Java 1.2 How-To/JavaHowTo.iso/3rdParty/jbuilder/unsupported/JDK1.2beta3/SOURCE/SRC.ZIP/java/security/Provider.java

Java Source | 1998-03-20 | 5.1 KB | 205 lines

/*
 * @(#)Provider.java    1.28 98/03/18
 *
 * Copyright 1996, 1997 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.security;

import java.io.*;
import java.util.*;

/**
 * This class represents a "provider" for the
 * Java Security API.  A provider implements some or all parts of
 * Java Security, including:<ul>
 *
 * <li>Algorithms (such as DSA, RSA, MD5 or SHA-1).
 *
 * <li>Key generation and management facilities (such as for
 * algorithm-specific keys).
 *
 * </ul>
 *
 * <p>Each provider has a name and a version number, and is configured
 * in each runtime it is installed in.
 *
 * <p>There is a default provider that comes standard with the JDK. It is
 * called the SUN Provider.
 *
 * See <a href =
 * "../guide/security/CryptoSpec.html#Provider">The Provider Class</a>
 * in the "Java Cryptography Architecture API Specification & Reference"
 * for information about how providers work and how to install them.
 *
 * @version 1.28 98/03/18
 * @author Benjamin Renaud */

public abstract class Provider extends Properties {

    private String name;
    private String info;
    private double version;

    /**
     * Constructs a provider with the specified name, version number,
     * and information.
     *
     * @param name the provider name.
     *
     * @param version the provider version number.
     *
     * @param info a description of the provider and its services.
     */
    protected Provider(String name, double version, String info) {
    this.name = name;
    this.version = version;
    this.info = info;
    }

    /**
     * Constructs a provider with the specified name. Assigns it
     * version 1.0.
     *
     * @param name the provider name.
     */
    Provider(String name) {
    this(name, 1.0, "no information available");
    }

    /**
     * Returns the name of this provider.
     *
     * @return the name of this provider.
     */
    public String getName() {
    return name;
    }

    /**
     * Returns the version number for this provider.
     *
     * @return the version number for this provider.
     */
    public double getVersion() {
    return version;
    }

    /**
     * Returns a human-readable description of the provider and its
     * services.  This may return an HTML page, with relevant links.
     *
     * @return a description of the provider and its services.
     */
    public String getInfo() {
    return info;
    }


    static Provider loadProvider(String name) {

    try {
        Class cl = Class.forName(name);
        Object instance = cl.newInstance();

        if (instance instanceof Provider) {
        return (Provider)instance;
        }

    } catch (Exception e) {
        debug("error loading provider " + name, e);
    }
    return null;
    }


    /**
     * Returns a string with the name and the version number
     * of this provider.
     *
     * @return the string with the name and the version number
     * for this provider.
     */
    public String toString() {
    return name + " version " + version;
    }

    /*
     * override 3 methods from Hashtable to ensure that provider
     * information can only be changed if the caller has the appropriate
     * permissions.
     */

    /**
     * Clears this provider so that it no longer contains the properties
     * used to look up facilities implemented by the provider.
     *
     * @since JDK1.2
     */
    public synchronized void clear() {
    check("Provider.clear."+name);
    super.clear();
    }

    /**
     * Sets the <code>key</code> property to have the specified
     * <code>value</code>.
     *
     * @param key the property key.
     *
     * @param value the property value.
     *
     * @return the previous value of the specified property
     * (<code>key</code>), or null if it did not have one.
     *
     * @since JDK1.2
     */
    public synchronized Object put(Object key, Object value) {
    check("Provider.put."+name);
    return super.put(key, value);
    }

    /**
     * Removes the <code>key</code> property (and its corresponding
     * <code>value</code>).
     *
     * @param key the key for the property to be removed.
     *
     * @return the value to which the key had been mapped,
     * or null if the key did not have a mapping.
     *
     * @since JDK1.2
     */
    public synchronized Object remove(Object key) {
    check("Provider.remove."+name);
    return super.remove(key);
    }

    private static void check(String directive) {
         SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkSecurityAccess(directive);
        }
    }

    private static void debug(String msg) {
    Security.debug(msg);
    }

    private static void debug(String msg, Throwable t) {
    Security.debug(msg, t);
    }

    // Declare serialVersionUID to be compatible with JDK1.1
    static final long serialVersionUID = -4298000515446427739L;
}