Ajax使用原生态JS验证用户名是否存在

直接上代码:
reg_ajax.html

  

  

    

      
用户名
      

      

    
    

      
邮箱
      

      

    
  

请求的Servlet代码如下，UserServlet.java

package cn.bestchance.servlet;

import java.io.IOException;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class UserServlet
 */
@WebServlet("/userServlet")
public class UserServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;


  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doPost(request, response);
  }

  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username=request.getParameter("username");
    //这里使用ArrayList代替从数据库中查询数据
    ArrayList userList =new ArrayList();
    userList.add("admin");
    userList.add("test");
    userList.add("chance");
    //验证用户名是否存在
    boolean flag = false;
    for (String string : userList) {
      if(string.equals(username)){
        flag = true;
        break;
      }
    }
    if(flag){//用户名已存在
      response.getWriter().print("yes");
    }else{//用户名不存在
      response.getWriter().print("no");
    }
  }

}

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