Cannot forward after response has been committed

ITted
自己不懂那就去麻烦一下百度大哥了，得到一个不是很明确的答案：这个是错误是由于response多次提交引起的。
既然如此，那就看看自己什么地方多次使用跳转了吧。
错误代码如下：

 package com.neeke.calc.control;  import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import java.util.*; import com.neeke.calc.bean.LogicBean; import com.neeke.calc.bean.EntITyBean;  public class CalcServlet extends HttpServlet {     private static final String CONTENT_TYPE = "text/html; charset=GBK";      //InITialize global variables     public void inIT() throws ServletException {     }      //Process the HTTP Get request     public void doGet(HttpServletRequest request, HttpServletResponse response) throws             ServletException, IOException {         response.setContentType(CONTENT_TYPE);         request.setCharacterEncoding("GBK");         String money = request.getParameter("earning").trim();         String local = request.getParameter("localTax").trim();         String temp = "";         double earning = 0;         double localTax = 0;         if (money != null && local != null) {             if (money.equals("") || local.equals("")) {                 temp = "未输入收入或当地税额！";                 request.setAttribute("result", temp);                 request.setAttribute("result", temp);                 request.getRequestDispatcher("/error.jsp").forward(request,                         response);              } else {                 try {                     earning = Double.parseDouble(money);                     localTax = Double.parseDouble(local);                 } catch (NumberFormatException ex) {                     temp = "输入内容有误！";                     request.setAttribute("result", temp);                     request.getRequestDispatcher("/error.jsp").forward(request,                             response);                  }                 EntITyBean ebean = new EntITyBean();                 LogicBean lbean = new LogicBean();                 ebean.setYourTax(lbean.calculateTax(earning, localTax));                 request.setAttribute("bean", ebean);                 request.getRequestDispatcher("/result.jsp").forward(request,                         response);              }         }     }      //Process the HTTP Post request     public void doPost(HttpServletRequest request, HttpServletResponse response) throws             ServletException, IOException {         doGet(request, response);     }      //Clean up resources     public void destroy() {     } } package com.neeke.calc.control;<br/><br/>import javax.servlet.*;<br/>import javax.servlet.http.*;<br/>import java.io.*;<br/>import java.util.*;<br/>import com.neeke.calc.bean.LogicBean;<br/>import com.neeke.calc.bean.Ent<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>yBean;<br/><br/>public class CalcServlet extends HttpServlet {<br/>    private static final String CONTENT_TYPE = "text/html; charset=GBK";<br/><br/>    //In<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>ialize global variables<br/>    public void in<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>() throws ServletException {<br/>    }<br/><br/>    //Process the HTTP Get request<br/>    public void doGet(HttpServletRequest request, HttpServletResponse response) throws<br/>            ServletException, IOException {<br/>        response.setContentType(CONTENT_TYPE);<br/>        request.setCharacterEncoding("GBK");<br/>        String money = request.getParameter("earning").trim();<br/>        String local = request.getParameter("localTax").trim();<br/>        String temp = "";<br/>        double earning = 0;<br/>        double localTax = 0;<br/>        if (money != null && local != null) {<br/>            if (money.equals("") || local.equals("")) {<br/>                temp = "未输入收入或当地税额！";<br/>                request.setAttribute("result", temp);<br/>                request.setAttribute("result", temp);<br/>                request.getRequestDispatcher("/error.jsp").forward(request,<br/>                        response);<br/><br/>            } else {<br/>                try {<br/>                    earning = Double.parseDouble(money);<br/>                    localTax = Double.parseDouble(local);<br/>                } catch (NumberFormatException ex) {<br/>                    temp = "输入内容有误！";<br/>                    request.setAttribute("result", temp);<br/>                    request.getRequestDispatcher("/error.jsp").forward(request,<br/>                            response);<br/><br/>                }<br/>                Ent<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>yBean ebean = new Ent<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>yBean();<br/>                LogicBean lbean = new LogicBean();<br/>                ebean.setYourTax(lbean.calculateTax(earning, localTax));<br/>                request.setAttribute("bean", ebean);<br/>                request.getRequestDispatcher("/result.jsp").forward(request,<br/>                        response);<br/><br/>            }<br/>        }<br/>    }<br/><br/>    //Process the HTTP Post request<br/>    public void doPost(HttpServletRequest request, HttpServletResponse response) throws<br/>            ServletException, IOException {<br/>        doGet(request, response);<br/>    }<br/><br/>    //Clean up resources<br/>    public void destroy() {<br/>    }<br/>}<br/>
修改后的代码：

