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 Security Standard Algorithm Names Specification. Consult the release documentation for your implementation to see if any other algorithms are supported.
Since:
1.2
See Also:
AlgorithmParameterSpec, DSAParameterSpec, KeyPairGenerator

Constructors

Modifier Constructor Description
protected AlgorithmParameters​(AlgorithmParametersSpi paramSpi, Provider provider, String algorithm)

Creates an AlgorithmParameters object.

Methods

Modifier and Type Method Description
String getAlgorithm()

Returns the name of the algorithm associated with this parameter object.
byte[] getEncoded()

Returns the parameters in their primary encoding format.
byte[] getEncoded​(String format)

Returns the parameters encoded in the specified scheme.
static AlgorithmParameters getInstance​(String algorithm)

Returns a parameter object for the specified algorithm.
static AlgorithmParameters getInstance​(String algorithm, String provider)

Returns a parameter object for the specified algorithm.
static AlgorithmParameters getInstance​(String algorithm, Provider provider)

Returns a parameter object for the specified algorithm.
<T extends AlgorithmParameterSpec>
T		 getParameterSpec​(Class<T> paramSpec)

Returns a (transparent) specification of this parameter object.
Provider getProvider()

Returns the provider of this parameter object.
void init​(byte[] params)

Imports the specified parameters and decodes them according to the primary decoding format for parameters.
void init​(byte[] params, String format)

Imports the parameters from params and decodes them according to the specified decoding scheme.
void init​(AlgorithmParameterSpec paramSpec)

Initializes this parameter object using the parameters specified in paramSpec.
String toString()

Returns a formatted string describing the parameters.

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

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

Returns a parameter object for the specified algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new AlgorithmParameters object encapsulating the AlgorithmParametersSpi implementation from the first Provider that supports the specified algorithm is returned.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

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

Implementation Note:
The JDK Reference Implementation additionally uses the jdk.security.provider.preferred Security property to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned by Security.getProviders().
Parameters:
algorithm - the name of the algorithm requested. See the AlgorithmParameters section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
Returns:
the new parameter object
Throws:
NoSuchAlgorithmException - if no Provider supports an AlgorithmParametersSpi implementation for the specified algorithm
NullPointerException - if algorithm is null
See Also:
Provider

getInstance

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

Returns a parameter object for the specified algorithm.

A new AlgorithmParameters object encapsulating the AlgorithmParametersSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

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

Parameters:
algorithm - the name of the algorithm requested. See the AlgorithmParameters section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
provider - the name of the provider.
Returns:
the new parameter object
Throws:
IllegalArgumentException - if the provider name is null or empty
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
NullPointerException - if algorithm is null
See Also:
Provider

getInstance

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

Returns a parameter object for the specified algorithm.

A new AlgorithmParameters object encapsulating the AlgorithmParametersSpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.

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

Parameters:
algorithm - the name of the algorithm requested. See the AlgorithmParameters section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
provider - the name of the provider.
Returns:
the new parameter object
Throws:
IllegalArgumentException - if the provider is null
NoSuchAlgorithmException - if an AlgorithmParameterGeneratorSpi implementation for the specified algorithm is not available from the specified Provider object
NullPointerException - if algorithm 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.

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