Java Servlet 多线程解析请求体

Question

我实现了一个异步Servlet，它需要解析请求正文并将解析结果存储在缓存中。我应该在 Servlet 中实现 parseBody() 函数还是实现一个新类来进行解析？最佳实践是什么？

这是我当前的代码片段:

public class DocFeedServlet extends FeedServlet {

private static final Logger LOGGER = LoggerFactory.getLogger(DocFeedServlet.class);
private static final ObjectMapper OBJECTMAPPER = new ObjectMapper();


public void init(ServletConfig config) throws ServletException {
    super.init(config);
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
    resp.setStatus(HttpServletResponse.SC_BAD_REQUEST);
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {

    final AsyncContext asyncContext = req.startAsync();
    asyncContext.start(new Runnable() {
        @Override
        public void run() {
            String bodyStr = getBody(req);
            if (bodyStr.isEmpty()) {
                resp.setStatus(HttpServletResponse.SC_BAD_REQUEST);
                asyncContext.complete();
                return;
            }

            int ignoreTime = Integer.parseInt(req.getParameter(Constant.PARAM_IGNORE_TIME));

            List<MockDocCacheKeyVal> mockDocCacheKeyVals = new ArrayList<>();
            List<String> docUpdateFields = new ArrayList<>();
            List<List<String>> docKeepFields = new ArrayList<List<String>>();
            List<String> uuidsToRemove = new ArrayList<>();

            int parseRet = parseBody(bodyStr, mockDocCacheKeyVals, docUpdateFields, docKeepFields, uuidsToRemove, ignoreTime);

            if (parseRet != 0) {
                resp.setStatus(HttpServletResponse.SC_OK);
            } else {
                resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
            }
            asyncContext.complete();
        }
    });
}

protected int parseBody(String body, List<MockDocCacheKeyVal> mockDocCacheKeyVals, List<String> docUpdateFields, List<List<String>> docKeepFields, List<String> uuidsToRemove, int ignoreTime) {
    try {
        ObjectReader reader = OBJECTMAPPER.reader(new TypeReference<List<Document>>() { });
        List<Document> documents = reader.readValue(body);
        for (Document doc : documents) {
            if (doc.getAction() != null && doc.getAction().equalsIgnoreCase(Constant.DOC_FEED_ACTION_DELETE)) {
                if (doc.getUuid() != null) {
                    uuidsToRemove.add(doc.getUuid());
                }
                continue;
            }
            if (doc.getA() != null) {

            } else if (doc.getB() != null) {

            } else {
                DocumentUtils.pruneWeightSet(doc.getC(), cPruneSize);
                DocumentUtils.pruneWeightSet(doc.getD(), dPruneSize);
                DocumentUtils.pruneWeightSet(doc.getE(), ePruneSize);
            }
        }
        return documents.size();
    } catch (Exception e) {
        LOGGER.error(e.getMessage());
    }
    return 0;
}
}

谢谢。

Answer 1

异步请求正文读取是通过 HttpServletRequest.getInputStream().setReadListener(ReadListener) 完成的Servlet 3.1 中引入的概念

您只会根据来自 ReadListener 的事件进行读取，并且您只会读取足够的内容而不会阻塞。 (因此无法读取数兆字节缓冲区!)。

这个 API 正是您正在寻找的，但是 there be land mines here ，所以在完成之前请确保您完全理解该 API。