GUACAMOLE-220: Add EMPTY_SET convenience constant to all core set interfaces.

extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/sharing/user/SharedUser.java

@@ -35,9 +35,6 @@ import org.apache.guacamole.net.auth.RelatedObjectSet;
 import org.apache.guacamole.net.auth.User;
 import org.apache.guacamole.net.auth.permission.ObjectPermissionSet;
 import org.apache.guacamole.net.auth.permission.SystemPermissionSet;
-import org.apache.guacamole.net.auth.simple.SimpleObjectPermissionSet;
-import org.apache.guacamole.net.auth.simple.SimpleRelatedObjectSet;
-import org.apache.guacamole.net.auth.simple.SimpleSystemPermissionSet;
 
 /**
  * An immutable implementation of User which defines READ permission for each of
@@ -122,7 +119,7 @@ public class SharedUser implements User {
 
     @Override
     public SystemPermissionSet getSystemPermissions() throws GuacamoleException {
-        return new SimpleSystemPermissionSet();
+        return SystemPermissionSet.EMPTY_SET;
     }
 
     @Override
@@ -145,22 +142,22 @@ public class SharedUser implements User {
 
     @Override
     public ObjectPermissionSet getUserGroupPermissions() throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getSharingProfilePermissions() throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getActiveConnectionPermissions() throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public RelatedObjectSet getUserGroups() throws GuacamoleException {
-        return new SimpleRelatedObjectSet();
+        return RelatedObjectSet.EMPTY_SET;
     }
 
     @Override

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/RelatedObjectSet.java

@@ -19,8 +19,10 @@
 
 package org.apache.guacamole.net.auth;
 
+import java.util.Collections;
 import java.util.Set;
 import org.apache.guacamole.GuacamoleException;
+import org.apache.guacamole.GuacamoleSecurityException;
 
 /**
  * An arbitrary set of existing objects sharing some common relation. Unlike a
@@ -75,4 +77,28 @@ public interface RelatedObjectSet {
      */
     void removeObjects(Set<String> identifiers) throws GuacamoleException;
 
+    /**
+     * An immutable instance of RelatedObjectSEt which contains no objects.
+     */
+    static final RelatedObjectSet EMPTY_SET = new RelatedObjectSet() {
+
+        @Override
+        public Set<String> getObjects() throws GuacamoleException {
+            return Collections.<String>emptySet();
+        }
+
+        @Override
+        public void addObjects(Set<String> identifiers)
+                throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+        @Override
+        public void removeObjects(Set<String> identifiers)
+                throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+    };
+
 }

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/permission/ObjectPermissionSet.java

@@ -20,8 +20,10 @@
 package org.apache.guacamole.net.auth.permission;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Set;
 import org.apache.guacamole.GuacamoleException;
+import org.apache.guacamole.GuacamoleSecurityException;
 
 
 /**
@@ -126,4 +128,54 @@ public interface ObjectPermissionSet extends PermissionSet<ObjectPermission> {
     void removePermissions(Set<ObjectPermission> permissions)
             throws GuacamoleException;
 
+    /**
+     * An immutable instance of ObjectPermissionSet which contains no
+     * permissions.
+     */
+    static final ObjectPermissionSet EMPTY_SET = new ObjectPermissionSet() {
+
+        @Override
+        public boolean hasPermission(ObjectPermission.Type permission,
+                String identifier) throws GuacamoleException {
+            return false;
+        }
+
+        @Override
+        public void addPermission(ObjectPermission.Type permission,
+                String identifier) throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+        @Override
+        public void removePermission(ObjectPermission.Type permission,
+                String identifier) throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+        @Override
+        public Collection<String> getAccessibleObjects(Collection<ObjectPermission.Type> permissions,
+                Collection<String> identifiers) throws GuacamoleException {
+            return Collections.<String>emptySet();
+        }
+
+        @Override
+        public Set<ObjectPermission> getPermissions()
+                throws GuacamoleException {
+            return Collections.<ObjectPermission>emptySet();
+        }
+
+        @Override
+        public void addPermissions(Set<ObjectPermission> permissions)
+                throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+        @Override
+        public void removePermissions(Set<ObjectPermission> permissions)
+                throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+    };
+
 }

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/permission/SystemPermissionSet.java

@@ -19,8 +19,10 @@
 
 package org.apache.guacamole.net.auth.permission;
 
+import java.util.Collections;
 import java.util.Set;
 import org.apache.guacamole.GuacamoleException;
+import org.apache.guacamole.GuacamoleSecurityException;
 
 
 /**
@@ -81,4 +83,48 @@ public interface SystemPermissionSet extends PermissionSet<SystemPermission> {
     void removePermissions(Set<SystemPermission> permissions)
             throws GuacamoleException;
 
