使用Spring MVC的Multipartfile上的NullPointer

Question

似乎我的情况很简单，所以我猜问题是愚蠢的。尽管如此……我看不出来。

我正在尝试接受一个文件集合的上传，并一直在看这篇文章作为指导:

http://viralpatel.net/blogs/spring-mvc-multiple-file-upload-example/

下面是表单上传客户端:

<form:form method="post" action="save.html" modelAttribute="uploadArtifact" enctype="multipart/form-data">
    <div class="controls" id="artifacts">                               
        <input type="file" id="uploader" class="multi"/>        
    </div>
    <div>
        <input type="submit" value="Upload" />
    </div>
</form:form>

Model/Bean代码:

public class ArtifactModel {
private List<MultipartFile> artifacts;
public List<MultipartFile> getArtifacts() {
    return artifacts;
}
public void setArtifacts(List<MultipartFile> artifacts) {
    this.artifacts = artifacts;
}
}

…控制器代码:

@Controller
public class ArtifactController {
    private static Log logger = LogFactory.getLog(ArtifactController.class);
    // @Autowired
    // ArtifactService artifactService;
    @RequestMapping(value = "/getUploadDialog", method = RequestMethod.GET)
    public String displayForm() {
        return "uploadArtifacts";
    }
    @RequestMapping(value = "/save", method = RequestMethod.POST)
    public void save(
            @ModelAttribute("uploadArtifact") ArtifactModel uploadArtifact,
            Model map) {
        logger.info("Received file upload request with     "+uploadArtifact.getArtifacts().size()+" files");
            List<MultipartFile> files = uploadArtifact.getArtifacts();
        List<String> fileNames = new ArrayList<String>();
        if (null != files && files.size() > 0) {
            for (MultipartFile multipartFile : files) {
                String fileName = multipartFile.getOriginalFilename();
                fileNames.add(fileName);
                // Handle file content - multipartFile.getInputStream()
                logger.info("Received file with filename: " + fileName);
            }
        }
        map.addAttribute("files", fileNames);
    }
}

当我试图调用ArtifactModel对象上的getter时，我得到了一个NullPointerException，该对象应该来自uploadArtifact @ModelAttribute参数…

我已经查看了浏览器调试器，看到客户端正在发送数据…

建议吗?

Answer 1

我想你在文件输入元素中缺少了一个属性。

尝试添加:

name='artifacts[0]'