Java Programming

I have been programming in java for around a year now and I have only used it for standalone desktop applications. I am now forced to make a website for a series of applets, and I have got most of them working online now. My question is, apart from applets and little programs, how helpful is java for overall web developing. For example, how can you code a login script with java (not the java part, but how can you make it interact with the browser, etc)

Thanks in advance