響應已提交後無法轉發 - Servlet

Question

我正在嘗試從HTTPSession中註銷並將用戶重定向到登錄頁面。

下面是我完整的Http servlet代碼。

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 LogoutServlet extends HttpServlet { 

@Override 
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
{ 
    super.doGet(req, resp); 
    processRequest(req, resp); 
} 

@Override 
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
{ 
    super.doPost(req, resp); 
    processRequest(req, resp); 
} 

private void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
{ 
    final HttpSession session = request.getSession(false); 
    if (session != null) 
    { 
     session.invalidate(); 
    } 

    response.sendRedirect("/login.html"); 
    //getServletContext().getRequestDispatcher("/login.html").forward(request, response); 
} 

}

但是，得到以下異常：

java.lang.IllegalStateException: Cannot forward after response has been committed 
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:339) 
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329) 
at com.controller.LogoutServlet.processRequest(LogoutServlet.java:41) 

Answer 1

刪除來電

super.doGet(req, resp); // and 
super.doPost(req, resp); 

基類的實現只是一味的拋出GET或不支持POST錯誤消息。

// HttpServlet#doGet() calls 
resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, msg); 

上面的行是已經提交了響應。

Answer 2

你爲什麼不重定向，而不是前鋒？

response.sendRedirect("/login.html");