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Java SecurityManager checkPackageAccess() method with example

SecurityManager Class checkPackageAccess() method: Here, we are going to learn about the checkPackageAccess() method of SecurityManager Class with its syntax and example.
Submitted by Preeti Jain, on December 16, 2019

SecurityManager Class checkPackageAccess() method

• checkPackageAccess() method is available in java.lang package.
• We call getProperty("package.access") to get a list of restricted package and it checks when 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("accessClassInPackage."+pkg_name).
• checkPackageAccess() 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.
• checkPackageAccess() method may throw an exception at the time of checking restricted packages.
  • SecurityException – This exception may throw when the calling thread does not have the right to retrieve the package given by the method parameter and it is used loadClass() of ClassLoader().
  • NullPointerException – This exception may throw when the given parameter is null.

Syntax:

    public void checkPackageAccess(String pkg_name);

Parameter(s):

• String pkg_name – represents the name of the package.

Return value:

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

Example:

// Java program to demonstrate the example 
// of void checkPackageAccess(String pkg_name)
// method of SecurityManager 

public class CheckPackageAccess extends SecurityManager {
    // override checkPackageAccess() method of SecurityManager
    public void checkPackageAccess(String pkg_name) {
        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 CheckPackageAccess object
        CheckPackageAccess cpa = new CheckPackageAccess();

        // By using setSecurityManager() method is to set the
        // security manager
        System.setSecurityManager(cpa);

        // By using CheckPackageAccess(pkg_name) method is to check 
        // that package is accessible
        cpa.checkPackageAccess("java.lang");

        // Display the message
        System.out.println("Not Restricted..");
    }
}

Output

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