Cannot create a session after the response has been committed

来源：猿天地

链接：http://cxytiandi.com/blog/detail/1699

刚好今天博客功能正式上线，然而上线之后出了一个bug

java.lang.IllegalStateException: Cannot create a session after the response has been committed

意思是说在response提交之后不能操作session了，我也就奇怪了，本地开发的时候没出现这个问题啊。

唯一不一样的是线上用的nginx做转发,还有就是我是从一个action里重定向到另外一个action时出的错。

根据异常提示看了下问题出在一个Filter里面

HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
String path = req.getContextPath();
String basePath = "";
if (System.getProperty("os.name").toLowerCase().startsWith("linux")) {
    basePath = "http://cxytiandi.com";
} else {
    basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort();
}
if(contains(req.getRequestURI())){
    if(req.getSession().getAttribute("login_userId") == null){
resp.sendRedirect(basePath + path + "/login?backUrl=" + basePath + req.getRequestURI());
    }
} 
chain.doFilter(request, response);

这是Filter里面的代码，按照异常信息应该是下面这句代码不能在response之后操作session

req.getSession().getAttribute("login_userId")

改完后代码如下

HttpServletRequest req = (HttpServletRequest) request;
Object login_userId = req.getSession().getAttribute("login_userId");
HttpServletResponse resp = (HttpServletResponse) response;
String path = req.getContextPath();
String basePath = "";
if (System.getProperty("os.name").toLowerCase().startsWith("linux")) {
    basePath = "http://cxytiandi.com";
} else {
    basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort();
}
if(contains(req.getRequestURI())){
    if(login_userId == null){
resp.sendRedirect(basePath + path + "/login?backUrl=" + basePath + req.getRequestURI());
    }
} 
chain.doFilter(request, response);

在转换response之前操作session就可以了。