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获取正在运行的JVM的参数(Getting the parameters of a running JVM)

有没有办法获取正在运行的JVM的参数？ 有没有像jstat一样的命令行工具，它将JVM的pid作为输入，并返回其起始参数？ 我对启动JVM时给出的-Xmx和-Xms值特别感兴趣。 谢谢。
编辑 ：澄清我的限制。 我们要检查的JVM正在生产服务器上运行。 这就是为什么我们更喜欢最小的破坏。 我们可以使用jstat来监视JVM，所以我们希望有一个类似的简单解决方案来访问这些参数。
编辑 ：我们也尝试使用jvisualvm获取参数。 但为了连接到远程jvm，我们需要运行jstatd并修改JVM的安全设置，我们发现它们在生产服务器上是非常具有破坏性和危险性的。

Is there a way to get the parameters of a running JVM? Is there a command line tool like jstat which takes as input the pid of the JVM and returns its starting parameters? I am particularly interested in the -Xmx and -Xms values that were given when starting the JVM. Thank you.
Edit: To clarify my constraints. The JVM we would like to check is running on a production server. That's why, we prefer the minimum disruption. We are able to monitor the JVM using jstat, and so we hope there's a similar simple solution to access the parameters.
Edit: We also tried to get the parameters using jvisualvm. But in order to connect to a remote jvm, we need to run jstatd and modify the security settings of the JVM, which we found to be very disruptive and risky on a production server.

原文：https://stackoverflow.com/questions/5317152

更新时间：2023-06-07 07:06

最满意答案

 感谢Neil Slater，我终于找到了正确的解决方案。 我需要在最终结果中结合使用 DstIn + Over的复合操作 ：  
  def watermark(opacity = 0.99, size = 'm')
    manipulate! do |img|
      logo = Magick::Image.read("#{Rails.root}/app/assets/images/watermark#{size}.png").first
      logo.alpha(Magick::ActivateAlphaChannel) 

      white_canvas = Magick::Image.new(logo.columns, logo.rows) { self.background_color = "none" }
      white_canvas.alpha(Magick::ActivateAlphaChannel)
      white_canvas.opacity = Magick::QuantumRange - (Magick::QuantumRange * opacity)

      # Important: DstIn composite operation (white canvas + watermark)
      logo_opacity = logo.composite(white_canvas, Magick::NorthWestGravity, 0, 0, Magick::DstInCompositeOp)
      logo_opacity.alpha(Magick::ActivateAlphaChannel)

      # Important: Over composite operation (original image + white canvas watermarked)
      img = img.composite(logo_opacity, Magick::NorthWestGravity, 0, 0, Magick::OverCompositeOp)
    end
  end

Thanks to Neil Slater, I finally found the right solution. I need a combination of composite operation of DstIn + Over in my finalt result: 
  def watermark(opacity = 0.99, size = 'm')
    manipulate! do |img|
      logo = Magick::Image.read("#{Rails.root}/app/assets/images/watermark#{size}.png").first
      logo.alpha(Magick::ActivateAlphaChannel) 

      white_canvas = Magick::Image.new(logo.columns, logo.rows) { self.background_color = "none" }
      white_canvas.alpha(Magick::ActivateAlphaChannel)
      white_canvas.opacity = Magick::QuantumRange - (Magick::QuantumRange * opacity)

      # Important: DstIn composite operation (white canvas + watermark)
      logo_opacity = logo.composite(white_canvas, Magick::NorthWestGravity, 0, 0, Magick::DstInCompositeOp)
      logo_opacity.alpha(Magick::ActivateAlphaChannel)

      # Important: Over composite operation (original image + white canvas watermarked)
      img = img.composite(logo_opacity, Magick::NorthWestGravity, 0, 0, Magick::OverCompositeOp)
    end
  end

获取正在运行的JVM的参数(Getting the parameters of a running JVM)

最满意答案

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