AJAX 04: 发起校验用户名的ajax请求
1. register.jsp
2. VerifyUsernameServlet.java
3. UserService.java
4. VerifyUsernameServlet.java
5. register.jsp
效果:
1. register.jsp
2. VerifyUsernameServlet.java
3. UserService.java
4. VerifyUsernameServlet.java
5. register.jsp
效果: