高手帮忙！在线急等！

[mahf]

public void doPost(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
String a = null;
if (a == null) {
rt = this.getServletContext().getRequestDispatcher("/mahfjsp.jsp");
rt.forward(request, response);
}

if (a == null) {
rt = this.getServletContext().getRequestDispatcher("/ma.jsp");
rt.forward(request, response);
}

}

上面代码执行可以，但有错误！如何解决谢谢大家！
错误信息：
java.lang.IllegalStateException: Cannot forward after response has been committed

at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:367)

at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:355)

at cs.maServlet.doPost(maServlet.java:34)

at cs.maServlet.doGet(maServlet.java:19)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)

at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)

at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)

at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190)

at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)

at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246)

at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)

at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)

at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)

at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2347)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)

at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)

at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)

at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)

at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)

at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)

at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)

at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)

at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)

at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)

at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1027)

at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1125)

at java.lang.Thread.run(Thread.java:536)

[pleonheart]

ResponseDispatcher rt = null;
if (a == null) {
rt = this.getServletContext().getRequestDispatcher("/mahfjsp.jsp");
rt.forward(request, response);
}

[pleonheart]

晕死，应该是RequestDispachter

[希偌]

if (a == null) {
rt = this.getServletContext().getRequestDispatcher("/mahfjsp.jsp");
}

if (a == null) {
rt = this.getServletContext().getRequestDispatcher("/ma.jsp");
}
rt.forward(request, response);

[mahf]

条件没错，如何执行完前一请求后退出doPost！

[mahf]

ResponseDispatcher rt = null;
定义了！！！