服务提供方提供文件下载功能，当Part返回null时，会抛出空指针异常

[SenixCoder]

异常堆栈如下

java.lang.NullPointerException: 
	at org.apache.servicecomb.foundation.vertx.http.DownloadUtils.prepareDownloadHeader(DownloadUtils.java:45) 
	at org.apache.servicecomb.foundation.vertx.http.StandardHttpServletResponseEx.sendPart(StandardHttpServletResponseEx.java:107) 
	at org.apache.servicecomb.common.rest.filter.inner.ServerRestArgsFilter.beforeSendResponseAsync(ServerRestArgsFilter.java:78) 
	at org.apache.servicecomb.common.rest.filter.HttpServerFilterBeforeSendResponseExecutor.safeInvoke(HttpServerFilterBeforeSendResponseExecutor.java:52) 
	at org.apache.servicecomb.common.rest.filter.HttpServerFilterBeforeSendResponseExecutor.doRun(HttpServerFilterBeforeSendResponseExecutor.java:82) 
	at org.apache.servicecomb.common.rest.filter.HttpServerFilterBeforeSendResponseExecutor.run(HttpServerFilterBeforeSendResponseExecutor.java:44) 
	at org.apache.servicecomb.common.rest.AbstractRestInvocation.executeHttpServerFilters(AbstractRestInvocation.java:283) 
	at org.apache.servicecomb.common.rest.AbstractRestInvocation.sendResponse(AbstractRestInvocation.java:277) 
	at org.apache.servicecomb.common.rest.AbstractRestInvocation.sendResponseQuietly(AbstractRestInvocation.java:262) 
	at org.apache.servicecomb.common.rest.AbstractRestInvocation.lambda$doInvoke$2(AbstractRestInvocation.java:245) 
	at com.huawei.mateinfo.sdk.service.handler.ProviderMetricsHandler.lambda$onResponse$0(ProviderMetricsHandler.java:52) 
	at org.apache.servicecomb.tracing.zipkin.ZipkinTracingHandler.lambda$onResponse$0(ZipkinTracingHandler.java:74) 
	at org.apache.servicecomb.core.handler.impl.ProducerOperationHandler.syncInvoke(ProducerOperationHandler.java:108) 
	at org.apache.servicecomb.core.handler.impl.ProducerOperationHandler.invoke(ProducerOperationHandler.java:60) 
	at org.apache.servicecomb.core.handler.impl.ProducerOperationHandler.handle(ProducerOperationHandler.java:51) 
	at org.apache.servicecomb.core.Invocation.next(Invocation.java:307) 
	at org.apache.servicecomb.tracing.zipkin.ZipkinTracingHandler.handle(ZipkinTracingHandler.java:52) 
	at org.apache.servicecomb.tracing.zipkin.ZipkinProviderTracingHandler.handle(ZipkinProviderTracingHandler.java:24) 
	at org.apache.servicecomb.core.Invocation.next(Invocation.java:307) 
	at com.huawei.mateinfo.sdk.service.handler.ProviderMetricsHandler.handle(ProviderMetricsHandler.java:41) 
	at org.apache.servicecomb.core.Invocation.next(Invocation.java:307) 
	at org.apache.servicecomb.common.rest.AbstractRestInvocation.doInvoke(AbstractRestInvocation.java:245) 
	at org.apache.servicecomb.common.rest.AbstractRestInvocation.invoke(AbstractRestInvocation.java:219) 
	at org.apache.servicecomb.common.rest.AbstractRestInvocation.runOnExecutor(AbstractRestInvocation.java:203) 
	at org.apache.servicecomb.common.rest.AbstractRestInvocation.lambda$scheduleInvocation$0(AbstractRestInvocation.java:162) 
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_292]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_292]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_292]

报错代码为

    if (responseEx.getHeader(HttpHeaders.CONTENT_TYPE.toString()) == null) {
      responseEx.setHeader(HttpHeaders.CONTENT_TYPE.toString(), part.getContentType());
    }

此处没有对part进行判空；或者应当变为其他处理

[liubao68]

你能提供一个使用例子，演示出现part为空的场景吗？

[SenixCoder]

   public Part exportItemsByProjectAndModule(String projectName, String moduleName, ExportConfig exportConfig) {
        List<DataPackBo> dpList = dataPackService.getByProjectNameAndModuleName(projectName, moduleName);
        if (CollectionUtils.isEmpty(dpList)) {
            return null;
        }

        File zipFile = dataPackService.export(dpList, projectName);
        return new FilePart(null, zipFile).setDeleteAfterFinished(true).setSubmittedFileName(zipFile.getName());
    }

[liubao68]

fixed in #2527 , try 2.5.1