public abstract class

TransformService

extends Object
implements Transform
java.lang.Object
   ↳ javax.xml.crypto.dsig.TransformService

Class Overview

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.

Summary

[Expand]
Inherited Constants
From interface javax.xml.crypto.dsig.Transform
Protected Constructors
TransformService()
Default constructor, for invocation by subclasses.
Public Methods
final String getAlgorithm()
Returns the URI of the algorithm supported by this TransformService.
static TransformService getInstance(String algorithm, String mechanismType, String provider)
Returns a TransformService that supports the specified algorithm URI (ex: XPATH2) and mechanism type (ex: DOM) as supplied by the specified provider.
static TransformService getInstance(String algorithm, String mechanismType)
Returns a TransformService that supports the specified algorithm URI (ex: XPATH2) and mechanism type (ex: DOM).
static TransformService getInstance(String algorithm, String mechanismType, Provider provider)
Returns a TransformService that supports the specified algorithm URI (ex: XPATH2) and mechanism type (ex: DOM) as supplied by the specified provider.
final String getMechanismType()
Returns the mechanism type supported by this TransformService.
final Provider getProvider()
Returns the provider of this TransformService.
abstract void init(TransformParameterSpec params)
Initializes this TransformService with the specified parameters.
abstract void init(XMLStructure parent, XMLCryptoContext context)
Initializes this TransformService with the specified parameters and document context.
abstract void marshalParams(XMLStructure parent, XMLCryptoContext context)
Marshals the algorithm-specific parameters.
[Expand]
Inherited Methods
From class java.lang.Object
From interface javax.xml.crypto.AlgorithmMethod
From interface javax.xml.crypto.XMLStructure
From interface javax.xml.crypto.dsig.Transform

Protected Constructors

protected TransformService ()

Default constructor, for invocation by subclasses.

Public Methods

public final String getAlgorithm ()

Returns the URI of the algorithm supported by this TransformService.

Returns
  • the algorithm URI

public static TransformService getInstance (String algorithm, String mechanismType, String provider)

Returns a TransformService that supports the specified algorithm URI (ex: 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

public static TransformService getInstance (String algorithm, String mechanismType)

Returns a TransformService that supports the specified algorithm URI (ex: 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.

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

public static TransformService getInstance (String algorithm, String mechanismType, Provider provider)

Returns a TransformService that supports the specified algorithm URI (ex: 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

public final String getMechanismType ()

Returns the mechanism type supported by this TransformService.

Returns
  • the mechanism type

public final Provider getProvider ()

Returns the provider of this TransformService.

Returns
  • the provider

public abstract void init (TransformParameterSpec params)

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

public abstract void init (XMLStructure parent, XMLCryptoContext context)

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

public abstract void marshalParams (XMLStructure parent, XMLCryptoContext context)

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