readfileaction.java

jdk-6u10-docs java开发宝典

/*
 * @(#)ReadFileAction.java
 *
 * Copyright 2001-2002 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or 
 * without modification, are permitted provided that the following 
 * conditions are met:
 * 
 * -Redistributions of source code must retain the above copyright  
 * notice, this  list of conditions and the following disclaimer.
 * 
 * -Redistribution in binary form must reproduct the above copyright 
 * notice, this list of conditions and the following disclaimer in 
 * the documentation and/or other materials provided with the 
 * distribution.
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of 
 * contributors may be used to endorse or promote products derived 
 * from this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any 
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND 
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY 
 * EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY 
 * DAMAGES OR LIABILITIES  SUFFERED BY LICENSEE AS A RESULT OF  OR 
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 * 
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 */

import java.security.PrivilegedAction;
import java.io.*;

/**
 * This class implements the PrivilegedAction interface to demonstrate the
 * reading of a file that belongs to the client. This code will be 
 * executed by the server while impersonating the client principal.
 */
public class ReadFileAction implements PrivilegedAction {

    private String fileName;

    /**
     * Contructs a ReadFileAction instance.
     *
     * @param kerberosPrincipalName the name of the Kerberos principal
     * who owns the file that will be read. The filename is constructed
     * from the name of the principal.
     */
    public ReadFileAction(String kerberosPrincipalName) {
	/*
	 * Separate the realm component from the name and use the rest of
	 * it for constructing the filename. If the principal name is
	 * "joe@REALM" then the file that will be read is
	 * "data/joe_info.txt". The path separator "/" might be "\" in the
	 * case of Windows.
	 */
	int realmSeparatorPos = kerberosPrincipalName.lastIndexOf('@');
	fileName = "data" + File.separatorChar 
	    + kerberosPrincipalName.substring(0, realmSeparatorPos)
	    + "_info.txt";
    }

    /**
     * Does the actual reading of the file. It displays the text contained
     * in the file.
     */
    public Object run() {
	System.out.println("===============================================");
	System.out.println("Reading file: " + fileName);
	try {
	    BufferedReader reader = new BufferedReader(new FileReader(fileName));
	    String str = reader.readLine();
	    while (str != null) {
		System.out.println(str);
		str = reader.readLine();
	    }
	} catch (IOException e) {
	    System.err.println(e);
	}
	System.out.println("===============================================");
	return null;
    }
}