原生ajax实现用户名校验

前台index.jsp

  
    
    
  
  
  用户注册
 

   用户名：
   
   密码：
   
 
  

后台servlet

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

/**
 * Created by ttc on 17-5-27.
 */
@WebServlet(name = "ValidUserServlet",urlPatterns = "/valid.do")
public class ValidUserServlet extends HttpServlet {
    private List lst = new ArrayList();
    public void init() throws javax.servlet.ServletException
    { /* compiled code */
        lst.add("zhangsan");
        lst.add("lisi");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String strName = request.getParameter("username");
        //contains---包含
        PrintWriter pw = response.getWriter();
        if(lst.contains(strName))//用户已存在
        {
            pw.print("1");
        }
        else
        {
            pw.print("0");
        }
    }

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

    }
}