javax.xml.crypto.dsig
class TransformService

java.lang.Object javax.xml.crypto.dsig.TransformService

All Implemented Interfaces:

Transform

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 {@link #getInstance 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 {@link java.security.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");
 

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 {@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 Transform or CanonicalizationMethod 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.

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.

TransformService

protected TransformService()

Default constructor, for invocation by subclasses.

getAlgorithm

public final String getAlgorithm()

Returns the URI of the algorithm supported by this TransformService.

Returns:

the algorithm URI

getInstance

public static TransformService getInstance(String algorithm,
                                           String mechanismType)
                                    throws NoSuchAlgorithmException

Returns a TransformService that supports the specified algorithm URI (ex: {@link 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 {@link Security#getProviders() 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:

NoSuchAlgorithmException - if no Provider supports a TransformService implementation for the specified algorithm and mechanism type

getInstance

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

Returns a TransformService 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 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:

NoSuchAlgorithmException - if a TransformService implementation for the specified algorithm and mechanism type is not available from the specified Provider object

getInstance

public static TransformService getInstance(String algorithm,
                                           String mechanismType,
                                           String provider)
                                    throws NoSuchAlgorithmException,
                                           NoSuchProviderException

Returns a TransformService 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.

Note that the list of registered providers may be retrieved via the {@link Security#getProviders() 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:

NoSuchAlgorithmException - if a TransformService implementation for the specified algorithm and mechanism type is not available from the specified provider

NoSuchProviderException - if the specified provider is not registered in the security provider list

getMechanismType

public final String getMechanismType()

Returns the mechanism type supported by this TransformService.

Returns:

the mechanism type

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 {@link #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

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:

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:

MarshalException - if the parameters cannot be marshalled