)

class ImageSave(webapp.RequestHandler):
    def post(self):
        homepage = HomePage()
        thumbnail = self.request.get("img")
        firm_name = self.request.get("firm_name")
        homepage.thumbnail = db.Blob(thumbnail)
        homepage.firm_name = firm_name
        homepage.put()

        self.redirect("/imageupload")

class ImageResize(webapp.RequestHandler):
    def post(self):
        q = HomepageImage.all()
        q.filter("firm_name", "mta")
        qTable = q.get()

        if qTable:
            qTable.thumbnail = db.Blob(images.resize(self.request.get("img"), 32, 32))
            db.put(qTable)
        else:
            self.response.out.write("""firm not found""")
        self.redirect("/imageupload")

class DisplayImage(webapp.RequestHandler):
    def get(self):
...
        query = HomePage.all()
        query.filter("firm_name", "mta")
        result = query.get()

        self.response.out.write("""firm name: %s""" % result.firm_name)

        #self.response.out.write("""<img src="img?img_id=%s"></img>""" %
        #chenged this line as systempuntoout's comment to:
        self.response.out.write("""<img src="/image?img_id=%s"></img>""" %
        result.key())
        #but I still get the same error
class Image(webapp.RequestHandler):
    def get(self):
...
    #I am adding the next line to show that "img_id" is an empty string.
    #why "img_id" empty here?

    img_id = self.request.get("img_id")
    logging.info("""**************************img_id: %s**************************""" % img_id)
    #**************************img_id: **************************

        homepage = db.get(self.request.get("img_id"))

        if homepage.thumbnail:
            self.response.headers['Content-Type'] = "image/jpg"
            self.response.out.write(homepage.thumbnail)
        else:
            self.response.out.write("no image")


application = webapp.WSGIApplication(
[
("/imageresize",ImageResize),
("/imageupload", ImageUpload),
("/displayimage", DisplayImage),
("/imagesave", ImageSave),
("/image", Image),
],                                      
debug=True
)

def main():
    run_wsgi_app(application)
if __name__ == "__main__":
    main()

Answer 1

你把图片的来源指向了一个没有定义的错误的 img 路径。
正确的链接应该指向 /image，像这样：

<img src="/image?img_id=%s"></img>

我用我的修改测试了你的代码，结果运行得很好：

from google.appengine.ext import db
from google.appengine.api import users
from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app
import logging


class HomePage(db.Model):
    thumbnail = db.BlobProperty()
    firm_name = db.StringProperty()

class ImageUpload(webapp.RequestHandler):
    def get(self):
        self.response.out.write("""
        <form action="/imagesave" enctype="multipart/form-data" method="post">
        <div><label>firm name:</label> <input type="text" name="firm_name" size=40></div>
        <div><input type="file" name="img" /></div>
        <div><input type="submit" value="Upload image"></div>
        </form>
        """)

class ImageSave(webapp.RequestHandler):
    def post(self):
        homepage = HomePage()
        thumbnail = self.request.get("img")
        firm_name = self.request.get("firm_name")
        homepage.thumbnail = db.Blob(thumbnail)
        homepage.firm_name = firm_name
        homepage.put()
        self.redirect("/imageupload")

class ImageResize(webapp.RequestHandler):
    def post(self):
        q = HomepageImage.all()
        q.filter("firm_name", "mta")
        qTable = q.get()
        if qTable:
            qTable.thumbnail = db.Blob(images.resize(self.request.get("img"), 32, 32))
            db.put(qTable)
        else:
            self.response.out.write("""firm not found""")
        self.redirect("/imageupload")

class DisplayImage(webapp.RequestHandler):
    def get(self):
        query = HomePage.all()
        query.filter("firm_name", "mta")
        result = query.get()
        self.response.out.write("""firm name: %s""" % result.firm_name)
        self.response.out.write("""<img src="/image?img_id=%s"></img>""" %
        result.key())

class Image(webapp.RequestHandler):
    def get(self):
        img_id = self.request.get("img_id")
        logging.info("""**************************img_id: %s**************************""" % img_id)
        homepage = db.get(self.request.get("img_id"))
        if homepage.thumbnail:
                self.response.headers['Content-Type'] = "image/jpg"
                self.response.out.write(homepage.thumbnail)
        else:
                self.response.out.write("no image")


application = webapp.WSGIApplication(
[
("/imageresize",ImageResize),
("/imageupload", ImageUpload),
("/displayimage", DisplayImage),
("/imagesave", ImageSave),
("/image", Image),
],                                      
debug=True
)

def main():
    run_wsgi_app(application)
if __name__ == "__main__":
    main()