/*

 * Copyright (c) 2005, 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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/*

 * $Id: TransformService.java,v 1.6.4.1 2005/09/15 12:42:11 mullan Exp $

 */

package javax.xml.crypto.dsig;

import java.security.InvalidAlgorithmParameterException;

import java.security.NoSuchAlgorithmException;

import java.security.NoSuchProviderException;

import java.security.Provider;

import java.security.Provider.Service;

import java.security.Security;

import java.util.*;

import javax.xml.crypto.MarshalException;

import javax.xml.crypto.XMLStructure;

import javax.xml.crypto.XMLCryptoContext;

import javax.xml.crypto.dsig.spec.TransformParameterSpec;

/**

 * A Service Provider Interface for transform and canonicalization algorithms.

 *

 * <p>Each instance of <code>TransformService</code> supports a specific

 * transform or canonicalization algorithm and XML mechanism type. To create a

 * <code>TransformService</code>, call one of the static

 * {@link #getInstance getInstance} methods, passing in the algorithm URI and

 * XML mechanism type desired, for example:

 *

 * <blockquote><code>

 * TransformService ts = TransformService.getInstance(Transform.XPATH2, "DOM");

 * </code></blockquote>

 *

 * <p><code>TransformService</code> implementations are registered and loaded

 * using the {@link java.security.Provider} mechanism.  Each

 * <code>TransformService</code> service provider implementation should include

 * a <code>MechanismType</code> service attribute that identifies the XML

 * mechanism type that it supports. If the attribute is not specified,

 * "DOM" is assumed. For example, a service provider that supports the

 * XPath Filter 2 Transform and DOM mechanism would be specified in the

 * <code>Provider</code> subclass as:

 * <pre>

 *     put("TransformService." + Transform.XPATH2,

 *         "org.example.XPath2TransformService");

 *     put("TransformService." + Transform.XPATH2 + " MechanismType", "DOM");

 * </pre>

 * <code>TransformService</code> implementations that support the DOM

 * mechanism type must abide by the DOM interoperability requirements defined

 * in the

 * <p>

 * Once a <code>TransformService</code> has been created, it can be used

 * to process <code>Transform</code> or <code>CanonicalizationMethod</code>

 * objects. If the <code>Transform</code> or <code>CanonicalizationMethod</code>

 * exists in XML form (for example, when validating an existing

 * <code>XMLSignature</code>), the {@link #init(XMLStructure, XMLCryptoContext)}

 * method must be first called to initialize the transform and provide document

 * context (even if there are no parameters). Alternatively, if the

 * <code>Transform</code> or <code>CanonicalizationMethod</code> is being

 * created from scratch, the {@link #init(TransformParameterSpec)} method

 * is called to initialize the transform with parameters and the

 * {@link #marshalParams marshalParams} method is called to marshal the

 * parameters to XML and provide the transform with document context. Finally,

 * the {@link #transform transform} method is called to perform the

 * transformation.

 * <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>TransformService</code> instance

 * concurrently should synchronize amongst themselves and provide the

 * necessary locking. Multiple threads each manipulating a different

 * <code>TransformService</code> instance need not synchronize.

 *

 * @author Sean Mullan

 * @author JSR 105 Expert Group

 * @since 1.6

 */

public abstract class TransformService implements Transform {

    private String algorithm;

    private String mechanism;

    private Provider provider;

    /**

     * Default constructor, for invocation by subclasses.

     */

    protected TransformService() {}

    /**

     * Returns a <code>TransformService</code> that supports the specified

     * algorithm URI (ex: {@link Transform#XPATH2}) and mechanism type

     * (ex: DOM).

     *

     * <p>This method uses the standard JCA provider lookup mechanism to

     * locate and instantiate a <code>TransformService</code> implementation

     * of the desired algorithm and <code>MechanismType</code> service

     * attribute. It traverses the list of registered security

     * <code>Provider</code>s, starting with the most preferred

     * <code>Provider</code>. A new <code>TransformService</code> object

     * from the first <code>Provider</code> that supports the specified

     * algorithm and mechanism type 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 URI of the algorithm

