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AlgorithmParameters.javaAPI DocJava SE 5 API11945Fri Aug 26 14:57:14 BST 2005java.security

AlgorithmParameters

public class AlgorithmParameters extends Object
This class is used as an opaque representation of cryptographic parameters.

An AlgorithmParameters object for managing the parameters for a particular algorithm can be obtained by calling one of the getInstance factory methods (static methods that return instances of a given class).

There are two ways to request such an implementation: by specifying either just an algorithm name, or both an algorithm name and a package provider.

  • If just an algorithm name is specified, the system will determine if there is an AlgorithmParameters implementation for the algorithm requested available in the environment, and if there is more than one, if there is a preferred one.
  • If both an algorithm name and a package provider are specified, the system will determine if there is an implementation in the package requested, and throw an exception if there is not.

Once an AlgorithmParameters object is returned, it must be initialized via a call to init, using an appropriate parameter specification or parameter encoding.

A transparent parameter specification is obtained from an AlgorithmParameters object via a call to getParameterSpec, and a byte encoding of the parameters is obtained via a call to getEncoded.

author
Jan Luehe
version
1.24, 05/05/04
see
java.security.spec.AlgorithmParameterSpec
see
java.security.spec.DSAParameterSpec
see
KeyPairGenerator
since
1.2

Fields Summary
private Provider
provider
private AlgorithmParametersSpi
paramSpi
private String
algorithm
private boolean
initialized
Constructors Summary
protected AlgorithmParameters(AlgorithmParametersSpi paramSpi, Provider provider, String algorithm)
Creates an AlgorithmParameters object.

param
paramSpi the delegate
param
provider the provider
param
algorithm the algorithm


                         
      
				     
    
	this.paramSpi = paramSpi;
	this.provider = provider;
	this.algorithm = algorithm;
    
Methods Summary
public final java.lang.StringgetAlgorithm()
Returns the name of the algorithm associated with this parameter object.

return
the algorithm name.

        return this.algorithm;
    
public final byte[]getEncoded()
Returns the parameters in their primary encoding format. The primary encoding format for parameters is ASN.1, if an ASN.1 specification for this type of parameters exists.

return
the parameters encoded using their primary encoding format.
exception
IOException on encoding errors, or if this parameter object has not been initialized.

	if (this.initialized == false) {
	    throw new IOException("not initialized");
	}
	return paramSpi.engineGetEncoded();
    
public final byte[]getEncoded(java.lang.String format)
Returns the parameters encoded in the specified scheme. If format is null, the primary encoding format for parameters is used. The primary encoding format is ASN.1, if an ASN.1 specification for these parameters exists.

param
format the name of the encoding format.
return
the parameters encoded using the specified encoding scheme.
exception
IOException on encoding errors, or if this parameter object has not been initialized.

	if (this.initialized == false) {
	    throw new IOException("not initialized");
	}
	return paramSpi.engineGetEncoded(format);
    
public static java.security.AlgorithmParametersgetInstance(java.lang.String algorithm)
Generates a parameter object for the specified algorithm.

If the default provider package provides an implementation of the requested algorithm, an instance of AlgorithmParameters containing that implementation is returned. If the algorithm is not available in the default package, other packages are searched.

The returned parameter object must be initialized via a call to init, using an appropriate parameter specification or parameter encoding.

param
algorithm the name of the algorithm requested.
return
the new parameter object.
exception
NoSuchAlgorithmException if the algorithm is not available in the environment.

	try {
	    Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters",
					     (String)null);
	    return new AlgorithmParameters((AlgorithmParametersSpi)objs[0],
					   (Provider)objs[1],
					   algorithm);
	} catch(NoSuchProviderException e) {
	    throw new NoSuchAlgorithmException(algorithm + " not found");
	}
    
public static java.security.AlgorithmParametersgetInstance(java.lang.String algorithm, java.lang.String provider)
Generates a parameter object for the specified algorithm, as supplied by the specified provider, if such an algorithm is available from the provider.

