Google App Engine ApiProxy在保存文件时委托NullPointerException

Question

我尝试将文件保存到Google App Engine并遵循其文档，但不断在CreateOrReplace方法行上获取NullPointerException。已经发现gcsService已经创建了。有什么想法吗？

public String getFileUrl(MultipartFile file) throws CustomException {

    String unique = UUID.randomUUID().toString();
    String fileName = unique + ".jpeg";

    GcsFilename gcsFilename = new GcsFilename("MY_BUCKET", fileName);

    try {
        GcsOutputChannel outputChannel = GcsServiceFactory.createGcsService().createOrReplace(gcsFilename, GcsFileOptions.getDefaultInstance());
        copy(file.getInputStream(), Channels.newOutputStream(outputChannel));
    } catch (IOException e) {
        e.printStackTrace();
    }

    ImagesService imagesService = ImagesServiceFactory.getImagesService();

    ServingUrlOptions options = ServingUrlOptions.Builder
            .withGoogleStorageFileName("/gs/MY_BUCKET/" + fileName)
            .secureUrl(true);

    return imagesService.getServingUrl(options);
}

包含依赖：

<dependency>
        <groupId>com.google.appengine.tools</groupId>
        <artifactId>appengine-gcs-client</artifactId>
        <version>0.7</version>
    </dependency>

获得：

RetryHelper(32.34 s, 6 attempts, com.google.appengine.tools.cloudstorage.GcsServiceImpl$1@74c3f0b0): Too many failures, giving up

日志中有例外：

c.g.a.tools.cloudstorage.RetryHelper     : RetryHelper(1.386 s, x attempts, com.google.appengine.tools.cloudstorage.GcsServiceImpl$1@6bd1dbe9): Attempt #x failed [java.io.IOException: java.lang.NullPointerException], sleeping for x ms

提前致谢！

修改

在com.google.apphosting.api上找到ApiProxy类

public static ApiProxy.Delegate getDelegate() {
    return delegate;
}

返回NULL。

有什么想法吗？