捕获并记录响应正文 [英] Capture and log the response body

问题描述

我有一个处理某些 HTTP 请求和响应的 servlet.我想在发送回客户端之前记录响应正文.有什么方法可以在响应主体作为 HttpServletResponse 对象从 servlet 发送之前捕获它?

I have a servlet that handle certain HTTP requests and responses. I want to log the response body before sending back to the client. Is there any way that I can capture the response body before it is send as a HttpServletResponse object from the servlet?

推荐答案

如果我理解正确，您想记录响应 body 吗?这是一项非常昂贵的任务，但如果这是业务需求......

If I understand you correctly, you want to log the response body? That's a pretty expensive task, but if that's the business requirement...

正如@duffymo 所指出的，Filter 是一个合适的地方.您可以通过将传入的 ServletResponse 替换为 HttpServletResponseWrapper 实现，将 HttpServletResponse#getWriter() 替换为自己的实现，将响应正文复制到某个缓冲区中.使用替换的响应继续过滤器链后，只需记录副本.

As @duffymo pointed, a Filter is a suitable place for this. You can capture the response body by replacing the passed-in ServletResponse with a HttpServletResponseWrapper implementation which replaces the HttpServletResponse#getWriter() with an own implementation which copies the response body into some buffer. After continuing the filter chain with the replaced response, just log the copy.

以下是 doFilter() 方法的启动示例:

Here's a kickoff example how the doFilter() method can look like:

public void doFilter(ServletRequest request, final ServletResponse response, FilterChain chain) throws IOException, ServletException {
    final CopyPrintWriter writer = new CopyPrintWriter(response.getWriter());
    chain.doFilter(request, new HttpServletResponseWrapper((HttpServletResponse) response) {
        @Override public PrintWriter getWriter() {
            return writer;
        }
    });
    logger.log(writer.getCopy());
}

CopyPrintWriter 如下所示:

public class CopyPrintWriter extends PrintWriter {

    private StringBuilder copy = new StringBuilder();

    public CopyPrintWriter(Writer writer) {
        super(writer);
    }

    @Override
    public void write(int c) {
        copy.append((char) c); // It is actually a char, not an int.
        super.write(c);
    }

    @Override
    public void write(char[] chars, int offset, int length) {
        copy.append(chars, offset, length);
        super.write(chars, offset, length);
    }

    @Override
    public void write(String string, int offset, int length) {
        copy.append(string, offset, length);
        super.write(string, offset, length);
    }

    public String getCopy() {
        return copy.toString();
    }

}

将此过滤器映射到您希望为其记录响应的 url-pattern 上.请记住，不会以这种方式记录二进制/静态内容，如图像、CSS、JS 文件等.您想通过使用足够具体的 url-pattern 来排除它们，例如*.jsp 或仅在相关 servlet 的 servlet-name 上.如果您无论如何都想记录二进制/静态内容(我没有看到任何好处)，那么您也需要以相同的方式替换 HttpServletResponse#getOutputStream().

Map this filter on an url-pattern for which you'd like to log responses for. Keep in mind that binary/static content like images, CSS, JS files and so on won't be logged this way. You'd like to exclude them by using a specific enough url-pattern, e.g. *.jsp or just on the servlet-name of the servlet in question. If you want to log binary/static content anyway (for which I don't see any benefit), then you need to replace the HttpServletResponse#getOutputStream() the same way as well.

这篇关于捕获并记录响应正文的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！