javascript - Alfresco JavaScript/Rhino 多线程处理和并发

Question

让我们考虑两个独立的 Alfresco Rhino-JavaScript 任务，它们竞争创建同一文件夹:

var shared = companyhome.childByNamePath("shared");
var newFolderName = "folder-x";
var newFolder = shared.childByNamePath(newFolderName);
if (newFolder==null) {
    java.lang.Thread.sleep(10000);//remove this line in second thread
    newFolder = shared.createFolder(newFolderName);
    if (newFolder==null){
        logger.error("error: "+newFolderName);
    } else {
        logger.info("success: "+newFolderName);
    }
} else {
    logger.info("already exists: "+newFolderName);
}

如果我们在 sleep (10 秒)的情况下运行第一个脚本，在没有 sleep 的情况下运行第二个脚本，则:

• 第二个脚本将创建文件夹“folder-x”
• 第一个脚本会出现“文件或文件夹folder-x已存在”异常

让我们想象一下许多竞争线程试图创建随机文件夹。 是否有像信号量或原子操作之类的东西只阻止创建指定的文件夹(不阻止其他文件夹)？

Answer 1

抱歉，我明白了，这只是微不足道的......

方法createFolder()是原子的，如果文件夹已经创建，我们只需要处理异常:

var getOrCreateFolder = function(parent, newFolderName){
    var newFolder = parent.childByNamePath(newFolderName);
    if (newFolder==null) {
        try {
            java.lang.Thread.sleep(10000);//remove this line in second thread
            newFolder = parent.createFolder(newFolderName);
            return {folder:newFolder,isNew:true};

        } catch (e) {
            newFolder = parent.childByNamePath(newFolderName);
            if (newFolder!=null){
                return {folder:newFolder,isNew:false};
            } else {
                throw e;
            }
        }
    } else {
        return {folder:newFolder,isNew:false};
    }
};

var shared = companyhome.childByNamePath("shared");
var newFolderName = "folder-x";
var folderDto = getOrCreateFolder(shared,newFolderName);
if (folderDto.folder==null) {
    logger.error("error: "+newFolderName);
} else {
    logger.info("done: "+newFolderName+", new: "+folderDto.isNew);
}