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## 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 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

Field Summary

Fields inherited from interface javax.xml.crypto.dsig.Transform
`BASE64, ENVELOPED, XPATH, XPATH2, XSLT`

Constructor Summary
`protected` | `TransformService()` Default constructor, for invocation by subclasses.

Method Summary
`String` | `getAlgorithm()` Returns the URI of the algorithm supported by this `TransformService`.
`static TransformService` | `getInstance(String algorithm, String mechanismType)` Returns a `TransformService` that supports the specified algorithm URI (ex: `Transform.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: `Transform.XPATH2`) and mechanism type (ex: DOM) as supplied by the specified provider.
`static TransformService` | `getInstance(String algorithm, String mechanismType, String provider)` Returns a `TransformService` that supports the specified algorithm URI (ex: `Transform.XPATH2`) and mechanism type (ex: DOM) as supplied by the specified provider.
`String` | `getMechanismType()` Returns the mechanism type supported by this `TransformService`.
`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.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Methods inherited from interface javax.xml.crypto.dsig.Transform
`getParameterSpec, transform, transform`

Methods inherited from interface javax.xml.crypto.XMLStructure
`isFeatureSupported`

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 `Provider`s, 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:
    `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

### 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

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