java - 无法迭代 List

Question

以下是我从网页上传多个文件的函数。我的文件位于 MultipartFile --> 文件变量列表中。我无法迭代每个文件。然而 log.info("file"+files) 打印了 file[]。这意味着文件返回“[]”。这是什么意思？我哪里出错了？

public String addNodeAndDocNew(TreeType treeType, ObjectId parentNodeId, NodeType nodeType, String displayName, String attrList, List<MultipartFile> files, String userId,
        String passwd) {
    String result = "";
    log.info("file"+ files);
    log.info("userId=" + userId);
    log.info("passwd=" + passwd);
    log.info("nodeType=" + nodeType);
    log.info("displayName=" + displayName);
    if (attrList != null)
        log.info("attributesList=" + attrList.toString());
    ObjectId nodeId = null;
    for(MultipartFile file : files)
    {
        log.info("Yess");
        if (file.isEmpty()) {
            log.info("Nothing attached, just adding node, not the doc");
            nodeId = addNode(treeType, parentNodeId, nodeType, displayName, attrList, userId, passwd);
            if (nodeId != null)
                log.info("Just added node, no doc sent");
        }

        else {
            log.info("file=" + file.getOriginalFilename());
            nodeId = addNode(treeType, parentNodeId, nodeType, displayName, attrList, userId, passwd);
            if (nodeId != null) {
                docService.uploadDoc(nodeId, file, userId, passwd);
                log.info("Added node, and doc");
            } else {
                log.info("addNode() returned null");
            }
        }

    if (nodeId != null) {
        log.info("addNodeAndDoc completed for node id : " + nodeId.toString());
        result += nodeId.toString()+ "@@";
    } else
        return null;
    }
    log.info("Yess1");
    return result;
}

Answer 1

However log.info(files) printed File[].

所以，你给定的数组是空的。这就是为什么你不能迭代它! ;)