The Java Developers Almanac 1.4

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e218. Listing All Permissions Granted to Classes Loaded from a URL or Directory

A code base is a location of class or jar files specified using a URL. The URL may refer to a location on the Internet or a directory in the local file system. This example retrieves all the permissions granted to a particular class that's been loaded from a code base.

These permissions are effective only if the security manager is installed (see e212 Enabling the Security Manager). However, with a security manager installed, a class will require permission to execute Class.getProtectionDomain() and Policy.getPermissions().

    URL codebase = null;
    try {
        // Get permissions for a URL
        codebase = new URL("http://java.sun.com/");
    
        // Get permissions for a directory
        codebase = new File("c:\\users\\almanac\\").toURL();
        codebase = new File(System.getProperty("user.home")).toURL();
    } catch (MalformedURLException e) {
    } catch (IOException e) {
    }
    
    // Construct a code source with the code base
    CodeSource cs = new CodeSource(codebase, null);
    
    // Get all granted permissions
    PermissionCollection pcoll = Policy.getPolicy().getPermissions(cs);
    
    // View each permission in the permission collection
    Enumeration enum = pcoll.elements();
    for (; enum.hasMoreElements(); ) {
        Permission p = (Permission)enum.nextElement();
    }

When the above example is run with the following policy file:

    grant codeBase "http://java.sun.com/-" {
        // Give permission to read all system properties
        permission java.util.PropertyPermission "*", "read";
    };
    
    grant codeBase "file:${user.home}/*" {
        // Give permission to execute all runtime-protected methods
        permission java.lang.RuntimePermission "*";
    };

using the following command:

    java -Djava.security.policy==my.policy MyApp

the permissions for the URL http://java.sun.com/ are:

    (java.util.PropertyPermission * read)

and the permissions for the directory System.getProperty("user.home") are:

    (java.lang.RuntimePermission *)