Java SecurityManager checkPackageDefinition（）方法与示例

SecurityManager类的checkPackageDefinition()方法 (SecurityManager Class checkPackageDefinition() method)

checkPackageDefinition() method is available in java.lang package.
checkPackageDefinition()方法在java.lang包中可用。
We call getProperty("package.definition") to get a list of restricted packages and it checks when our pkg_name starts with or similar to any of the list of restricted packages and when it matches then it calls checkPermission with the RuntimePermission("defineClassInPackage."+pkg_name).
我们调用getProperty(“ package.definition”)来获取受限程序包列表，它会检查何时pkg_name以任何受限程序包列表开头或相似，并且何时匹配，然后使用RuntimePermission(“ defineClassInPackage)调用checkPermission。 “ + pkg_name)。
checkPackageDefinition() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
checkPackageDefinition()方法是一种非静态方法，只能通过类对象访问，如果尝试使用类名称访问该方法，则会收到错误消息。
checkPackageDefinition() method may throw an exception at the time of defining the class in the given package.
在给定包中定义类时， checkPackageDefinition()方法可能会引发异常。

SecurityException – This exception may throw when the calling thread does not have the right to define classes in the given package.
SecurityException-当调用线程无权在给定包中定义类时，可能引发此异常。

Syntax:

句法：

    public void checkPackageDefinition(String pkg_def);

Parameter(s):

参数：

String pkg_def – represents the name of the package.
字符串pkg_def –表示软件包的名称。

Return value:

返回值：

The return type of this method is void, it returns nothing.

此方法的返回类型为void ，不返回任何内容。

Example:

例：

// Java program to demonstrate the example 
// of void checkPackageDefinition(String pkg_def)
// method of SecurityManager 
public class checkPackageDefinition extends SecurityManager {
// override checkPackageDefinition() method of SecurityManager
public void checkPackageDefinition(String pkg_def) {
throw new SecurityException("Restricted...");
}
public static void main(String[] args) throws Exception {
// By using setProperty() method is to set the policy property 
// with security manager
System.setProperty("java.security.policy", "file:/C:/java.policy");
// Instantiating a checkPackageDefinition object
checkPackageDefinition cpd = new checkPackageDefinition();
// By using setSecurityManager() method is to set the
// security manager
System.setSecurityManager(cpd);
// By using checkPackageDefinition(pkg_def) method is to check 
// that package is defined or not
cpd.checkPackageDefinition("java.lang");
// Display the message
System.out.println("Not Restricted..");
}
}

Output

输出量

Exception in thread "main" java.lang.SecurityException: Restricted...at checkPackageDefinition.checkPackageDefinition(checkPackageDefinition.java:8)at checkPackageDefinition.main(checkPackageDefinition.java:25)