创建 DiskFileItem 时出现 java.lang.NullPointerException

Question

我正在尝试编写一个单元测试来使用 Spring 3 处理文件上传控制器。现在，如果我通过控制器将图像发送到我的服务方法，则一切正常。但是，当进行直接单元测试时，我遇到了空指针异常。

当我手动实例化 DiskFilteItem 内的属性“dfos”时，它似乎为 null，但在从控制器检索 MultipartFile 时会填充该属性。

    File file = new File("//Users//test//Downloads//testimage.jpg");
    log.info("found file: " +file.exists());
    log.info("file size: " +file.length());
    String fieldName = "field";
    String contentType = "image/jpeg";
    boolean isFormField = false;
    String fileName = "testimage.jpg";
    int sizeThreshold = 10240;

    DiskFileItemFactory factory = new DiskFileItemFactory();

    DiskFileItemFactory factory = new DiskFileItemFactory();
    // throws null pointer
    FileItem fi = factory.createItem(fieldName,contentType,isFormField,fileName);

    // so does this one
    DiskFileItem item = new DiskFileItem(fieldName, contentType, isFormField, fileName, sizeThreshold, file);
    MultipartFile f = new CommonsMultipartFile(item);

我觉得我的设置中缺少一些愚蠢的东西。我的 pom 文件包含以下依赖项。

    <dependency>
        <groupId>commons-fileupload</groupId>
        <artifactId>commons-fileupload</artifactId>
        <version>1.2.2</version>
    </dependency>
    <dependency>
        <groupId>commons-io</groupId>
        <artifactId>commons-io</artifactId>
        <version>2.0</version>
    </dependency>

此代码抛出以下堆栈跟踪

java.lang.NullPointerException
 at org.apache.commons.fileupload.disk.DiskFileItem.getSize(DiskFileItem.java:316)
 at org.springframework.web.multipart.commons.CommonsMultipartFile.(CommonsMultipartFile.java:60)
 at ImgurClientTest.testUploadImage(ImgurClientTest.java:58)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
 at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
 at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
 at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
 at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
 at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:82)
 at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
 at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:240)
 at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
 at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
 at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
 at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
 at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
 at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
 at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
 at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
 at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
 at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:180)
 at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
 at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:65)

Answer 1

我遇到了同样的问题。问题是 DiskFileItem.getSize() 与 DiskFileItem.getOutputStream() 暂时耦合，因为内部字段在 getOutputStream 中初始化并使用在getSize中。

解决方案是

final File TEST_FILE = new File("src/test/resources/test.jpg");
final DiskFileItem diskFileItem = new DiskFileItem("file", "image/jpeg", true, TEST_FILE.getName(), 100000000, TEST_FILE.getParentFile());
diskFileItem.getOutputStream();

在将 diskFileItem 传递给 CommonsMultipartFile 的构造函数之前执行此操作。

Answer 2

该日志的这一部分说了什么？

log.info("found file: " +file.exists());
log.info("file size: " +file.length());

但我认为问题可能是因为这个：

File file = new File("//Users//test//Downloads//");

它看起来像是指向一个目录而不是一个文件，所以也许这就是为什么当您想要获取 < 的大小时您会收到 NullPointerException 的原因代码>磁盘文件项

Answer 3

如果上面的解决方案都不适合您，就像我遇到的那样:)只需放弃 DiskFileItem 并使用以下解决方案：

  final File fileToUpload = new File("src/test/resources/files/test.txt");
  final MultiValueMap<String, Object> request = new LinkedMultiValueMap<String, Object>();
  request.add("file", new FileSystemResource(fileToUpload.getAbsolutePath()));

Answer 4

虽然不完全与问题相关。在将一些文件上传代码部署到 GAE 时，我遇到了同样的异常。我从这里修改了systempuntoout的代码在GAE上使用apache fileupload（它使用apache commons）然后工作得很好。

Answer 5

new DiskFileItem(fieldName, contentType, isFormField, fileName, sizeThreshold, file);

结果为 null 值。查看 文档 以了解内容错误或者您可能传递了一些 null 作为参数