     * @param mechanismType the type of the XML processing mechanism and

     *   representation

     * @return a new <code>TransformService</code>

     * @throws NullPointerException if <code>algorithm</code> or

     *   <code>mechanismType</code> is  <code>null</code>

     * @throws NoSuchAlgorithmException if no <code>Provider</code> supports a

     *   <code>TransformService</code> implementation for the specified

     *   algorithm and mechanism type

     * @see Provider

     */

    public static TransformService getInstance

        (String algorithm, String mechanismType)

        throws NoSuchAlgorithmException {

        if (mechanismType == null || algorithm == null) {

            throw new NullPointerException();

        }

        boolean dom = false;

        if (mechanismType.equals("DOM")) {

            dom = true;

        }

        Provider[] provs = Security.getProviders();

        for (Provider p : provs) {

            Service s = p.getService("TransformService", algorithm);

            if (s != null) {

                String value = s.getAttribute("MechanismType");

                if ((value == null && dom) ||

                    (value != null && value.equals(mechanismType))) {

                    Object obj = s.newInstance(null);

                    if (obj instanceof TransformService) {

                        TransformService ts = (TransformService) obj;

                        ts.algorithm = algorithm;

                        ts.mechanism = mechanismType;

                        ts.provider = p;

                        return ts;

                    }

                }

            }

        }

        throw new NoSuchAlgorithmException

            (algorithm + " algorithm and " + mechanismType

                 + " mechanism not available");

    }

    /**

     * Returns a <code>TransformService</code> that supports the specified

     * algorithm URI (ex: {@link Transform#XPATH2}) and mechanism type

     * (ex: DOM) as supplied by the specified provider. Note that the specified

     * <code>Provider</code> object does not have to be registered in the

     * provider list.

     *

     * @param algorithm the URI of the algorithm

     * @param mechanismType the type of the XML processing mechanism and

     *   representation

     * @param provider the <code>Provider</code> object

     * @return a new <code>TransformService</code>

     * @throws NullPointerException if <code>provider</code>,

     *   <code>algorithm</code>, or <code>mechanismType</code> is

     *   <code>null</code>

     * @throws NoSuchAlgorithmException if a <code>TransformService</code>

     *   implementation for the specified algorithm and mechanism type is not

     *   available from the specified <code>Provider</code> object

     * @see Provider

     */

    public static TransformService getInstance

        (String algorithm, String mechanismType, Provider provider)

        throws NoSuchAlgorithmException {

        if (mechanismType == null || algorithm == null || provider == null) {

            throw new NullPointerException();

        }

        boolean dom = false;

        if (mechanismType.equals("DOM")) {

            dom = true;

        }

        Service s = provider.getService("TransformService", algorithm);

        if (s != null) {

            String value = s.getAttribute("MechanismType");

            if ((value == null && dom) ||

                (value != null && value.equals(mechanismType))) {

                Object obj = s.newInstance(null);

                if (obj instanceof TransformService) {

                    TransformService ts = (TransformService) obj;

                    ts.algorithm = algorithm;

                    ts.mechanism = mechanismType;

                    ts.provider = provider;

                    return ts;

                }

            }

        }

        throw new NoSuchAlgorithmException

            (algorithm + " algorithm and " + mechanismType

                 + " mechanism not available from " + provider.getName());

    }

    /**

     * Returns a <code>TransformService</code> that supports the specified

     * algorithm URI (ex: {@link Transform#XPATH2}) and mechanism type

     * (ex: DOM) as supplied by the specified provider. 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 URI of the algorithm

     * @param mechanismType the type of the XML processing mechanism and

     *   representation

     * @param provider the string name of the provider

     * @return a new <code>TransformService</code>

     * @throws NoSuchProviderException if the specified provider is not

     *   registered in the security provider list

     * @throws NullPointerException if <code>provider</code>,

     *   <code>mechanismType</code>, or <code>algorithm</code> is

     *   <code>null</code>

     * @throws NoSuchAlgorithmException if a <code>TransformService</code>

     *   implementation for the specified algorithm and mechanism type is not

     *   available from the specified provider

     * @see Provider

     */

    public static TransformService getInstance

        (String algorithm, String mechanismType, String provider)

        throws NoSuchAlgorithmException, NoSuchProviderException {

        if (mechanismType == null || algorithm == null || provider == null) {

            throw new NullPointerException();

        } else if (provider.length() == 0) {

            throw new NoSuchProviderException();

        }

        boolean dom = false;

        if (mechanismType.equals("DOM")) {

            dom = true;

        }

        Provider p = Security.getProvider(provider);

        if (p == null) {

            throw new NoSuchProviderException("No such provider: " +

                                              provider);

