SecurityManager checkPackageAccess() Method

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Description

The java.lang.SecurityManager.checkPackageAccess(String pkg) method throws a SecurityException if the calling thread is not allowed to access the package specified by the argument. This method is used by the loadClass method of class loaders.

This method first gets a list of restricted packages by obtaining a comma-separated list from a call to java.security.Security.getProperty("package.access"), and checks to see if pkg starts with or equals any of the restricted packages. If it does, then checkPermission gets called with the RuntimePermission("accessClassInPackage."+pkg) permission. If this method is overridden, then super.checkPackageAccess should be called as the first line in the overridden method.

Declaration

Following is the declaration for java.lang.SecurityManager.checkPackageAccess() method

public void checkPackageAccess(String pkg)

Parameters

  • pkg -- the package name.

Return Value

This method does not return a value.

Exception

  • SecurityException -- if the calling thread does not have permission to access the specified package.

  • NullPointerException -- if the package name argument is null.

Example

Our examples require that the permissions for each command is blocked. A new policy file was set that allows only the creating and setting of our Security Manager. The file is in C:/java.policy and contains the following text:

grant {
  permission java.lang.RuntimePermission "setSecurityManager";
  permission java.lang.RuntimePermission "createSecurityManager";
  permission java.lang.RuntimePermission "usePolicy";
};

The following example shows the usage of lang.SecurityManager.checkPackageAccess() method.

package com.tutorialspoint;

public class SecurityManagerDemo extends SecurityManager {

   // checkPackageAccess needs to be overriden
   @Override
   public void checkPackageAccess(String pkg) {
      throw new SecurityException();
   }

   public static void main(String[] args) {


      // set the policy file as the system securuty policy
      System.setProperty("java.security.policy", "file:/C:/java.policy");

      // create a security manager
      SecurityManagerDemo sm = new SecurityManagerDemo();

      // set the system security manager
      System.setSecurityManager(sm);

      // perform the check
      sm.checkPackageAccess("com.tutorialspoint");

      // print a message if we passed the check
      System.out.println("Allowed!");
   }
}

Let us compile and run the above program, this will produce the following result:

Exception in thread "main" java.lang.SecurityException



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