缓存请求 content 的 HttpServletRequest 包装类

public static class ContentCachingHttpServletRequestWrapper extends HttpServletRequestWrapper {
    /**
     * request body (include application/x-www-form-urlencoded)
     */
    private byte[] content;
    /**
     * multi part
     */
    private final Map<String, List<Part>> partMap = new HashMap<>();

    public ContentCachingHttpServletRequestWrapper(final HttpServletRequest request) throws IOException {
        super(request);
        final String contentType =
                Optional.ofNullable(request.getHeader("Content-Type")).map(String::toLowerCase).orElse("");
        if (contentType.contains("multipart/form-data")) {
            try {
                Optional.ofNullable(request.getParts()).filter(parts -> !parts.isEmpty())
                        .map(parts -> parts.stream().collect(Collectors.groupingBy(Part::getName)))
                        .ifPresent(partMap::putAll);
            } catch (final ServletException e) {
                // Nothing to do
            }
            return;
        }
        content = IOUtils.toByteArray(new InputStreamReader(request.getInputStream()), StandardCharsets.UTF_8);
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        final ByteArrayInputStream inputStream = Optional.ofNullable(content).map(ByteArrayInputStream::new)
                .orElseGet(() -> new ByteArrayInputStream(new byte[0]));
        return new ServletInputStream() {
            @Override
            public boolean isFinished() {
                return false;
            }

            @Override
            public boolean isReady() {
                return true;
            }

            @Override
            public void setReadListener(final ReadListener readListener) {
            }

            @Override
            public int read() throws IOException {
                return inputStream.read();
            }
        };
    }

    @Override
    public Collection<Part> getParts() throws IOException, ServletException {
        return partMap.values().stream().flatMap(Collection::stream).collect(Collectors.toList());
    }

    @Override
    public Part getPart(final String name) throws IOException, ServletException {
        return Optional.ofNullable(partMap.get(name)).flatMap(parts -> parts.stream().findFirst()).orElse(null);
    }

    /**
     * 获取 content
     *
     * @return 请求 content
     */
    public byte[] getContentAsByteArray() {
        return Optional.ofNullable(content).orElseGet(() -> new byte[0]);
    }
}