使用Grails中的会话登录+注册

Question

我正在使用session和PasswordCodec utils开发登录/注册页面。当我注册新用户时，它会生成以下错误...

    Cannot invoke method getBytes() on null object. Stacktrace follows:
Message: Cannot invoke method getBytes() on null object
    Line | Method
->>   15 | doCall    in PasswordCodec$__clinit__closure1
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
|     10 | doCall    in samplelogin.UserController$_closure1
|    195 | doFilter  in grails.plugin.cache.web.filter.PageFragmentCachingFilter
|     63 | doFilter  in grails.plugin.cache.web.filter.AbstractFilter
|   1145 | runWorker in java.util.concurrent.ThreadPoolExecutor
|    615 | run       in java.util.concurrent.ThreadPoolExecutor$Worker
^    722 | run . . . in java.lang.Thread

下面是我的UserController代码......

    package samplelogin
import javax.servlet.http.HttpSession

class UserController {

    def registration = {
        // new user posts his registration details
        if (request.method == 'POST') {
            // create domain object and assign parameters using data binding
            def u = new User(params)
            u.passwordHashed = u.password.encodeAsPassword()
            if (! u.save()) {
                // validation failed, render registration page again
                return [user:u]
            } else {
                // validate/save ok, store user in session, redirect to homepage
                session.user = u
                redirect(controller:'main')
            }
        } else if (session.user) {
            // don't allow registration while user is logged in
            redirect(controller:'main')
        }
    }

    def login = {
        if (request.method == 'POST') {
            def passwordHashed = params.password.encodeAsPassword()
            def u = User.findByUsernameAndPasswordHashed(params.username, passwordHashed)
            if (u) {
                // username and password match -> log in
                session.user = u
                redirect(controller:'main')
            } else {
                flash.message = "User not found"
                redirect(controller:'main')
            }
        } else if (session.user) {
            // don't allow login while user is logged in
            redirect(controller:'main')
        }
    }

    def logout = {
        session.invalidate()
        redirect(controller:'main')
    }
}

以下是我的PasswordCodec.groovy工具代码......

  import java.security.MessageDigest
import sun.misc.BASE64Encoder
import sun.misc.CharacterEncoder

class PasswordCodec {
    static encode = { str ->
        MessageDigest md = MessageDigest.getInstance('SHA')
        md.update(str.getBytes('UTF-8'))
        return (new BASE64Encoder()).encode(md.digest())
    }
}

我还在bootstrap.groovy init方法中创建了一个虚拟用户，但是当我尝试登录时，通过查看flash消息收到“user not find”。 任何帮助都是有益的。