securitysupport.java

java1.6众多例子参考

/*
 * Copyright 2002,2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.xerces.internal.impl.dv;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;

import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;

/**
 * This class is duplicated for each subpackage so keep it in sync.
 * It is package private and therefore is not exposed as part of any API.
 * 
 * @xerces.internal
 */
final class SecuritySupport {

    private static final SecuritySupport securitySupport = new SecuritySupport();

    /**
     * Return an instance of this class.
     */
    static SecuritySupport getInstance() {
        return securitySupport;
    }

    ClassLoader getContextClassLoader() {
        return (ClassLoader)
        AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
                ClassLoader cl = null;
                try {
                    cl = Thread.currentThread().getContextClassLoader();
                } catch (SecurityException ex) { }
                return cl;
            }
        });
    }
    
    ClassLoader getSystemClassLoader() {
        return (ClassLoader)
        AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
                ClassLoader cl = null;
                try {
                    cl = ClassLoader.getSystemClassLoader();
                } catch (SecurityException ex) {}
                return cl;
            }
        });
    }
    
    ClassLoader getParentClassLoader(final ClassLoader cl) {
        return (ClassLoader)
        AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
                ClassLoader parent = null;
                try {
                    parent = cl.getParent();
                } catch (SecurityException ex) {}
                
                // eliminate loops in case of the boot
                // ClassLoader returning itself as a parent
                return (parent == cl) ? null : parent;
            }
        });
    }
    
    String getSystemProperty(final String propName) {
        return (String)
        AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
                return System.getProperty(propName);
            }
        });
    }
    
    FileInputStream getFileInputStream(final File file)
    throws FileNotFoundException
    {
        try {
            return (FileInputStream)
            AccessController.doPrivileged(new PrivilegedExceptionAction() {
                public Object run() throws FileNotFoundException {
                    return new FileInputStream(file);
                }
            });
        } catch (PrivilegedActionException e) {
            throw (FileNotFoundException)e.getException();
        }
    }
    
    InputStream getResourceAsStream(final ClassLoader cl,
            final String name)
    {
        return (InputStream)
        AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
                InputStream ris;
                if (cl == null) {
                    ris = ClassLoader.getSystemResourceAsStream(name);
                } else {
                    ris = cl.getResourceAsStream(name);
                }
                return ris;
            }
        });
    }
    
    boolean getFileExists(final File f) {
        return ((Boolean)
                AccessController.doPrivileged(new PrivilegedAction() {
                    public Object run() {
                        return new Boolean(f.exists());
                    }
                })).booleanValue();
    }
    
    long getLastModified(final File f) {
        return ((Long)
                AccessController.doPrivileged(new PrivilegedAction() {
                    public Object run() {
                        return new Long(f.lastModified());
                    }
                })).longValue();
    }
    
    private SecuritySupport () {}
}