Module java.xml.crypto
Package javax.xml.crypto.dsig

Class TransformService

  • All Implemented Interfaces:
    AlgorithmMethod, Transform, XMLStructure
    public abstract class TransformService
extends Object
implements Transform
    A Service Provider Interface for transform and canonicalization algorithms.

    Each instance of TransformService supports a specific transform or canonicalization algorithm and XML mechanism type. To create a TransformService, call one of the static getInstance methods, passing in the algorithm URI and XML mechanism type desired, for example:

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

    TransformService implementations are registered and loaded using the Provider mechanism. Each TransformService service provider implementation should include a MechanismType 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 Provider subclass as: 

         put("TransformService." + Transform.XPATH2,
         "org.example.XPath2TransformService");
     put("TransformService." + Transform.XPATH2 + " MechanismType", "DOM");
    TransformService implementations that support the DOM mechanism type must abide by the DOM interoperability requirements defined in the DOM Mechanism Requirements section of the API overview. See the Service Providers section of the API overview for a list of standard mechanism types.

    Once a TransformService has been created, it can be used to process Transform or CanonicalizationMethod objects. If the Transform or CanonicalizationMethod exists in XML form (for example, when validating an existing XMLSignature), the 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 Transform or CanonicalizationMethod is being created from scratch, the init(TransformParameterSpec) method is called to initialize the transform with parameters and the marshalParams method is called to marshal the parameters to XML and provide the transform with document context. Finally, the transform method is called to perform the transformation.

    Concurrent Access

    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.

    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 TransformService instance concurrently should synchronize amongst themselves and provide the necessary locking. Multiple threads each manipulating a different TransformService instance need not synchronize.

    Since:
    1.6

    • Constructor Detail

      • TransformService

        protected TransformService()
        Default constructor, for invocation by subclasses.

    • Method Detail

      • getInstance

        public static TransformService getInstance​(String algorithm,
                                           String mechanismType)
                                    throws NoSuchAlgorithmException
        Returns a TransformService that supports the specified algorithm URI (ex: Transform.XPATH2) and mechanism type (ex: DOM).

        This method uses the standard JCA provider lookup mechanism to locate and instantiate a TransformService implementation of the desired algorithm and MechanismType service attribute. It traverses the list of registered security Providers, starting with the most preferred Provider. A new TransformService object from the first Provider that supports the specified algorithm and mechanism type is returned.

        Note that the list of registered providers may be retrieved via the Security.getProviders() method.

        Implementation Note:
        The JDK Reference Implementation additionally uses the jdk.security.provider.preferred Security property to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned by Security.getProviders().
        Parameters:
        algorithm - the URI of the algorithm
        mechanismType - the type of the XML processing mechanism and representation
        Returns:
        a new TransformService
        Throws:
        NullPointerException - if algorithm or mechanismType is null
        NoSuchAlgorithmException - if no Provider supports a TransformService implementation for the specified algorithm and mechanism type
        See Also:
        Provider

      • getInstance

        public static TransformService getInstance​(String algorithm,
                                           String mechanismType,
                                           Provider provider)
                                    throws NoSuchAlgorithmException
        Returns a TransformService that supports the specified algorithm URI (ex: Transform.XPATH2) and mechanism type (ex: DOM) as supplied by the specified provider. Note that the specified Provider object does not have to be registered in the provider list.
        Parameters:
        algorithm - the URI of the algorithm
        mechanismType - the type of the XML processing mechanism and representation
        provider - the Provider object
        Returns:
        a new TransformService
        Throws:
        NullPointerException - if provider, algorithm, or mechanismType is null
        NoSuchAlgorithmException - if a TransformService implementation for the specified algorithm and mechanism type is not available from the specified Provider object
        See Also:
        Provider

      • getInstance

        public static TransformService getInstance​(String algorithm,
                                           String mechanismType,
                                           String provider)
                                    throws NoSuchAlgorithmException,
                                           NoSuchProviderException
        Returns a TransformService that supports the specified algorithm URI (ex: Transform.XPATH2) and mechanism type (ex: DOM) as supplied by the specified provider. 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.

        Parameters:
        algorithm - the URI of the algorithm
        mechanismType - the type of the XML processing mechanism and representation
        provider - the string name of the provider
        Returns:
        a new TransformService
        Throws:
        NoSuchProviderException - if the specified provider is not registered in the security provider list
        NullPointerException - if provider, mechanismType, or algorithm is null
        NoSuchAlgorithmException - if a TransformService implementation for the specified algorithm and mechanism type is not available from the specified provider
        See Also:
        Provider

      • getMechanismType

        public final String getMechanismType()
        Returns the mechanism type supported by this TransformService.
        Returns:
        the mechanism type

      • getAlgorithm

        public final String getAlgorithm()
        Returns the URI of the algorithm supported by this TransformService.
        Specified by:
        getAlgorithm in interface AlgorithmMethod
        Returns:
        the algorithm URI

      • getProvider

        public final Provider getProvider()
        Returns the provider of this TransformService.
        Returns:
        the provider

      • marshalParams

        public abstract void marshalParams​(XMLStructure parent,
                                   XMLCryptoContext context)
                            throws MarshalException
        Marshals the algorithm-specific parameters. If there are no parameters to be marshalled, this method returns without throwing an exception.
        Parameters:
        parent - a mechanism-specific structure containing the parent node that the marshalled parameters should be appended to
        context - the XMLCryptoContext containing additional context (may be null if not applicable)
        Throws:
        ClassCastException - if the type of parent or context is not compatible with this TransformService
        NullPointerException - if parent is null
        MarshalException - if the parameters cannot be marshalled