使用JAVA编写的自定义算法加密网页字段

An example of AES encryption using JavaScript can be found here. Depending on your use case, https encryption may be a better option, or can at least provide an additional layer of privacy. I think the key question to ask yourself is whether the data on the server should be opaque to anyone but the client. If the server is going to use the data in its plaintext form, then https is a relatively safe, easy and robust option. If the server doesn't need the data, then having the user encrypt at the client in JavaScript would allow your server to maintain those sensitive fields in a way that would be useless to your own employees, but useful to the client who could regenerate the same key to decrypt it.

If you want to encrypt on client side and decrypt on server side, you'll have to do it with javascript on client side; maybe you can do it with an applet and that way use Java on client side, but that seems troublesome.

I think you better look into https.

I think a better way would be using https if you have the option to do so. Why reinvent the wheel?