Spring Service Method Logic
Perhaps if this method:

this.userDao.getUser(entity);


Accepted just a String as input (the username?) and possibly a password, you could then call it without having to mess around creating the UserEntity beans. 

So this:

UserEntity entity = new UserEntity();
BeanUtils.copyProperties(bean, entity);

// Gets user from DB based on UserBean's username and password.
// Returns null if not found.
entity = this.userDao.getUser(entity);


Would become

UserEntity entity = this.userDao.getUser(bean.getUserName());


Maybe rename the entity/bean variable too to some thing that makes it a bit clearer what they are. 

Also in the second half of the method, there seems to be no need to copy the properties to a UserBean and then back again. Just update the time since last login on the UserEntity directly.