如果jar文件>特定大小,Applet无法在Windows 7上加载Java 1.7

Question

我们有一个相当复杂的签名小程序,自从我们几年前开发它以来一直很好用.在我们关心的所有操作系统/浏览器配置中,它可以在Java 1.5和1.6上运行良好.

它在Windows 7或Vista上的任何浏览器中都不适用于Java 1.7.我们已经看到它适用于Windows XP.此applet在Apache使用mod_proxy连接到Tomcat 6的站点中运行.

这些都是背景信息,因为我将问题简化为一个非常简单的未签名小程序:

package myapplet;
import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;

public class MyApplet extends Applet {
    private static final long    serialVersionUID    = 1L;

    public void paint(Graphics g) {
        g.drawRect(0, 0, 250, 100);
        g.setColor(Color.blue);
        g.drawString("Look at me, I'm a Java Applet!", 10, 50);
    }
}

如果将这个applet类放入一个jar文件中,另一个文件将jar文件的总(压缩)大小超过大约18KB,那么当由本地运行的Tomcat 6(或Apache 2.2)提供服务时,applet不会加载.

我通过向jar文件添加文本文件并更改文本文件的大小来玩.我通过在文本文件中添加一个字符来实现它从工作到不工作的程度.

查看带有跟踪的控制台日志,它正在尝试下载jar文件.这是我认为悬挂的主题:

"thread applet-com.bright.assetbank.clientsideedit.myapplet.MyApplet-1" prio=4 tid=0x048d8c00 nid=0x19b8 runnable [0x0700d000]
    java.lang.Thread.State: RUNNABLE
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.read(Unknown Source)
    at java.net.SocketInputStream.read(Unknown Source)
    at java.io.BufferedInputStream.read1(Unknown Source)
    at java.io.BufferedInputStream.read(Unknown Source)
    - locked <0x29fd75b0> (a java.io.BufferedInputStream)
    at sun.net.www.MeteredStream.read(Unknown Source)
    - locked <0x29fd75d0> (a sun.net.www.http.KeepAliveStream)
    at java.io.FilterInputStream.read(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection$HttpInputStream.read(Unknown Source)
    at java.io.BufferedInputStream.read1(Unknown Source)
    at java.io.BufferedInputStream.read(Unknown Source)
    - locked <0x29fd7630> (a java.io.BufferedInputStream)
    at java.io.FilterInputStream.read(Unknown Source)
    at sun.plugin.PluginURLJarFileCallBack.downloadJAR(Unknown Source)
    at sun.plugin.PluginURLJarFileCallBack.access$000(Unknown Source)
    at sun.plugin.PluginURLJarFileCallBack$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.plugin.PluginURLJarFileCallBack.retrieve(Unknown Source)
    at sun.net.www.protocol.jar.URLJarFile.retrieve(Unknown Source)
    at sun.net.www.protocol.jar.URLJarFile.getJarFile(Unknown Source)
    at sun.net.www.protocol.jar.JarFileFactory.get(Unknown Source)
    at sun.net.www.protocol.jar.JarURLConnection.connect(Unknown Source)
    at sun.plugin.net.protocol.jar.CachedJarURLConnection.connect(Unknown Source)
    at sun.plugin.net.protocol.jar.CachedJarURLConnection.getJarFileInternal(Unknown Source)
    - locked <0x29f2a938> (a sun.plugin.net.protocol.jar.CachedJarURLConnection)
    at sun.plugin.net.protocol.jar.CachedJarURLConnection.getJarFile(Unknown Source)
    - locked <0x29f2a938> (a sun.plugin.net.protocol.jar.CachedJarURLConnection)
    at com.sun.deploy.security.DeployURLClassPath$JarLoader.getJarFile(Unknown Source)
    at com.sun.deploy.security.DeployURLClassPath$JarLoader.access$1000(Unknown Source)
    at com.sun.deploy.security.DeployURLClassPath$JarLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.deploy.security.DeployURLClassPath$JarLoader.ensureOpen(Unknown Source)
    at com.sun.deploy.security.DeployURLClassPath$JarLoader.<init>(Unknown Source)
    at com.sun.deploy.security.DeployURLClassPath$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.deploy.security.DeployURLClassPath.getLoader(Unknown Source)
    at com.sun.deploy.security.DeployURLClassPath.getLoader(Unknown Source)
    - locked <0x29dc7e98> (a com.sun.deploy.security.DeployURLClassPath)
    at com.sun.deploy.security.DeployURLClassPath.getResource(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader$2.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.plugin2.applet.Plugin2ClassLoader.findClassHelper(Unknown Source)
    at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
    - locked <0x29dc7ed8> (a sun.plugin2.applet.Applet2ClassLoader)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
    - locked <0x29dc7f78> (a sun.plugin2.applet.Applet2ClassLoader)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
    - locked <0x29dc7f78> (a sun.plugin2.applet.Applet2ClassLoader)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
    at sun.plugin2.applet.Plugin2Manager.initAppletAdapter(Unknown Source)
    at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

