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

Class TransformService

java.lang.Object
javax.xml.crypto.dsig.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. See the TransformService section in the Java Security Standard Algorithm Names Specification for a list of standard algorithm URIs and 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 Details

    • TransformService

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

  • Method Details

    • 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. See the TransformService section in the Java Security Standard Algorithm Names Specification for a list of standard transform algorithms.
      mechanismType - the type of the XML processing mechanism and representation. See the TransformService section in the Java Security Standard Algorithm Names Specification for a list of standard mechanism types.
      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. See the TransformService section in the Java Security Standard Algorithm Names Specification for a list of standard transform algorithms.
      mechanismType - the type of the XML processing mechanism and representation. See the TransformService section in the Java Security Standard Algorithm Names Specification for a list of standard mechanism types.
      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. See the TransformService section in the Java Security Standard Algorithm Names Specification for a list of standard transform algorithms.
      mechanismType - the type of the XML processing mechanism and representation. See the TransformService section in the Java Security Standard Algorithm Names Specification for a list of standard mechanism types.
      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

    • init

      public abstract void init​(TransformParameterSpec params) throws InvalidAlgorithmParameterException
      Initializes this TransformService with the specified parameters.

      If the parameters exist in XML form, the init(XMLStructure, XMLCryptoContext) method should be used to initialize the TransformService.

      Parameters:
      params - the algorithm parameters (may be null if not required or optional)
      Throws:
      InvalidAlgorithmParameterException - if the specified parameters are invalid for this algorithm

    • 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

    • init

      public abstract void init​(XMLStructure parent, XMLCryptoContext context) throws InvalidAlgorithmParameterException
      Initializes this TransformService with the specified parameters and document context.
      Parameters:
      parent - a mechanism-specific structure containing the parent structure
      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
      InvalidAlgorithmParameterException - if the specified parameters are invalid for this algorithm