The returned parameter object must be initialized via a call to init, using an appropriate parameter specification or parameter encoding.

param
algorithm the name of the algorithm requested.
param
provider the name of the provider.
return
the new parameter object.
exception
NoSuchAlgorithmException if the algorithm is not available in the package supplied by the requested provider.
exception
NoSuchProviderException if the provider is not available in the environment.
exception
IllegalArgumentException if the provider name is null or empty.
see
Provider

	if (provider == null || provider.length() == 0)
	    throw new IllegalArgumentException("missing provider");
	Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters",
					 provider);
	return new AlgorithmParameters((AlgorithmParametersSpi)objs[0],
				       (Provider)objs[1],
				       algorithm);
    
public static java.security.AlgorithmParametersgetInstance(java.lang.String algorithm, java.security.Provider provider)
Generates a parameter object for the specified algorithm, as supplied by the specified provider, if such an algorithm is available from the provider. Note: the provider doesn't have to be registered.

The returned parameter object must be initialized via a call to init, using an appropriate parameter specification or parameter encoding.

param
algorithm the name of the algorithm requested.
param
provider the name of the provider.
return
the new parameter object.
exception
NoSuchAlgorithmException if the algorithm is not available in the package supplied by the requested provider.
exception
IllegalArgumentException if the provider is null.
see
Provider
since
1.4

	if (provider == null)
	    throw new IllegalArgumentException("missing provider");
	Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters",
					 provider);
	return new AlgorithmParameters((AlgorithmParametersSpi)objs[0],
				       (Provider)objs[1],
				       algorithm);
    
public final TgetParameterSpec(java.lang.Class paramSpec)
Returns a (transparent) specification of this parameter object. paramSpec identifies the specification class in which the parameters should be returned. It could, for example, be DSAParameterSpec.class, to indicate that the parameters should be returned in an instance of the DSAParameterSpec class.

param
paramSpec the specification class in which the parameters should be returned.
return
the parameter specification.
exception
InvalidParameterSpecException if the requested parameter specification is inappropriate for this parameter object, or if this parameter object has not been initialized.

	if (this.initialized == false) {
	    throw new InvalidParameterSpecException("not initialized");
	}
	return paramSpi.engineGetParameterSpec(paramSpec);
    
public final java.security.ProvidergetProvider()
Returns the provider of this parameter object.

return
the provider of this parameter object

	return this.provider;
    
public final voidinit(java.security.spec.AlgorithmParameterSpec paramSpec)
Initializes this parameter object using the parameters specified in paramSpec.

param
paramSpec the parameter specification.
exception
InvalidParameterSpecException if the given parameter specification is inappropriate for the initialization of this parameter object, or if this parameter object has already been initialized.

	if (this.initialized)
	    throw new InvalidParameterSpecException("already initialized");
	paramSpi.engineInit(paramSpec);
	this.initialized = true;
    
public final voidinit(byte[] params)
Imports the specified parameters and decodes them according to the primary decoding format for parameters. The primary decoding format for parameters is ASN.1, if an ASN.1 specification for this type of parameters exists.

param
params the encoded parameters.
exception
IOException on decoding errors, or if this parameter object has already been initialized.

	if (this.initialized)
	    throw new IOException("already initialized");
	paramSpi.engineInit(params);
	this.initialized = true;
    
public final voidinit(byte[] params, java.lang.String format)
Imports the parameters from params and decodes them according to the specified decoding scheme. If format is null, the primary decoding format for parameters is used. The primary decoding format is ASN.1, if an ASN.1 specification for these parameters exists.

param
params the encoded parameters.
param
format the name of the decoding scheme.
exception
IOException on decoding errors, or if this parameter object has already been initialized.

	if (this.initialized)
	    throw new IOException("already initialized");
	paramSpi.engineInit(params, format);
	this.initialized = true;
    
public final java.lang.StringtoString()
Returns a formatted string describing the parameters.

return
a formatted string describing the parameters, or null if this parameter object has not been initialized.

	if (this.initialized == false) {
	    return null;
	}
	return paramSpi.engineToString();