On 9/13/2012 8:13 AM, Christopher Schultz wrote:
Large sites will use a single URL that ends up resolving the images
from some kind of data source. That data source might be a disk (e.g.
you could forward to the DefaultServlet) or a database (relational or
otherwise) where you would write your own servlet to retrieve the data
yourself.
I would use a servlet that gets the image identifier from the request
parameters or "path info" and then continues from there. As Konstantin
points out, using Tomcat's "aliases" feature means that these requests
may have to perform a linear search through all the aliases to find
the requested resource. If you write a custom servlet, it will likely
perform much better than that.
this is what I am doing it right now and maybe bit different from what
large sites do.I can see the point and can write filter which will scan
the request url and point it to respective images directory and then
serve it.
I store the images in the respective directory, for example for category
A with subcategory sc, I store in C://A/sc and then write images names
to the database.
and via jsp
I get this in this format,
img src ="A/test/{Imagename}" with image name coming from the database.
Below is way it looks in requests.
URL Method Result Type Received Taken Initiator
Wait Start Request Response Cache read Gap
/our/UploadedImages/sc/cl1.jpg GET 200 image/jpeg 40.73
KB 0.54 s <img> 219 0 405 141 0 967
/our/UploadedImages/sc/cl2.jpg GET 200 image/jpeg 45.33
KB 327 ms <img> 219 0 249 78 0 1186
/our/UploadedImages/sc/cl3.jpg GET 200 image/jpeg 26.39
KB 405 ms <img> 219 0 140 265 0 1108
/our/UploadedImages/sc/cl4.jpg GET 200 image/jpeg 40.73
KB 0.51 s <img> 219 0 281 234 0 998
/our/UploadedImages/sc/cl5.jpg GET 200 image/jpeg 23.43
KB 0.51 s <img> 219 0 405 110 0
However I am not getting if I am writing the single servlet which
resolves the images uri, how will it help in improving performance ? If
Images are in different directories, isn't tomcat needs to scan that
directory and resolve it ?
Initially I had a single directory,but though it would be nightmare in
case of maintenance, so thought of refactoring it now.
>>>>
3. Having 200 aliases means that Tomcat would have to try 200
different prefixes for each resource lookup. Maybe it would not be
noticeable (compared to the other time spent in delivering a
response), but it still seems like a waste of time.
Why should it do resource lookup when I am telling it to look at the exact
directory by giving it the exact name of the file ? In fact while storing also
I am
giving it the exact directory path to where it needs to store ?
Do you believe my understanding the way aliases works is incorrect ?
2. It is possible to define a system property (via -D in the options
list at startup, or via catalina.properties file) and reference it as
${propname}.
This approach will require me to refactor my existing code,so I will think of
using this in my next module.There are couple of things I am planning to get it
dynamically ,but again somewhat scared if I can ever write thread safe
servlets/classes which can serve multiple concurrent requests.Currently I have
close to 50% of code which is reused.But I need to deal with this sooner the
better else I am going to have war file which will be atleast 40mb in size with
unmanageable number of jsp/servlets/beans.
Thanks Chris and Konstantio for replies.Currently I am on 7.027/7.011 and maybe
after some days, I will upgrade to 7.030 or still better have one more TC for
testing purpose.
- Kiran Badi
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