Question

我在我的java webserver（实际上是appengine）中创建了一个过滤器，用于记录传入请求的参数。我还想记录我的网络服务器写的结果响应。虽然我可以访问响应对象，但我不确定如何从中获取实际的字符串/内容响应。

有什么想法吗？

Answer 1

您需要创建一个Filter，其中您使用自定义HttpServletResponseWrapper实施包装ServletResponse参数，其中您覆盖getOutputStream()和getWriter()以返回自定义ServletOutputStream实现，其中您复制基本抽象OutputStream#write(int b)方法中的写入字节。然后，您将包装的自定义HttpServletResponseWrapper传递给FilterChain#doFilter()调用，最后您应该能够在调用之后获得复制的响应。

换句话说，Filter：

@WebFilter("/*") public class ResponseLogger implements Filter { @Override public void init(FilterConfig config) throws ServletException { // NOOP. } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException { if (response.getCharacterEncoding() == null) { response.setCharacterEncoding("UTF-8"); // Or whatever default. UTF-8 is good for World Domination. } HttpServletResponseCopier responseCopier = new HttpServletResponseCopier((HttpServletResponse) response); try { chain.doFilter(request, responseCopier); responseCopier.flushBuffer(); } finally { byte[] copy = responseCopier.getCopy(); System.out.println(new String(copy, response.getCharacterEncoding())); // Do your logging job here. This is just a basic example. } } @Override public void destroy() { // NOOP. } }

自定义HttpServletResponseWrapper：

public class HttpServletResponseCopier extends HttpServletResponseWrapper { private ServletOutputStream outputStream; private PrintWriter writer; private ServletOutputStreamCopier copier; public HttpServletResponseCopier(HttpServletResponse response) throws IOException { super(response); } @Override public ServletOutputStream getOutputStream() throws IOException { if (writer != null) { throw new IllegalStateException("getWriter() has already been called on this response."); } if (outputStream == null) { outputStream = getResponse().getOutputStream(); copier = new ServletOutputStreamCopier(outputStream); } return copier; } @Override public PrintWriter getWriter() throws IOException { if (outputStream != null) { throw new IllegalStateException("getOutputStream() has already been called on this response."); } if (writer == null) { copier = new ServletOutputStreamCopier(getResponse().getOutputStream()); writer = new PrintWriter(new OutputStreamWriter(copier, getResponse().getCharacterEncoding()), true); } return writer; } @Override public void flushBuffer() throws IOException { if (writer != null) { writer.flush(); } else if (outputStream != null) { copier.flush(); } } public byte[] getCopy() { if (copier != null) { return copier.getCopy(); } else { return new byte[0]; } } }

自定义ServletOutputStream：

public class ServletOutputStreamCopier extends ServletOutputStream { private OutputStream outputStream; private ByteArrayOutputStream copy; public ServletOutputStreamCopier(OutputStream outputStream) { this.outputStream = outputStream; this.copy = new ByteArrayOutputStream(1024); } @Override public void write(int b) throws IOException { outputStream.write(b); copy.write(b); } public byte[] getCopy() { return copy.toByteArray(); } }

Answer 2

BalusC解决方案没问题，但很少过时。 Spring现在有它的特色。您需要做的只是使用[ContentCachingResponseWrapper]，其方法为public byte[] getContentAsByteArray()。

我建议制作WrapperFactory，使其可以配置，无论是使用默认的ResponseWrapper还是ContentCachingResponseWrapper。

Answer 3

虽然BalusC's answer在大多数情况下都可以使用，但您必须小心flush调用 - 它会提交响应，而不能写其他任何内容，例如。通过以下过滤器。我们在Websphere环境中发现了一些非常类似的问题，其中交付的响应只是部分的。

根据this question，根本不应该调用flush，你应该让它在内部调用。

我通过使用TeeWriter（它将流分成2个流）并在＆＃34;分支流＆＃34;中使用非缓冲流解决了刷新问题。用于记录目的。那么在flush打电话是不必要的。

private HttpServletResponse wrapResponseForLogging(HttpServletResponse response, final Writer branchedWriter) {
    return new HttpServletResponseWrapper(response) {
        PrintWriter writer;

        @Override
        public synchronized PrintWriter getWriter() throws IOException {
            if (writer == null) {
                writer = new PrintWriter(new TeeWriter(super.getWriter(), branchedWriter));
            }
            return writer;
        }
    };
}

然后你可以这样使用它：

protected void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException {
    //...
    StringBuilderWriter branchedWriter = new org.apache.commons.io.output.StringBuilderWriter();
    try {
        chain.doFilter(request, wrapResponseForLogging(response, branchedWriter));
    } finally {
        log.trace("Response: " + branchedWriter);
    }
}

为了酿造而简化了代码。

Answer 4

我对appengine不是很熟悉，但你在Tomcat中需要一些Access Log Valve。其属性模式;格式化布局，用于标识请求和要记录的响应中的各种信息字段，或单词common或combined以选择标准格式。

看起来appengine内置了log filtering的功能。

apply a servlet filter

Answer 5

与其创建自定义HttpServletResponseWrapper，还可以使用ContentCachingResponseWrapper，因为它提供了getContentAsByteArray（）方法。

public void doFilterInternal(HttpServletRequest servletRequest, HttpServletResponse servletResponse,
            FilterChain filterChain) throws IOException, ServletException {

        HttpServletRequest request = servletRequest;
        HttpServletResponse response = servletResponse;
        ContentCachingRequestWrapper requestWrapper = new ContentCachingRequestWrapper(request);
        ContentCachingResponseWrapper responseWrapper =new ContentCachingResponseWrapper(response);
        try {
            super.doFilterInternal(requestWrapper, responseWrapper, filterChain);

        } finally {

            byte[] responseArray=responseWrapper.getContentAsByteArray();
            String responseStr=new String(responseArray,responseWrapper.getCharacterEncoding());
            System.out.println("string"+responseStr);       
            /*It is important to copy cached reponse body back to response stream
            to see response */
            responseWrapper.copyBodyToResponse();

        }

    }

如何读取和复制HTTP servlet响应输出流内容以进行日志记录

5 个答案: