preservlet.java

ajax验证用户输入例子

package cn.edu.bit.servlet;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class PreServlet extends HttpServlet {

	public String[] usernameList;

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws IOException, ServletException {
		
		response.setContentType("text/xml;charset=UTF-8");

	    response.setHeader("Cache-Control", "no-cache");	 

		String username = (String) request.getParameter("user_name");
		
		String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>";

		if (username.equals("") || username == null) {
			
			xml +="<message><info>Username is required !</info></message>";
		}else if(this.IsContain(username))
		{
			xml += "<message><info>The username has exsites,Please choose other username!</info></message>";
		}
		else
		{
			xml += "<message><info>合法!</info></message>";
		}
		
		response.getWriter().write(xml);
	}

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

	public void init(ServletConfig config) throws ServletException {
		usernameList = new String[] { "Tom", "Jerry", "Brain" };
	}

	public boolean IsContain(String param) {
		for (int i = 0; i < usernameList.length; i++) {
			if (usernameList[i].equals(param)) {
				return true;
			} else
				continue;
		}

		return false;
	}

}