Class 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).

Once an AlgorithmParameters object is obtained, 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.

Every implementation of the Java platform is required to support the following standard AlgorithmParameters algorithms:

• AES
• DES
• DESede
• DiffieHellman
• DSA

These algorithms are described in the AlgorithmParameters section of the Java Cryptography Architecture Standard Algorithm Name Documentation. Consult the release documentation for your implementation to see if any other algorithms are supported.

Constructors

AlgorithmParameters

protected AlgorithmParameters(AlgorithmParametersSpi paramSpi,
                              Provider provider,
                              String algorithm)

Creates an AlgorithmParameters object.

Parameters:

paramSpi - the delegate

provider - the provider

algorithm - the algorithm

Methods

getAlgorithm

public final String getAlgorithm()

Returns the name of the algorithm associated with this parameter object.

Returns:

the algorithm name.

getInstance

public static AlgorithmParameters getInstance(String algorithm)
                                       throws NoSuchAlgorithmException

Parameters:

algorithm - the name of the algorithm requested. See the AlgorithmParameters section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

Returns:

the new parameter object.

Throws:

NoSuchAlgorithmException - if no Provider supports an AlgorithmParametersSpi implementation for the specified algorithm.

See Also:

Provider

getInstance

public static AlgorithmParameters getInstance(String algorithm,
                                              String provider)
                                       throws NoSuchAlgorithmException,
                                              NoSuchProviderException

Parameters:

algorithm - the name of the algorithm requested. See the AlgorithmParameters section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

provider - the name of the provider.

Returns:

the new parameter object.

Throws:

NoSuchAlgorithmException - if an AlgorithmParametersSpi implementation for the specified algorithm is not available from the specified provider.

NoSuchProviderException - if the specified provider is not registered in the security provider list.

IllegalArgumentException - if the provider name is null or empty.

See Also:

Provider

getInstance

public static AlgorithmParameters getInstance(String algorithm,
                                              Provider provider)
                                       throws NoSuchAlgorithmException

Parameters:

algorithm - the name of the algorithm requested. See the AlgorithmParameters section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

provider - the name of the provider.

Returns:

the new parameter object.

Throws:

NoSuchAlgorithmException - if an AlgorithmParameterGeneratorSpi implementation for the specified algorithm is not available from the specified Provider object.

IllegalArgumentException - if the provider is null.

Since:

1.4

See Also:

Provider

getProvider

public final Provider getProvider()

Returns the provider of this parameter object.

Returns:

the provider of this parameter object

init

public final void init(AlgorithmParameterSpec paramSpec)
                throws InvalidParameterSpecException

Initializes this parameter object using the parameters specified in paramSpec.

Parameters:

paramSpec - the parameter specification.

Throws:

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

init

public final void init(byte[] params)
                throws IOException

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.

Parameters:

params - the encoded parameters.

Throws:

IOException - on decoding errors, or if this parameter object has already been initialized.

init

public final void init(byte[] params,
                       String format)
                throws IOException

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.

Parameters:

params - the encoded parameters.

format - the name of the decoding scheme.

Throws:

IOException - on decoding errors, or if this parameter object has already been initialized.

getParameterSpec

public final <T extends AlgorithmParameterSpec> T getParameterSpec(Class<T> paramSpec)
                                                            throws InvalidParameterSpecException

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.

Type Parameters:

T - the type of the parameter specification to be returrned

Parameters:

paramSpec - the specification class in which the parameters should be returned.

Returns:

the parameter specification.

Throws:

InvalidParameterSpecException - if the requested parameter specification is inappropriate for this parameter object, or if this parameter object has not been initialized.

getEncoded

public final byte[] getEncoded()
                        throws IOException

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.

Returns:

the parameters encoded using their primary encoding format.

Throws:

IOException - on encoding errors, or if this parameter object has not been initialized.

getEncoded

public final byte[] getEncoded(String format)
                        throws IOException

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.

Parameters:

format - the name of the encoding format.

Returns:

the parameters encoded using the specified encoding scheme.

Throws:

IOException - on encoding errors, or if this parameter object has not been initialized.

toString

public final String toString()

Returns a formatted string describing the parameters.

Overrides:

toString in class Object

Returns:

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