注册页面对数据进行校验，Ajax的使用-数据唯一性

    
    
    
    



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package com.etime.servlet;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "LoginServlet", value = "/LoginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取名字
        String username = request.getParameter("username");
        boolean flag;
        //假设数据库只有admin用户
        if ("admin".equals(username)){
            //用户已经存在
            flag = false;
        } else {
            //用户不存在
            flag = true;
        }
        PrintWriter writer = response.getWriter();
        writer.print(flag);
        writer.close();
    }
}