Java中禁止的包名（Prohibited package name）

由于定义了以java开始的包(java.mypackage)，编译时错误：

java.lang.SecurityException: Prohibited package name: java.mypackage
	at java.lang.ClassLoader.preDefineClass(ClassLoader.java:479)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:614)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
	at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
	at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
Exception in thread "main"

根据异常信息，定位到java.lang.ClassLoader.preDefineClass进行排查，发现以下代码片断：

/* Determine protection domain, and check that:
        - not define java.* class,
        - signer of this class matches signers for the rest of the classes in package.
*/
    private ProtectionDomain preDefineClass(String name,
	ProtectionDomain protectionDomain)
    {
	if (!checkName(name))
	    throw new NoClassDefFoundError("IllegalName: " + name);
	if ((name != null) && [color=red]name.startsWith("java.")[/color]) {
	    throw new SecurityException("Prohibited package name: " +
			name.substring(0, name.lastIndexOf('.')));
	}
	if (protectionDomain == null) {
	    protectionDomain = getDefaultDomain();
	}

	if (name != null)
	    checkCerts(name, protectionDomain.getCodeSource());

	return protectionDomain;
    }

......

// true if the name is null or has the potential to be a valid binary name
    private boolean checkName(String name) {
	if ((name == null) || (name.length() == 0))
   	    return true;
	if ((name.indexOf('/') != -1)
	    || (!VM.allowArraySyntax() && (name.charAt(0) == '[')))
   	    return false;
 	return true;
    }

可以看出preDefineClass方法首先对类名进行了检查，发现以java作为一级包名，则抛出安全异常：禁止使用的包名！

这条安全异常是由Java类加载的“双亲委派模型”（详见这里）所导致的。在双亲委派模型中，由父加载类加载的类，下层加载器是不能加载的。本例中最高层加载器BootstrapClassLoader加载了classpath路径下所定义的java.*包内的类，而java.research包就不能由BootstrapClassLoader的下层加载器AppClassLoader加载了。这也是java安全机制中对于恶意代码所采取的防护措施。

另参见：http://dev.csdn.net/develop/article/45/article/39/39272.shtm

评论

2 楼 skygege20 2015-07-24  

2015-7-24 16:09:14 org.apache.catalina.core.StandardContext listenerStart
严重: Exception sending context initialized event to listener instance of class org.tv189.core.web.ContextLoaderListener
java.lang.NoClassDefFoundError: IllegalName: com.tv189.elip/ax/user/service/dao/AXUserAnswerCalcDao
at java.lang.ClassLoader.preDefineClass(ClassLoader.java:476)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:625)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)

1 楼 skygege20 2015-07-24  

那怎么解决这种问题呢？