在过滤器中添加标头作为响应？

Question

我需要在每个响应中添加标头.我打算在下面做

public class MyFilter extends OncePerRequestFilter {

    @Override
    protected void doFilterInternal(HttpServletRequest request,
                                    HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {

        filterChain.doFilter(request, response);
            response.addHeader("Access-Control-Allow-Origin", "*"); 
    }

}

我想这样做之后filterChain.doFilter(request, response),一旦控制器处理它,我只是在返回客户端之前添加标题.这是对的吗 ？

但按照如何编写响应过滤器？

chain.doFilter返回之后,对响应采取任何措施都为时已晚.此时,整个响应已发送到客户端,您的代码无法访问它.

以上陈述对我来说不合适.我不能添加标题后filterChain.doFilter(request, response)？如果不是为什么？

我正在使用spring mvc.

Answer 1

在filterChain.doFilter被叫之后,对响应采取任何措施都为时已晚.此时,整个响应已发送给客户端.

您需要在自己的类中构建一个包装响应,将这些包装器传递给doFilter方法并处理包装器中的任何处理.

已有响应包装器:HttpServletResponseWrapper您可以扩展.例如:

public class MyResponseRequestWrapper extends HttpServletResponseWrapper{
    public MyResponseRequestWrapper(HttpServletResponse response) {
        super(response);
    }
}

你的过滤器:

@Override
protected void doFilterInternal(HttpServletRequest request,
                                HttpServletResponse response, FilterChain filterChain)
        throws ServletException, IOException {

    HttpServletResponse myResponse = (HttpServletResponse) response;
    MyResponseRequestWrapper responseWrapper = new MyResponseRequestWrapper(myResponse);
    responseWrapper.addHeader("Access-Control-Allow-Origin", "*");
    filterChain.doFilter(request, myResponse);
}

Answer 2

我在我的项目中使用 Spring 3.0.x：

public class MyFilter extends OncePerRequestFilter {
    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException
    {
        response.addHeader("headerName", "headerValue");
        filterChain.doFilter(request, response);
    }
}

工作正常。