Java, Tomcat 6: saving files to local HD

I've searching for this for a while now online (Google, and StackOverflow), but haven't yet come across this question. Maybe my query is not correct (please redirect then!)

I've developed and set up a WebApp on TomCat 6 under Linux. Tomcat isn't running in a virtual host environment yet, I have full control over server. Therefore, .war file is saved to Tomcat's standard deploy dir. The issue I have is with images: different web services provide differently-sized images which need to be presented in uniform sizes.

I download them and resize them without problems, but have to store a local copy of the image as this takes some time if done real-time, plus a lot of bandwidth waste. I don't save them under the .war's temp dir under Tomcat, due to case where a server shutdown would force me to reload all images.

I have created a different directory under /home/username/开发者_开发问答images, which I then serve under a different subdomain through regular Apache, and the HTML code generated in the .jsp is simply a correct URL to the file. Works great if the image doesn't exist. However, due to permission issues, the Tomcat instance cannot remove or overwrite files already created, even though I've marked the folder where images are stored with 777 permissions. As an aside, I don't see need to give it 777 perms, but with 755 (for example), I had permission issues even when trying to save a new file.

So: is there a better solution (I considered database, but the images dir is now 250mb, and I see no need to overload the db so much)?

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Don't store the images in the database. Your /home/user/www.example.com/resources approach is in the correct direction, just sort out the privileges issue. Make sure the path is in a group where the user who runs tomcat (tomcat?) belongs in and reduce the 777 because it's too broad.

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It is a little unclear as to whether tomcat and another user are writing, or only tomcat.

If it is only tomcat, the directory in question should be owned by tomcat, and the permissions can be either 750 (setting the group to match apache's group) or 755 (the group doesn't matter, anyone on the machine can read the files).

Note that if some other user is writing files, you have to be trickier. In that case, you need 775, user tomcat, group tomcat, and put the additional user(s) in the tomcat group. If those users are in multiple groups, you can use the group sticky bit on the directory to force the group to remain tomcat. In this case, anyone on the machine can read those files.

The documentation for chown and chmod should be of great help.

(Yes, I do realize that this question is very old, but the same principles apply, and no one seemed to give a clear answer).

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What specifically is happening with the permissions? Tomcat will be running as some userid (say tomcat1) and will be creating files presumably owned by the same user (tomcat1). If your files are being created with a different owner, then that will explain why you can't overwrite existing downloads and you'll need to work out why the ownership is differen. If it's not ownership, then are the files being created without write permission to the user. In this case, consider explicitly setting the permissions on each file saved to allow the owner to write to it, or change the umask of the user account.