急Struts2 Spring和Hibernate整合时 有关文本输出的Action抛错误

急~Struts2 Spring和Hibernate整合时 有关文本输出的Action抛异常
只是做了一个返回文本的Action
XML code
<action name="user" class="userAction" >
            <result name="success" type="plainText"></result>
        </action>

Java code
@SuppressWarnings("serial")
public class UserAction extends ActionSupport{

    public String doLogout(){
        
        try {
            HttpServletResponse response = ServletActionContext.getResponse(); 
            
            ActionContext.getContext().getSession().clear();
            
            PrintWriter out = response.getWriter();      
            response.setContentType("text/plain;charset=utf-8");   
            response.setHeader("Cache-Control", "no-cache");   
            out.write("{'msg':'"+StringUtil.chinaToUnicode("你安全退出了!")+"'}");  
           
        } catch (Exception e) {
            // TODO: handle exception
        }
        finally{
            return SUCCESS;
        }
        
    }
    
}


2010-11-29 14:49:03 org.apache.jasper.runtime.JspFactoryImpl internalGetPageContext
严重: Exception initializing page context
java.lang.IllegalStateException: Cannot create a session after the response has been committed
at org.apache.catalina.connector.Request.doGetSession(Request.java:2377)
at org.apache.catalina.connector.Request.getSession(Request.java:2097)
at org.apache.catalina.connector.RequestFacade.getSession(RequestFacade.java:833)
at javax.servlet.http.HttpServletRequestWrapper.getSession(HttpServletRequestWrapper.java:216)
at org.apache.catalina.core.ApplicationHttpRequest.getSession(ApplicationHttpRequest.java:547)
at org.apache.catalina.core.ApplicationHttpRequest.getSession(ApplicationHttpRequest.java:493)
at javax.servlet.http.HttpServletRequestWrapper.getSession(HttpServletRequestWrapper.java:224)
at org.apache.jasper.runtime.PageContextImpl._initialize(PageContextImpl.java:146)
at org.apache.jasper.runtime.PageContextImpl.initialize(PageContextImpl.java:124)
at org.apache.jasper.runtime.JspFactoryImpl.internalGetPageContext(JspFactoryImpl.java:107)
at org.apache.jasper.runtime.JspFactoryImpl.getPageContext(JspFactoryImpl.java:63)
at org.apache.jsp.error_jsp._jspService(error_jsp.java:50)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:646)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:551)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:488)
at org.apache.struts2.dispatcher.ServletDispatcherResult.doExecute(ServletDispatcherResult.java:156)
at org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:186)
at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:361)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:265)
at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)