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	/*
	* Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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	* questions.
	*/

	package java.security.cert;

	import java.security.AccessController;
	import java.security.InvalidAlgorithmParameterException;
	import java.security.NoSuchAlgorithmException;
	import java.security.NoSuchProviderException;
	import java.security.PrivilegedAction;
	import java.security.Provider;
	import java.security.Security;
	import java.util.Objects;

	import sun.security.jca.*;
	import sun.security.jca.GetInstance.Instance;

	/**
	* A class for building certification paths (also known as certificate chains).
	* <p>
	* This class uses a provider-based architecture.
	* To create a {@code CertPathBuilder}, call
	* one of the static {@code getInstance} methods, passing in the
	* algorithm name of the {@code CertPathBuilder} desired and optionally
	* the name of the provider desired.
	*
	* <p>Once a {@code CertPathBuilder} object has been created, certification
	* paths can be constructed by calling the {@link #build build} method and
	* passing it an algorithm-specific set of parameters. If successful, the
	* result (including the {@code CertPath} that was built) is returned
	* in an object that implements the {@code CertPathBuilderResult}
	* interface.
	*
	* <p>The {@link #getRevocationChecker} method allows an application to specify
	* additional algorithm-specific parameters and options used by the
	* {@code CertPathBuilder} when checking the revocation status of certificates.
	* Here is an example demonstrating how it is used with the PKIX algorithm:
	*
	* <pre>
	* CertPathBuilder cpb = CertPathBuilder.getInstance("PKIX");
	* PKIXRevocationChecker rc = (PKIXRevocationChecker)cpb.getRevocationChecker();
	* rc.setOptions(EnumSet.of(Option.PREFER_CRLS));
	* params.addCertPathChecker(rc);
	* CertPathBuilderResult cpbr = cpb.build(params);
	* </pre>
	*
	* <p>Every implementation of the Java platform is required to support the
	* following standard {@code CertPathBuilder} algorithm:
	* <ul>
	* <li>{@code PKIX}</li>
	* </ul>
	* This algorithm is described in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#certpathbuilder-algorithms">
	* CertPathBuilder section</a> of the
	* Java Security Standard Algorithm Names Specification.
	* Consult the release documentation for your implementation to see if any
	* other algorithms are supported.
	*
	* <p>
	* <b>Concurrent Access</b>
	* <p>
	* The static methods of this class are guaranteed to be thread-safe.
	* Multiple threads may concurrently invoke the static methods defined in
	* this class with no ill effects.
	* <p>
	* However, this is not true for the non-static methods defined by this class.
	* Unless otherwise documented by a specific provider, threads that need to
	* access a single {@code CertPathBuilder} instance concurrently should
	* synchronize amongst themselves and provide the necessary locking. Multiple
	* threads each manipulating a different {@code CertPathBuilder} instance
	* need not synchronize.
	*
	* @see CertPath
	*
	* @since 1.4
	* @author Sean Mullan
	* @author Yassir Elley
	*/
	public class CertPathBuilder {

	/*
	* Constant to lookup in the Security properties file to determine
	* the default certpathbuilder type. In the Security properties file,
	* the default certpathbuilder type is given as:
	* <pre>
	* certpathbuilder.type=PKIX
	* </pre>
	*/
	private static final String CPB_TYPE = "certpathbuilder.type";
	private final CertPathBuilderSpi builderSpi;
	private final Provider provider;
	private final String algorithm;

	/**
	* Creates a {@code CertPathBuilder} object of the given algorithm,
	* and encapsulates the given provider implementation (SPI object) in it.
	*
	* @param builderSpi the provider implementation
	* @param provider the provider
	* @param algorithm the algorithm name
	*/
	protected CertPathBuilder(CertPathBuilderSpi builderSpi, Provider provider,
	String algorithm)
	{
	this.builderSpi = builderSpi;
	this.provider = provider;
	this.algorithm = algorithm;
	}