以下是Java控制台中的最后4行:

network: Cache entry not found [url: http://localhost/editor.jar, version: null]
network: Connecting http://localhost/editor.jar with proxy=DIRECT
network: Connecting http://localhost:80/ with proxy=DIRECT
network: Connecting http://localhost/editor.jar with cookie "csrftoken=523154b2e73a76b6f2088464bd4df4f7"

一些其他信息:

• 在浏览器中运行Java 7的Windows Vista上,如果取消选中"启用黑名单吊销检查",则会加载我们的主applet(由Apache-> mod_proxy-> tomcat提供).如果选中此选项,则不会加载.在Windows 7上取消选中此功能无效(即无法正常工作).
• 我尝试在Tomcat(本地),Apache(本地)和Apache(在我通过Internet访问的远程服务器上)托管我的测试applet.对于每一个都有一个jar文件大小,applet不会加载到该文件大小 - 但是,这个大小在Web服务器之间变化.例如,在远程服务器上,jar文件可能要大得多 - 在不加载之前必须超过1MB.

尝试加载在Windows 7或Vista上的浏览器中运行Java 7的applet时,有没有其他人看到这种行为？有解决方案吗？

有关如何重现此问题的分步说明:

• 将上面的代码复制到名为Myapplet的名为MyApplet.java的文件中
• 编译代码,即javac MyApplet.java
• 创建一个jar文件:cd到myapplet的父目录,然后输入jar -cvf editor.jar myapplet
• 创建一个简单的HTML页面来显示applet.

例如:

<html>  
    <body>
        <applet code="myapplet.MyApplet" name="MyApplet" width="300" height="300" archive= "editor.jar" ></applet>
    </body>
</html>

• 将此HTML文件和jar文件放在同一目录中,并从Web服务器(例如Apache或Tomcat)提供服务.
• 在Windows 7操作系统上访问Chrome或IE中的此HTML页面.小程序将加载正常!
• 重复上述步骤,但这次在创建jar文件之前将一个小文件(例如<2KB)放入myapplet目录(MyApplet.class旁边).这也应该有效.
• 重复,但这次在创建jar文件之前将一个大图像(例如> 100KB)放入myapplet目录(MyApplet.class旁边).jar文件现在会很大.这不起作用,即applet不会加载.如果是,并且您使用的是Windows 7,请告诉我.在测试时,不要忘记applet已缓存,因此请在java控制台中按x键刷新类加载器缓存,然后按f5刷新浏览器.

Answer 1

Java bug 数据库中bug 7183450的解决方法修复了此问题，即添加

-Djava.net.preferIPv4Stack=true 

到 JVM 参数。

例如，要运行我的测试小程序（请参阅上面问题中的示例）：

<html>  
    <body>
        <applet code="myapplet.MyApplet" name="MyApplet" width="300" height="300" archive= "editor.jar" >
        <param name="java_arguments" value="-Djava.net.preferIPv4Stack=true">
    </applet>
    </body>
</html>

这可能是因为托管我们的小程序的远程服务器当前不允许 IPv6 通信通过其防火墙。

有趣的是，我们的一些 Windows 7 机器在运行 Java 1.7_05 时即使使用此解决方法仍然无法工作，但在升级到 Java 1.7_06（现已可用）时却可以（使用此解决方法）工作。