Java-Filter实现权限拦截
要求：用户登录之后才能进入主页，用户注销后就不能进入主页了！
首先我们写一个登录的页面
登录然后登录的 servlet ，登录成功或者登录失败
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取前端请求的参数
String username = req.getParameter("username");
if (username.equals("admin")){ //登录成功
req.getSession().setAttribute("USER_SESSION",req.getSession().getId());
resp.sendRedirect("/sys/success.jsp"); //假如用户名正确，就重定向到sys/success.jsp
}else { //登录成功
resp.sendRedirect("/error.jsp");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}然后写一个登录失败的jsp，注销后跳转到登录界面
错误
没有权限，用户名错误
返回登录页面我们发现无论成功与否都能进入成功主页：所以我们添加一个过滤器 注销后移除session
public class LogoutServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Object user_session = req.getSession().getAttribute("USER_SESSION");
if (user_session!=null){
req.getSession().removeAttribute("USER_SESSION");
resp.sendRedirect("/Login.jsp");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}public class SysFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
//通过强转拿到session
HttpServletRequest request = (HttpServletRequest) servletRequest;
HttpServletResponse response = (HttpServletResponse) servletResponse;
if (request.getSession().getAttribute("USER_SESSION")==null){
response.sendRedirect("/error.jsp");
}
filterChain.doFilter(servletRequest,servletResponse);
}
@Override
public void destroy() {
}
}这样过滤以后就拦截了进入主页
为了节约性能：我们建一个文件来放我们的 USER_SESSION------>Constant
public class Constant {
public final static String USER_SESSION = "USER_SESSION";
}
filter实现拦截.png
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