我想知道如果 @Controller 方法返回 Callable 接口，如何從請(qǐng)求正文中讀取過濾器中的響應(yīng)。我的過濾器看起來像這樣。響應(yīng)始終為空。有什么辦法解決這個(gè)問題嗎？僅使用 AsyncListener 才允許這樣做嗎？@Componentpublic class ResposeBodyXmlValidator extends OncePerRequestFilter { private final XmlUtils xmlUtils; private final Resource xsdResource; public ResposeBodyXmlValidator( XmlUtils xmlUtils, @Value("classpath:xsd/some.xsd") Resource xsdResource ) { this.xmlUtils = xmlUtils; this.xsdResource = xsdResource; } @Override protected void doFilterInternal( HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, FilterChain filterChain ) throws ServletException, IOException { ContentCachingResponseWrapper response = new ContentCachingResponseWrapper(httpServletResponse); doFilter(httpServletRequest, response, filterChain); if (MediaType.APPLICATION_XML.getType().equals(response.getContentType())) { try { xmlUtils.validate(new String(response.getContentAsByteArray(), response.getCharacterEncoding()), xsdResource.getInputStream()); } catch (IOException | SAXException e) { String exceptionString = String.format("Chyba p?i volání %s\nNevalidní vystupní XML: %s", httpServletRequest.getRemoteAddr(), e.getMessage()); response.setContentType(MediaType.TEXT_PLAIN_VALUE + "; charset=UTF-8"); response.setCharacterEncoding(StandardCharsets.UTF_8.name()); response.getWriter().print(exceptionString); } } response.copyBodyToResponse(); // I found this needs to be added at the end of the filter }}
1 回答
德瑪西亞99
TA貢獻(xiàn)1770條經(jīng)驗(yàn) 獲得超3個(gè)贊
Callable 的問題在于調(diào)度程序 servlet 本身會(huì)啟動(dòng)異步處理，并且過濾器會(huì)在實(shí)際處理請(qǐng)求之前退出。
當(dāng) Callable 到達(dá)調(diào)度程序 servlet 時(shí)，它通過釋放所有過濾器（過濾器基本上完成其工作）來從池中釋放容器線程。當(dāng) Callable 產(chǎn)生結(jié)果時(shí)，會(huì)使用相同的請(qǐng)求再次調(diào)用調(diào)度程序 servlet，并且響應(yīng)會(huì)立即由 Callable 返回的數(shù)據(jù)完成。這是由類型的 request 屬性處理的，AsyncTaskManager該屬性保存有關(guān)異步請(qǐng)求處理的一些信息。這可以用Filter和進(jìn)行測試HandlerInterceptor。Filter只執(zhí)行一次但HandlerInterceptor執(zhí)行了兩次（原始請(qǐng)求和Callable完成工作后的請(qǐng)求）
當(dāng)您需要讀取請(qǐng)求和響應(yīng)時(shí)，解決方案之一是像這樣重寫dispatcherServlet：
@Bean
@Primary
public DispatcherServlet dispatcherServlet(WebApplicationContext context) {
return new DispatcherServlet(context) {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
ContentCachingRequestWrapper requestWrapper = new ContentCachingRequestWrapper(request);
ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper(response);
super.service(requestWrapper, responseWrapper);
responseWrapper.copyBodyToResponse();
}
};
}
這樣您就可以確?？梢远啻巫x取請(qǐng)求和響應(yīng)。另一件事是像這樣添加 HandlerInterceptor （您必須傳遞一些數(shù)據(jù)作為請(qǐng)求屬性）：
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws
Exception {
Object asyncRequestData = request.getAttribute(LOGGER_FILTER_ATTRIBUTE);
if (asyncRequestData == null) {
request.setAttribute(LOGGER_FILTER_ATTRIBUTE, new AsyncRequestData(request));
}
return true;
}
@Override
public void afterCompletion(
HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex
) throws Exception {
Object asyncRequestData = request.getAttribute(LOGGER_FILTER_ATTRIBUTE);
if (asyncRequestData != null && response instanceof ContentCachingResponseWrapper) {
log(request, (ContentCachingResponseWrapper) response, (AsyncRequestData) asyncRequestData);
}
}
afterCompletion方法僅在異步請(qǐng)求完全處理后調(diào)用一次。preHandle被調(diào)用兩次，因此您必須檢查屬性是否存在。在afterCompletion中，調(diào)用的響應(yīng)已經(jīng)存在，如果您確實(shí)想要替換它，您應(yīng)該調(diào)用response.resetBuffer().
這是一種可能的解決方案，并且可能有更好的方法。
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