Java for Web学习笔记（四三）：Filter（5）用于认证

一个简单的认证Filter

简单的Filter，登录界面为/login，如果登录成功，session中带有username。

public class AuthenticationFilter implements Filter {

public void init(FilterConfig fConfig) throws ServletException { }

public void destroy() {}

public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain) throws IOException,ServletException{
HttpSession session = ((HttpServletRequest)request).getSession(false);
if(session == null || session.getAttribute("username") == null){
System.out.println("redirect to /login ... ");
((HttpServletResponse)response).sendRedirect("/login");
}else{
System.out.println("username = "  + session.getAttribute("username"));
chain.doFilter(request, response);
}
}
}

定义Filter

采用代码设置方式，对/sessions，/tickets的url要求经过认证的filter。

public class Configurator implements ServletContextListener {

    public void contextDestroyed(ServletContextEvent sce)  { 
    }

    public void contextInitialized(ServletContextEvent sce)  { 
         ServletContext context = sce.getServletContext();
         FilterRegistration.Dynamic registration = context.addFilter("AuthenticationFilter", AuthenticationFilter.class);
         //registration.setAsyncSupported(true);
         registration.addMappingForUrlPatterns(null, false, "/sessions","/tickets");
    }
}

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