Servlet – 身份验证过滤器

Servlet 是在支持Java的 Web 服务器或应用程序服务器上运行的 Java 程序。它们用于处理从网络服务器获得的请求，处理请求，产生响应，然后将响应发送回网络服务器。

Servlet 中的身份验证过滤器

认证可以在过滤器中完成。在这里，我们将在 ServletFilter 类中验证用户的密码；如果密码是“geeksforgeeks” ，请求将被发送到 Gfg servlet；否则，将显示错误消息。

实现：让我们看一个利用过滤器对用户进行身份验证的简单示例。我们在这里生成了四个文件：

• 索引.html
• 女朋友。Java
• 小服务过滤器。Java
• web.xml

文件： index.html

HTML

  
               Name: < input type = "text" name = "name" / > < br / > < br / >
  
                                    Password: < input type = "password" name = "password" / > < br / > < br / >
  
                                            
  
                                                    < / form >

示例 1-A：

Java

// Java Program to Illustrate ServletFilter Class
  
// Importing required classes
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.*;
  
// Class
// Implementing Filter class
public class ServletFilter 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("geeksforgeeks")) {
  
            // Sending request to next
            chain.doFilter(req, resp);
        }
  
        // Password incorrect
        else {
            out.print("username or password is wrong");
            RequestDispatcher rd
                = req.getRequestDispatcher("index.html");
            rd.include(req, resp);
        }
    }
    public void destroy() {}
}

示例 1-B：

Java

// Java Program to Illustrate GFG Class
  
// Importing required classes
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
  
// Class
// Derived from HttpServlet class
public class GFG extends HttpServlet {
  
    // Getting request response
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
        throws ServletException, IOException
    {
  
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
  
        out.print("welcome to GEEKSFORGEEKS");
  
        // Closing connections to
        // avoid any memory leakage
        out.close();
    }
}

文件： web.xml

XML

  
   
    Gfg  
    Gfg  
    
    
    
    Gfg  
    /servlet1  
    
      
   
  f1  
  ServletFilter  
    
    
  f1  
  /servlet1  
    
      

输出：

Click on the login button, if the password is correct then the above message will be shown to the user.