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Java SecurityManager checkWrite() Method
Description
The Java SecurityManager checkWrite(FileDescriptor fd) method throws a SecurityException if the calling thread is not allowed to write to the specified file descriptor. This method calls checkPermission with the RuntimePermission("writeFileDescriptor") permission.
If you override this method, then you should make a call to super.checkWrite at the point the overridden method would normally throw an exception.
Declaration
Following is the declaration for java.lang.SecurityManager.checkWrite() method
public void checkWrite(FileDescriptor fd)
Parameters
fd − the system-dependent file descriptor.
Return Value
This method does not return a value.
Exception
SecurityException − if the calling thread does not have permission to access the specified file descriptor.
NullPointerException − if the file descriptor 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.checkWrite() method.
package com.tutorialspoint; import java.io.FileDescriptor; public class SecurityManagerDemo extends SecurityManager { 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 FileDescriptor fd=new FileDescriptor(); sm.checkWrite(fd); // print a message if we passed the check System.out.println("Allowed!"); } }
Output
Let us compile and run the above program, this will produce the following result −
Exception in thread "main" java.lang.UnsupportedOperationException: The Security Manager is deprecated and will be removed in a future release at java.base/java.lang.System.setSecurityManager(System.java:430) at com.tutorialspoint.SecurityManagerDemo.main(SecurityManagerDemo.java:14)
Note − Security Manager has been deprecated since version 17 and marked for removal.