java - 每个 getResourceAsStream 都会读取整个 jar

Question

我正在分析一个 Java 小程序的启动时间。我注意到每次请求 jar 中的资源时，都会完全读取一个大小为 5MB 的巨大 jar。例如。图像日志配置文件、I18N 文件等....它应该那样做吗？是否可以跳到正确的点？是否可以只读取一次文件？如果我切换到 cache_archiv_ex 并添加预加载指令会有帮助吗？打开 jar 文件的示例:

java.io.FileInputStream.open(String)
java.io.FileInputStream.<init>(File)
com.sun.deploy.cache.DeployCacheHandler$2.run()
java.security.AccessController.doPrivileged(PrivilegedExceptionAction)
com.sun.deploy.cache.DeployCacheHandler.get(URI, String, Map)
sun.net.www.protocol.http.HttpURLConnection.plainConnect()
sun.net.www.protocol.http.HttpURLConnection.connect()
sun.net.www.protocol.http.HttpURLConnection.getInputStream()
sun.plugin.PluginURLJarFileCallBack.downloadJAR(URLConnection, boolean)
sun.plugin.PluginURLJarFileCallBack.access$000(PluginURLJarFileCallBack, URLConnection, boolean)
sun.plugin.PluginURLJarFileCallBack$2.run()
java.security.AccessController.doPrivileged(PrivilegedExceptionAction)
sun.plugin.PluginURLJarFileCallBack.retrieve(URL)
sun.net.www.protocol.jar.URLJarFile.retrieve(URL, URLJarFile$URLJarFileCloseController)
sun.net.www.protocol.jar.URLJarFile.getJarFile(URL, URLJarFile$URLJarFileCloseController)
sun.net.www.protocol.jar.JarFileFactory.get(URL, boolean)
sun.net.www.protocol.jar.JarURLConnection.connect()
sun.plugin.net.protocol.jar.CachedJarURLConnection.connect()
sun.plugin.net.protocol.jar.CachedJarURLConnection.getInputStream()
java.net.URL.openStream()
java.lang.ClassLoader.getResourceAsStream(String)
sun.plugin2.applet.Applet2ClassLoader.getResourceAsStream(String)
..
.. (real application code stack...)
..
..
java.awt.event.InvocationEvent.dispatch()
java.awt.EventQueue.dispatchEvent(AWTEvent)
java.awt.EventDispatchThread.pumpOneEventForFilters(int)
java.awt.EventDispatchThread.pumpEventsForFilter(int, Conditional, EventFilter)
java.awt.EventDispatchThread.pumpEventsForHierarchy(int, Conditional, Component)
java.awt.EventDispatchThread.pumpEvents(int, Conditional)
java.awt.EventDispatchThread.pumpEvents(Conditional)
java.awt.EventDispatchThread.run()

Answer 1

getResourceAsStream 正在调用 CachedJarURLConnection。您确定它没有缓存 jar 并且只下载一次吗？如果是，我会确保您的 Web 服务器不会每次都在 jar 上报告不同或不正确的上次更新日期。