        }

        Service s = p.getService("TransformService", algorithm);

        if (s != null) {

            String value = s.getAttribute("MechanismType");

            if ((value == null && dom) ||

                (value != null && value.equals(mechanismType))) {

                Object obj = s.newInstance(null);

                if (obj instanceof TransformService) {

                    TransformService ts = (TransformService) obj;

                    ts.algorithm = algorithm;

                    ts.mechanism = mechanismType;

                    ts.provider = p;

                    return ts;

                }

            }

        }

        throw new NoSuchAlgorithmException

            (algorithm + " algorithm and " + mechanismType

                 + " mechanism not available from " + provider);

    }

    private static class MechanismMapEntry implements Map.Entry<String,String> {

        private final String mechanism;

        private final String algorithm;

        private final String key;

        MechanismMapEntry(String algorithm, String mechanism) {

            this.algorithm = algorithm;

            this.mechanism = mechanism;

            this.key = "TransformService." + algorithm + " MechanismType";

        }

        public boolean equals(Object o) {

            if (!(o instanceof Map.Entry)) {

                return false;

            }

            Map.Entry<?,?> e = (Map.Entry<?,?>) o;

            return (getKey()==null ?

                    e.getKey()==null : getKey().equals(e.getKey())) &&

                   (getValue()==null ?

                    e.getValue()==null : getValue().equals(e.getValue()));

        }

        public String getKey() {

            return key;

        }

        public String getValue() {

            return mechanism;

        }

        public String setValue(String value) {

            throw new UnsupportedOperationException();

        }

        public int hashCode() {

            return (getKey()==null ? 0 : getKey().hashCode()) ^

                   (getValue()==null ? 0 : getValue().hashCode());

        }

    }

    /**

     * Returns the mechanism type supported by this <code>TransformService</code>.

     *

     * @return the mechanism type

     */

    public final String getMechanismType() {

        return mechanism;

    }

    /**

     * Returns the URI of the algorithm supported by this

     * <code>TransformService</code>.

     *

     * @return the algorithm URI

     */

    public final String getAlgorithm() {

        return algorithm;

    }

    /**

     * Returns the provider of this <code>TransformService</code>.

     *

     * @return the provider

     */

    public final Provider getProvider() {

        return provider;

    }

    /**

     * Initializes this <code>TransformService</code> with the specified

     * parameters.

     *

     * <p>If the parameters exist in XML form, the

     * {@link #init(XMLStructure, XMLCryptoContext)} method should be used to

     * initialize the <code>TransformService</code>.

     *

     * @param params the algorithm parameters (may be <code>null</code> if

     *   not required or optional)

     * @throws InvalidAlgorithmParameterException if the specified parameters

     *   are invalid for this algorithm

     */

    public abstract void init(TransformParameterSpec params)

        throws InvalidAlgorithmParameterException;

    /**

     * Marshals the algorithm-specific parameters. If there are no parameters

     * to be marshalled, this method returns without throwing an exception.

     *

     * @param parent a mechanism-specific structure containing the parent

     *    node that the marshalled parameters should be appended to

     * @param context the <code>XMLCryptoContext</code> containing

     *    additional context (may be <code>null</code> if not applicable)

     * @throws ClassCastException if the type of <code>parent</code> or

     *    <code>context</code> is not compatible with this

     *    <code>TransformService</code>

     * @throws NullPointerException if <code>parent</code> is <code>null</code>

     * @throws MarshalException if the parameters cannot be marshalled

     */

    public abstract void marshalParams

        (XMLStructure parent, XMLCryptoContext context)

        throws MarshalException;

    /**

     * Initializes this <code>TransformService</code> with the specified

     * parameters and document context.

     *

     * @param parent a mechanism-specific structure containing the parent

     *    structure

     * @param context the <code>XMLCryptoContext</code> containing

     *    additional context (may be <code>null</code> if not applicable)

     * @throws ClassCastException if the type of <code>parent</code> or

     *    <code>context</code> is not compatible with this

     *    <code>TransformService</code>

     * @throws NullPointerException if <code>parent</code> is <code>null</code>

     * @throws InvalidAlgorithmParameterException if the specified parameters

     *   are invalid for this algorithm

     */

    public abstract void init(XMLStructure parent, XMLCryptoContext context)

        throws InvalidAlgorithmParameterException;

}