While my team was working on our project, one day the server ran twice with no reason. This made errors but worked well on the page.
The error was because we send a command to the servlet, and when the server runs twice, the command goes well on the first place and works well on the page. But on the second place there's no command to send so the error showed up as "command is null".
Anyway I fixed this by comparing project files between the normal project when the server was normal and this odd version.
The problem was at the heather.jsp file.
<link rel="shortcut icon" href="#"> This short line was the problem. # made the server ran twice. I don't know the reason, but after I deleted the line, everything went well.
