提交響應後無法轉發按下按鈕

在我的項目中，我使用了主頁Browse.jsp，可以在其中添加/編輯/刪除用戶。我有3個按鈕「添加」和「編輯」和「刪除」。但是，當我按任何按鈕，我有錯誤。提交響應後無法轉發按下按鈕

這是我BrowseServlet

public class BrowseServlet extends HttpServlet { 

protected void service (HttpServletRequest req, HttpServletResponse resp) 
    throws ServletException, IOException{ 
    if (req.getParameter("addButton") !=null){ 
     add (req, resp); 
    } else if (req.getParameter("editButton") !=null){ 
     edit (req, resp); 
    } else if (req.getParameter("deleteButton") !=null){ 
     delete (req, resp); 
    } else if (req.getParameter("detailsButton") !=null){ 
     details (req, resp); 
    } 
    browse(req, resp); 

} 

private void details(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
    // TODO Auto-generated method stub 

} 

private void delete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{ 
    // TODO Auto-generated method stub 

} 

private void edit(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{ 
    String idStr = req.getParameter("id"); 
    if (idStr == null || idStr.trim().length() == 0) { 
     req.setAttribute("error", "You must select the user"); 
     req.getRequestDispatcher("/browse.jsp").forward(req, resp); 
     return; 
    } 
    try{ 
     User user = DaoFactory.getInstance().getUserDao().find(new Long(idStr)); 
     req.getSession().setAttribute("user", user); 
    } catch (Exception e) { 
     req.setAttribute("error", "ERROR:" + e.toString()); 
     req.getRequestDispatcher("/browse.jsp").forward(req, resp); 
     return; 
    } 
    req.getRequestDispatcher("/edit").forward(req, resp); 

} 

private void add(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
    req.getRequestDispatcher("/add").forward(req, resp); 


} 

private void browse(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
    Collection users; 
    try { 
     users = DaoFactory.getInstance().getUserDao().findAll(); 
     req.getSession().setAttribute("users", users); 
     req.getRequestDispatcher("/browse.jsp").forward(req, resp); 
    } catch (DatabaseException e) { 
     throw new ServletException(e); 
    } 

} 

}

這是我AddServlet

public class AddServlet extends EditServlet { 




protected void processUser(User user) throws DatabaseException { 
    DaoFactory.getInstance().getUserDao().create(user); 
} 

protected void showPage(HttpServletRequest req, HttpServletResponse resp) 
     throws ServletException, IOException { 
    req.getRequestDispatcher("/add.jsp").forward(req, resp); 
} 

}

這是我的WEB-INF BROWSE.jsp

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> 
<html> 
<head><title>User management </title></head> 
<body> 
<form action="<%=request.getContextPath()%>/browse" method="post"> 
<table id="UserTable" border="1"> 
<tr> 
<th></th> 
    <th>First Name</th> 
    <th>Last Name</th> 
    <th>Date of birth</th> 
</tr> 
<c:forEach var="user" items="${session.Scope.users}"> 
<tr> 
<td><input type="radio" name="id" id="id" value="${user.id}"</td> 
    <td>${user.firstName}</td> 
    <td>${user.lastName}</td> 
    <td>${user.dateOfBirth}</td> 
</tr> 
</c:forEach> 
</table> 
<input type="submit" name="addButton" value="Add"> 
<input type="submit" name="editButton" value="Edit"> 
<input type="submit" name="deleteButton" value="Delete"> 
<input type="submit" name="detailsButton" value="Details"> 
</form> 
<c:if test="${requestScope.error != null}"> 
<script> 
    alert('${requestScope.error}'); 
</script> 
</c:if> 
</body> 
</html>

ADD.jsp

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> 
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%> 
<html> 
<head><title>User management. Add </title></head> 
<body> 
<form action="<%=request.getContextPath()%>/add" method="post"> 
    First name <input type="text" name="firstName" value=""><br> 
    Last name <input type="text" name="lastName" value=""><br> 
    Date of birth <input type="text" name="date" value=""><br> 
    <input type="submit" name="okButton" value="Ok"> 
    <input type="submit" name="cancelButton" value="Cancel"> 
</form> 
<c:if test="${requestScope.error != null}"> 
<script> 
    alert('${requestScope.error}'); 
</script> 
</c:if> 
</body> 
</html>

但我有這個錯誤，當我試圖推動「Add按鈕」

type Exception report 

message 

description The server encountered an internal error() that prevented it from fulfilling this request. 

exception 

java.lang.IllegalStateException: Cannot forward after response has been committed 
com.rudniev.usermanagment.web.BrowseServlet.browse(Unknown Source) 
com.rudniev.usermanagment.web.BrowseServlet.service(Unknown Source) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:802) 
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.12 logs.

來源

2012-12-10 user1892013

你總是調用browse()以及不管調用的動作。所以有效地，當一個動作被調用時（這反過來已經執行了它），你正在執行第二個前進。

也許你想把它放在else塊？

if (req.getParameter("addButton") !=null){ 
    add (req, resp); 
} else if (req.getParameter("editButton") !=null){ 
    edit (req, resp); 
} else if (req.getParameter("deleteButton") !=null){ 
    delete (req, resp); 
} else if (req.getParameter("detailsButton") !=null){ 
    details (req, resp); 
} else { 
    browse(req, resp); 
}

來源

2012-12-10 15:45:51 BalusC

我改變它，但是當我推加我有什麼關係（沒有錯誤和沒有頁）......什麼是錯的） – user1892013

噢，對不起，我太傻了，我看不到我的小錯誤，現在可以，謝謝） – user1892013

不客氣。 – BalusC

提交響應後無法轉發按下按鈕

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