	/**
	* Returns a {@code CertPathBuilder} object that implements the
	* specified algorithm.
	*
	* <p> This method traverses the list of registered security Providers,
	* starting with the most preferred Provider.
	* A new CertPathBuilder object encapsulating the
	* CertPathBuilderSpi implementation from the first
	* Provider that supports the specified algorithm is returned.
	*
	* <p> Note that the list of registered providers may be retrieved via
	* the {@link Security#getProviders() Security.getProviders()} method.
	*
	* @implNote
	* The JDK Reference Implementation additionally uses the
	* {@code jdk.security.provider.preferred}
	* {@link Security#getProperty(String) Security} property to determine
	* the preferred provider order for the specified algorithm. This
	* may be different than the order of providers returned by
	* {@link Security#getProviders() Security.getProviders()}.
	*
	* @param algorithm the name of the requested {@code CertPathBuilder}
	* algorithm. See the CertPathBuilder section in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#certpathbuilder-algorithms">
	* Java Security Standard Algorithm Names Specification</a>
	* for information about standard algorithm names.
	*
	* @return a {@code CertPathBuilder} object that implements the
	* specified algorithm
	*
	* @throws NoSuchAlgorithmException if no {@code Provider} supports a
	* {@code CertPathBuilderSpi} implementation for the
	* specified algorithm
	*
	* @throws NullPointerException if {@code algorithm} is {@code null}
	*
	* @see java.security.Provider
	*/
	public static CertPathBuilder getInstance(String algorithm)
	throws NoSuchAlgorithmException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	Instance instance = GetInstance.getInstance("CertPathBuilder",
	CertPathBuilderSpi.class, algorithm);
	return new CertPathBuilder((CertPathBuilderSpi)instance.impl,
	instance.provider, algorithm);
	}

	/**
	* Returns a {@code CertPathBuilder} object that implements the
	* specified algorithm.
	*
	* <p> A new CertPathBuilder object encapsulating the
	* CertPathBuilderSpi implementation from the specified provider
	* is returned. The specified provider must be registered
	* in the security provider list.
	*
	* <p> Note that the list of registered providers may be retrieved via
	* the {@link Security#getProviders() Security.getProviders()} method.
	*
	* @param algorithm the name of the requested {@code CertPathBuilder}
	* algorithm. See the CertPathBuilder section in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#certpathbuilder-algorithms">
	* Java Security Standard Algorithm Names Specification</a>
	* for information about standard algorithm names.
	*
	* @param provider the name of the provider.
	*
	* @return a {@code CertPathBuilder} object that implements the
	* specified algorithm
	*
	* @throws IllegalArgumentException if the {@code provider} is
	* {@code null} or empty
	*
	* @throws NoSuchAlgorithmException if a {@code CertPathBuilderSpi}
	* implementation for the specified algorithm is not
	* available from the specified provider
	*
	* @throws NoSuchProviderException if the specified provider is not
	* registered in the security provider list
	*
	* @throws NullPointerException if {@code algorithm} is {@code null}
	*
	* @see java.security.Provider
	*/
	public static CertPathBuilder getInstance(String algorithm, String provider)
	throws NoSuchAlgorithmException, NoSuchProviderException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	Instance instance = GetInstance.getInstance("CertPathBuilder",
	CertPathBuilderSpi.class, algorithm, provider);
	return new CertPathBuilder((CertPathBuilderSpi)instance.impl,
	instance.provider, algorithm);
	}

