struts2 java.lang.IllegalStateException: getWriter() has already been called for this response(异常解决)

 预告: 重点请看最后面。

做excel导出时遇到的问题,很多时候会遇到此错误,异常如下:

java.lang.IllegalStateException: getWriter() has already been called for this response
	at org.apache.catalina.connector.Response.getOutputStream(Response.java:628)
	at org.apache.catalina.connector.ResponseFacade.getOutputStream(ResponseFacade.java:196)
	at com.wrt.action.order.EndOrderAction.exportInfo(EndOrderAction.java:143)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:446)
	at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:285)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
	at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
	at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
	at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
	at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)

背景如下:
使用Struts2框架,点击某个按钮实现列表excel导出
2.大致代码如下
public void exportInfo(){
		try {
			//web对象
			HSSFWorkbook wb = new HSSFWorkbook();
			//创建表头等
			HSSFSheet sheet = wb.createSheet("test1");
			//创建行
			HSSFRow row = sheet.createRow(0);
			//创建列
			HSSFCell cell = row.createCell(0);
			//**************省略excel创建部分..
			HttpServletResponse response = ServletActionContext.getResponse();
			OutputStream output = getRepsonse().getOutputStream();  
			response.reset(); 
			response.setHeader("Content-disposition", "attachment; filename=details.xls");  
		    response.setContentType("application/msexcel");          
		    wb.write(output);
		    output.close();
			System.out.println("成功创建excel文件");
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
 
最终解决方案,将response.reset(); 放到OutputStream output = getRepsonse().getOutputStream();前面,
HttpServletResponse response = ServletActionContext.getResponse();
			response.reset(); 
			OutputStream output = getRepsonse().getOutputStream();  
			response.setHeader("Content-disposition", "attachment; filename=details.xls");  
		    response.setContentType("application/msexcel");  

 运行效果如下成功。 
.


原因,避免可能出现未关闭的 getWriter(),使用了response.reset();进行刷新,而此时却在未刷新的情况下进行了OutputStream output = getRepsonse().getOutputStream();操作.....    简之:就是位置放错了  .



会出现如下异常的三种可能:
1.通过 response.reset(); 刷新可能存在一些未关闭的getWriter().  来源:http://blog.csdn.net/wonder4/article/details/8476603
2.struts2请求方法中返回了success此类会返回数据或者界面的,举例如下:
public String saveSubmitOrder(){
return "success";
}
改成
public String saveSubmitOrder(){
return null;
}
或者void。
3.存在多个 getWriter且未关闭状态,或者getWriter与OutputStream同时出现。

总之,一个请求过来只会有一个返回结果,如果存在两个或以上则会出现此异常.






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