SecurityManager checkLink(String) in Java

checkLink(String): This method is available in the java.lang.SecurityManager class of Java.

Syntax:

void java.lang.SecurityManager.checkLink(String lib)

This method takes one argument. This method throws a SecurityException if the calling thread is not allowed to dynamic link the library code specified by the string argument file.

The argument is either a simple library name or a complete filename.

This method is invoked for the current security manager by methods load and loadLibrary of class Runtime.

Parameters: One parameter is required for this method.

lib: the name of the library.

Returns: NA

Throws:

1. SecurityException - if the calling thread does not have permission to dynamically link the library.

2. NullPointerException - if the lib argument is null.

Approach 1: SecurityException 

Java

package com.SecurityManager;

public class SecurityManagercheckLink {
    public static void main(String[] args) {

        SecurityManager securityManager = new SecurityManager();

        String lib = "C:\\Windows\\System32\\crypt32.dl";
        securityManager.checkLink(lib);
        System.out.println("Successfully check the access");
    }
}

Output:

Exception in thread "main" java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "loadLibrary.C:\Windows\System32\crypt32.dl")
	at java.base/java.security.AccessControlContext.checkPermission(AccessControlContext.java:472)
	at java.base/java.security.AccessController.checkPermission(AccessController.java:1036)
	at java.base/java.lang.SecurityManager.checkPermission(SecurityManager.java:408)
	at java.base/java.lang.SecurityManager.checkLink(SecurityManager.java:694)
	at com.SecurityManager.SecurityManagercheckLink.main(SecurityManagercheckLink.java:9)

Approach 2: NullPointerException

Java

package com.SecurityManager;

public class SecurityManagercheckLink {
    public static void main(String[] args) {

        SecurityManager securityManager = new SecurityManager();

        String lib = null;
        securityManager.checkLink(lib);
        System.out.println("Successfully check the access");
    }
}

Output:

Exception in thread "main" java.lang.NullPointerException: library can't be null
	at java.base/java.lang.SecurityManager.checkLink(SecurityManager.java:692)
	at com.SecurityManager.SecurityManagercheckLink.main(SecurityManagercheckLink.java:9)

Some other methods of SecurityManager

SecurityManager(): This method constructs a new SecurityManager.

checkAccept(String, int): This method throws a SecurityException if the calling thread is not permitted to accept a socket connection from the specified host and port number.

checkAccess(Thread): This method throws a SecurityException if the calling thread is not allowed to modify the thread argument.

checkAccess(ThreadGroup): This method throws a SecurityException if the calling thread is not allowed to modify the thread group argument.

checkConnect(String, int): This method throws a SecurityException if the calling thread is not allowed to open a socket connection to the specified host and port number.

checkConnect(String, int, Object): This method throws a SecurityException if the specified security context is not allowed to open a socket connection to the specified host and port number.

checkCreateClassLoader(): This method throws a SecurityException if the calling thread is not allowed to create a new class loader.

checkDelete(String): This method throws a SecurityException if the calling thread is not allowed to delete the specified file.

checkExec(String): This method throws a SecurityException if the calling thread is not allowed to create a subprocess.

checkExit(int): This method throws a SecurityException if the calling thread is not allowed to cause the Java Virtual Machine to halt with the specified status code.

checkLink(String): This method throws a SecurityException if the calling thread is not allowed to dynamic link the library code specified by the string argument file.

checkListen(int): This method throws a SecurityException if the calling thread is not allowed to wait for a connection request on the specified local port number.

checkMulticast(InetAddress): This method throws a SecurityException if the calling thread is not allowed to use(join/leave/send/receive) IP multicast.

checkPackageAccess(String): This method throws a SecurityException if the calling thread is not allowed to access the specified package.

checkPackageDefinition(String): This method throws a SecurityException if the calling thread is not allowed to define classes in the specified package.

checkPermission(Permission): This method throws a SecurityException if the requested access, specified by the given permission, is not permitted based on the security policy currently in effect.

checkPermission(Permission, Object): This method throws a SecurityException if the specified security context is denied access to the resource specified by the given permission.

checkPrintJobAccess(): This method throws a SecurityException if the calling thread is not allowed to initiate a print job request.

checkPropertiesAccess(): This method throws a SecurityException if the calling thread is not allowed to access or modify the system properties.

checkPropertyAccess(String): This method throws a SecurityException if the calling thread is not allowed to access the system property with the specified key name.

checkRead(FileDescriptor): This method throws a SecurityException if the calling thread is not allowed to read from the specified file descriptor.

checkRead(String): This method throws a SecurityException if the calling thread is not allowed to read the file specified by the string argument.

checkRead(String, Object): This method throws a SecurityException if the specified security context is not allowed to read the file specified by the string argument.

checkSecurityAccess(String): This method determines whether permission with the specified target name should be granted or denied.

checkSetFactory(): This method throws a SecurityException if the calling thread is not allowed to set the socket factory used by ServerSocket or Socket or the stream handler factory used by URL.

checkWrite(FileDescriptor):  This method throws a SecurityException if the calling thread is not allowed to write to the specified file descriptor.

checkWrite(String): This method throws a SecurityException if the calling thread is not allowed to write to the file specified by the string argument.

getSecurityContext(): This method creates an object that encapsulates the current execution environment.

getThreadGroup(): This method returns the thread group into which to instantiate any new thread being created at the time this is being called.