	/**
	* Returns a {@code CertPathBuilder} object that implements the
	* specified algorithm.
	*
	* <p> A new CertPathBuilder object encapsulating the
	* CertPathBuilderSpi implementation from the specified Provider
	* object is returned. Note that the specified Provider object
	* does not have to be registered in the provider list.
	*
	* @param algorithm the name of the requested {@code CertPathBuilder}
	* algorithm. See the CertPathBuilder section in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#certpathbuilder-algorithms">
	* Java Security Standard Algorithm Names Specification</a>
	* for information about standard algorithm names.
	*
	* @param provider the provider.
	*
	* @return a {@code CertPathBuilder} object that implements the
	* specified algorithm
	*
	* @throws IllegalArgumentException if the {@code provider} is
	* {@code null}
	*
	* @throws NoSuchAlgorithmException if a {@code CertPathBuilderSpi}
	* implementation for the specified algorithm is not available
	* from the specified {@code Provider} object
	*
	* @throws NullPointerException if {@code algorithm} is {@code null}
	*
	* @see java.security.Provider
	*/
	public static CertPathBuilder getInstance(String algorithm,
	Provider provider) throws NoSuchAlgorithmException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	Instance instance = GetInstance.getInstance("CertPathBuilder",
	CertPathBuilderSpi.class, algorithm, provider);
	return new CertPathBuilder((CertPathBuilderSpi)instance.impl,
	instance.provider, algorithm);
	}

	/**
	* Returns the provider of this {@code CertPathBuilder}.
	*
	* @return the provider of this {@code CertPathBuilder}
	*/
	public final Provider getProvider() {
	return this.provider;
	}

	/**
	* Returns the name of the algorithm of this {@code CertPathBuilder}.
	*
	* @return the name of the algorithm of this {@code CertPathBuilder}
	*/
	public final String getAlgorithm() {
	return this.algorithm;
	}

	/**
	* Attempts to build a certification path using the specified algorithm
	* parameter set.
	*
	* @param params the algorithm parameters
	* @return the result of the build algorithm
	* @throws CertPathBuilderException if the builder is unable to construct
	* a certification path that satisfies the specified parameters
	* @throws InvalidAlgorithmParameterException if the specified parameters
	* are inappropriate for this {@code CertPathBuilder}
	*/
	public final CertPathBuilderResult build(CertPathParameters params)
	throws CertPathBuilderException, InvalidAlgorithmParameterException
	{
	return builderSpi.engineBuild(params);
	}

	/**
	* Returns the default {@code CertPathBuilder} type as specified by
	* the {@code certpathbuilder.type} security property, or the string
	* {@literal "PKIX"} if no such property exists.
	*
	* <p>The default {@code CertPathBuilder} type can be used by
	* applications that do not want to use a hard-coded type when calling one
	* of the {@code getInstance} methods, and want to provide a default
	* type in case a user does not specify its own.
	*
	* <p>The default {@code CertPathBuilder} type can be changed by
	* setting the value of the {@code certpathbuilder.type} security property
	* to the desired type.
	*
	* @see java.security.Security security properties
	* @return the default {@code CertPathBuilder} type as specified
	* by the {@code certpathbuilder.type} security property, or the string
	* {@literal "PKIX"} if no such property exists.
	*/
	public static final String getDefaultType() {
	String cpbtype =
	AccessController.doPrivileged(new PrivilegedAction<>() {
	public String run() {
	return Security.getProperty(CPB_TYPE);
	}
	});
	return (cpbtype == null) ? "PKIX" : cpbtype;
	}

	/**
	* Returns a {@code CertPathChecker} that the encapsulated
	* {@code CertPathBuilderSpi} implementation uses to check the revocation
	* status of certificates. A PKIX implementation returns objects of
	* type {@code PKIXRevocationChecker}. Each invocation of this method
	* returns a new instance of {@code CertPathChecker}.
	*
	* <p>The primary purpose of this method is to allow callers to specify
	* additional input parameters and options specific to revocation checking.
	* See the class description for an example.
	*
	* @return a {@code CertPathChecker}
	* @throws UnsupportedOperationException if the service provider does not
	* support this method
	* @since 1.8
	*/
	public final CertPathChecker getRevocationChecker() {
	return builderSpi.engineGetRevocationChecker();
	}
	}

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