Java Applet 不缓存
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Java Applet not caching
提问by John Fogerty
I'm having a problem with a Java applet I've deployed that is refusing to be cached in the jvm's "sticky" cache (or by the browser). For some reason every time a user loads the page this applet is on, the jvm re-downloads the jar file from the server which causes a long delay.
我部署的 Java 小程序出现问题，该小程序拒绝缓存在 jvm 的“粘性”缓存（或浏览器）中。出于某种原因，每次用户加载此小程序所在的页面时，jvm 都会从服务器重新下载 jar 文件，这会导致很长的延迟。
The webpage containing the applet is being accessed via the internet, so according to Sun's Java applet documentationI'm using an <applet>tag rather than an <object>or <embed>tag.
包含小程序的网页是通过 Internet 访问的，因此根据Sun 的 Java 小程序文档，我使用的是<applet>标签而不是<object>or<embed>标签。
Any help debugging or identifying the problem would be much appreciated.
任何帮助调试或识别问题将不胜感激。
Below is the full applet tag I'm using:
下面是我正在使用的完整小程序标签：
<applet alt="Scanning Applet failed to load" archive="scanning.jar"
code="scanning.scanlet.class" codebase="/java/" codetype="application/java"
height="30" mayscript="True" name="scanlet" width="200">
<param name="domain" value="192.168.12.23" />
<param name="publishName" value="scan_attachment" />
<param name="publishURL" value="http://192.168.12.23/draft/update/52" />
<param name="curURL" value="http://192.168.12.23/draft/edit/52" />
Your browser is unable to process the Java <APPLET> tag needed to display this applet
<br />
One solution would be to download a better web browser like
<a href="http://www.mozilla.com/firefox">Mozilla's Firefox</a>
</applet>
回答by eppesuig
I had the very same problem and found a trick that need to be applied server side. It seems that jars aren't cached if their mime type is incorrect. Please check your server reply using the application/java-archive mime type.
我遇到了同样的问题，并发现了一个需要在服务器端应用的技巧。如果 jar 的 mime 类型不正确，它们似乎不会被缓存。请使用 application/java-archive mime 类型检查您的服务器回复。
Another problem I found is related to a specific jar. My archive parameter was listing many jars, but only a few were cached. I found that all jars upto a specific one where cached, all remaining jars weren't cached at all. While loading applet, I pressed "5" in its java console and found this message just after the last cached jar: cache: signed entry missing from jar . I still don't know what is wrong with this file, but I moved that jar at the end of the archive parameter list. This "fixed" the problem.
我发现的另一个问题与特定的 jar 有关。我的存档参数列出了许多 jar，但只有少数被缓存。我发现所有 jars 都缓存到一个特定的 jars，所有剩余的 jars 根本没有缓存。在加载小程序时，我在它的 Java 控制台中按下了“5”，并在最后一个缓存的 jar 之后发现了这条消息： cache: signed entry missing from jar 。我仍然不知道这个文件有什么问题，但我在存档参数列表的末尾移动了那个 jar。这“修复”了问题。
回答by ArtemGr
Personally I solved the caching issues by using cache_archive and cache_version parameters docummented at http://java.sun.com/javase/6/docs/technotes/guides/plugin/developer_guide/applet_caching.html
我个人通过使用http://java.sun.com/javase/6/docs/technotes/guides/plugin/developer_guide/applet_caching.html 上记录的cache_archive 和 cache_version 参数解决了缓存问题
My cache_version is based on the actual file modification date, e.g.
我的 cache_version 基于实际的文件修改日期，例如
val archive = libs.map("/" + _.getPath).mkString (", ")
val version = libs.map(_.getUpdated / 1000 / 20 - 59281420).mkString (", ")
and to work with MSIE it looks as:
并与 MSIE 一起工作，它看起来像：
if (msie) {
cms write <OBJECT
classid="clsid:CAFEEFAC-0016-0000-0000-ABCDEFFEDCBA"
codebase="http://java.sun.com/update/1.6.0/jinstall-6-windows-i586.cab"
width="100%" height="100%">
...
<PARAM name="cache_archive" value={archive}/>
<PARAM name="cache_version" value={version}/>
</OBJECT>
} else {
cms write <applet ...
cache_archive={archive} cache_version={version}></applet>
}
回答by Patrick Ecord
For me I had to remove the Jar files from the Archive tag and just have it in the cache_archive parameter, and specify the versions that way it doesn't piggy back to the server for last modified date
对我来说，我必须从 Archive 标签中删除 Jar 文件，并将其放在 cache_archive 参数中，并指定版本，这样它就不会在最后修改日期捎带回服务器
Fixed it in firefox for me
在 Firefox 中为我修复了它
回答by Jon Onstott
This official article describes how you can change your APPLET tag to increase caching:
这篇官方文章描述了如何更改 APPLET 标签以增加缓存：
http://java.sun.com/products/plugin/1.3/docs/appletcaching.html
http://java.sun.com/products/plugin/1.3/docs/appletcaching.html
