Servlet获取URL地址。在HttpServletRequest类里，有以下六个取URL的函数：
getContextPath 取得项目名
getServletPath 取得Servlet名
getPathInfo 取得Servlet后的URL名，不包括URL参数
getRequestURL 取得不包括参数的URL
getRequestURI 取得不包括参数的URI，即去掉协议和服务器名的URL
相对应的函数的值如下：
getContextPath：/ServletTest
getServletPath：/main
getPathInfo：/index/testpage/test
getRequestURL：http://localhost:8080/ServletTest/main/index/testpage/test
getRequestURI：/ServletTest/main/index/testpage/test
验证用户名
package com.glut.demo;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ValidateUserName extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("aa");
List usernames = Arrays.asList("AAA","BBB","CCC");
String username = request.getParameter("username");
System.out.println("aa");
String result = null;
if(usernames.contains(username)){
result = "该用户名已经被使用";
}else{
result = "该用户名可以使用";
}
response.setContentType("text/html");
response.getWriter().print(result);
}
}
index.jsp
Ajax请求demo
$(function(){
$(":input[name='username']").change(function(){
var val = $(this).val();
val = $.trim(val);
if(val != " "){
var url = "${pageContext.request.contextPath} servlet/ValidateUserName";
var args = {"username":val,"time":new Date()};
$.post(url,args,function(data){
$("#message").html(data);
});
}
});
});
Username:
