如何根据Content-type添加响应头;在提交响应之前获取Content-type [英] How to add response headers based on Content-type; getting Content-type before the response is committed

问题描述

我想为所有 image / * 和文字/设置过期标头CSS 。我在过滤器中这样做。但是：

I want to set the Expires header for all image/* and text/css. I'm doing this in a Filter. However:

• 在调用 chain.doFilter（..）内容类型之前尚未实现


• 在调用 chain.doFilter（..）之后设置了Content-type，但内容也是如此-length，禁止添加新标头（至少在Tomcat实现中）

• before calling chain.doFilter(..) the Content-type is not yet "realized"
• after calling chain.doFilter(..) the Content-type is set, but so is content-length, which forbids adding new headers (at least in Tomcat implementation)

我可以使用所请求资源的扩展名，但是一些css文件是由richfaces通过从jar文件中取出来生成的，文件的名称不是 x.css ，但是 /xx/yy/zz.xcss/DATB /...。

I can use the extensions of the requested resource, but since some of the css files are generated by richfaces by taking them from inside jar-files, the name of the file isn't x.css, but is /xx/yy/zz.xcss/DATB/....

那么，有没有办法获得Content-type在提交响应之前。

So, is there a way to get the Content-type before the response is committed.

推荐答案

是的，实现 HttpServletResponseWrapper 并覆盖 setContentType （）。

class AddExpiresHeader extends HttpServletResponseWrapper {
    private static final long ONE_WEEK_IN_MILLIS = 604800000L;

    public AddExpiresHeader(HttpServletResponse response) {
        super(response);
    }

    public void setContentType(String type) {
        if (type.startsWith("text") || type.startsWith("image")) {
            super.setDateHeader("Expires", System.currentTimeMillis() + ONE_WEEK_IN_MILLIS);
        }
        super.setContentType(type);
    }
}

并按如下方式使用：

chain.doFilter(request, new AddExpiresHeader((HttpServletResponse) response));

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