KeyFactory

java.lang.Object
- java.security.KeyFactory

```
public class KeyFactory
extends Object
```
Key factories are used to convert keys (opaque cryptographic keys of type Key) into key specifications (transparent representations of the underlying key material), and vice versa.
Key factories are bi-directional. That is, they allow you to build an opaque key object from a given key specification (key material), or to retrieve the underlying key material of a key object in a suitable format.
Multiple compatible key specifications may exist for the same key. For example, a DSA public key may be specified using DSAPublicKeySpec or X509EncodedKeySpec. A key factory can be used to translate between compatible key specifications.
The following is an example of how to use a key factory in order to instantiate a DSA public key from its encoding. Assume Alice has received a digital signature from Bob. Bob also sent her his public key (in encoded format) to verify his signature. Alice then performs the following actions:
```
 X509EncodedKeySpec bobPubKeySpec = new X509EncodedKeySpec(bobEncodedPubKey);
 KeyFactory keyFactory = KeyFactory.getInstance("DSA");
 PublicKey bobPubKey = keyFactory.generatePublic(bobPubKeySpec);
 Signature sig = Signature.getInstance("DSA");
 sig.initVerify(bobPubKey);
 sig.update(data);
 sig.verify(signature);
 
```
Every implementation of the Java platform is required to support the following standard KeyFactory algorithms:
- DiffieHellman
- DSA
- RSA
These algorithms are described in the KeyFactory 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.
从以下版本开始:

1.2

另请参阅:

Key, PublicKey, PrivateKey, KeySpec, DSAPublicKeySpec, X509EncodedKeySpec

构造器概要

构造器
限定符构造器说明

protected KeyFactory(KeyFactorySpi keyFacSpi, Provider provider, String algorithm)
Creates a KeyFactory object.

构造器
限定符	构造器	说明
`protected`	`KeyFactory(KeyFactorySpi keyFacSpi, Provider provider, String algorithm)`	Creates a KeyFactory object.

方法概要

所有方法静态方法实例方法具体方法
限定符和类型	方法	说明
`PrivateKey`	`generatePrivate(KeySpec keySpec)`	Generates a private key object from the provided key specification (key material).
`PublicKey`	`generatePublic(KeySpec keySpec)`	Generates a public key object from the provided key specification (key material).
`String`	`getAlgorithm()`	Gets the name of the algorithm associated with this `KeyFactory`.
`static KeyFactory`	`getInstance(String algorithm)`	Returns a KeyFactory object that converts public/private keys of the specified algorithm.
`static KeyFactory`	`getInstance(String algorithm, String provider)`	Returns a KeyFactory object that converts public/private keys of the specified algorithm.
`static KeyFactory`	`getInstance(String algorithm, Provider provider)`	Returns a KeyFactory object that converts public/private keys of the specified algorithm.
`<T extends KeySpec> T`	`getKeySpec(Key key, Class<T> keySpec)`	Returns a specification (key material) of the given key object.
`Provider`	`getProvider()`	Returns the provider of this key factory object.
`Key`	`translateKey(Key key)`	Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 构造器详细资料
  - KeyFactory
```
protected KeyFactory(KeyFactorySpi keyFacSpi,
                     Provider provider,
                     String algorithm)
```
    Creates a KeyFactory object.
    
    参数:
    
    keyFacSpi - the delegate
    
    provider - the provider
    
    algorithm - the name of the algorithm to associate with this KeyFactory
- 方法详细资料
  - getInstance
```
public static KeyFactory getInstance(String algorithm)
                              throws NoSuchAlgorithmException
```
    Returns a KeyFactory object that converts public/private keys of the specified algorithm.
    This method traverses the list of registered security Providers, starting with the most preferred Provider. A new KeyFactory object encapsulating the KeyFactorySpi 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.
    
    参数:
    
    algorithm - the name of the requested key algorithm. See the KeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    
    返回:
    
    the new KeyFactory object.
    
    抛出:
    
    NoSuchAlgorithmException - if no Provider supports a KeyFactorySpi implementation for the specified algorithm.
    