 package com.neeke.calc.control;  import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import java.util.*; import com.neeke.calc.bean.LogicBean; import com.neeke.calc.bean.EntITyBean;  public class CalcServlet extends HttpServlet {     private static final String CONTENT_TYPE = "text/html; charset=GBK";      //InITialize global variables     public void inIT() throws ServletException {     }      //Process the HTTP Get request     public void doGet(HttpServletRequest request, HttpServletResponse response) throws             ServletException, IOException {         response.setContentType(CONTENT_TYPE);         request.setCharacterEncoding("GBK");         String money = request.getParameter("earning").trim();         String local = request.getParameter("localTax").trim();         String temp = "";         double earning = 0;         double localTax = 0;         if (money != null && local != null) {             boolean y = false;             if (money.equals("") || local.equals("")) {                 temp = "未输入收入或当地税额！";                 request.setAttribute("result", temp);                 y = true;             } else {                 try {                     earning = Double.parseDouble(money);                     localTax = Double.parseDouble(local);                 } catch (NumberFormatException ex) {                     temp = "输入内容有误！";                     y = true;                 }             }             if (y) {                 request.setAttribute("result", temp);                 request.getRequestDispatcher("/error.jsp").forward(request,                         response);              } else {                 EntITyBean ebean = new EntITyBean();                 LogicBean lbean = new LogicBean();                 ebean.setYourTax(lbean.calculateTax(earning, localTax));                 request.setAttribute("bean", ebean);                 request.getRequestDispatcher("/result.jsp").forward(request,                         response);              }          }      }      //Process the HTTP Post request     public void doPost(HttpServletRequest request, HttpServletResponse response) throws             ServletException, IOException {         doGet(request, response);     }      //Clean up resources     public void destroy() {     } } package com.neeke.calc.control;<br/><br/>import javax.servlet.*;<br/>import javax.servlet.http.*;<br/>import java.io.*;<br/>import java.util.*;<br/>import com.neeke.calc.bean.LogicBean;<br/>import com.neeke.calc.bean.Ent<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>yBean;<br/><br/>public class CalcServlet extends HttpServlet {<br/>    private static final String CONTENT_TYPE = "text/html; charset=GBK";<br/><br/>    //In<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>ialize global variables<br/>    public void in<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>() throws ServletException {<br/>    }<br/><br/>    //Process the HTTP Get request<br/>    public void doGet(HttpServletRequest request, HttpServletResponse response) throws<br/>            ServletException, IOException {<br/>        response.setContentType(CONTENT_TYPE);<br/>        request.setCharacterEncoding("GBK");<br/>        String money = request.getParameter("earning").trim();<br/>        String local = request.getParameter("localTax").trim();<br/>        String temp = "";<br/>        double earning = 0;<br/>        double localTax = 0;<br/>        if (money != null && local != null) {<br/>            boolean y = false;<br/>            if (money.equals("") || local.equals("")) {<br/>                temp = "未输入收入或当地税额！";<br/>                request.setAttribute("result", temp);<br/>                y = true;<br/>            } else {<br/>                try {<br/>                    earning = Double.parseDouble(money);<br/>                    localTax = Double.parseDouble(local);<br/>                } catch (NumberFormatException ex) {<br/>                    temp = "输入内容有误！";<br/>                    y = true;<br/>                }<br/>            }<br/>            if (y) {<br/>                request.setAttribute("result", temp);<br/>                request.getRequestDispatcher("/error.jsp").forward(request,<br/>                        response);<br/><br/>            } else {<br/>                Ent<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>yBean ebean = new Ent<a href=" [url]http://www.ineeke.cn[/url]" Class="keylink" title="IT"  Target="IT" >IT</a>yBean();<br/>                LogicBean lbean = new LogicBean();<br/>                ebean.setYourTax(lbean.calculateTax(earning, localTax));<br/>                request.setAttribute("bean", ebean);<br/>                request.getRequestDispatcher("/result.jsp").forward(request,<br/>                        response);<br/><br/>            }<br/><br/>        }<br/><br/>    }<br/><br/>    //Process the HTTP Post request<br/>    public void doPost(HttpServletRequest request, HttpServletResponse response) throws<br/>            ServletException, IOException {<br/>        doGet(request, response);<br/>    }<br/><br/>    //Clean up resources<br/>    public void destroy() {<br/>    }<br/>}<br/>
经过对比可以看出问题出在

 if (money.equals("") || local.equals("")) {                 temp = "未输入收入或当地税额！";                 request.setAttribute("result", temp);                 request.setAttribute("result", temp);                 request.getRequestDispatcher("/error.jsp").forward(request,                         response);              } else {                 try {                     earning = Double.parseDouble(money);                     localTax = Double.parseDouble(local);                 } catch (NumberFormatException ex) {                     temp = "输入内容有误！";                     request.setAttribute("result", temp);                     request.getRequestDispatcher("/error.jsp").forward(request,                             response);                  } if (money.equals("") || local.equals("")) {<br/>                temp = "未输入收入或当地税额！";<br/>                request.setAttribute("result", temp);<br/>                request.setAttribute("result", temp);<br/>                request.getRequestDispatcher("/error.jsp").forward(request,<br/>                        response);<br/><br/>            } else {<br/>                try {<br/>                    earning = Double.parseDouble(money);<br/>                    localTax = Double.parseDouble(local);<br/>                } catch (NumberFormatException ex) {<br/>                    temp = "输入内容有误！";<br/>                    request.setAttribute("result", temp);<br/>                    request.getRequestDispatcher("/error.jsp").forward(request,<br/>                            response);<br/><br/>                }<br/>
不过究竟为什么这样就会出错就不清楚了，以前写的好像也有过多次跳转的这个，但是都没有错的啊！郁闷了~~~不过知道问题出在哪里了，以后尽量避免这样写就是了。o(∩_∩)o...
本文来源于：尼克技术博客 [url]http://www.ineeke.cn/[/url] , 原文地址： [url]http://www.ineeke.cn/archives/Cannot-forward-after-response-has-been-committed/[/url]