你需要创建一个，在
Filter其中
ServletResponse用自定义
HttpServletResponseWrapper实现包装参数，在其中覆盖
getOutputStream()和
getWriter()并返回一个自定义
ServletOutputStream实现，在该实现中你将写入的字节复制到基本抽象
OutputStream#write(int b)方法中。然后，你将包装的自定义传递
HttpServletResponseWrapper给
FilterChain#doFilter()调用，最后，你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. }}习惯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]; } }}习惯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(); }}
