fileupload源码分析-优快云博客

本文介绍了一种生成唯一标识符的方法，并展示了如何基于此标识符创建临时文件。强调了同步保护的重要性，避免使用字符串拼接提高效率。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

private static String getUniqueId()
{
    int current;
    synchronized (DefaultFileItem.class)
    {
      current = counter++;
    }
    String id = Integer.toString(current);

    if (current < 100000000)
    {
      id = ("00000000" + id).substring(id.length());
    }
    return id;
}
private static String getUniqueId()
{
    int current;
    synchronized (DefaultFileItem.class)
    {
      current = counter++;
    }
    String id = Integer.toString(current);

    if (current < 100000000)
    {
      id = ("00000000" + id).substring(id.length());
    }
    return id;
}

1.不要用""+整数来拼接字符串。调用Integer.toString高效
2.公有数据加同步保护

protected File getTempFile()
{
    File tempDir = this.repository;
    if (tempDir == null)
    {
      tempDir = new File(System.getProperty("java.io.tmpdir"));
    }

    String fileName = "upload_" + getUniqueId() + ".tmp";

    File f = new File(tempDir, fileName);
    f.deleteOnExit();
    return f;
}
注意删除f.deleteOnExit在jvm退出的时候删除文件