java过滤器---用户登陆校验的简单实例

核心功能：对于用户的访问进行校验，看用户是否已经登陆

1.登陆界面代码如下：

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>









          username: 
           passsword: 
           
   

2.过滤器代码如下：

package Filter;


import java.io.IOException;
import java.nio.channels.SeekableByteChannel;


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.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;


//当你访问success.jsp时，进行过滤检查，检查你是否已经登陆


@WebFilter(filterName="LoginFilter",value="/*")


public class LoginFilter implements Filter {
private FilterConfig  config;


@Override
public void destroy() {
}

@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
//进行强制类型转换，从而可以互获取HttpSession中保存的username
 HttpServletRequest request=(HttpServletRequest)arg0;
 HttpServletResponse response=(HttpServletResponse)arg1;
 HttpSession session=request.getSession();
 //用过滤器解决乱码的问题,可以将字符集的参数保存在默认的FilterConfig人后进行读取
       request.setCharacterEncoding("utf-8");
 //将参数保存到初始化的FilterConfig中
 //返回的是一个字符串数组
   String noFilterPaths=config.getInitParameter("noFilterPaths");
 //我们将其按；符号切割成字符串数组
 String[] nopaths=noFilterPaths.split(";");  
for(int i=0;i //如果包含初始化的不过滤字段，则放行
if(request.getRequestURL().indexOf(nopaths[i])!=-1){
arg2.doFilter(arg0, arg1);
return;
}  
}   
 if(session.getAttribute("username")!=null
 &&session.getAttribute("username")!=""){
 //如果session保存有用户信息，则放行
 arg2.doFilter(arg0, arg1);
 
 System.out.println(session.getAttribute("username"));
 
 }else{
 //如果校验失败，则返回登陆界面
 response.sendRedirect(request.getContextPath()+"/Login.jsp");  
 }  
}
@Override
public void init(FilterConfig arg0) throws ServletException {
config=arg0;

}
}

3.Servlet代码如下：

package Servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginServlet extends HttpServlet {

	
	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//来自login.jsp提交的数据进行处理验证、
		//先获取来自表单的数据
		String  username=request.getParameter("username");
		String  password=request.getParameter("password");
		//先将获取到的用户名保存到session中
         HttpSession  session=request.getSession();
		session.setAttribute("username",username);
		//获取到的username会乱码,可以进行强制类型转换
	    System.out.println(username.toString());
		//对用户名和密码进行验证
		if("admin".equals(username)&&"admin".equals(password)){
			//校验成功,跳转到成功页面
			//用的请求重定向的方法
			response.sendRedirect(request.getContextPath()+"/success.jsp");
			//或者内部转发的方法也可以
			//request.getRequestDispatcher("success.jsp").forward(request, response);			
		}else{
			response.sendRedirect(request.getContextPath()+"/fail.jsp");
		}
		
	}	
	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		doGet(request, response);
	}
	@Override
	public void init() throws ServletException {
	
	}
}