keypairgenerator.java

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     * @see Provider
     *
     * @since 1.4
     */
    public static KeyPairGenerator getInstance(String algorithm,
					       Provider provider) 
	throws NoSuchAlgorithmException
    {
	if (provider == null)
	    throw new IllegalArgumentException("missing provider");
	Object[] objs = Security.getImpl(algorithm, "KeyPairGenerator",
					 provider);
	if (objs[0] instanceof KeyPairGenerator) {
	    KeyPairGenerator keyPairGen = (KeyPairGenerator)objs[0];
	    keyPairGen.provider = (Provider)objs[1];
	    return keyPairGen;
	} else {
	    KeyPairGenerator delegate =
		new Delegate((KeyPairGeneratorSpi)objs[0], algorithm);
	    delegate.provider = (Provider)objs[1];
	    return delegate;
	}
    }

    /** 
     * Returns the provider of this key pair generator object.
     * 
     * @return the provider of this key pair generator object
     */
    public final Provider getProvider() {
	return this.provider;
    }

    /**
     * Initializes the key pair generator for a certain keysize using
     * a default parameter set and the <code>SecureRandom</code>
     * implementation of the highest-priority installed provider as the source
     * of randomness.
     * (If none of the installed providers supply an implementation of
     * <code>SecureRandom</code>, a system-provided source of randomness is
     * used.)
     *
     * @param keysize the keysize. This is an
     * algorithm-specific metric, such as modulus length, specified in
     * number of bits.
     *
     * @exception InvalidParameterException if the <code>keysize</code> is not
     * supported by this KeyPairGenerator object.
     */
    public void initialize(int keysize) {
	initialize(keysize, new SecureRandom());
    }

    /**
     * Initializes the key pair generator for a certain keysize with
     * the given source of randomness (and a default parameter set).
     *
     * @param keysize the keysize. This is an
     * algorithm-specific metric, such as modulus length, specified in
     * number of bits.
     * @param random the source of randomness.
     *
     * @exception InvalidParameterException if the <code>keysize</code> is not
     * supported by this KeyPairGenerator object.
     *
     * @since 1.2
     */
    public void initialize(int keysize, SecureRandom random) {
	// This does nothing, because either
	// 1. the implementation object returned by getInstance() is an
	//    instance of KeyPairGenerator which has its own 
	//    initialize(keysize, random) method, so the application would
	//    be calling that method directly, or
	// 2. the implementation returned by getInstance() is an instance
	//    of Delegate, in which case initialize(keysize, random) is
	//    overridden to call the corresponding SPI method.
	// (This is a special case, because the API and SPI method have the
	// same name.)
    }

    /**
     * Initializes the key pair generator using the specified parameter 
     * set and the <code>SecureRandom</code>
     * implementation of the highest-priority installed provider as the source
     * of randomness.
     * (If none of the installed providers supply an implementation of
     * <code>SecureRandom</code>, a system-provided source of randomness is
     * used.).
     *
     * <p>This concrete method has been added to this previously-defined
     * abstract class.
     * This method calls the KeyPairGeneratorSpi 
     * {@link KeyPairGeneratorSpi.html#
     * initialize(java.security.spec.AlgorithmParameterSpec,
     * java.security.SecureRandom) initialize} method, 
     * passing it <code>params</code> and a source of randomness (obtained
     * from the highest-priority installed provider or system-provided if none
     * of the installed providers supply one).
     * That <code>initialize</code> method always throws an
     * UnsupportedOperationException if it is not overridden by the provider.
     *
     * @param params the parameter set used to generate the keys.
     *
     * @exception InvalidAlgorithmParameterException if the given parameters
     * are inappropriate for this key pair generator.
     *
     * @since 1.2
     */
    public void initialize(AlgorithmParameterSpec params)
	throws InvalidAlgorithmParameterException {
	    initialize(params, new SecureRandom());
    }

