Servlet认证过滤器介绍和用法详解

我们可以在过滤器中执行身份验证。在这里, 我们将检查过滤器类中用户提供的密码, 如果给定的密码是admin, 它将把请求转发到WelcomeAdmin servlet, 否则将显示错误消息。
使用过滤器验证用户的示例
让我们看一下使用过滤器验证用户身份的简单示例。
在这里, 我们创建了4个文件：

index.html
MyFilter.java
AdminServlet.java
web.xml

index.html

< form action="servlet1"> Name:< input type="text" name="name"/> < br/> Password:< input type="password" name="password"/> < br/> < input type="submit" value="http://www.srcmini.com/login"> < /form>

MyFilter.java

import java.io.IOException; import java.io.PrintWriter; import javax.servlet.*; public class MyFilter implements Filter{public void init(FilterConfig arg0) throws ServletException {} public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException { PrintWriter out=resp.getWriter(); String password=req.getParameter("password"); if(password.equals("admin")){ chain.doFilter(req, resp); //sends request to next resource } else{ out.print("username or password error!"); RequestDispatcher rd=req.getRequestDispatcher("index.html"); rd.include(req, resp); }} public void destroy() {}}

AdminServlet.java

import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.*; public class AdminServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.print("welcome ADMIN"); out.close(); } }

web.xml

< web-app> < servlet> < servlet-name> AdminServlet< /servlet-name> < servlet-class> AdminServlet< /servlet-class> < /servlet> < servlet-mapping> < servlet-name> AdminServlet< /servlet-name> < url-pattern> /servlet1< /url-pattern> < /servlet-mapping> < filter> < filter-name> f1< /filter-name> < filter-class> MyFilter< /filter-class> < /filter> < filter-mapping> < filter-name> f1< /filter-name> < url-pattern> /servlet1< /url-pattern> < /filter-mapping> < /web-app>

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