Core Java™ 2 Volume II - Advanced Features, Seventh Edition

Security Managers and Permissions

Once a class has been loaded into the virtual machine by a class loader or by the default class loading mechanism and checked by the verifier, the third security mechanism of the Java platform springs into action: the security manager. A security manager is a class that controls whether a specific operation is permitted. Operations checked by a security manager include the following:

• Whether the current thread can create a new class loader

• Whether the current thread can halt the virtual machine

• Whether a class can access a member of another class

• Whether the current thread can access a local file

• Whether the current thread can open a socket connection to an external host

• Whether a class can start a print job

• Whether ...