# Class Certificate

java.lang.Object
java.security.cert.Certificate

All Implemented Interfaces:
  `Serializable`

Direct Known Subclasses:
  `X509Certificate`

public abstract class Certificate extends Object implements Serializable

Abstract class for managing a variety of identity certificates. An identity certificate is a binding of a principal to a public key which is vouched for by another principal. (A principal represents an entity such as an individual user, a group, or a corporation.)

This class is an abstraction for certificates that have different formats but important common uses. For example, different types of certificates, such as X.509 and PGP, share general certificate functionality (like encoding and verifying) and some types of information (like a public key).

X.509, PGP, and SDSI certificates can all be implemented by subclassing the Certificate class, even though they contain different sets of information, and they store and retrieve the information in different ways.

Since:
  1.2
See Also:
  - `X509Certificate`
  - `CertificateFactory`
  - Serialized Form

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `protected static class`
  `Certificate.CertificateRep`
  Alternate `Certificate` class for serialization.

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `Certificate(String type)`
  Creates a certificate of the specified type.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `equals(Object other)`
  Compares this certificate for equality with the specified object.
  `abstract byte[]`
  `getEncoded()`
  Returns the encoded form of this certificate.
  `abstract PublicKey`
  `getPublicKey()`
  Gets the public key from this certificate.
  `final String`
  `getType()`
  Returns the type of this certificate.
  `int`
  `hashCode()`
  Returns the hashcode value for this certificate from its encoded form.
  `abstract String`
  `toString()`
  Returns a string representation of this certificate.
  `abstract void`
  `verify(PublicKey key)`
  Verifies that this certificate was signed using the private key that corresponds to the specified public key.
  `abstract void`
  `verify(PublicKey key, String sigProvider)`
  Verifies that this certificate was signed using the private key that corresponds to the specified public key.
  `void`
  `verify(PublicKey key, Provider sigProvider)`
  Verifies that this certificate was signed using the private key that corresponds to the specified public key.
  `protected Object`
  `writeReplace()`
  Replace the `Certificate` to be serialized with a `CertificateRep` object containing the type and encoded bytes of the `Certificate`.

  ### Methods declared in class java.lang.Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### Certificate

    protected Certificate(String type)
    Creates a certificate of the specified type.
    Parameters:
      `type` - the standard name of the certificate type. See the CertificateFactory section in the Java Security Standard Algorithm Names Specification for information about standard certificate types.

- ## Method Details

  - ### getType

    public final String getType()
    Returns the type of this certificate.
    Returns:
      the type of this certificate.

  - ### equals

    public boolean equals(Object other)
    Compares this certificate for equality with the specified object. If the `other` object is an `instanceof` `Certificate`, then its encoded form is retrieved and compared with the encoded form of this certificate.
    Overrides:
      `equals` in class `Object`
    Parameters:
      `other` - the object to test for equality with this certificate.
    Returns:
      true iff the encoded forms of the two certificates match, false otherwise.
    See Also:
      - `Object.hashCode()`
      - `HashMap`

  - ### hashCode

    public int hashCode()
    Returns the hashcode value for this certificate from its encoded form.
    Overrides:
      `hashCode` in class `Object`
    Returns:
      the hashcode value for this certificate from its encoded form
    See Also:
      - `Object.equals(java.lang.Object)`
      - `System.identityHashCode(java.lang.Object)`

  - ### getEncoded

    public abstract byte[] getEncoded() throws CertificateEncodingException
    Returns the encoded form of this certificate. It is assumed that each certificate type would have only a single form of encoding; for example, X.509 certificates would be encoded as ASN.1 DER.
    Returns:
      the encoded form of this certificate
    Throws:
      `CertificateEncodingException` - if an encoding error occurs.

  - ### verify

    public abstract void verify(PublicKey key) throws CertificateException, NoSuchAlgorithmException, InvalidKeyException, NoSuchProviderException, SignatureException
    Verifies that this certificate was signed using the private key that corresponds to the specified public key.
    Parameters:
      `key` - the PublicKey used to carry out the verification.
    Throws:
      `NoSuchAlgorithmException` - on unsupported signature algorithms.
      `InvalidKeyException` - on incorrect key.
      `NoSuchProviderException` - if there's no default provider.
      `SignatureException` - on signature errors.
      `CertificateException` - on encoding errors.

  - ### verify

    public abstract void verify(PublicKey key, String sigProvider) throws CertificateException, NoSuchAlgorithmException, InvalidKeyException, NoSuchProviderException, SignatureException
    Verifies that this certificate was signed using the private key that corresponds to the specified public key. This method uses the signature verification engine supplied by the specified provider.
    Parameters:
      `key` - the PublicKey used to carry out the verification.
      `sigProvider` - the name of the signature provider.
    Throws:
      `NoSuchAlgorithmException` - on unsupported signature algorithms.
      `InvalidKeyException` - on incorrect key.
      `NoSuchProviderException` - on incorrect provider.
      `SignatureException` - on signature errors.
      `CertificateException` - on encoding errors.

  - ### verify

    public void verify(PublicKey key, Provider sigProvider) throws CertificateException, NoSuchAlgorithmException, InvalidKeyException, SignatureException
    Verifies that this certificate was signed using the private key that corresponds to the specified public key. This method uses the signature verification engine supplied by the specified provider. Note that the specified Provider object does not have to be registered in the provider list.

    This method was added to version 1.8 of the Java Platform Standard Edition. In order to maintain backwards compatibility with existing service providers, this method cannot be `abstract` and by default throws an `UnsupportedOperationException`.

    Parameters:
      `key` - the PublicKey used to carry out the verification.
      `sigProvider` - the signature provider.
    Throws:
      `NoSuchAlgorithmException` - on unsupported signature algorithms.
      `InvalidKeyException` - on incorrect key.
      `SignatureException` - on signature errors.
      `CertificateException` - on encoding errors.
      `UnsupportedOperationException` - if the method is not supported
    Since:
      1.8

  - ### toString

    public abstract String toString()
    Returns a string representation of this certificate.
    Overrides:
      `toString` in class `Object`
    Returns:
      a string representation of this certificate.

  - ### getPublicKey

    public abstract PublicKey getPublicKey()
    Gets the public key from this certificate.
    Returns:
      the public key.

  - ### writeReplace

    protected Object writeReplace() throws ObjectStreamException
    Replace the `Certificate` to be serialized with a `CertificateRep` object containing the type and encoded bytes of the `Certificate`.
    Returns:
      a `CertificateRep` object containing the type and encoded bytes of the `Certificate`
    Throws:
      `ObjectStreamException` - if a `CertificateRep` object representing this `Certificate` could not be created
    Since:
      1.3