.htaccess: Redirect Trailing Slashes - apache

Question

I have a rewrite rule below in my .htaccess file in the root directory:
RewriteEngine On
# Exclude .css / .js / ...
RewriteCond ${REQUEST_URI} ^.+$
RewriteCond %{REQUEST_FILENAME} \.(gif|jpe?g|png|js|css|swf|php|ico|txt|pdf|xml)$ [OR]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d [OR]
RewriteCond %{REQUEST_FILENAME} -l
RewriteRule ^ - [L]
# Rewrite Rule
RewriteRule ^([^/]*)/([^/]*)$ /index.php?category=$1&product=$2
So the URL http://example.com/data1/data2 give me category=data1 and product=data2.
The problem is that the below URLs are not working:
http://example.com/data1 # Not Working (Page Not Found)
http://example.com/data1/data2/ # Not Working (Page Not Found)
But these URLs are working:
http://example.com/data1/ # Works -> category=data1
http://example.com/data1/data2 # Works -> category=data1 & product=data2
How can I redirect the first two URLs to the second one?
OR/AND
Do something that all URLs are redirect to the non-trailing slash one. So the URLs below:
http://example.com/data1/
http://example.com/data1/data2/
are redirect to these:
http://example.com/data1
http://example.com/data1/data2

Answer 1

To avoid trailing slashes alltogether, do a redirect
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+)/$ /$1 [R,L]
To match a URL with just one element, you might use a second rule
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.+)$ /index.php?category=$1&product= [L]
or
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.+)$ /index.php?category=$1 [L]
Putting all together gives
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+)/$ /$1 [R,L]
RewriteRule ^(.+?)/(.+)$ /index.php?category=$1&product=$2 [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.+)$ /index.php?category=$1 [L]