+    /**
+     * An immutable instance of SystemPermissionSet which contains no
+     * permissions.
+     */
+    static final SystemPermissionSet EMPTY_SET = new SystemPermissionSet() {
+
+        @Override
+        public boolean hasPermission(SystemPermission.Type permission)
+                throws GuacamoleException {
+            return false;
+        }
+
+        @Override
+        public void addPermission(SystemPermission.Type permission)
+                throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+        @Override
+        public void removePermission(SystemPermission.Type permission)
+                throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+        @Override
+        public Set<SystemPermission> getPermissions()
+                throws GuacamoleException {
+            return Collections.<SystemPermission>emptySet();
+        }
+
+        @Override
+        public void addPermissions(Set<SystemPermission> permissions)
+                throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+        @Override
+        public void removePermissions(Set<SystemPermission> permissions)
+                throws GuacamoleException {
+            throw new GuacamoleSecurityException("Permission denied.");
+        }
+
+    };
+
 }

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleObjectPermissionSet.java

@@ -41,7 +41,10 @@ public class SimpleObjectPermissionSet implements ObjectPermissionSet {
     private Set<ObjectPermission> permissions = Collections.<ObjectPermission>emptySet();
 
     /**
-     * Creates a new empty SimpleObjectPermissionSet.
+     * Creates a new empty SimpleObjectPermissionSet. If you are not extending
+     * SimpleObjectPermissionSet and only need an immutable, empty
+     * ObjectPermissionSet, consider using {@link ObjectPermissionSet#EMPTY_SET}
+     * instead.
      */
     public SimpleObjectPermissionSet() {
     }

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleRelatedObjectSet.java

@@ -37,7 +37,10 @@ public class SimpleRelatedObjectSet implements RelatedObjectSet {
     private Set<String> identifiers = Collections.<String>emptySet();
 
     /**
-     * Creates a new empty SimpleObjectPermissionSet.
+     * Creates a new empty SimpleRelatedObjectSet. If you are not extending
+     * SimpleRelatedObjectSet and only need an immutable, empty
+     * RelatedObjectSet, consider using {@link RelatedObjectSet#EMPTY_SET}
+     * instead.
      */
     public SimpleRelatedObjectSet() {
     }

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleSystemPermissionSet.java

@@ -38,7 +38,10 @@ public class SimpleSystemPermissionSet implements SystemPermissionSet {
     private Set<SystemPermission> permissions = Collections.<SystemPermission>emptySet();
 
     /**
-     * Creates a new empty SimpleSystemPermissionSet.
+     * Creates a new empty SimpleSystemPermissionSet. If you are not extending
+     * SimpleSystemPermissionSet and only need an immutable, empty
+     * SystemPermissionSet, consider using {@link SystemPermissionSet#EMPTY_SET}
+     * instead.
      */
     public SimpleSystemPermissionSet() {
     }

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleUser.java

@@ -193,7 +193,7 @@ public class SimpleUser extends AbstractUser {
     @Override
     public SystemPermissionSet getSystemPermissions()
             throws GuacamoleException {
-        return new SimpleSystemPermissionSet();
+        return SystemPermissionSet.EMPTY_SET;
     }
 
     @Override
@@ -217,23 +217,23 @@ public class SimpleUser extends AbstractUser {
     @Override
     public ObjectPermissionSet getUserGroupPermissions()
             throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getActiveConnectionPermissions()
             throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getSharingProfilePermissions() {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public RelatedObjectSet getUserGroups() throws GuacamoleException {
-        return new SimpleRelatedObjectSet();
+        return RelatedObjectSet.EMPTY_SET;
     }
 
     @Override

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleUserGroup.java

@@ -62,57 +62,57 @@ public class SimpleUserGroup extends AbstractIdentifiable implements UserGroup {
     @Override
     public SystemPermissionSet getSystemPermissions()
             throws GuacamoleException {
-        return new SimpleSystemPermissionSet();
+        return SystemPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getConnectionPermissions()
             throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getConnectionGroupPermissions()
             throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getUserPermissions()
             throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getUserGroupPermissions()
             throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getActiveConnectionPermissions()
             throws GuacamoleException {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public ObjectPermissionSet getSharingProfilePermissions() {
-        return new SimpleObjectPermissionSet();
+        return ObjectPermissionSet.EMPTY_SET;
     }
 
     @Override
     public RelatedObjectSet getUserGroups() throws GuacamoleException {
-        return new SimpleRelatedObjectSet();
+        return RelatedObjectSet.EMPTY_SET;
     }
 
     @Override
     public RelatedObjectSet getMemberUsers() throws GuacamoleException {
-        return new SimpleRelatedObjectSet();
+        return RelatedObjectSet.EMPTY_SET;
     }
 
     @Override
     public RelatedObjectSet getMemberUserGroups() throws GuacamoleException {
-        return new SimpleRelatedObjectSet();
+        return RelatedObjectSet.EMPTY_SET;
     }
 
 }