policyファイルを指定して権限を与えて実行

sample.policy

grant {
	permission java.security.AllPermission;
};

SampleProject\SampleProject.java

package sampleproject;

import lib.Lib;

/**
 *
 * @author java
 */
public class SampleProject {

    public static void main(String[] args) {
        Lib l = new Lib();
        l.method();
    }
}

Lib\Lib.java

package lib;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.stream.Stream;

/**
 *
 * @author java
 */
public class Lib {
    public void method() {
        try {
            Stream<Path> s = Files.list(Paths.get("C:\\dirtest"));
            s.forEach(System.out::println);
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

C:\Users\java\Documents\NetBeansProjects\SampleProject\build\classes>java -cp .;C:\Users\java\Documents\NetBeansProjects\Lib\dist\Lib.jar -Djava.security.manager -Djava.security.policy=C:\Users\java\Documents\NetBeansProjects\SampleProject\sample.policy sampleproject.SampleProject
C:\dirtest\showa.txt
C:\dirtest\test.java
C:\dirtest\test.txt
C:\dirtest\testfile.txt
C:\dirtest\testmakefile.txt
C:\dirtest\testwritefile.txt

codeBaseでLib.jarだけに権限を与えたポリシーで動かすと、SampleProjectの権限がないのでエラーになる

sample2.policy

grant codeBase "file:C:/Users/java/Documents/NetBeansProjects/Lib/dist/Lib.jar" {
	permission java.security.AllPermission;
};

C:\Users\java\Documents\NetBeansProjects\SampleProject\build\classes>java -cp .;C:\Users\java\Documents\NetBeansProjects\Lib\dist\Lib.jar -Djava.security.manager -Djava.security.policy=C:\Users\java\Documents\NetBeansProjects\SampleProject\sample2.policy sampleproject.SampleProject
Exception in thread "main" java.security.AccessControlException: access denied ("java.io.FilePermission" "C:\dirtest" "read")
        at java.base/java.security.AccessControlContext.checkPermission(AccessControlContext.java:472)
        at java.base/java.security.AccessController.checkPermission(AccessController.java:897)
        at java.base/java.lang.SecurityManager.checkPermission(SecurityManager.java:322)
        at java.base/java.lang.SecurityManager.checkRead(SecurityManager.java:661)
        at java.base/sun.nio.fs.WindowsPath.checkRead(WindowsPath.java:847)
        at java.base/sun.nio.fs.WindowsFileSystemProvider.newDirectoryStream(WindowsFileSystemProvider.java:520)
        at java.base/java.nio.file.Files.newDirectoryStream(Files.java:472)
        at java.base/java.nio.file.Files.list(Files.java:3699)
        at lib.Lib$1.run(Lib.java:25)
        at java.base/java.security.AccessController.doPrivileged(Native Method)
        at lib.Lib.method(Lib.java:21)
        at sampleproject.SampleProject.main(SampleProject.java:17)

LibをdoPrivileged(PrevilegedAction)として実行すると権限がSampleProjectではなく
Libの権限で実行される

Lib\Lib.java

package lib;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.stream.Stream;

/**
 *
 * @author java
 */
public class Lib {
    public void method() {
        AccessController.doPrivileged(new PrivilegedAction<Object>() {
            @Override
            public Object run() {
                try {
                    Stream<Path> s = Files.list(Paths.get("C:\\dirtest"));
                    s.forEach(System.out::println);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
                return null;
            }
        });
    }
}

C:\Users\java\Documents\NetBeansProjects\SampleProject\build\classes>java -cp .;C:\Users\java\Documents\NetBeansProjects\Lib\dist\Lib.jar -Djava.security.manager -Djava.security.policy=C:\Users\java\Documents\NetBeansProjects\SampleProject\sample2.policy sampleproject.SampleProject
C:\dirtest\showa.txt
C:\dirtest\test.java
C:\dirtest\test.txt
C:\dirtest\testfile.txt
C:\dirtest\testmakefile.txt
C:\dirtest\testwritefile.txt