从 Java 小程序中写入文件时遇到问题 [英] Trouble writing file from within a java applet

问题描述

我创建了简单的 Java 类来测试小程序的文件写入:
更新出现

I have created simple Java class to test file writes from applets:
update appeared

public class localfile extends Applet{
public localfile(){
    try {
        File f = new File("testfile.txt");
        BufferedWriter out = new BufferedWriter(new FileWriter(f,true));
        out.write("test");
        out.close();
    }
    catch(Exception x)
       System.err.println(x.toString());
   }
}

我已经创建并签署了 jar:

I have created and signed jar:

jar cvf localfile.jar localfile.java
jarsigner localfile.jar yourkey

html 看起来像:<applet code="localfile.class" archive="localfile.jar", width=300, height=600>

html looks like: <applet code="localfile.class" archive="localfile.jar", width=300, height=600>

我每次运行这个小程序时得到的错误是:

The error I get every time I run this applet is:

java.lang.SecurityException: trusted loader attempted to load sandboxed resource from file:/home/w/test/
at com.sun.deploy.security.CPCallbackHandler$ParentCallback.check(CPCallbackHandler.java:308)
at com.sun.deploy.security.CPCallbackHandler$ParentCallback.access$1400(CPCallbackHandler.java:121)
at com.sun.deploy.security.CPCallbackHandler$ChildElement.checkResource(CPCallbackHandler.java:473)
at sun.plugin2.applet.Plugin2ClassLoader.checkResource(Plugin2ClassLoader.java:701)
at sun.plugin2.applet.Applet2ClassLoader.findClass(Applet2ClassLoader.java:206)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Plugin2ClassLoader.java:520)
at sun.plugin2.applet.Plugin2Manager.createApplet(Plugin2Manager.java:2940)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Plugin2Manager.java:1444)
at java.lang.Thread.run(Thread.java:619)
Exception: java.lang.SecurityException: trusted loader attempted to load sandboxed resource from file:/home/w/test/

奇怪的是:我创建了类似的小程序来读取文件，并且运行正常.

What is strange: I have created similar applet to read files and it works ok.

有什么想法吗?

我在浏览器和小程序查看器上都运行了这个小程序.奇怪的是小程序在小程序查看器上不起作用并抛出异常，但在浏览器上它很好.

I was running this applet on both browser and applet viewer. What is strange given applet doesn't work on applet viewer and throws exception, but on browser it is fine.

java.security.AccessControlException: access denied (java.util.PropertyPermission java.security.policy write)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.System.setProperty(System.java:725)
at localfile.<init>(localfile.java:15)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:785)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:714)
at sun.applet.AppletPanel.run(AppletPanel.java:368)
at java.lang.Thread.run(Thread.java:619)

所以，除了这种奇怪的行为，我认为我的问题已经解决了.谢谢大家:)

So, beside this strange behaviour I consider my problem solved. Thanks everyone:)

推荐答案

通过一些调整，您可以在 jar 中包含一个策略文件.有关详细信息，请参阅 SO 问题 jar 策略文件.

With some finagling, you can include a policy file in a jar. Refer to the SO question jar policy file for more information.

否则，请考虑制作一个 Java WebStart 应用程序，它可以更轻松地读/写文件.

Otherwise, consider making a Java WebStart application, which can read/write files more easily.

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