    另请参阅:
    
    Provider
  - getInstance
```
public static KeyFactory getInstance(String algorithm,
                                     String provider)
                              throws NoSuchAlgorithmException,
                                     NoSuchProviderException
```
    Returns a KeyFactory object that converts public/private keys of the specified algorithm.
    A new KeyFactory object encapsulating the KeyFactorySpi 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.
    
    参数:
    
    algorithm - the name of the requested key algorithm. See the KeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    
    provider - the name of the provider.
    
    返回:
    
    the new KeyFactory object.
    
    抛出:
    
    NoSuchAlgorithmException - if a KeyFactorySpi 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.
    
    另请参阅:
    
    Provider
  - getInstance
```
public static KeyFactory getInstance(String algorithm,
                                     Provider provider)
                              throws NoSuchAlgorithmException
```
    Returns a KeyFactory object that converts public/private keys of the specified algorithm.
    A new KeyFactory object encapsulating the KeyFactorySpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.
    
    参数:
    
    algorithm - the name of the requested key algorithm. See the KeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    
    provider - the provider.
    
    返回:
    
    the new KeyFactory object.
    
    抛出:
    
    NoSuchAlgorithmException - if a KeyFactorySpi implementation for the specified algorithm is not available from the specified Provider object.
    
    IllegalArgumentException - if the specified provider is null.
    
    从以下版本开始:
    
    1.4
    
    另请参阅:
    
    Provider
  - getProvider
```
public final Provider getProvider()
```
    Returns the provider of this key factory object.
    
    返回:
    
    the provider of this key factory object
  - getAlgorithm
```
public final String getAlgorithm()
```
    Gets the name of the algorithm associated with this KeyFactory.
    
    返回:
    
    the name of the algorithm associated with this KeyFactory
  - generatePublic
```
public final PublicKey generatePublic(KeySpec keySpec)
                               throws InvalidKeySpecException
```
    Generates a public key object from the provided key specification (key material).
    
    参数:
    
    keySpec - the specification (key material) of the public key.
    
    返回:
    
    the public key.
    
    抛出:
    
    InvalidKeySpecException - if the given key specification is inappropriate for this key factory to produce a public key.
  - generatePrivate
```
public final PrivateKey generatePrivate(KeySpec keySpec)
                                 throws InvalidKeySpecException
```
    Generates a private key object from the provided key specification (key material).
    
    参数:
    
    keySpec - the specification (key material) of the private key.
    
    返回:
    
    the private key.
    
    抛出:
    
    InvalidKeySpecException - if the given key specification is inappropriate for this key factory to produce a private key.
  - getKeySpec
```
public final <T extends KeySpec> T getKeySpec(Key key,
                                              Class<T> keySpec)
                                       throws InvalidKeySpecException
```
    Returns a specification (key material) of the given key object. keySpec identifies the specification class in which the key material should be returned. It could, for example, be DSAPublicKeySpec.class, to indicate that the key material should be returned in an instance of the DSAPublicKeySpec class.
    
    类型参数:
    
    T - the type of the key specification to be returned
    
    参数:
    
    key - the key.
    
    keySpec - the specification class in which the key material should be returned.
    
    返回:
    
    the underlying key specification (key material) in an instance of the requested specification class.
    
    抛出:
    
    InvalidKeySpecException - if the requested key specification is inappropriate for the given key, or the given key cannot be processed (e.g., the given key has an unrecognized algorithm or format).
  - translateKey
```
public final Key translateKey(Key key)
                       throws InvalidKeyException
```
    Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.
    
    参数:
    
    key - the key whose provider is unknown or untrusted.
    
    返回:
    
    the translated key.
    
    抛出:
    
    InvalidKeyException - if the given key cannot be processed by this key factory.

类 KeyFactory

构造器概要

方法概要

从类继承的方法 java.lang.Object

构造器详细资料

KeyFactory

方法详细资料

getInstance

getInstance

getInstance

getProvider

getAlgorithm

generatePublic

generatePrivate

getKeySpec

translateKey