struts2报错： getWriter() has already been called for this response

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

Struts2常报getWriter() has already been called for this response

这个异常。我们在操作各种IO流时，也很容易报这个异常，所以io流报错时，可以借鉴本文。

1.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 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)

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();
}
}

3.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");

小结：应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。

4.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().

2.struts2请求方法中返回了success此类会返回数据或者界面的返回值。举例如下：

public String saveSubmitOrder(){
return "success";
}
//改成
public String saveSubmitOrder(){
return null;
}

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.