java - Spring 启动: Async request not returning anything

Question

Js:

$('#loaderImage').show();

$http.get('/utilities/longProcess')
    .success(function(data, status, headers, config) {
        console.log('Completed');
        $scope.sampleJSON = data.pmdStructureWrapper;
        $scope.sampleJSONDuplicates = data.pmdDuplicates;
        $scope.$watch('sampleJSON', setTimeout(function() {
            $('.panel-body li').each(function() {
                if ($.trim($(this).text()) === "") {
                    $(this).hide();
                }
            });
        }, 1000));
        $('#loaderImage').hide();
    })
    .error(function(data, status, header, config) {

    });

Controller :

@RequestMapping("/utilities/longProcess")
    public DeferredResult<String> async(HttpServletResponse response, HttpServletRequest request) {
        DeferredResult<String> dr = new DeferredResult<>();
        CompletableFuture.supplyAsync(() -> {
            return callURL(response, request);
        }, ex).thenAccept((String message) -> {
            dr.setResult(message);
        });
        return dr;
    }

private String callURL(HttpServletResponse response, HttpServletRequest request){
    PMDMainWrapper pmdMainWrapper = new PMDMainWrapper();
    Map<String, PMDStructureWrapper> codeReviewByClass = new HashMap<>();
    String partnerURL = this.partnerURL;
    String toolingURL = this.toolingURL;
    Cookie[] cookies = request.getCookies();
    List<PMDStructure> violationStructure = null;
    try {
        violationStructure = metadataLoginUtil.startReviewer(partnerURL, toolingURL, cookies);
    } catch (Exception e) {
        e.printStackTrace();
    }

    PMDStructureWrapper pmdStructureWrapper = null;
    List<PMDStructure> pmdStructureList = null;
    List<PMDStructure> pmdDuplicatesList = new ArrayList<>();
    int size = violationStructure.size();

    long start = System.currentTimeMillis();
    for (int i = 0; i < size; i++) {
        if (codeReviewByClass.containsKey(violationStructure.get(i).getName())) {
            PMDStructureWrapper pmdStructureWrapper1 = codeReviewByClass.get(violationStructure.get(i).getName());
            List<PMDStructure> pmdStructures = pmdStructureWrapper1.getPmdStructures();
            pmdStructures.add(violationStructure.get(i));
            pmdStructureWrapper1.setPmdStructures(pmdStructures);

        } else {
            pmdStructureList = new ArrayList<>();
            pmdStructureList.add(violationStructure.get(i));
            pmdStructureWrapper = new PMDStructureWrapper();
            pmdStructureWrapper.setPmdStructures(pmdStructureList);
            codeReviewByClass.put(violationStructure.get(i).getName(), pmdStructureWrapper);
        }
    }

    long stop = System.currentTimeMillis();

    LOGGER.info("Total Time Taken from PMDController "+  String.valueOf(stop-start));
    if (!codeReviewByClass.isEmpty()) {
        pmdMainWrapper.setPmdStructureWrapper(codeReviewByClass);
        pmdMainWrapper.setPmdDuplicates(pmdDuplicatesList);
        Gson gson = new GsonBuilder().create();
        return gson.toJson(pmdMainWrapper);
    }

    return "";
}

我将使用异步进程，因为当应用程序托管在heroku中时，需要近120秒才能将结果返回到页面，但根据heroku文档，其余API应在30秒内返回，否则它将终止进程，

但在实现上述逻辑后，我仍然看到超时错误。我在 javascript console.log('Completed'); 中保留了控制台日志，但只有当它从 callURL 方法返回结果时才会打印该日志，该方法花费的时间超过120 秒返回。

我想要实现的是，当 UI 发送请求时，它应该不断接收一条表示仍在加载的消息，以便请求不会超时？

Answer 1

CompletableFuture.supplyAsync() 在不同的线程中运行指定的供应商(默认情况下来自 ForkJoinThreadPool)。 thenAccept() 方法仅在上一次执行返回后运行。因此，在您的情况下，它不会快速返回，您只是在不同的线程中调用长时间运行的调用。

相反，定义一个公共(public)对象，充当缓存(例如HttpSession)，并使CompletableFuture返回存储在那里的对象。并且仅当缓存为空时才执行callURL():

@RequestMapping("/utilities/longProcess")
public CompletableFuture<String> async(HttpServletResponse response, HttpServletRequest request) {
    HttpSession session = request.getSession();
    return CompletableFuture.supplyAsync(() -> session.getAttribute("CACHED_RESULT"))
            .thenComposeAsync(obj -> {
                if (obj == null) {
                    CompletableFuture.supplyAsync(() -> callUrl(request, response))
                            .thenAccept(result -> session.setAttribute("CACHED_RESULT", result));
                    return CompletableFuture.completedFuture("not ready yet");
                }
                return CompletableFuture.completedFuture(obj.toString());
            });

您还可以添加时间戳来查看上次调用 callUrl() 的时间，并且在进行了一次调用后就不要再次调用 callUrl()调用但尚未收到答复。