使用filter过滤器实现简单用户登录验证（不用配置web.xml文件）
一、filter过滤器的作用
- 如果想要获取中文字符，或者是显示提交的中文，就需要添加以下代码，来防止乱码的情况发生。
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
- 如果只是设置一个页面的情况，上述方法是可以实现的。但是，要是很多个页面要显示中文的话，上述方法就过于繁琐。这种情况下要实现显示中文的功能，就要用到filter过滤器。这样就实现了，一处编码，到处执行的用途。
二、实现简单用户登录验证
- （1）登录界面：login.jsp文件
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
<form action="LoginServlet" method="post">
用户名：<input type="text" name="username"/><br/>
密码：<input type="password" name="pwd"/><br/>
<input type="submit" value="提交"/>
</form>
<a href="result1.jsp">验证登录</a>
</body>
</html>
- （2）servlet交互文件：LoginServlet.java
package com.filter.servlet;
import java.io.IOException;
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 javax.servlet.http.HttpSession;
/**
* Servlet implementation class LoginServlet
*/
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
System.out.println("进入servlet......");
String username = request.getParameter("username");
String pwd = request.getParameter("pwd");
//获取Session
HttpSession session = request.getSession();
//验证用户名和密码是否有效
//将用户名放入session 并且设置名称为uname(在过滤器中获取时，直接获取uname)
session.setAttribute("uname",username);
//设定session的有效期
session.setMaxInactiveInterval(10);
//将获取的用户名和密码打印在页面上
response.getWriter().print("用户名："+username);
response.getWriter().print("
");
response.getWriter().print("密码："+pwd);
System.out.println("退出servlet......");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
- （3）filter过滤器文件：LoginFilter.java
package com.filter.servlet;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* Servlet Filter implementation class LoginFilter
*/
//设置不被过滤的信息
@WebFilter(filterName="LoginFilter",
urlPatterns = "/*",
initParams = {
@WebInitParam(name="noFilterUrl",value
="login.jsp,LoginServlet")
})
public class LoginFilter implements Filter {
//定义一个字符串数组
private String[] noFilter;
/**
* Default constructor.
*/
public LoginFilter() {
// TODO Auto-generated constructor stub
}
/**
* @see Filter#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}
/**
* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
// TODO Auto-generated method stub
// place your code here
HttpServletRequest req = (HttpServletRequest)request;
HttpServletResponse resp = (HttpServletResponse) response;
//获取用户的session
HttpSession session = req.getSession();
//session是用来保存服务端的用户信息
String username =(String) session.getAttribute("uname");
if(username != null) {
chain.doFilter(request, response);
}
else {
//用户没有登录
String url = req.getRequestURI();//获取用户请求地址
for(String temp : noFilter) {
if(url.indexOf(temp)!= -1){
chain.doFilter(request, response);
return ;
}
}
resp.sendRedirect("login.jsp");
}
}
/**
* @see Filter#init(FilterConfig)
*/
public void init(FilterConfig fConfig) throws ServletException {
// TODO Auto-generated method stub
//使用字符分割函数，对noFilter进行赋值
noFilter = fConfig.getInitParameter("noFilterUrl").split(",");
}
}
- （4）验证结果文件：result.jsp文件
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
用户名：${uname}
</body>
</html>