This is an abstract class that defines the methods common to all
CertPaths. Subclasses can handle different kinds of
certificates (X.509, PGP, etc.).
All CertPath objects have a type, a list of
Certificates, and one or more supported encodings. Because the
CertPath class is immutable, a CertPath cannot
change in any externally visible way after being constructed. This
stipulation applies to all public fields and methods of this class and any
added or overridden by subclasses.
The type is a String that identifies the type of
Certificates in the certification path. For each
certificate cert in a certification path certPath,
cert.getType().equals(certPath.getType()) must be
The list of Certificates is an ordered List of
zero or more Certificates. This List and all
of the Certificates contained in it must be immutable.
Each CertPath object must support one or more encodings
so that the object can be translated into a byte array for storage or
transmission to other parties. Preferably, these encodings should be
well-documented standards (such as PKCS#7). One of the encodings supported
by a CertPath is considered the default encoding. This
encoding is used if no encoding is explicitly requested (for the
getEncoded() method, for instance).
All CertPath objects are also Serializable.
CertPath objects are resolved into an alternate
CertPathRep object during serialization. This allows
a CertPath object to be serialized into an equivalent
representation regardless of its underlying implementation.
CertPath objects can be created with a
CertificateFactory or they can be returned by other classes,
such as a CertPathBuilder.
By convention, X.509 CertPaths (consisting of
X509Certificates), are ordered starting with the target
certificate and ending with a certificate issued by the trust anchor. That
is, the issuer of one certificate is the subject of the following one. The
certificate representing the TrustAnchor should not be
included in the certification path. Unvalidated X.509 CertPaths
may not follow these conventions. PKIX CertPathValidators will
detect any departure from these conventions that cause the certification
path to be invalid and throw a CertPathValidatorException.
All CertPath objects must be thread-safe. That is, multiple
threads may concurrently invoke the methods defined in this class on a
single CertPath object (or more than one) with no
ill effects. This is also true for the List returned by
Requiring CertPath objects to be immutable and thread-safe
allows them to be passed around to various pieces of code without worrying
about coordinating access. Providing this thread-safety is
generally not difficult, since the CertPath and
List objects in question are immutable.