    /**
     * Initializes the key pair generator with the given parameter 
     * set and source of randomness.
     *
     * <p>This concrete method has been added to this previously-defined
     * abstract class.
     * This method calls the KeyPairGeneratorSpi {@link 
     * KeyPairGeneratorSpi.html#
     * initialize(java.security.spec.AlgorithmParameterSpec,
     * java.security.SecureRandom) initialize} method, 
     * passing it <code>params</code> and <code>random</code>.
     * That <code>initialize</code>
     * method always throws an
     * UnsupportedOperationException if it is not overridden by the provider.
     *
     * @param params the parameter set used to generate the keys.
     * @param random the source of randomness.
     *
     * @exception InvalidAlgorithmParameterException if the given parameters
     * are inappropriate for this key pair generator.
     *
     * @since 1.2
     */
    public void initialize(AlgorithmParameterSpec params,
			   SecureRandom random)
	throws InvalidAlgorithmParameterException
    {
	// This does nothing, because either
	// 1. the implementation object returned by getInstance() is an
	//    instance of KeyPairGenerator which has its own 
	//    initialize(params, random) method, so the application would
	//    be calling that method directly, or
	// 2. the implementation returned by getInstance() is an instance
	//    of Delegate, in which case initialize(params, random) is
	//    overridden to call the corresponding SPI method.
	// (This is a special case, because the API and SPI method have the
	// same name.)
    }

    /**
     * Generates a key pair.
     *
     * <p>If this KeyPairGenerator has not been initialized explicitly,
     * provider-specific defaults will be used for the size and other
     * (algorithm-specific) values of the generated keys.
     *
     * <p>This will generate a new key pair every time it is called.
     *
     * <p>This method is functionally equivalent to 
     * {@link #generateKeyPair() generateKeyPair}.
     *
     * @return the generated key pair
     *
     * @since 1.2
     */
    public final KeyPair genKeyPair() {
	return generateKeyPair();
    }

    /**
     * Generates a key pair.
     *
     * <p>If this KeyPairGenerator has not been initialized explicitly,
     * provider-specific defaults will be used for the size and other
     * (algorithm-specific) values of the generated keys.
     *
     * <p>This will generate a new key pair every time it is called.
     * 
     * <p>This method is functionally equivalent to 
     * {@link #genKeyPair() genKeyPair}.
     *
     * @return the generated key pair
     */
    public KeyPair generateKeyPair() {
	// This does nothing (except returning null), because either:
	//
	// 1. the implementation object returned by getInstance() is an
	//    instance of KeyPairGenerator which has its own implementation
	//    of generateKeyPair (overriding this one), so the application
	//    would be calling that method directly, or
	//
	// 2. the implementation returned by getInstance() is an instance
	//    of Delegate, in which case generateKeyPair is
	//    overridden to invoke the corresponding SPI method.
	//
	// (This is a special case, because in JDK 1.1.x the generateKeyPair
	// method was used both as an API and a SPI method.)
        return null;
    }


    /*
     * The following class allows providers to extend from KeyPairGeneratorSpi
     * rather than from KeyPairGenerator. It represents a KeyPairGenerator
     * with an encapsulated, provider-supplied SPI object (of type
     * KeyPairGeneratorSpi).
     * If the provider implementation is an instance of KeyPairGeneratorSpi,
     * the getInstance() methods above return an instance of this class, with
     * the SPI object encapsulated.
     *
     * Note: All SPI methods from the original KeyPairGenerator class have been
     * moved up the hierarchy into a new class (KeyPairGeneratorSpi), which has
     * been interposed in the hierarchy between the API (KeyPairGenerator)
     * and its original parent (Object).
     */

    static class Delegate extends KeyPairGenerator {

	// The provider implementation (delegate)
	private KeyPairGeneratorSpi kpairGenSpi;

	// constructor
	public Delegate(KeyPairGeneratorSpi kpairGenSpi, String algorithm) {
	    super(algorithm);
	    this.kpairGenSpi = kpairGenSpi;
	}
    
	// engine method
	public void initialize(int keysize, SecureRandom random) {
	    kpairGenSpi.initialize(keysize, random);
	}

	// engine method
	public void initialize(AlgorithmParameterSpec params,
			       SecureRandom random)
	    throws InvalidAlgorithmParameterException {
		kpairGenSpi.initialize(params, random);;
	}

	// engine method
	public KeyPair generateKeyPair() {
	    return kpairGenSpi.generateKeyPair();
	}
    }
}